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List of Piping Design Companies in India

Due to the recession in the Oil and Gas Industry/Market, Many of you may be trying to find some good jobs in good organizations. There are many organizations in India that recruit Piping Engineers and Piping Designers. But most of us are aware of only a few of them.

In this post, I will list down the names of a few of the organizations which I know. I request all the readers to add more company names with location (and if possible email id or contact number of the recruiter) in the comments section which I will include in the main list from time to time. This way we will be able to know the names of the other organizations.

Top Engineering Design Companies in INDIA for Piping Jobs

In the next step, by searching the internet we can get the contact information of the required company and apply for it. This way we will be able to apply in many organizations. And who knows that this endeavor may bring some results too as many times if the requirement of the organization is very less they may not advertise in newspapers or job sites. Wherever possible I will provide the email ids of the concerned HR. But many a time those contacts change frequently. If you know the email ids of the HR (As many of you might be working in the listed organizations) then please share that mail id in the comments section for the benefit of the job seeker.

Top Piping Design Companies in India

Piping Engineering companies are distributed all over India. For ease of finding, I will list them according to the city.

Piping Engineering Companies in Mumbai

Sr NoCompany NameOffice AddressHR Email ID
1WorleyLodha i-Think Techno Campus, B Wing, 5th Floor, Off Pokhran Road No. 2, Majiwada, Thane West, Thane, Maharashtra 400601, India; Phone: +91 22 6781 8000 Priyanka.Chourasia@worley.com
Tapaswi.Chandra@Worley.com
2Petrofac7th Floor, Ventura Central Avenue, Hiranandani Business Park, Hiranandani Gardens, Powai, Mumbai, Maharashtra 400076, India: Phone: +91 22 3051 3100
3Technip EnergiesB1 – 701/701A, Boomerang Building, Chandivali Farm Road, Andheri East, Yadav Nagar, Chandivali, Powai, Mumbai, Maharashtra 400072, India; Phone: +91 22 6700 2000Hiring_India@technipenergies.com
4GS Engineering2nd floor, D wing, Jolly Board Tower, I Think Techno Campus,, Kanjurmarg Station Rd, Kanjurmarg East, Mumbai, Maharashtra 400042, India; Phone: +91 22 4138 5000
5Technimont 504,Tecnimont House, Link Rd, Chincholi Bunder, Malad West, Mumbai, Maharashtra 400064, India; Phone: +91 22 6694 5555
6Toyo EngineeringVillage Road, Toyo Technology Centre, 71, Kanjur Village Rd, Kanjurmarg East, Mumbai, Maharashtra 400042, India; Phone: +91 22 2573 5000 in.placement@toyo-eng.com
7Udhe IndiaUhde India Private Limited,Uhde House,Lal Bahadur Shastri Marg,Vikhroli (West),Mumbai 400 083, India,Tel : 91 22 6796 8000
8SNC Lavalin2nd Floor, Tradestar, J.B.Nagar, Andheri-Kurla Road, Andheri East, Mumbai, Maharashtra 400059, India; Phone: +91 22 6789 2600
9NELUnit No.1101-1108, 11th Floor Windfall Sahara Plaza Complex, Andheri Kurla Rd, J.B.Nagar, Andheri (East), Mumbai, Maharashtra 400059, India; Phone: +91 22 4039 0505 hr@nel-india.com
10Mott MacdonaldWinchester Building, South Avenue, Road, Hiranandani Gardens, Powai, Mumbai, Maharashtra 400076, India; Phone: +91 22 4908 0100 Swati.Prabhu@mottmac.com/ miloni.mehta@mottmac.com
11Burns & Mcdonnell400 079, Block A, Sixth Floor, Godrej IT Park – P2 Godrej & Boyce Complex, Pirojsha Nagar Vikhroli, W, Mumbai, 400079, India; Phone: +91 22 2519 6600 careers@burnsmcd.in
12Rolta IndiaRolta Tower A MIDC, Rolta Technology Park, Andheri East, Mumbai, Maharashtra 400093, India; Phone: +91 22 2926 6666
13Techint5th Floor, iThink Techno Campus, Pokhran Road No. 2, Off Eastern Express Highway, Behind TCS, Thane, Maharashtra 400607, India; Phone: +91 22 6113 3500Contact HR Manager Mr. Jogendraa Nakhawa on 022-61133500 (Mail Id: jogendra.nakhawa@techint.in)
14Aker SolutionsBeta building, i-Think Techno Campus, Aker Powergas Pvt Ltd, Nehru Nagar, Kanjurmarg East, Mumbai, Maharashtra 400042, India; Phone: +91 22 6691 5901
15Reliance Engineering31, Narayan Plaza Ind. Estate, Chandivali Road, Andheri East, Mumbai, Maharashtra 400072, India; Phone: +91 22 2847 4646
16Essar EngineeringF/41 Palm Acres CHSL,Mahatma Phule Road,Mulund East,Mumbai, 400081, near Gawanpada, Mumbai, Maharashtra 400081, India; Phone: +91 99677 95973
17TCE (Tata Consulting Engineers Ltd)Unit No NB 1502 & SB -1501, 15th floor, Empire Tower, Cloud City Campus, GUT NO 31, Village Elthan, Kalwa Industrial Estate, Thane Belapur Road Airoli, Navi Mumbai, Maharashtra 400708, India; Phone: +91 22 6114 8181 tceconnect@tce.co.in
www.tce.co.in/careers
18Citec EngineeringMindspace, Building no.1, 4th Floor, Plot No Gen 2/1/F TTC Industrial Area, MIDC, Shiravane, Juinagar, Navi Mumbai, Maharashtra 400706, India; Phone: +91 22 6768 0200shilpa.deshmukh@citec.com
19Chemtex
20Indian Oil TankingIOT Infrastructure & Energy Services Ltd. Plot No. Y2, Near Nahur Railway Station, Off CEAT Tyre Road, Nahur (W), Mumbai – 400078.Tel: (+91) 22 6152 4500/600
21Aarvi EnconB1-603, Innova, Marathon NextGen G.K. Road, Opp. Peninsula Park, Lower Parel West, Mumbai, Maharashtra 400013, India; Phone: +91 22 6662 6890
22Pyramid E&C6th Floor, B Wing, I-Think Techno Campus,Behind Viviana Mall,, Pokhran Road No.2,Off,Eastern Express Highway,, Thane West, Maharashtra 400607, India; Phone: +91 22 6212 1000
23Atec India
24Ausenco
25Kepples
26L&T-Hydrocarbontalent.offshore@larsentoubro.com
27Hector & Streak Consulting Pvt. Ltd. hr17@hectorandstreak.com
28Tauraus Contractors jobs@tauruscontractors.com
29Manav Corporate Consultants info@manavconsultants.com
30Innovsource services Private Limited meghnab@innovsource.com
31AtkinsVikhroli, MumbaiRecruitment.GTC@atkinsglobal.com
32United Youepcindia@unitedyou.com
33Pyramid E&CThanehr@pyramidenc.com

Piping Design Companies in Gurgaon/ Gurugram

Sr NoCompany NameOffice AddressHR Email ID
1Bechtel
2Fluor Daniel
3Lahmeyer
4GS Engineering
5GE (General Electric)
6Mcdermott
7Punj Lloyd
8KBR
9Siemens
10Toshiba
11Honeywell
12Doosan
13Alstom India
14IOTL
15Katzstroy
16The BIM Engineershr@thebimengineers.com
Ph No: +91-8810360478

Piping Companies in Pune

Sr NoCompany nameOffice AddressHR Email ID
1Black & Veatch
2Udhe India
3Praj IndustriesPraj Industries Ltd; Praj Tower, 274 & 275, Bhumkar Chowk, Hinjewadi Road, Hinjewadi, Pune-411057poojaingale@praj.net
Ph No-+91-20-71802000
4Air Productsmohantm1@airproducts.com
5Neilsoft
6Chandan Tech
7Arya System
8Equinox
9Plantech
10Transtech
11Delta Group
12Aquatech
13Va Tech Wabag Limited
14Citec EngineeringMidas Tower, 6th Floor part B, Plot No. 44, Rajiv Gandhi Infotech Park, 411057 Hinjawadi Phase I, Pune, Maharashtra; Phone: +91 20 6656 1313
15Frames Indiamkulkarni@plugpower.com

Piping Engineering Companies in Chennai

Sr NoCompany NameOffice AddressHR Email ID
1TechnipFMC
2Petrofac
3Mcdermott
4Exterron Energy
5SaipemSaipem India Projects Pvt Ltd, Perugundi, Chennai-600096sipcareers@saipem.com
6Dow Chemical
7Petrocil Engineers & Consultants Pvt Ltdprakash@petrocil.com

Piping Design Companies in Noida

Sr NoCompany Name Office AddressHR Email ID
1Samsung Engineeringrecruitment.sei@samsung.com
2TechnipFMC
3S&B-Valdel
4CH2M Hill
5CTCI
6ISGECA-4, Sector 24; Noida – 201 301, U.P., India

Piping Design Companies in Vadodara (Baroda)

Sr NoCompany NameOffice AddressHR Email ID/Contact Details
1LindeLinde House, Vasna – Bhayli Main Rd, near Nilamber Circle, Saiyed Vasna, Vadodara, Gujarat 391410, India; Phone: +91 265 305 6789
2L&T-SNLL&T- Knowledge City, L&T Service Rd, Madhavpura, Vadodara, Gujarat 390019, India; Phone: +91 265 245 6000 recruitment@lntsnl.com
3L&T-Chiyoda5th L&T Knowledge City, West Block 1 N.H. 8 Ajwa-Waghodia Crossing Gate no. 1, Gujarat 390019, India; Phone: +91 265 244 2000jobs@lntchiyoda.com,
+91 265 2442020
4WorleyWorley India Pvt Ltd, Vadodara, 4th Floor, Notus Pride – IT Park, Sarabhai Campus, Genda Cir, Vadodara, Gujarat 390023, IndiaTapaswi.Chandra@Worley.com
Perumal.Raj@Worley.com
Chaitali.Shah@Worley.com
5Zeppelin Systems India Pvt LtdZeppelin Systems India Pvt Ltd. Level 4, ADM Building, Alembic Campus, Alembic Road, Vadodara – 390003. INDIA. Phone:+91-265-2291710 info@zeppelin-india.com
6Shiva Engineering Service1st floor, ABS towers, Old Padra Road, Vadodara, Gujarat, India; Tel : +91-265-2357316, 2357318, 2357319 info@shiva-engineering.com
7L&T Technology ServicesL&T Technology Services Limited, Ashish Complex, Revenue Sur. No. 370/2(Part) VI, Opposite Geb Substation, N.H.No.8, Chhani, Chhani Road. Vadodara, Gujarat, India india.careers@ltts.com
8LISEGA India Private Limited75VF+5HV, Shushil Park Society, Pratham Avenue, Akota, Vadodara, Gujarat 390007, India
9Air Products India Pvt. Ltd6th to 9th Floor, Notus IT Park, Sarabhai Campus, Gorwa Rd, Vadodara, 390023, Indiamohantm1@airproducts.com
10Bechtel India Pvt Ltd2nd & 3rd Floor, A2 Building, Sarabhai Campus, Gorwa Rd, near Courtyard by Marriott hotel, Subhanpura, Vadodara, Gujarat 390016, India+91 265 616 8000
11VCare Engineering Pvt Ltd301/A, Block E, Notus Pride IT Park, Sarabhai Campus, Subhanpura Rd, Gorwa, Vadodara, Gujarat 390023, Indiahr@vcare-global.com
12Tech Mahindra (KBR)8599+WM6, Genda Cir, Alkapuri, Vadodara, Gujarat 390023, India
13Petroexcel Technology Services (P) Limited403-412, Zorba, Akshar Chowk, Besides Reliance Mega Mall, Old Padra Rd, Hira Nagar, Tandalja, Vadodara, Gujarat 390007, India
14Thyssenkrupp Group, IOCL Refinery94FH+467, Karachiya, Vadodara, Gujarat 391310, India
15Nuberg EngineeringPlot No. 678, 679, GIDC, Fulwadi, Gujarat 393110, India
16Quanta Process Solutions Pvt LtdQuanta House, Bhailal Amin Road, Gorwa, Vadodara, Gujarat 390003, India+91 265 229 1067
17Libra
18Aarti Industries Ltd.Keval Corporate Park, 1, Canal Rd, Chhani, Vadodara, Gujarat 390024, India+91 22 6797 6666
19Engineers India Limited4th & 5th Floor, Meghdhanush, Race Course Rd, Near Transpek Circle, Bird Circle, ICICI Bank, Paris Nagar, Alkapuri, Vadodara, Gujarat 390007, India
20Fluor Daniel India Private Limited7th Floor, Notus IT Park, Dr Vikram Sarabhai Marg, Block D, Campus, Subhanpura, Vadodara, Gujarat 390023, India
21General Electric (GE)
22Honeywell85GC+WHM, BIDC Gorwa Estate, Gorwa, Vadodara, Gujarat 390003, India
23Ion Exchange India Ltd
24Kent PLC3rd Floor, Tower A, Temenos Business Park, Atladara, Vadodara, Gujarat 390007, India
25L&T Power
26MAN Energy Solutions
27Meinhardt EPCM (India) Private Limited
28Nuberg Engineering Ltd.
29Projects & Development India Ltd (PDIL)
30Rishabh Engineering Services
31TakViksh Engineering
32Tata Consulting Engineers
33Sunrise Engg Solutions Pvt Ltd
34Siemens
35Suzlon Group
36Paramount Limited
37Alembic Group

Piping Companies in Delhi

Sr NoCompany NameOffice AddressHR Email ID
1Air Liquide
2Triune
3EIL
4L&T-Faridabad
5Honeywell

Piping Design Companies in Kolkata

Sr NoCompany nameOffice AddressHR Email ID
1Wood (AMEC FW)
2Development Consultants Pvt LtdDevelopment Consultant House, Block: DG-IV, Sector-II, Salt Lake, Kolkata-700091hrrecruit@in.dclgroup.com
3Richard Design Services
4Paharpur Cooling Tower
5Worley
6L&T-SNL

Piping Engineering Companies in Bangalore / Bengaluru

Sr NoCompany NameOffice AddressHR Email ID
1TaalTechrecruitment@taaltech.com
swathisavanth@taaltech.com
2TCE
3GE
4L&T Valdel
5Suez Water Technologies
6Quest Global Engineering Services
7Veolia
8Sidvin Energy Engineeringcareers@sidvincoretech.com

Other Piping Engineering Companies from India

  • DGS: Hyderabad: careers@dgsts.com
  • Padink Engineering: Bengaluru: hr@padink.in

Few more Resources for you..

Top EPC companies of UAE (Abu Dhabi, Dubai, and Sharjah) to try for employment opportunities

If anyone of you knows the HR Email ids of any of the listed companies please share them in the comments section in Company Name-Email ID format as this database will be helpful for all of us. Thanks in Advance.

Examples of Hazards of Pressure Testing

What is Pressure Testing?

Pressure testing is a process of verifying the strength, integrity, and safety of a pressurized system or component. It involves pressurizing the system or component with a fluid or gas, usually water or air, to a predetermined level and monitoring the pressure to ensure that it remains stable over a specified period of time.

The purpose of pressure testing is to identify any leaks or weaknesses in the system or component that could lead to failure under normal operating conditions. By subjecting the system or component to a higher pressure than it would normally experience, any weaknesses or defects in the material or construction can be detected.

There are several types of pressure tests, including hydrostatic testing, pneumatic testing, and vacuum testing. Each type of test is designed to assess different aspects of the system or component, such as its ability to withstand pressure, its resistance to leaks, and its overall integrity.

Pressure testing is commonly used in a wide range of industries, including oil and gas, manufacturing, construction, and aerospace. It is a critical step in ensuring the safety and reliability of pressurized systems and components.

Hazards of Pressure Testing

Everybody knows that Pressure Testing (Hydro test, Pneumatic Test, or Pressure Test) is a highly hazardous activity and there are many examples of incidents that had already happened. So the utmost care must be exercised to manage safety during pressure testing.

While pressure testing is an important safety measure to ensure the integrity of pressurized systems, it also involves certain hazards that should be taken into account to prevent accidents and injuries. Some of the hazards associated with pressure testing include:

  • Explosion or rupture: If the system or component being tested is unable to withstand the pressure, it may explode or rupture, causing damage to the equipment and potential injury or death to anyone nearby.
  • Projectile hazards: If a component fails during the test, it may release fragments or debris at high velocity, which can cause serious injury or damage to equipment and structures.
  • Chemical hazards: The fluid or gas used to pressurize the system may be hazardous if it leaks or is released, potentially causing chemical burns or respiratory problems.
  • Noise hazards: The noise generated during pressure testing can be very loud, potentially causing hearing damage if proper hearing protection is not used.
  • Thermal hazards: The pressurized fluid or gas may generate heat during the test, potentially causing burns or other thermal injuries.

To prevent these hydro testing hazards, proper safety measures should be taken, including wearing appropriate personal protective equipment (PPE), maintaining a safe distance from the test area, using proper containment and ventilation measures, and following established safety procedures and protocols. It is also important to ensure that the equipment used for pressure testing is properly maintained and calibrated to prevent accidents and ensure accurate results.

In the below paragraphs, We will provide examples of five such incidents that can be used to understand the hazards and dangers involved during pressure testing.

Hydro-test of a new vertical vessel

Explosion of a vertical vessel during hydrotesting
Fig. 1: Explosion of a vertical vessel during hydro testing

Refer to Fig. 1. The image shows an exploded vessel that happened during hydro testing of a new vessel. The root cause of the incident is not known fully. But there was some brainstorming and people thought that hydro-testing with “very cold” water could be a contributing factor. The good news is that no injuries occurred.

Learning from the Incident

It is learned that water temperature during hydro testing is critical. It is suggested to maintain the metal and water temperature at least at 16°C or at least 10°C above the impact test temperature of the metal during pressure testing.

Filling of a vertical tank

This incident happened while filling the tank (Refer to Fig. 2) with water from a fire hydrant. As the relief valve could not displace the air fast enough for the volume of water that was being pumped in, The top of the tank blew off suddenly.

Fortunately, no injury happened, but an operator was on top of the tank a few seconds before.

Top of tank blew off during hydrotesting
Fig. 2: The top of the tank blew off during hydro testing

Lessons Learned from the Incident

Before filling and emptying operations, drain and venting systems must be thoroughly inspected and checked.

Emptying a vertical tank

Refer to Fig. 3. While the tank was being emptied, it suddenly collapsed. Root cause analysis shows that a plastic sheet that was protecting the roof was trapped in the vent which created a vacuum. So it is a must to inspect the venting systems before filling and emptying operations.

There was no injury. It should be noted that this type of incident is not that unusual.

Collapse of tank during hydrotesting
Fig. 3: Collapse of a tank during hydro testing

Sphere collapse

During the filling of a 2000 m3 LPG sphere (Fig. 4), Its legs suddenly collapsed. One nearby person was killed and one was seriously injured.

The research found that the sphere was approximately 80% full of fresh water. The vessel’s last hydro-test was 10 years ago and the last inspection of its legs was done 5 years ago.

The main cause was the Severe corrosion of the legs under the concrete fire protection. The corrosion occurred due to water ingress between the concrete and the steel legs. The water protective cap that was located over the concrete was not sufficient to keep the water out. It was verified later that the steel legs had their thickness reduced by up to 8 mm, with pitting holes of up to 10 cm2.

Sphere Collapsed during hydrotesting
Fig. 4: Sphere Collapsed during hydro testing

Thorough investigation and tests confirmed that the following factors contributed to the sphere collapse:

  • The poor design of the water caps over the fire-proofing concrete was allowing the water to penetrate the steel beams and the concrete.
  • Vertical cracks in the concrete let water in.
  • Poor workmanship during Repairs had been done to the concrete.
  • The new concrete had not adhered to the old concrete, again letting water in.
  • The deluge system had been tested with saltwater, increasing the possibility of corrosion.

Learning from the incident

A complete inspection must be performed visually and if required with NDT before pressure testing of an old vessel. This inspection must include the vessel, nozzles, appurtenances, and supporting structures.

Emptying of a gearbox

To speed up the removal of 250 liters of oil from a gearbox (Fig. 5), the gauge hole was plugged and the breather was connected to the 6-bar air network. The gearbox exploded and threw missiles around seriously damaging surrounding piping and structure. Fortunately, there was no injury.

Gear box explosion
Fig. 5: Gear-box explosion

Even though a gearbox is not a pressure vessel, its productivity may lead to a risky attitude.

Recommended Actions for Pressure Testing

Tests may be a routine operation pressure but do not forget that in fact, pressurization is energy storage. Its instantaneous release works like a bomb and may cause severe damage to persons and equipment.

Good preparation is always essential to avoid incidents. It is recommended to use the following checklist:

  • Based on relevant standards and specifications, A detailed checklist procedure must be prepared which shall cover the testing operation from filling up to emptying the vessel.
  • Good coordination is of utmost importance to avoid performing the hydro-test at the same time as other operations. Most reputed companies use work permit procedure / Job Hazard Analysis methodology.
  • The equipment must be in good condition and adequately maintained and certified.
  • Testing equipment shall be kept as far as practicable from the recording and pumping station.
  • New Testing equipment must be checked before using it.
  • The test area must be roped off,
  • During the test, from filling up until the end of depressurization, all non-essential people must be out of the test area,
  • The test crew must attend a toolbox talk,
  • Wearing PPE must be made mandatory for all personnel involved in testing.
  • Leak inspection must be performed at least 15 minutes after the test pressure has been reached and this has to be inspected only by designated personnel.
  • While under pressure or during pressure-up stages, never tamper with, or tighten any fittings (i.e. connections, bolts, hoses, etc).

Few more useful resources for you…

What is Engineering Process Safety?
Safety Rules during A Field Visit By A Design Engineer
An article on Crane safety during Construction
HAZOP (Hazard and Operability) Study: A brief introduction
An article on Excavation Hazards at Construction Sites
Hazardous Area- Theory, Classification and Equipment selection: A short presentation

Liquified Natural Gas (LNG): Properties, Uses, Origin, Composition, Process, Companies

Liquefied Natural Gas (LNG) is a natural gas that has been cooled to a temperature of -162°C (-260°F) at atmospheric pressure, which results in the gas transforming into a liquid state. This process, called liquefaction, reduces the volume of natural gas by about 600 times, making it easier and more economical to transport and store.

LNG is primarily composed of methane, which is the main component of natural gas. It is produced by cooling natural gas to its boiling point, which causes it to condense into a liquid. The resulting LNG is clear, odorless, non-corrosive, and non-toxic.

LNG is typically stored in insulated tanks and transported in special carriers, such as LNG ships or tanker trucks. It can be used as a fuel for power generation, heating, and transportation, or as a feedstock for producing chemicals and other products.

Due to its high energy density and low environmental impact, LNG is becoming an increasingly popular alternative to other fossil fuels, such as coal and oil. It is also considered a bridge fuel toward a low-carbon future, as it can help reduce greenhouse gas emissions compared to other fossil fuels.

Liquefied Natural Gas or LNG is natural gas with the primary element as methane. The Liquefied Natural Gas is converted to liquid form for ease of transport and storage. While in liquid form, Liquified Natural Gas takes up around 1/600th of the volume of its gaseous form. So, LNG can easily be transported in liquid form in locations where natural gas transportation through pipelines is not feasible. Special tankers carry this liquefied natural gas to the terminals where the LNG is returned to the gaseous phase and distributed through pipelines.

Characteristics of Liquefied Natural Gas

Liquefied natural gas or LNG is colorless, odorless, non-toxic, and non-corrosive. The main characteristics of liquefied natural gas are

  • It is a cryogenic liquid so must be handled using special materials and technologies.
  • LNG is stored in special containers.
  • It is a fossil fuel created by organic deposited materials.
  • The boiling point of LNG is typically -162 Deg. C
  • The density of liquefied natural gas varies between 430 Kg/m3 to 470 Kg/m3.
  • At ambient conditions, LNG will convert to vapor form.
  • LNG is non-flammable.
  • Liquefied Natural Gas has a very hot flame temperature means it rapidly burns and creates huge heat because its heat of combustion is 50.2 MJ/kg.
  • It is hazardous if not contained properly.
  • LNG is a very good source of energy.

Uses of Liquefied Natural Gas

LNG or liquefied natural gas is used widely for the following applications.

  • To generate electricity or power.
  • Used as fuel for industrial and commercial boilers.
  • for heating water and buildings, to cook in residential applications.
  • For Road transport as LNG vehicles
  • For sea transport in ships, ferries, etc
  • Used as fuels for furnaces, fluid bed dryers
  • As marine fuel

Origin of Natural Gas

Natural gas exists in nature under pressure in rock reservoirs in the Earth’s crust, either in conjunction with and dissolved in heavier hydrocarbons and water or by itself. It is produced from the reservoir similarly to or in conjunction with crude oil.

Natural gas has been formed by the degradation of organic matter accumulated in the past millions of years. Two main mechanisms (biogenic and thermogenic) are responsible for this degradation. Natural gas produced from geological formations comes in a wide array of compositions. The varieties of gas compositions can be broadly categorized into three distinct groups:

  • Non-associated gas – it occurs in conventional gas fields
  • Associated gas – it occurs in conventional oil fields, and
  • Unconventional natural gas.

Unconventional gas

It occurs outside of the former two. The most common types of unconventional gas are:

  • Tight gas – natural gas produced from reservoir rocks with such low permeability that massive hydraulic fracturing is necessary to produce the well at economic rates;
  • Coalbed methane – methane adsorbed into the solid matrix of the coal;
  • Natural gas from geo-pressurized aquifers;
  • Gas hydrates – methane clathrate is a solid clathrate compound in which a large amount of methane is trapped within a crystal structure of water, forming a solid similar to ice;
  • Deep gas

Composition of Natural Gas

Natural gas is a complex mixture of hydrocarbon and non-hydrocarbon constituents and exists as a gas under atmospheric conditions.

Raw natural gas typically consists primarily of methane (CH4), the shortest and lightest hydrocarbon molecule. It also contains varying amounts of:

  • Heavier gaseous hydrocarbons: ethane (C2H6), propane (C3H8), normal butane (n-C4H10), iso-butane (i-C4H10), pentanes, and even higher molecular weight hydrocarbons.
  • Acid gases: carbon dioxide (CO2), hydrogen sulfide (H2S), and mercaptans such as methanethiol (CH3SH) and ethanethiol (C2H5SH).
  • Other gases: nitrogen (N2) and helium(He).
  • Water: water vapor and liquid.
  • Liquid hydrocarbons: crude oil and/or gas condensates.
  • Mercury: only trace amounts.

Refer to the table in Figure 1 for a typical composition of Natural gas.

Table showing typical composition of natural gas
Fig. 1: Table showing the typical composition of natural gas

LNG Process

Naturally, liquefaction is advantageous as it can be transported or stored in a greater quantity. The LNG Process is the process of liquefaction. The process of cooling the gaseous LNG to -259°F or -162°C for transforming it into liquid is known as the LNG Process. The process is actually a chain of methods, hence popularly known as LNG Process Chain.

Natural Gas – Exploration to End-User

Fig. 2 below shows the flow chart for Liquefied natural gas exploration.

Flow chart showing exploration of natural gas
Fig. 2: Flow chart showing the exploration of natural gas

LNG Plant

An LNG plant refines the crude natural gas received from deep within the earth and condenses it into a pure, concentrated, efficient, liquid form of energy. Three basic processing steps are performed in the LNG plant. These are:

  • Purification of the extracted natural gas by removing dust, acid gases (CO2), helium, water, and heavy hydrocarbons.
  • Liquefaction by condensing and cooling it to approximately −162 °C.
  • Transportation of the liquefied natural gas to the consumer by sea or road transport.

Typical processes of a 2-train LNG plant are shown in Fig. 3.

A typical 2 train LNG plant
Fig. 3: A typical 2-train LNG plant

Liquefaction Temperatures of LNG

Image showing liquefaction temperature
Fig. 4: Image showing liquefaction temperature

LNG Process Flow

Fig. 5 shows a Schematic of a Simple Refrigeration Cycle (LNG Process Flow)

Natural Gas Liquefaction Techniques

Different LNG Process liquefaction techniques include:

  • Single Refrigeration cycle
  • Multiple Refrigeration cycles
  • Self Refrigerated cycles
  • Cascade Processes
  • The cooling of natural gas involves the use of refrigerants which could either be pure component refrigerants or mixed component refrigerants.
Schematic of a Simple Refrigeration Cycle
Fig. 5: Schematic of a Simple Refrigeration Cycle

LNG Process Liquefaction Technologies

LNG process liquefaction is performed using various technologies mentioned below:

  1. CASCADE PROCESS by ConocoPhillips
  2. C3MR or AP-X by Air Products
  3. DMR by Shell
  4. Mixed Fluid Cascade – MFC by Linde
  5. Liquefin by Axens / Air Liquide

Liquefied Natural Gas by CASCADE Process

  • Most Straight Forward of All Processes
  • Kenai Plant Continuous Operation 1969
  • CoP License, Plant Build by Bechtel.
  • The raw gas is first treated to remove typical contaminants.
  • Next, the treated gas is chilled, cooled, and condensed to -162 ˚C in succession using propane, ethylene, and methane.
  • The last stage is pumping LNG to storage tanks and awaiting shipment.
Schematic of Cascade process
Fig. 6: Schematic of Cascade process
  • Pure component Refrigerants
  • Specific operating ranges for each component
  • Mixed Refrigerants
  • Modified to meet specific cooling demands.
  • Helps improve the process efficiency
  • Mixed refrigerants are mainly composed of hydrocarbons ranging from methane to pentane, Nitrogen, and CO2. Typically, Methane – 25-30%, Ethane – 45-55%, Propane – 15-20%, Nitrogen – 1-5%, and Butane – 1-2%.

Liquefied Natural Gas by Single MR Process

  • Significant improvement from Cascade Process
  • The use of Coil wound Heat Exchangers & MR refrigerant simplified the process.
  • Mixed Refrigerant offered a way to provide the required refrigeration over the temperature range required.

C3MR process of Liquefaction of LNG Process

  • Introduction of Propane as Pre-cooling to liquefication
  • Improved Efficiency, increased single train capacity
  • Reduction in MR refrigerant volumetric flow due to pre-cooling by Propane
  • Train size continued to grow with larger drivers & larger compressors
  • Liquefication capacity up to 5 MMTPA.
Schematic of C3MR process
Fig. 7: Schematic of the C3MR process

Liquefied Natural Gas by AP-X Hybrid LNG Process

  • Improved C3-MR process – pre-cooling by Propane, liquefaction using MR, and sub-cooling using Nitrogen Cycle.
  • Nitrogen Cycle has a simple & efficient expander loop.
  • Increased capacity by a reduction in volume flow of MR (40%of C3MR) & Propane (20% of C3MR).
  • Liquefication capacity up to 8.0 MMTPA.
  • Nitrogen Cycle is a simplified version of the cycle employed by Air Products in Air Separation plants.

Why Nitrogen:

  • Higher vapor pressure at the required liquefication temperature of Natural Gas
  • The relatively smaller volumetric flow rate in low-pressure Nitrogen circuits.
  • Improved efficiency by reducing pressure losses

DMR LNG Liquefaction Process

  • DMR – Dual Mixed Refrigerant is very similar to C3MR
  • The difference is in the utilization of a second pre-cooling refrigerant component.
  • The use of two mixed refrigerant cycles allows full utilization of power in a design with two mechanically driven compressors.
  • It allows keeping the compressors at their best efficiency point over a very wide range of ambient temperature variations and changes in feed gas composition.
  • The natural gas stream is cooled via two stages. The first stage cools natural gas to -50°C while the second column cools natural gas to LNG at -160°C.

Liquefied Natural Gas using Liquefin by Axens (Air Liquide)

  • Developed by IFPEN and AXENS, now owned by Air Liquide.
  • a highly efficient process and provides the most cost-competitive LNG product per ton.
  • is optimized best with the Brazed Aluminium Heat Exchanger, leading to further cost reductions and scalable output.
  • Compact and modular design
  • Balanced refrigeration power allows for identical refrigerant compressor drivers
  • Very cost-effective solution

Codes and Standards for Liquefied Natural Gas

Stringent code and standard guidelines are followed at every step of the LNG process to ensure safety. The primary LNG codes and standards are

  • NFPA 59A
  • EN1473
  • EN 1160
  • EN 14620
  • EN 1474
  • EN 1532
  • EN 13645
  • 33 CFR Part 127
  • API 620
  • JGA-107-RPIS
  • JGA-108-RPAS
  • JGA-102
  • JGA-103
  • OISD 194
  • NFPA 30.

Types of Liquefied Natural Gases

There are two main types of liquefied natural gas (LNG), which are based on the processes used to produce them:

  1. Associated Gas LNG: This type of LNG is produced as a by-product of oil extraction from oil fields that contain natural gas. When the oil is extracted, the natural gas is separated and liquefied. Associated Gas LNG typically has a higher content of hydrocarbons other than methane, such as ethane and propane, which makes it suitable for use as a feedstock for producing petrochemicals.
  2. Non-Associated Gas LNG: This type of LNG is produced from natural gas fields that do not have any associated oil. The natural gas is extracted from the fields and processed to remove impurities before being liquefied. Non-Associated Gas LNG typically has a higher methane content than Associated Gas LNG, which makes it suitable for use as a fuel for power generation, heating, and transportation.

Both types of LNG have similar properties and can be used interchangeably, although their specific applications may differ depending on their composition and quality.

LNG pricing

The pricing of Liquefied Natural Gas is not straightforward. In the current LNG contracts, three major pricing systems are prevalent as mentioned below:

  • Oil-indexed contract. Primary user countries are Japan, Korea, Taiwan, and China.
  • Oil, oil products, and other energy carriers indexed contracts. Specifically used in Continental Europe; and
  • Market-indexed contracts. Used mostly in the US and the UK.;
  • The equation used for the calculation of an indexed price is as follows:

CP = BP + β X

Here,

  • BP: constant part or base price
  • β: gradient
  • X: indexation

The above-mentioned formula finds its wide use in Asian LNG SPAs. The base price is represented by various non-oil factors but is usually a constant determined by negotiation at a level that can prevent LNG prices from falling below a certain level. It thus varies regardless of oil price fluctuation.

Quality of Liquefied Natural Gas

In the LNG Business, the quality of LNG is one of the most important issues. During trading, any natural gas that does not meet the agreed specifications is termed as “off-specification” or “off-quality” LNG. That’s why the LNG Quality must be regulated. Such regulations serve the following purposes:

  • Ensures the distributed gas is non-corrosive and non-toxic.
  • Guards against liquid or hydrate formation in the networks.
  • Allow interchangeability of the distributed gases by limiting the parameter variation ranges. Such parameters are the content of inert gases, calorific value, Incomplete Combustion Factor, Wobbe index, Soot Index, Yellow Tip Index, etc.

The quality of liquefied natural gas is measured at the delivery point by instruments like gas chromatograph.

Amount of the sulfur and mercury content and the calorific value are the most important gas quality concerns. To ensure the lowest concentration of sulfur and mercury in LNG, the liquefaction process must be accurately refined and tested.
The other concern for LNG is the heating value. In terms of heating value, the natural gas markets can be grouped into three markets as follows:

  • Asia (Japan, Korea, Taiwan) with a gross calorific value (GCV) higher than 43 MJ/m3(n), i.e. 1,090 Btu/SCF, known as rich gas distribution.
  • the UK and the US, with a GCV usually lower than 42 MJ/m3(n), i.e. 1,065 Btu/SCF, known as lean gas distribution
  • Continental Europe with the acceptable GCV range is quite wide: approx. 39 to 46 MJ/m3(n), i.e. 990 to 1,160 Btu/scf.

Sometimes to increase the heating value of liquefied natural gas, propane and butane are injected. In general, the price of lean LNG in terms of energy value is lower as compared to the rich LNG.

LNG Safety

Natural gas is the most environmentally friendly fossil fuel with the lowest CO2 emissions per unit of energy. But, Natural gas, being fuel and a combustible substance, must be handled with care. For the design, construction, and operation of liquefied natural gas facilities, proper measures must be taken to ensure safe and reliable operation.

However, LNG in its liquid form can not ignite and is not explosive. For LNG to burn, it must vaporize first and mix with air in the proper proportions. During leakage, LNG rapidly vaporizes and turns into a gas that easily mixes with the air. In such a case, there is a risk of ignition causing fire and thermal radiation hazards.

What is Floating Liquefied Natural Gas or FLNG?

Floating Liquefied Natural Gas (FLNG) is a technology used to produce, liquefy, store, and transfer LNG at sea. It involves using a specialized vessel that is equipped with liquefaction facilities and can be moored at a natural gas field to produce and process gas in situ.

FLNG technology enables the production of LNG from offshore natural gas fields that are too small or too remote to justify the cost of building onshore liquefaction facilities. It also allows for greater flexibility in LNG production, as the vessel can be moved from one location to another depending on the demand for LNG.

The FLNG vessel typically includes a processing plant, storage tanks, and a liquefaction plant that cools the natural gas to its liquid state. The LNG is then stored in onboard tanks until it can be transferred to LNG carriers for transportation to markets around the world.

The main advantage of FLNG technology is its ability to produce LNG at the source of natural gas, which reduces the need for long-distance pipelines and onshore liquefaction plants. This can result in significant cost savings and reduced environmental impact compared to traditional LNG production methods. However, FLNG technology also has some challenges, including the need for specialized vessels and the potential for safety and environmental risks associated with offshore operations.

Liquefied Natural Gas vs Propane

Liquefied Natural Gas (LNG) and propane are both forms of liquefied gases that can be used as fuels. However, there are some differences between the two:

  • Composition: LNG is primarily composed of methane, while propane is a hydrocarbon gas composed of propane molecules.
  • Production: LNG is produced by cooling natural gas to its boiling point, while propane is produced as a by-product of natural gas processing and crude oil refining.
  • Energy content: LNG has a lower energy content per unit volume than propane, which means that a larger volume of LNG is required to provide the same amount of energy as propane.
  • Storage and transportation: LNG is typically stored and transported in insulated tanks at cryogenic temperatures of around -162°C (-260°F), while propane is stored and transported as a liquid under pressure at room temperature.
  • Applications: LNG is primarily used as a fuel for power generation, heating, and transportation, while propane is commonly used for heating, cooking, and as a fuel for vehicles and industrial processes.

Both LNG and propane are considered cleaner-burning fuels compared to other fossil fuels like coal and oil, as they produce fewer emissions of pollutants and greenhouse gases. However, the choice of which fuel to use depends on the specific application and availability of the fuel.

Differences Between LPG and LNG

LPG (liquefied petroleum gas) and LNG (liquefied natural gas) are two types of liquefied gases that are commonly used as fuels. Here are some of the key differences between LPG and LNG:

  • Composition: LPG is a mixture of propane and butane gases, while LNG is primarily composed of methane.
  • Production: LPG is produced as a by-product of natural gas processing and crude oil refining, while LNG is produced by cooling natural gas to its boiling point.
  • Energy content: LNG has a lower energy content per unit volume than LPG, which means that a larger volume of LNG is required to provide the same amount of energy as LPG.
  • Storage and transportation: LPG is typically stored and transported as a liquid under pressure at room temperature, while LNG is stored and transported in insulated tanks at cryogenic temperatures of around -162°C (-260°F).
  • Applications: LPG is commonly used for heating, cooking, and as a fuel for vehicles and industrial processes, while LNG is primarily used as a fuel for power generation, heating, and transportation.
  • Availability: LPG is generally more widely available than LNG, as it is produced as a by-product of oil and natural gas extraction and processing. LNG production requires specialized facilities and transportation infrastructure.

Both LPG and LNG are considered cleaner-burning fuels compared to other fossil fuels like coal and oil, as they produce fewer emissions of pollutants and greenhouse gases. The choice of which fuel to use depends on the specific application, availability, and cost of the fuel.

Liquefied Natural Gas Companies

There are many companies involved in the production, transportation, and marketing of liquefied natural gas (LNG). Here are some of the largest and most well-known companies in the LNG industry:

  • Royal Dutch Shell: Shell is one of the world’s largest energy companies and is involved in all aspects of the LNG business, from production to transportation and marketing.
  • ExxonMobil: ExxonMobil is a global energy company that is involved in LNG production and marketing, as well as the development of LNG infrastructure.
  • Chevron: Chevron is a major player in the LNG industry, with interests in LNG production, transportation, and marketing.
  • Total: Total is a French multinational energy company that is involved in all aspects of the LNG business, from production to transportation and marketing.
  • BP: BP is a global energy company with interests in LNG production and marketing, as well as the development of LNG infrastructure.
  • Qatargas: Qatargas is a joint venture between Qatar Petroleum and several major international oil and gas companies, and is one of the largest producers of LNG in the world.
  • Cheniere Energy: Cheniere is a US-based energy company that specializes in LNG production and export, and is one of the largest LNG exporters in the world.
  • Woodside Energy: Woodside is an Australian energy company that is involved in LNG production and marketing, with a particular focus on the Asia-Pacific region.
  • Novatek: Novatek is a Russian energy company that is one of the largest producers of LNG in Russia and is expanding its LNG export capabilities.

ASME B31J & B31J Essentials: Why these are useful in Piping Stress Analysis?

Introduction to B31J Essentials in Caesar II

Many of you must be aware that Intergraph announced an extension of Caesar II 2017 in May 2017. B31J Essentials provides a set of calculations for revised SIFs and flexibility factors, as defined in the code ASME B31J-2017, Stress Intensification Factors (i-Factors), Flexibility Factors (k-Factors), and their Determination for Metallic Piping Components.

Benefits of Using the B31J Module of Caesar II

By using these revised SIFs and flexibilities, your stress analyses produce more accurate results. B31J Essentials provides the “more applicable data” referenced in recent editions of the piping codes. If someone is currently on CAESAR II maintenance and has installed CAESAR II 2017 (v.9.00), He can download the B31J Essentials installer from Intergraph Smart Support (https://smartsupport.intergraph.com) for free and install in their system. This article will try to inform what ASME B31J covers in brief.

What is ASME B31J?

For a long time, there was a need for a standard method to develop stress intensification factors (SIFs or i-factors) for ASME piping components and joints. At the time, the B31 Code books provided SIFs for various standard fittings and joints but did not provide guidance on how to conduct further research on existing SIFs or how to establish SIFs for nonstandard and other standard fittings or joints.

ASME B 31J is the outcome of recent research by MDC on current manufacturing practices in the SIF and k-factor test procedures, to provide a consistent and up-to-date table of SIFs and k-factors for metallic piping components.

ASME B 31J provides a standard approach for the development of SIFs, k-factors, and sustained stress multipliers for piping components and joints of all types, including standard, nonstandard, and proprietary fittings. However, this code still does not cover fittings that have a D/T ratio greater than 100 for which you have to be dependent on FEA analysis.

B31J Menu bars explaining the functions.
Fig. 1: B31J Menu bars explaining the functions.

Sustained stress multipliers are used to multiply the nominal bending stress due to sustained loading and reflect the collapse capacity of the metallic piping component or joint. Where more accurate sustained stresses are needed but an equation for the sustained stress is not given in the B31 Code book, nominal stresses due to sustained moments computed using the section modulus of the matching pipe should be multiplied by the appropriately sustained stress multiplier. Where the sustained stress is needed and an equation for the sustained stress is given in the Code book as a function of the SIF and provided in lieu of more applicable data, the sustained stress multipliers developed using the method in this Standard may be substituted as more applicable data and used with the nominal stress computed using the section modulus of the matching pipe.

Broadly The code provides the following:

Typical Output SIF results as calculated by B31J module of Caesar II
Fig. 2: Typical Output SIF results as calculated by the B31J module of Caesar II
  • Included the most applicable currently available stress intensification and flexibility factors compiled from test and analysis data for standard commercially available metallic components in a tabular format.
  • Nonmandatory Appendix A provides the standard method to develop stress intensification factors.
  • Nonmandatory Appendix B provides the standard method to develop branch connection flexibility factors.
  • Nonmandatory Appendix C demonstrates how the new branch connection k-factors should be used in the elastic analysis of piping systems, and
  • Nonmandatory Appendix D provides a standard method to develop sustained stress factors.

B31J Essentials is a FEATools (Version 3.0) but limited to only the B31J calculations (for SIFs and Flexibilities). One can access the B31J calculations by selecting the FEA Translation option from the CAESAR II Main Menu. The software starts FEATools, which provides the B31J computations for the translated CAESAR II model.

Steel Surface Coating for Corrosion Prevention

Surface coating for corrosion prevention is a critical aspect of preserving the integrity and longevity of steel structures and components. Corrosion, which is the gradual deterioration of metal due to chemical reactions in its environment, can lead to significant economic losses and safety hazards. Therefore, protecting steel surfaces from corrosion is essential in various industries, including piping, pipeline, construction, infrastructure, automotive, aerospace, and marine.

Surface coatings are designed to act as a barrier between the steel substrate and the corrosive environment, preventing the interaction that leads to corrosion. These coatings can be applied to various forms of steel, including sheet metal, structural steel, pipelines, and more.

What is Surface Coating?

Surface coating decorates and protects the surface on which it is applied. It can be defined as a homogeneous mixture of pigments, binders, solvents, and additives. The surface coating covers the surface completely and serves as an anti-corrosive agent. The success or failure of any coating is influenced by the following factors:

  • Substrate Condition
  • Surface condition and method of application
  • Environmental condition at which it is applied and expected to withstand during service
  • And last but not least the quality of paint used

Why Coat a Surface?

  • Decorates the surface on which it is applied.
  • Protects the surface from rust
  • Protects from micro-organisms like fungi and algae maintaining their original body.

RUST NEVER SLEEPS!!!

Corrosion of Steel

Before delving into surface coatings, it’s crucial to understand the mechanisms behind corrosion. Corrosion occurs due to electrochemical reactions between metal, moisture, and other corrosive agents. The most common types of corrosion include:

Uniform Corrosion: This is the most straightforward form of corrosion, where the entire surface of the steel corrodes uniformly. It typically occurs in environments with a consistent level of corrosivity.

Localized Corrosion: Localized corrosion includes pitting corrosion, crevice corrosion, and stress corrosion cracking (SCC). Pitting corrosion forms small, deep pits on the steel surface, while crevice corrosion occurs in gaps or crevices where moisture and oxygen are trapped. SCC is the result of tensile stresses and specific environmental conditions.

Galvanic Corrosion: Galvanic corrosion happens when two dissimilar metals are in electrical contact and immersed in an electrolyte. One metal corrodes rapidly (the anode), while the other remains protected (the cathode).

Figure showing rate of corrosion.
Fig. 1: Figure showing the rate of corrosion.

Corrosion Control

  • Using Inhibitive Primers Zinc phosphates/Chromate forms a passive layer with adhered rust.
  • Using Sacrificial Primer. Indirect catholic Protection by Zinc in Zinc-rich primers
  • Barrier Coatings. High DFT Coating System Isolates Surface from Corrosive Environment

Types of Surface Coatings

Surface coatings can be categorized into three main types: organic coatings, inorganic coatings, and metallic coatings.

Organic Coatings

Organic coatings are based on carbon-containing compounds and are widely used for corrosion prevention. They include:

  • Paints: Traditional paints consist of pigments, binders (resins), solvents, and additives. Epoxy, polyurethane, and acrylic paints are commonly used for steel surfaces. They provide good barrier protection and are available in various colors.
  • Powder Coatings: Powder coatings are applied as dry powder and then cured with heat. They are known for their durability, resistance to chemicals, and smooth finishes. Epoxy, polyester, and epoxy-polyester hybrid powders are commonly used.
  • Coil Coatings: Coil coatings are applied to steel coils before they are formed into specific shapes. They are commonly used in the automotive and construction industries.
  • Marine Coatings: Marine coatings are designed for steel structures exposed to harsh marine environments. They offer excellent corrosion resistance and are often used on ships, offshore platforms, and bridges.

Inorganic Coatings

Inorganic coatings are based on non-carbon compounds and include:

  • Zinc-rich Coatings: These coatings contain a high concentration of zinc particles, which act sacrificially to protect the steel substrate. Zinc-rich coatings are often used in harsh environments and as a primer for other coatings.
  • Phosphate Coatings: Phosphate coatings are commonly applied as a pre-treatment to improve the adhesion of organic coatings. They also provide some corrosion resistance.
  • Chromate Conversion Coatings: These coatings, often used on aluminum and zinc-coated steel, provide corrosion protection and enhance paint adhesion.

Metallic Coatings

Metallic coatings involve the deposition of a layer of another metal onto the steel surface. Common metallic coatings include:

  • Galvanizing: Galvanizing involves coating steel with a layer of zinc through hot-dip galvanizing or electro-galvanizing. Zinc provides sacrificial protection, and galvanized steel is widely used in construction and outdoor applications.
  • Aluminizing: Aluminizing involves applying a layer of aluminum to the steel surface, offering excellent corrosion resistance at high temperatures.
  • Tin Coatings: Tin coatings are used in the food and beverage industry for corrosion protection and as a barrier against contamination.

Composition of Paint or Surface Coat

The basic constituents of paints are

  • Pigments 5 to 25%
  • Binders 60 to 65%
  • Solvents 15 to 25%
  • Additives 1 to 5 %

The relative proposition of these ingredients can be varied to produce films with any desired physical and application characteristics

Pigments for Surface Coating

A finely divided powder that can disperse in media of various types to produce paints. It is insoluble in the medium. Important properties are

  • Color
  • Tinting Strength
  • Opacity
  • Fastness to light
  • Resistance to heat
  • The oil absorption of pigment
  • Particle size: Hiding Power, Gloss or smoothness, Rate of settling of pigment

Binders for Surface Coating

Binders are the heart of the paint system. Binders bind or cement the pigment particle into a coherent film that adheres to the substrate. The mechanical and resistive properties of the film are controlled very largely by the binder.

The durability of the paint depends on the quality and quantity of binder used!!!!

  • Convert the liquid coating on application to a solid dry film.
  • Provide gloss to film
  • Making the coating adhere to the substrate
  • Given the elasticity of the film
  • Resistance to water, chemicals, and abrasion
  • Disperse the pigments and extenders
  • Hold the pigment in suspension.

The Choice of Binder for Paint depends on the end use of the paint

Type of Binders

  • Drying oils: Vegetable oils on exposure to air, convert from liquid to solid through a process of oxidation. Can be a sole film former but most often mixed with resin
  • Resins: Most surface coatings contain a synthetic resin-based film former. Most decorative paints are based on oil-modified resins.

Few Important Binders/Resins

ALKYD Resins

  • Largest groups of synthetic resins.
  • They are oil-modified polyester
  • Good exterior durability
  • Low alkali and water resistance.

AMINO Resins: Melamine and urea-formaldehyde

Epoxy Resins:

  • Has excellent adhesion, hardness, chemical, and corrosion resistance
  • Can be used to do high-build paint
  • Poor exterior durability

Poly-amide Resins: Used as curing agents for epoxy resins.

Polyurethane Resins:

  • Good resistance to high temp, chemical and acid resistance, good resistance to various gases, alkali resistance.
  • Low resistance to solvents like ketones, esters

Chlorinated Rubber:

  • It is one pack of thermoplastic.
  • Have good Chemical resistance and good acid and alkali resistance.
  • Can be applied as high-build paint.
  • Disadvantage: Poor resistance to high temp and solvents like ketones, aromatic HC
  • Vinyl Resins:
  • Cellulose Resins: Widely used in auto-finishing
  • Acrylic Resins: Possess good light fastness, good adhesion, and excellent durability.

Solvents for Surface Coating

The primary function of the solvent is to dissolve film formers, thereby consistency suitable for the application. Choice solvent influences viscosity, drying and flow, and leveling.

Solvents are lost in the atmosphere, so it is an economic loss.

Solvents, in isolation or combination, are used in making thinner for the paints. 

Examples of solvents:

Hydrocarbon Solvent: Aliphatic, aromatic, solvent Naptha, alcohols, ketones, esters, etc.

Additives for Surface Coating

Used in a small amount to give a coating one or more desirable properties. The only difference between additives and other raw materials is that the amount of additives is very small. Properties that can be controlled through additives are:

  • Viscosity
  • Setting 
  • Drying
  • Gloss 
  • Opacity 
  • Bacterial action
  • Thickness
  • Deodorants, etc.

Classification of Paints and Surface Coatings

Paints can be classified based on:

  • The Physical state: Liquid Paint and Stiff Paint
  • The Thinner Used: Water thinnable and solvent thinnable
  • The End used: Decorative and protective.
  • Modes of film formation: Thermosetting and Thermoplastics
  • The order of application: Undercoat and topcoat
  • The extent of gloss: Glossy, semi-glossy, egg-shell. matt
  • Modes of Film Formation: Film formation is either by thermosetting or thermoplastics.

Thermoplastic (Non -convertibles):

In these coatings when the paint is applied on a surface, the solvent evaporates living resin to its original form spread over the surface. So change is only physical and can be reversed to its original form by using thinner. E.g Chlorinated Rubber

Thermosetting (Convertible):

Chemical changes occur in the coating and dry film is different from its liquid state. Ex. Epoxy, alkyds, etc.

Surface Preparation

Surface preparation is a crucial step before applying any coating. It involves the removal of contaminants, oxides, and rust from the steel surface to ensure proper adhesion and performance of the coating. Surface preparation is the most important part of a coating system. The surface preparation of the coating system is what a foundation is for a building.

Surface Preparation of Steel

Some of the common surface preparation methods are

  • Mechanical Cleaning: This includes techniques such as abrasive blasting (sandblasting), grinding, and wire brushing. Abrasive blasting is particularly effective in removing rust and scale.
  • Chemical Cleaning: Chemical methods involve the use of acids, alkaline solutions, or solvents to remove contaminants and rust. Pickling and phosphating are common chemical cleaning methods.
  • Electrocleaning: This process uses an electric current to remove contaminants from the steel surface. Electrocleaning is effective for removing organic residues.
  • Conversion Coatings: Conversion coatings, such as chromate and phosphate coatings, chemically modify the steel surface to enhance adhesion and corrosion resistance.

Some of the various surface preparation methods of steel are

  • Degreasing
  • Hand tool cleaning
  • Power tool cleaning
  • Flame Cleaning
  • Pickling
  • Abrasive Blast Cleaning
  • Wet Abrasive Blast Cleaning

International Standard of Blast Cleaning

Few International Standards for Blast Cleaning
Fig. 2: Few International Standards for Blast Cleaning

Paint or Surface Coat Application Methods

The choice of coating application method depends on factors such as the type of coating, the substrate, and the intended use. Common methods include:

a. Brushing and Rolling: Suitable for small-scale projects and touch-ups, this method involves manually applying coatings using brushes or rollers.

b. Spraying: Spraying is a versatile method suitable for both small and large projects. It includes airless spraying, air-assisted spraying, and electrostatic spraying, among others.

c. Dipping: Dipping involves immersing the steel substrate into a tank of coating material. It is often used for small, complex parts.

d. Powder Coating: Powder coatings are applied using an electrostatic gun that charges the powder particles, making them adhere to the grounded steel substrate. The coated part is then cured in an oven.

e. Hot-Dip Galvanizing: This method involves immersing the steel in molten zinc. It is commonly used for large structures and provides excellent corrosion protection.

Theoretical Coverage (Sq.M/Ltr) =(%Volume Solids X100)/DFT in microns

Surface Coating Performance Evaluation

To assess the effectiveness of a surface coating for corrosion prevention, various tests and standards are employed:

a. Salt Spray Test (ASTM B117): This test assesses a coating’s resistance to corrosion in a salt-laden atmosphere. It involves exposing coated samples to a salt spray and monitoring their corrosion over time.

b. Adhesion Test (ASTM D3359): Adhesion tests measure the ability of a coating to adhere to the substrate. Various methods, including cross-cut and pull-off tests, are used.

c. Cyclic Corrosion Tests: These tests simulate real-world corrosion conditions, including wet and dry cycles, temperature variations, and UV exposure.

d. Electrochemical Impedance Spectroscopy (EIS): EIS measures the electrical impedance of a coated surface and can provide insights into the coating’s corrosion resistance.

e. Coating Thickness Measurement (ASTM D7091): This test ensures that the coating thickness meets the specified requirements, as inadequate thickness can compromise corrosion protection.

Factors Affecting Surface Coating Performance

The performance of a surface coating can be influenced by several factors:

a. Substrate Quality: The condition and cleanliness of the steel surface before coating application are crucial for adhesion and overall performance.

b. Environmental Conditions: The exposure environment, including temperature, humidity, and corrosive agents, can impact the rate of corrosion.

c. Coating Thickness: The thickness of the coating layer affects its ability to provide a barrier against corrosion. Thicker coatings generally offer better protection.

d. Coating Quality: The quality of the coating application, including uniformity, coverage, and absence of defects, is critical for long-term performance.

e. Maintenance: Regular inspection and maintenance of coated surfaces are essential to identify and address any damage or degradation of the coating.

Maintenance and Repair of Coated Steel Surface

Maintenance and repair of coated steel surfaces are essential to ensure long-term corrosion protection. Common maintenance practices include:

a. Regular Inspection: Periodic visual inspections to detect any signs of coating damage, corrosion, or defects.

b. Cleaning: Removing dirt, debris, and contaminants from the coated surface to maintain the coating’s effectiveness.

c. Touch-up Painting: Repairing small areas of coating damage with compatible coatings to prevent further corrosion.

d. Recoating: When the existing coating reaches the end of its service life, recoating may be necessary to maintain protection.

e. Cathodic Protection: In some cases, cathodic protection systems can be used alongside coatings to provide additional corrosion protection.

Emerging Trends in Corrosion Prevention

The field of corrosion prevention is continually evolving. Some emerging trends include:

a. Nanotechnology: Nanocoatings, which incorporate nanoparticles, offer enhanced corrosion resistance and durability.

b. Smart Coatings: Smart coatings can sense and respond to changes in the environment, providing real-time corrosion protection.

c. Biodegradable Coatings: Environmentally friendly coatings that degrade over time without harming the environment are gaining popularity.

d. Self-healing Coatings: Self-healing coatings contain materials that can repair small defects and cracks, extending the life of the coating.

e. Corrosion Inhibitors: Advanced corrosion inhibitors, both organic and inorganic, are being developed for improved corrosion protection.

Fatigue Analysis: Definition, Methods, Types, Reasons, Failure Criteria, Caesar II Case Study

What is Fatigue Analysis?

Fatigue Analysis is the structural analysis of the failure tendency of systems when subjected to cyclical loads. Various software is available in the market to study fatigue behavior under cyclic loads. Fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. Continued cycling of high-stress concentrations may eventually cause a crack that propagates and results in leakages. This failure mechanism is called fatigue. Damage once done during the fatigue process is cumulative and normally unrecoverable.  

Fatigue analysis is performed to find out the satisfactory performance level of a structural member under cyclic loading. It estimates the performance of the member under all three stages of fatigue failure. This means fatigue analysis will give data related to crack initiation, crack propagation, and finally failure probability for a specific material.

What is Fatigue in Piping and Structural Applications?

Fatigue for piping or structural applications can be defined as a failure methodology under a repeated or varying load situation. That load never reaches to such a level that it can cause failure of the member in a single application. However, the cumulative effect of each cycle can cause the failure by crack initiation and propagation. It’s a slow process and takes time for complete failure.

Objective of Fatigue Analysis

The aim of fatigue analysis of piping or structural systems is to assess and predict the potential for fatigue failure in these systems over time by calculating fatigue life and total damage. Fatigue analysis is essential for ensuring the structural integrity and reliability of various engineering components, including pipes, bridges, aircraft structures, and more.

Fatigue Analysis Methods

Fatigue analysis is performed using any of the two methods listed below:

  • The Stress-Life (S-N) or S-N method of fatigue analysis or
  • The local Strain or Strain-Life (e-N) method of fatigue analysis

The S-N method of fatigue analysis is highly popular in the piping industry. The Caesar II software uses the S-N curve as input and compares the piping stresses with it to provide a safe time limit before failure as fatigue analysis output. The S-N curves for each material are established by standards like ASME Sec VIII-Div 2.

On the other hand, the (e-N) method of fatigue analysis which is also known as the Crack Initiation method concerns itself only with the initiation of the first crack.

Types of Fatigue

Fatigue can be grouped into two classes;

  • High cycle fatigue and
  • Low cycle fatigue.  

High Cycle Fatigue:

High-cycle fatigue involves little or no plastic action. Therefore, it is stress-governed. Normally, a fatigue curve (also called the S–N curve) is generated for every material by experimental tests that correlate applied stress with the number of cycles to cause failure. For high-cycle fatigue, the analysis is performed to determine the endurance limit, which is actually a stress level that can be applied an infinite number of times without showing any failure. As a general rule, the number of cycles 105 is considered a demarcation point for high and low cycle fatigue.

Low Cycle Fatigue:

The loading cycles applied in the piping design are normally very few in the order of a few thousand. This type of fatigue is identified as low-cycle fatigue. For low-cycle fatigue, the applied stress normally exceeds the yield strength of the material, which causes plastic instability in the specimen under test. But when strain is used as the controlled variable, the results in the low-cycle region are reliable as well as reproducible.  

Reason for Fatigue Analysis of Piping System

A piping system may be subjected to cyclic loading from various sources. Hence, it is always better to perform fatigue analysis during the design stage. For the Piping system, Cyclic loading is primarily due to:

  • Thermal Expansion & Contraction
  • Vibration due to Occasional loading
  • Pressure variation within the Piping system
  • Motion wave.
  • Due to Flow-induced Vibration

The fatigue process is divided into three stages: crack initiation from the continued cycling of high-stress concentrations, crack propagation to a critical size, and unstable rupture of the section.    

Factors Affecting Fatigue Behavior

The factors which affect the fatigue behavior are listed below:

  • Type and Nature of Loading.
  • Size of Component and stress or strain Distribution.
  • Surface finish and Directional Properties.
  • Stress or Strain Concentration.
  • Mean stress or Strain.
  • Environmental Effects.
  • Metallurgical Factors and Material Properties.
  • Strain Rate and Frequency Effects.

Characteristics of Low Cycle Fatigue

  • Characterized by high loads and a small number of cycles before failure.
  • Here failure occurs only with stress levels in the plastic range, i.e. significant plastic strain occurs during each cycle.
  • The stresses which cause fatigue failure in the piping are the peak stresses.
  • In piping design, most of the loading cycles encountered would be of the low-cycle type

Characteristics of High Cycle Fatigue

  • Characterized by a high number of cycles (Preferable N>10^4) with relatively low-stress levels, and the deformation is in the elastic range.
  • This type of fatigue failure is used in the design of rotating machinery.
  • This type of fatigue results from strain cycles in the elastic range.
  • A stress level, endurance limit, may be applied for an infinite time without failure, is calculated.

Fatigue Analysis Theory and Failure Criteria

While preparing fatigue curves, the strains obtained in the tests are multiplied by one-half of the elastic modulus to obtain pseudo-stress amplitude. This pseudo-stress is directly compared with the stresses calculated on the assumption of the elastic behavior of piping. During piping stress analysis, stress called alternating stress (Salt) is used which is defined as one-half of the calculated peak stress. Fatigue failure can be prevented by ensuring that the number of load cycles (N) associated with specific alternating stress is less than the number allowed in the S–N curve or endurance curve. However, in practical service conditions, a piping system is subjected to alternating stresses of different magnitudes. These changes in magnitudes make the direct use of the fatigue curves inapplicable since the curves are based on constant stress amplitude.   Fatigue tests of metallic materials and structures have provided the following main clues to the basic nature of fatigue:  

  • Fatigue failure, or cracking under repeated stress much lower than the ultimate tensile strength, is shown in most metals and alloys that exhibit some ductility in static tests. The magnitude of the applied alternating stress range is the controlling fatigue life parameter.
  • Failure depends upon the number of repetitions of a given range of stress rather than the total time under load. The speed of loading is a factor of secondary importance, except at elevated temperatures.
  • Some metals, including ferrous alloys, have a safe range of stress. Below this stress, called the “endurance limit or fatigue limit”, failure does not occur irrespective of the number of stress cycles.
  • Notches, grooves, or other discontinuities of section greatly decrease the stress amplitude that can be sustained for a given number of cycles.
  • The range of stress necessary to produce failure in a fixed number of cycles usually decreases as the mean tension stress of the loading cycle is increased.
  • Examination of fatigue fracture shows evidence of microscopic deformation, even in the apparently brittle region of origin and propagates of the crack. The plastic deformation that accompanies a spreading fatigue crack is usually limited in the extent to regions very near the crack.

Therefore, to make fatigue curves applicable for piping, some alternate approach is necessary.   One hypothesis asserts that the damage fraction of any stress level S is linearly proportional to the Ratio of the number of cycles of operation at the stress level to the total number of cycles that would produce failure at that stress level. This means that failure is predicted to occur if   U≥1.0 where U= Usage factor = ∑(ni/Ni) for all stress levels   Where ni= number of cycles operating at stress level i Ni= the number of cycles to failure at stress level i as per material fatigue curve.    

Fatigue Analysis Methods 

Fatigue Analysis considers the cumulative effect of all individual load cycles that may arise from temperature change, pressure fluctuation, wave motions, etc. If there are two or more types of stress cycles that produce significant stresses, their cumulative effect shall be evaluated as stipulated in Steps 1 through 6 below:

  1. Designate the specified number of times each type of stress cycle of types 1,2,3,…,n, will be repeated during the life of the component as n1, n2, n3,……., nn, respectively. In determining n1, n2, n3,……., nn, consideration shall be given to the superposition of cycles of various origins which produce the greatest total alternating stress range.  For example, if one type of stress cycle produces 1000 cycles of a stress variation from zero to +60,000 psi and another type of stress cycle produces 10,000 cycles of a stress variation from zero to -50,000 psi, the two cycles to be considered are shown below:
  • cycle type 1: n1=1000 and Salt1= (60000+50000)/2
  • cycle type 2: n2=9000 and Salt2= (0+50000)/2
  • For each type of stress cycle, determine the alternating stress intensity Salt, which for our application is one-half of the range between the expansion stress cycles (as shown above). These alternating stress intensities are designated as Salt1, Salt2, Saltn.
  • On the applicable design fatigue curve find the permissible number of cycles for each Salt computed. These are designated as N1, N2, …….Nn.
  • For each stress cycle calculate the usage factor U1, U2, …….Un where U1= n1/N1, U2= n2/N2,……..Un=nn/Nn.
  • Calculate the cumulative usage factor U as U=U1+U2+…….+Un.
  • The cumulative usage factor shall not exceed 1.0

Fatigue Analysis Softwares

Various software is available in the market with the potential for fatigue analysis. The most widely used fatigue analysis software are

Fatigue Analysis Steps

The majority of the established software mentioned above follows the same steps for performing fatigue analysis. The steps are

  • Determining the fatigue loading details like the calculation of the number of cycles in the design life of the member
  • Add this information to the software as input for fatigue analysis.
  • Define the material fatigue data (like the S-N curve) from Codes/Standards
  • Create the fatigue analysis load cases
  • Run the Analysis and
  • Process the output as relevant

Fatigue Curve

The plot of the Cyclic Stress capacity of a material is called the fatigue curve, also known as the S-N curve. ASME Section VIII Div 2 Provides a fatigue curve for various materials.  

Typical S-N Plot
Fig. 1: Typical S-N Plot

 Fatigue design curves are generated from test data by applying large safety margins to the average property curve.   While considering material fatigue in design, an additional safety margin is often applied against the cycles-to-failure at a given stress amplitude. As an example, if a component is cycled continuously over the same stress range (Any constant stress range), a design limit on allowable (permitted) cycles may correspond to the cycle life multiplied by a factor (safety margin) such as 0.8. This is the common safety margin employed in a vessel and piping design.   For every material, a fatigue curve is normally generated by an experimental analysis that correlates the peak stress range with the number of cycles to failure.

Design Fatigue Curve for Carbon and Low Alloy Steel
Fig. 2: Design Fatigue Curve for Carbon and Low Alloy Steel

 The alternating stress Sa is defined as one-half of the calculated peak stress.

The fatigue failure may be prevented by ensuring that the number of load cycles N that the system experiences is lower than the number permitted for the alternating stress developed.   The cumulative effect shall be evaluated in case there are two or more types of stress cycles that produce significant stresses. The material fatigue resistance at a given applied stress or strain range is a function of a number of factors, including material strength and ductility.  

When to Perform Fatigue Analysis

Normally the fatigue analysis is performed for existing plants to evaluate the actual cause of any failure. For new plants, the analysis can be performed only if the project specification permits it to do so. Refer to project guidelines on the application requirement for fatigue analysis.

Input for Fatigue Analysis

Before starting the analysis be ready with the following data which will be required during the analysis:

  • Fatigue Curve of the piping material
  • Enough process data for finding the total number of cycles throughout the design life of the piping system.

Steps for Fatigue Analysis using Caesar II

Assigning the fatigue curve data to the Piping Material in use:  

This is done on the Allowable auxiliary screen. Fatigue data may be entered directly or can be read from a text file by clicking the Fatigue Curves Button. Seven commonly used curves are available in \Caesar\System\*.Fat. (For Caesar versions 2012, 2013 &2014 you may not find it on a few computers, But these are available in earlier versions) Fatigue curves provide a series of S-N data that define the allowable stress with a given anticipated cycle and vice versa.

Defining the fatigue load cases:

For this purpose, a new stress type, FAT, has been already defined in the Caesar II database. For every fatigue case, the number of cycles anticipated must also be entered in the appropriate space.

Calculation of the fatigue stresses:

Caesar II automatically does this calculation for us. The fatigue stresses, unless explicitly defined by the applicable code are the same as Caesar II calculated stress intensity (Max Stress Intensity), in order to conform to the requirement of ASME Section VIII, Division 2 Appendix 5.

Determination of the Fatigue stress allowable:

The allowable stresses for fatigue analysis are required to be interpolated logarithmically from the fatigue curve based on the number of cycles (throughout its life) designated in the fatigue load cases. The calculated stress is assumed to be a peak-to-peak cycle value (i.e., thermal expansion, settlement, pressure, etc.) for static load cases, so the allowable stress can be extracted directly from the fatigue curve. On the other hand for harmonic and dynamic load cases, the calculated stress is assumed to be a zero–to-peak cycle value (i.e., vibration, earthquake, etc.), so the extracted allowable needs to be divided by 2 prior to use in the comparison.

Determination of the allowable number of cycles:

The flip side of calculating the allowable fatigue stress for the designated number of cycles is the calculation of the allowable number of cycles for the calculated stress level. This is done by logarithmically interpolating the “Cycles” axis of the fatigue curve based on the calculated stress value. Since static stresses are assumed to be peak-to-peak cycle values, the allowable number of cycles is interpolated directly from the fatigue curve. Since harmonic and dynamic stresses are assumed to be zero-to-peak cyclic values, the allowable number of cycles is interpolated using twice the calculated stress value.

Reporting the analysis results:

Caesar II provides two reports for viewing the results of load cases of stress type FAT; standard stress report and cumulative usage report. The first of these is the standard stress report for displaying the calculated fatigue stress and the fatigue allowable at each node. Stress reports could be generated individually for each load case and show whether any of the individual load cases in isolation would fail the system or not.

However, in situations where there is more than one cyclic load case potentially contributing to fatigue failure, the cumulative usage report is more appropriate. In order to generate this report, the user should select all of the FAT load cases that contribute to the overall system degradation (possible failure). The cumulative usage report lists for each node point the usage ratio (actual cycles divided by allowable cycles) and then sums (combines) these up for total cumulative Usage. A total value greater than 1.0 indicates a potential fatigue failure.

Fatigue Analysis Case Study

To perform fatigue analysis we need to calculate the thermal and pressure fluctuations the piping system will undergo in its design life. We have to calculate the worst possible cycles from preliminary data provided by the process/operation department. Let’s assume we received the following data from the process for a typical piping system.  

  • Operating cycle from ambient (40°C) to 425°C (400,000 cycles anticipated)
  • Shutdown external temperature variation from ambient (40°C) to -20°C (300,000 cycles anticipated)
  • Pressurization to 5.5 Bars (400,000 cycles anticipated)
  • Pressure fluctuations of plus/minus 1.5 Bars from the 5.5 Bars (1,000,000 cycles anticipated)

Now, in order to do a proper fatigue analysis, these should be grouped in sets of load pairs which represent the worst-case combination of stress ranges between extreme states which we can do in the following way (Refer to the attached Figure, Fig. 3 for proper understanding):  

Estimation of Number of Cycles for Fatigue Analysis
Fig.3: Estimation of Number of Cycles for Fatigue Analysis

The above figure (Fig. 3) explains the calculation of the worst-case cycle combination for fatigue analysis

  • From -20°C, 0 Bars to 425°C, 7 Bars.  300,000 Cycles
  • From 40°C, 0 Bars to 425°C, 7 Bars.:  100,000 Cycles
  • From 425°C, 4 Bars to 425°C, 7 Bars: 600,000 Cycles
  • From 425°C, 4 Bars to 425°C, 5.5 Bars: 400,000 Cycles

So in Caesar II, we can define the above data as follows (Refer Fig. 4): T1= 425°C; T2= -20°CP1= 5.5 Bar; P2= 4 Bar  and P3= 7 Bar

Fatigue Input in Caesar II for Analysis
Fig. 4: Fatigue Input in Caesar II for Analysis

Fig. 4 above shows the Caesar II spreadsheet explaining the input requirement   Now go to the load case editor and define load cases as shown in Fig. 5 for fatigue analysis. Click on the load cycles button to input the number of cycles calculated above.  

Creating Load Cases for Fatigue Analysis
Fig. 5: Creating Load Cases for Fatigue Analysis

Fig. 5 above shows the fatigue analysis Load cases that have to be created for Fatigue Analysis   Don’t forget that all load cases with stress type FAT (for fatigue) must have their expected number of Load Cycles specified.   After the load cases are prepared, run the analysis to find out the results from the output processor. Part of the output results are provided in the attached figures for your reference (Fig. 4 and Fig. 5)   The fatigue stress range (Maximum Stress Intensity as calculated in the Expansion stress case) may be checked against the fatigue curve allowable for each fatigue load case as shown in Fig 6.    

Output Screen showing stress range
Fig 6: Output Screen showing stress range

However, this is not a true evaluation of the situation, because it is not a case of “either-or.” The piping system is subjected to all of these load cases throughout its expected design life, not just one of them. Therefore, we must review the Cumulative Usage report, which shows the total effect of all fatigue load cases (or any combination selected by the user) on the design life of the system. Refer to Fig 7 for an example.  

Output Screen showing Cumulative usage factor
Fig. 7: Output Screen showing Cumulative usage factor

This report lists for each load case the expected number of cycles, the allowable number of cycles (based on the calculated stress), and the Usage Ratio (actual cycles divided by allowable cycles). The Usage Ratios are then summed for all selected load cases; if this sum exceeds 1.0, the system has exceeded its fatigue capabilities.