Load Case Editor vs Operation Mode Editor

Written by Alex Matveev in Piping Stress Analysis,Piping Stress Basics,Start-Prof

START-PROF has Smart Operation Mode Editor instead of Load Case Editor.

When you add new load F or support movement D in CAESAR II , you must add it into load case editor manually, thinking thoroughly well what load cases should be created to properly consider it. If you will not add this load F or movement D into Load Case Editor, CAESAR II will not consider loads in the analysis.

In START-PROF you just add the load F or support movement D. Nothing more. It will be added automatically in that load cases where it should be added.

CAESAR II users who use the START-PROF for a first time always ask us the same question: “Where is the Load Case Editor in START-PROF?” or “How to create load cases in START-PROF?”. But START-PROF doesn’t have Load Case Editor. You don’t need to create load cases. At all.

The situation is similar to moving from Car Manual Transmission to the modern Car Automatic Transmission.
People who drive only cars with manual transmission ask a lot of unnecessary questions: How does automatic transmission works? How to shift the gear manually? How can I be sure that automatic transmission will shift the gear correctly?
Young drivers just sit in the car and enjoy driving without any questions about transmission, because it is working perfect.

It is hard to imagine how to work without Load Case Editor for people who used it for a many years. They ask a lot of questions: How do automatic load cases work? How to change the load cases manually? How can I be sure that automatic load cases work correctly, where to see it?
But young engineers just draw piping in START-PROF and enjoy the quick analysis results.

Load Case Editor is just technology from the past. Our idea is that engineers should think about piping design (driving a car), but not about load cases (how does automatic transmission works).

Example 1

You want to add additional occasional force “F” caused by Relief Valve Thrust https://whatispiping.com/modeling-relief-valve-pressure-safety-valve-thrust-force-in-start-prof or slug flow loads https://whatispiping.com/how-to-model-slug-flow-loads

You have to create the following load cases manually:

L1: W+P for sustained stresses (SUS)
L2: W+P+T for support loads (OPE)
L3: W+P+T+F for support loads with force F (OPE+OCC)
L4: L2-L1 (Algebraic) for expansion stresses (EXP)
L5: L3-L2 (Algebraic) Internal forces difference between operational mode with force F (L3) and operational mode without force F (L2). This way we get the pure internal forces from force F, but considering nonlinear behavior of structure (gaps, one-way restraints etc.)
L6: L1+L5 (Scalar) occasional stress is equal to the sum of stresses from sustained loads (L1) and stresses from pure internal forces (L5)

To understand how to create these load cases and what results should be analyzed from each load case, what is the difference between “Algebraic” and “Scalar” sum, engineer must spend a lot of time reading the literature, attend training courses, ask other people at forums etc. Only piping stress engineers with 5-10 year experience can create the correct load cases for each special situation without any errors.

Example of possible incorrect load cases:

L1: W+P (SUS)
L2: W+P+T (OPE)
L3: W+P+T+F (OPE+OCC)
L4: T (EXP) MISTAKE: nonlinear piping behavior will not be considered properly
L5: W+P+F (OCC) MISTAKE: nonlinear piping behavior will not be considered properly

There can be a lot of other human mistakes while creating load cases. The reason can be lack of knowledge or just misprint. Or you can just forget to consider some special features.

In START-PROF you can’t do a mistake with load cases. It’s like a car with automatic transmission, car developers already adjusted it to get the best results. You just create additional force-based loading (1.1) for the main operation mode (1). Number of submodes is almost unlimited. For example you can specify 100 submodes to model waterhammer loads using static method at different moments of time.

And add the thrust force.

START-PROF has a standard load cases inside. You can’t see it in software as you can’t see the mechanism of the car automatic transmission while driving.
For above example the force F will be applied in L11. See the table for ASME B31.3 code below. This table is just example. Each piping code has own template load cases inside START-PROF which accumulated our piping stress engineering experience for last 50 years to get best and accurate results.

Load Cases L11 will be used to show displacements, loads, expansion joint deformations in the tables for user.

Load Cases L13 will be used to show occasional stresses

User can’t see the stresses from the L11 load case and can’t see the displacements from L13 load case. Because it doesn’t make sense.

Example 2

This diagram shows 39 loads cases from real project in CAESAR II, created manually. And shows operation modes in START-PROF that do the same job, but better, easier and faster (job analysis time in START-PROF is 2 times faster).

Operation modes are very easy to understand:

#1: OPE1 – operation mode with temperature 65 deg. Friction is switched off. Occasional wind loads added (4 directions +X, -X, +Y, -Y). Two additional load cases added: snow and ice loads. Hangers are selected in this mode. Also installation (cold) state calculated for this mode
#2: OPE2 – operation mode with temperature -100 deg.
Friction is switched off. Occasional wind loads added (4 directions +X, -X, +Y, -Y). Two additional load cases added: snow and ice loads.
#3: OPE3 – operation mode with temperature -47 deg.
Friction is switched off. Occasional wind loads added (4 directions +X, -X, +Y, -Y). Two additional load cases added: snow and ice loads.
#4: OPE1 – operation mode with temperature 65 deg. Friction is turned on. Occasional wind loads added (4 directions +X, -X, +Y, -Y). Two additional load cases added: snow and ice loads.
#5: OPE2 – operation mode with temperature -100 deg.
Friction is turned on. Occasional wind loads added (4 directions +X, -X, +Y, -Y). Two additional load cases added: snow and ice loads.
#6: OPE3 – operation mode with temperature -47 deg.
Friction is turned on. Occasional wind loads added (4 directions +X, -X, +Y, -Y). Two additional load cases added: snow and ice loads.
#7: Operation mode with no fluid weight, operation temperature 0 deg. Friction is turned on.
#8 Test mode. Test temperature and pressure used. Friction is turned on
Stress range is calculated between 1H-1C, 1H-2H, 2H-1C, where 1 and 2 is operation mode number (#1 and #2), H – hot state, C – cold (installation) state

Widely Used Piping Codes and Standards

Written by Anup Kumar Dey in Piping Design Basics

The huge expansion of the piping industry where it is today is mainly for the available codes, standards, and recommended practices. The main concern for designing any process plant is the safety of the personnel involved. Design of Piping systems complying with these codes, standards, or recommended practices ensures safety along with standardization of required items. Every piping engineer should possess a basic knowledge of the extensively used piping codes and standards. The following write-up will try to provide a sum-up of common piping codes and standards that are extensively used in the process piping industry.

Difference between Piping Codes and Standards

Codes in the piping industry prescribe requirements for the design, materials, fabrication, erection, examination, assembly, test, and inspection of piping systems, whereas standards contain design and construction rules and requirements for individual piping components such as elbows, tees, returns, flanges, valves, and other in-line items.

Compliance with the code is generally mandated by regulations imposed by regulatory and enforcement agencies. At times, the insurance carrier for the facility leaves hardly any choice for the owner but to comply with the requirements of a code or codes to ensure the safety of the workers and the general public.

On the other hand, compliance with piping standards is normally required by the rules of the applicable code or the purchaser’s specification.

Recommended Practice

Recommended Practices, prepared by professional organizations or professional bodies are an optional set of documents that can be used for good engineering practice.

Even though every country has its own codes and standards but still the American codes and standards are most widely used. The major codes and standards which are used in the day-to-day piping applications are listed below:

A. ASME Codes for Piping Industry

ASME B31: Code for Pressure Piping

ASME B31.3 – Process Piping Code

This piping code normally provides rules for piping found in petroleum refineries, chemical, pharmaceutical, textile, paper, semiconductor, and cryogenic plants, and related processing plants and terminals including piping for fluids like raw, intermediate, and finished chemicals, petroleum products, gas, steam, air and water, fluidized solids, refrigerants, cryogenic fluids, etc. For process piping professionals this code is of utmost importance.

This Code does not provide information on the following:

(a) piping systems designed for internal gage pressures at or above zero but less than 105 kPa (15 psi), provided the fluid handled is nonflammable, nontoxic, and not damaging to human tissues and its design temperature is from −29°C (−20°F) through 186°C (366°F).
(b) power boilers and boiler external piping which is required to conform to ASME B31.1.
(c) tubes, tube headers, crossovers, and manifolds of fired heaters, which are internal to the heater enclosure
(d) pressure vessels, heat exchangers, pumps, compressors, and other fluid handling or processing equipment, including internal piping and connections for external piping.
(e) piping covered by ASME B31.4, B31.8, or B31.11, although located on the company property
(f) plumbing, sanitary sewers, and storm sewers.
(g) piping for fire-protection systems
(h) piping covered by applicable governmental regulations

ASME B31.1 – Power Piping Code

This piping code provides requirements for piping typically found in electric power generating stations, in industrial and institutional plants, geothermal heating systems, and central and district heating and cooling systems. This code is mainly important for Power piping professionals. It does not apply to the piping systems covered by other sections of the Code for Pressure Piping, and other piping which is specifically excluded from the scope of this code.

ASME B31.4 – Pipeline Transportation Systems for Liquids and Slurries

This code provides requirements for piping transporting liquids between production facilities, tank farms, natural gas processing plants, plants and terminals, and within terminals, pumping, regulating, metering stations, and other delivery and receiving points.

ASME B31.5 – Refrigeration Piping and Heat Transfer Components

This code prescribes requirements for piping for refrigerants, heat transfer components, and secondary coolants for temperatures as low as -320 degrees F (-196 degrees C)

ASME B31.8 – Gas Transmission and Distribution Piping Systems

This code covers the piping transporting products that are mostly gas (Liquefied Petroleum Gas) between sources and terminals. This code also covers the safety aspects of the operation and maintenance of those facilities.

Other relevant ASME B codes for piping industries are

ASME B31.9 – Building Services Piping
ASME B 31.2 – Fuel Gas piping
AMSE B31.11 – Slurry Transportation Piping Systems.
ASME B31.12 – Hydrogen Piping and Pipelines.

B. ASME Boiler and Pressure Vessel Code

The ASME BPVC code contains 11 sections as mentioned below:

Section I Power Boilers
Section II Material Specifications
Section III Rules for Construction of Nuclear Power Plant Components
Section IV Heating Boilers
Section V Nondestructive Examination
Section VI Recommended Rules for Care and Operation of Heating Boilers
Section VII Recommended Rules for Care of Power Boilers
Section VIII Pressure Vessels
Section IX Welding and Brazing Qualifications
Section X Fiber-Reinforced Plastic Pressure Vessels
Section XI Rules for In-Service Inspection of Nuclear Power Plant Components

Out of these 11 sections, Section VIII is very important for Process Piping engineers.

C. Piping Component Standards

The major piping component standards that are used frequently are listed below:

ASME B16.1: Cast Iron Pipe Flanges and Flanged Fittings
ASME B36.10M: Welded and Seamless Wrought Steel Pipe
ASME B36.19M: Stainless Steel Pipe
ASME B16.9: Factory-Made Wrought Steel Buttwelding Fittings
ASME B16.5: Pipe Flanges and Flanged Fittings
ASME B16.37: Hydrostatic Testing of Control Valves
ASME B16.11: Forged Fittings, Socket Welding and Threaded
ASME B16.3: Malleable Iron Threaded Fittings, Class 150 and 300
ASME B16.4: Cast Iron Threaded Fittings, Classes 125 and 250
ASME B1.1: Unified Inch Screw Threads
ASME B16.20: Metallic Gaskets for Pipe Flanges
ASME B16.21: Nonmetallic Flat Gaskets for Pipe Flanges
ASME B16.25: Buttwelding Ends
ASME B16.10: Face-to-Face and End-To-End Dimensions of Valves
ASME B16.36: Orifice Flanges
ASME B16.34: Valves – Flanged, Threaded and Welding End
MSS SP-58: Pipe Hangers and Supports — Materials, Design, and Manufacture.
BS 6501, Part 1: Flexible Metal Hose
NFPA 1963: Standard for Fire Hose Connections

Refer to ASME code B31.3 for more of the component standards

D. ASTM Standards

The American Society for Testing and Materials (ASTM) is a scientific and technical organization that develops and publishes voluntary standards on the characteristics and performance of materials, products, systems, and services. The standards published by the ASTM include test procedures for determining or verifying characteristics, such as chemical composition and measuring performance, such as tensile strength and bending properties. The standards cover refined materials, such as steel, and basic products, such as machinery and fabricated equipment. The standards are developed by committees drawn from a broad spectrum of professional, industrial, and commercial interests. Many of the standards are made mandatory by reference to applicable piping codes.

The major ASTM standards are listed below:

A36: Carbon Structural Steel
A105: Carbon Steel Forgings, for Piping Applications
A106: Seamless Carbon Steel Pipe for High-Temperature Service
A312: Seamless, Welded, and Heavily Cold-Worked Austenitic Stainless Steel Pipe
A335: Seamless Ferritic Alloy Steel Pipe for High-Temperature Service
A358: Electric-Fusion-Welded Austenitic Chromium-Nickel Alloy Stainless Steel Pipe for High-Temperature Service and General Applications
A516: Pressure Vessel Plates, Carbon Steel, for Moderate and Lower-Temperature Service
A671: Electric-Fusion-Welded Steel Pipe for Atmospheric and Lower Temperatures
A672: Electric-Fusion-Welded Steel Pipe for High-Pressure Service at Moderate Temperatures
Suggested reading for more on ASTM standards: Refer to ASME B31.3 Specification index for Appendix A.

E. API Standards

The American Petroleum Institute (API) publishes specifications, bulletins, recommended practices, standards, and other publications as an aid to the procurement of standardized equipment and materials.

The major ones are listed below for your reference:

API RP 520: Recommended Practice for Sizing, Selection, and Installation of Pressure-Relieving Devices in Refineries.
API 610: Centrifugal Pumps for Petroleum, Petrochemical, and Natural Gas Industries
API 650: Welded Tanks for Oil Storage
API 661: Air-Cooled Heat Exchangers for General Refinery Service
API 560: Fired Heaters for General Refinery Service
API 617: Axial and Centrifugal Compressors and Expander-compressors for Petroleum, Chemical, and Gas Industry Services
API 618: Reciprocating Compressors for Petroleum, Chemical, and Gas Industry Services
API 612: Petroleum, Petrochemical, and Natural Gas Industries-Steam Turbines-Special-purpose Applications

For more API Standards refer to the API website for their catalog of published standards.

There are several other codes and standards which are used in the piping industry including the AMERICAN WATER WORKS ASSOCIATION (AWWA), AMERICAN WELDING SOCIETY (AWS), AMERICAN SOCIETY OF SANITARY ENGINEERS, AMERICAN SOCIETY OF CIVIL ENGINEERS, AMERICAN SOCIETY FOR NONDESTRUCTIVE TESTING, AMERICAN IRON AND STEEL INSTITUTE, EXPANSION JOINT MANUFACTURERS ASSOCIATION, MANUFACTURERS STANDARDIZATION SOCIETY OF THE VALVE AND FITTINGS INDUSTRY, NATIONAL FIRE PROTECTION ASSOCIATION, TUBULAR EXCHANGER MANUFACTURERS ASSOCIATION, etc.

Also, there are non-American standards like BRITISH STANDARDS AND SPECIFICATIONS, RUSSIAN CODES, DIN STANDARDS AND SPECIFICATIONS, JAPANESE STANDARDS AND SPECIFICATIONS, ISO STANDARDS AND SPECIFICATIONS, etc. The user is requested to venture more of these standards in his own interest. Some of the Russian codes are listed below:

F. Russian Codes

GOST 32388-2013 Process Piping Stress Analysis, GOST 32569-2013 Process Piping Design-
These codes provide requirements for process piping design and analysis. GOST 23388-2013 Code covers such aspects as vacuum piping stability, creep in high-temperature piping, cryogenic piping stress analysis requirements, seismic analysis, HDPE piping stress analysis

RD 10-249-98 – Power Piping. Design and Stress Analysis
This code provides requirements for piping typically found in electric power generating stations, in industrial and institutional plants, and geothermal heating systems except for district heating systems.

GOST R 55596-2013 District Heating Systems Stress Analysis, SP 124.13330.2012 District Heating Systems Design
This code provides requirements for buried and above-ground district heating piping systems design and analysis.
SP 36.13330.2012 – Gas and Oil Transmission Piping Systems. Design and Stress Analysis
This code provides requirements for pipelines transporting gas and oil between production facilities, tank farms, natural gas processing plants, plants and terminals and within terminals, pumping, regulating, metering stations, and other delivery and receiving.

GOST 34347-2017 Boiler and Pressure Vessel Code Design Requirements,
GOST 34233-2017 Boiler and Pressure Vessel Code Stress Analysis Requirements
GOST 34233.1-2017: General requirements
GOST 34233.2-2017: Cylindrical and conical shells, convex and flat bottoms and covers
GOST 34233.3-2017: Reinforcement of openings in shells and bottoms under internal and external pressure. Strength calculation of shells and bottoms under external static loads on the nozzle
GOST 34233.4-2017: Strength and leak-tightness calculation of flange joints
GOST 34233.5-2017: Calculation of shells and bottoms under the Influence of support loads
GOST 34233.6-2017: Strength calculation under low-cyclic loads
GOST 34233.7-2017: Heat-exchangers
GOST 34233.8-2017: Jacketed vessels
GOST 34233.9-2017: Vertical Column Vessels
GOST 34233.10-2017: Vessels involving hydrogen sulfide media
GOST 34233.11-2017: Method of strength calculation of shells and bottoms according to weld misalignment, angular misalignment, and shell no roundness
GOST 34233.12-2017: Requirements for representation of the strength calculations carried out on the computer
Piping Component Standards:
Pipes: GOST 10705, 10706, 11068, 2095, 3262, 550, 8696, 8731, 8733, 9940, 9941, 53383, OST series 108x, 34x, TU 14-3-1080, 14-3-1128, 14-3-1160 and lots of other standards
Bends: GOST 17375, 30753, OST series 108x. 34x and lots of other standards
Tees: GOST 17376, OST series 108x. 34x and lots of other standards
Flanges: GOST 33259 and lots of other standards

Stress Analysis of GRP / GRE / FRP Piping System Using Caesar II (ISO 14692)

Written by Anup Kumar Dey in Caesar II,Piping Stress Analysis,Piping Stress Basics

Glass Reinforced Piping (GRP) products, being proprietary, the choice of component sizes, fittings, and material types are limited depending on the supplier. Potential GRP vendors need to be identified early in the design stage to determine possible limitations of component availability. The mechanical properties and design parameters vary from vendor to vendor. Note that the stress analysis methodologies of Fiber Reinforced Piping (FRP) and Glass Reinforced Epoxy (GRE) are similar and performed following the ISO 14692 code. As the design parameters are dependent on the manufacturers, it is of utmost importance that before you proceed with stress analysis of such systems you must finalize the GRP/FRP/GRE vendor.

Several parameters (Fig. 1) for stress analysis have to be taken from the vendor.

Stress analysis of the GRP piping system is governed by ISO 14692 part 3. The GRP material being orthotropic the stress values in axial as well as hoop direction need to be considered during analysis. The following article will provide a guideline for stress analysis of the GRP piping system in a very simple format.

GRP/FRP Information Required from Vendor

Before you open the input spreadsheet of Caesar II communicate with the vendor through the mail and collect the following parameters as listed in Fig.1.

**Fig.1: Parameters required for stress analysis of GRP piping**

The values shown in the above figure are for example only. Actual values will differ from vendor to vendor. The above parameters are shown for a 6” pipe.

Inputs Required for GRP Stress Analysis

For performing the stress analysis of a GRP piping system following inputs are required:

GRP pipe parameters as shown in Fig. 1.
Pipe routing plan in the form of isometrics or piping GA.
Analysis parameters like design temperature, design pressure, operating temperature, fluid density, hydro test pressure, pipe diameter, thickness, etc.

Modeling GRP/FRP/GRE in Caesar II

Once all inputs as mentioned above are ready with you open the Caesar II spreadsheet. By default, Caesar will show B31.3 as the governing code. Now refer to Fig. 2 and change the parameters as mentioned below:

**Fig. 2: Caesar II input spreadsheet for GRP Piping (Simplified Envelope)**

Change the default code to ISO 14692.
Change the material to FRP (Caesar Database Material Number 20) as shown in Fig. 2. It will fill a few parameters from Caesar’s database. Update those parameters from vendor information.
Enter pipe OD and thickness from vendor information.
Keep corrosion allowance as 0.
Input T1, T2, P1, HP, and fluid density from the line list.
Update pipe density from the vendor information sheet, if the vendor does not provide the density of the pipe then you can keep this value unchanged.
On the right side below the code, enter the failure envelope data received from the vendor.
Enter thermal factor=0.85 if the pipe is carrying liquid, and enter 0.8 if the pipe carries gas.
After you have mentioned all the highlighted fields proceed to model by providing dimensions from the isometric/piping GA drawing. Add supports at the proper location from the isometric drawing.
Now click on the environment button and then on the special execution parameter. It will open the window as mentioned in Figure 3.

**Fig. 3: Typical Special Execution parameters Spreadsheet.**

Now Refer to Fig. 3 and change the highlighted parts from the available data.

Enter the GRP/FRP co-efficient of thermal expansion received from the vendor
Calculate the ratio of Shear Modulus and Axial modulus and input in the location.
In FRP laminate keep the default value if data is not available.
After the above changes click on the ok button.
While modeling, remember to change the OD and thickness of elbows/bends.

Modeling of GRE Bend and Tee Connections

The modeling of bends is a bit different as compared to CS piping. Normally, bend thicknesses are higher than the corresponding piping thickness. Additionally, you have to specify the parameter, (EpTp)/(EbTb), which is located at the Bend auxiliary dialogue box as shown in Fig. 4. This value affects the calculation of the flexibility factor for bends.
When you click on the SIF and Tee box in the Caesar II spreadsheet, you will find that only three options (Tee, Joint, and Qualified Tee) are available for you, as shown in Fig. 4. Each type has its own code equation for SIF calculation. Use the proper connection judiciously. It is always better to use SIF as 2.3 for both inplane and outplane SIF to adopt a maximum conservative approach.

Modelling of Elbows and Tees for FRP/ GRE piping — **Fig. 4: Modelling of Elbows and Tees for FRP/GRE piping**

Stress Analysis Load Cases for FRP Piping Systems:

ISO 14692 informs to prepare 3 load cases: Sustained, Sustained with thermal, and Hydro test. So accordingly, the following load cases are sufficient to analyze the GRP piping system

WW+HP …………………….HYDRO
W+T1+P1 …………………..OPERATING-MAXIMUM DESIGN TEMPERATURE
W+T2+P1 …………………..OPERATING-OPERATING TEMPERATURE
W+T3+P1 …………………..OPERATING-MINIMUM DESIGN TEMPERATURE
W+P1 ………………………..SUSTAINED

Here,

WW: Water-filled weight
HP=Hydrotest pressure
T1=Maximum design temperature
T2=Maximum operating temperature
T3=Minimum design temperature
P1=Design pressure, and
W=Content filled pipe weight

The expansion load cases are not required to be created as no allowable stress is available for them as per the code.

Note that, sometimes GRE piping network may have slug scenarios when carrying two-phase liquids. Again, they may have surge scenarios like firewater GRE pipe networks. So, those forces, if any, need to be considered additionally, as the case may be.

Again, if you are analyzing a piping system consisting of GRE pipe plus metallic piping, then expansion load cases need to be prepared.

While preparing the above load cases you have to specify the occasional load factors for each load case in the load case options menu as shown in Fig. 5. ISO 14692 considers hydro test case as an occasional case. In higher versions of Caesar II software (Caesar II-2016 onwards), these load factors are taken care of by default. So you need not enter the values. The option of these value entries will be available only if you define the stress type as occasional for those software versions.

**Fig. 5: Specifying Occasional Load factors in Caesar II for GRP/FRP piping system**

The default values of occasional load factors are 1.33 for the occasional case, 1.24 for the operating case, and 1.0 for the sustained case. These occasional load factors are multiplied with the system design factor (normally 0.67) to calculate the part factor for loading f2.

For aboveground GRP piping, the above load cases are sufficient. But if the line is laid underground, then two different Caesar II files are required. One for sustained and operating stress checks. The other is for hydro testing stress check as the buried depth during hydro testing is different from the original operation. Also, buried depth may vary in many places. So, Caesar II modeling should be done meticulously to take care of the exact effects.

For buried GRP pipe modeling, one needs to split the long lengths into shorter elements to get proper results. An element length of 3 m or less is advisable. Sometimes buried model contains a pipe slope, Those slopes are required to be modeled properly to get accurate results.

Code Stresses as per ISO 14692-2005

ISO 14692 2005 requires that the sum of all hoop stresses (σ_h, sum) and the sum of all axial stresses (σ_a, sum) be evaluated for all states of the piping system. CAESAR II evaluates these stresses for stress types OPE, SUS, and OCC. If the hoop stress is exceeded, the axial stress is not reported.

There are two stress envelopes in ISO 14692; Fully Measured Envelope and Simplified Envelope.

Stress Equations as per the Fully Measured Envelope

For Fully Measured Envelope; the inputs of σ_hl(1,1) and σ_al(1,1) are required in the piping input spreadsheet. The equations used in Caesar II software when analyzing using a fully measured envelope are as follows:

**Fig. 6: Code Equations for Fully Measured Envelope**

Stress Equations as per the Simplified Envelope

For Simplified Envelope, the inputs of σ_hl(1,1) and σ_al(1,1) are not required in the piping input spreadsheet. The equations used in Caesar II software when analyzing using a simplified envelope are as follows:

**Fig. 7: Code Equations for Simplified Envelope**

Explanation of the symbols used in the above equations:

The significance of the symbols that are used in the above-mentioned equations are:

f₂ = Part Factor for Loading
- 0.89 for Occasional Short-Term Loads
- 0.83 for Sustained Loads Including Thermal Loads
- 0.67 for Sustained Loads Excluding Thermal Loads
A₁ = Partial Factor for Temperature
A₂ = Partial Factor for Chemical Resistance
A₃ = Partial Factor for Cyclic Service
σ_qs = Qualified Stress (entered for bends, fittings, and joints)
σ_al(0,1) = Long-Term Axial Strength at 0:1 Stress Ratio
σ_al(1,1) = Long-Term Axial Strength at 1:1 Stress Ratio
σ_hl(1,1) = Long-Term Hoop Strength at 1:1 Stress Ratio
σ_al(2,1) = Long-Term Axial Strength at 2:1 Stress Ratio
σ_hl(2,1) = Long-Term Hoop Strength at 2:1 Stress Ratio
r = Bi-Axial Stress Ratio 2σ_al(0,1)/σ_qs (for simplified and rectangular envelopes)
σ_a,sum = Sum of All Axial Stresses {(σ_ap + σ_ab)² + 4ξ²}^1/2
σ_h,sum = Sum of All Hoop Stresses [σ_h² + 4ξ²]^1/2
σ_ap = Axial Pressure Stress
σ_ab = Axial Bending Stress
ξ = Torsion Stress
σ_h = Hoop Stress

Note that, in the year 2017, ISO 14692 received a new update, and there are many changes, which are explained here: What’s new in ISO 14692-2017?

Output Results from GRP Stress Analysis

Both stress and load data need to be checked for GRP piping. Normally the stresses are more than 90% (Even, sometimes it may be as high as 99.9%).

Few more related articles for you.

Stress Analysis of GRP / GRE / FRP Piping using START-PROF
What’s new in Revised ISO 14692: 2017 Edition
HYDROSTATIC FIELD TEST of GRP / GRE lines
Stress Analysis of GRP / GRE / FRP piping system using Caesar II
A short article on GRP Pipe for beginners

Online Video Course on FRP Pipe Stress Analysis

I have prepared a dedicated online course for explaining the steps followed in FRP/GRP/GRE pipe stress analysis using Caesar II.

Pre-Commissioning and Commissioning Checklist for Flare Package

Written by Anup Kumar Dey in Mechanical

Importance of Flare

All of you are aware that the flare is the last line of defense in the safe emergency release system in a refinery, chemical, petrochemical, or pharmaceutical plant. It uses to dispose of purged and wasted products from respective plants, unrecoverable gases emerging with oil from oil wells, vented gases from blast furnaces, unused gases from coke ovens, and gaseous water from chemical industries. So its design and construction have to be accurate and quality must be maintained.

Why use a Checklist for the Flare Package?

Checklists are very important tools for improving the quality and accuracy of any job. It helps engineers and designers to verify all important points while carrying out any work. It helps to reduce failure by compensating for the potential limits of human memory and attention. Any engineering design activity can be verified for accuracy, consistency, and completeness using a checklist. Checklists are an important document for quality audits. They are important in every task.

This checklist will highlight a few important points that should be checked before the commissioning of any flare packages. This list is not exhaustive, Readers are requested to add more points in the comments section.

Pre-Commissioning Checklist

The tag number and location coincide with the P&ID drawing number.
Check the Equipment visually for defects if any.
Confirm whether the vendor representative should be available for the commissioning
Check the equipment layout, and nameplate rating, and ensure conformity to specification.
Inspect and ensure the correct assembly of the equipment with the vendor P&ID
Check the insulation, if required, has been applied in accordance with the specification.
Check the suitability of flanges, facing, and gaskets for service conditions.
Check the alignment record of the equipment. All records should have the signature of the Owner’s Construction Representative.
Remove all temporary construction materials, facilities, and equipment.
Confirm that equipment grounding has been properly installed.
Confirm that all instruments have been installed in their proper locations
Confirm the equipment pre-commissioning/ commissioning procedure is available from the vendor and that operating personnel is thorough with the procedure.
Check the installation and support of all piping to ensure against vibration and fatigue in operation.

Provide scaffolding, safety lines, and barriers. Rope off the working area to keep out unauthorized personnel.
Check the inspection records of equipment.
Confirm that access ladders are properly fitted and fastened to the support clips provided
Check platforms have been installed to allow safe access to all valves and instrumentation that is located on the skid and they have been fitted with guard rails
Confirm that all connecting piping and valves have been installed on the skid, including isolation, control, instrumentation, and relief. Also, confirm that all instruments (local and those with transmitters) are properly installed.
Clean out all debris and test all drain systems free and clear, ready for start-up.
Check all operating blinds are installed as detailed in the drawing.
Remove all temporary construction materials, facilities, and equipment.
Confirm that the Manufacturer’s Test Certificate is available and that the information on the skid nameplate agrees with the certificate and is legible.
Confirm that the final external paint coating has been applied
Wherever applicable vessel, piping, pump, tank, the checklist should be applied.

Commissioning Checklist

Operational testing of the equipment including leak testing (at maximum operating pressure) Is carried out.
Operational and functional testing of instrumentation, control, and safety systems, including loop checking logic checking, operational testing of DCS/ESD systems, and package control systems.
Testing of CP system and all electrical power systems equipment, all motor runs, and test on lighting, power, and earthing systems. Energizing of switchboards and transformers
PSV inlet and outlet valves open and by-pass valves closed.
Check all the drain and vent valves.
The procedure for the start-up as per the Operating manual is clear to the Operator

Few more useful Resources for you…

Routing Of Flare And Relief Valve Piping: An article-Part 1
Flare systems: Major thrust points for stress analysis
Stress Analysis of PSV connected Piping Systems Using Caesar II
Articles related to Process Design
Piping Layout and Design Basics
Piping Stress Analysis Basics

Overview of Piping and Instrument Interface

Written by Anup Kumar Dey in Instrumentation,Piping Design Basics,Piping Interface

The main function of instrumentation in every process plant is to collect intelligence from the working plant and use those data to control the process parameters as per predefined conditions. Instruments in piping measure different process conditions like pressure, temperature, flow, density, and level as per the process requirement.

Piping engineers have a thorough interface with the instrumentation team for knowing the details of the instruments used. The main responsibilities as part of the instrument-piping interface are modeling these instruments in the 3D models at proper locations and providing appropriate access for operation and maintenance. While pipe-routing, special layout requirements near the instruments for their proper functioning must be ensured.

The instrumentation team provides instrument hook-up drawings explaining how a particular instrument is connected to the piping. The main interface with piping components, special requirements like upstream and downstream straight length requirements, connection types, valve types, access and maintenance requirements, instrumentation-piping scope demarcation, etc are provided clearly in the instrument hook-up drawings. Other deliverables to the piping department from the instrumentation team are:

Control valve datasheets.
Preliminary Instrument dimensional drawings and datasheets.
PSV sizing and reaction forces.
Panel and Other accessory details.

Piping has a regular interface with the Instruments for

Scope Break
Process Connections
Materials and BOM
Orientation

The interfaces are mostly standardized. However, these should be discussed with the C&A (Control and Automation or Instrumentation) team at an early stage of the project, preferably.

Some instruments give desired performance when installed in a particular position/orientation. (ex: Coriolis meter). When in doubt the functionality of the instrument should be discussed with the C&A engineer.

Types of instruments

Instruments in the piping industry can be classified into the following three groups:

In-line Instruments
On-line Instruments, and
Offline Instruments

In-line instruments:

In-line instruments are considered to be all instruments and components direct-mounted in or on process and utility lines or equipment and are subjected to the pressures and temperatures of the piping systems or equipment in or on which they are installed. Examples of a few inline instruments are given below.

On-line instruments:

On-line instruments are all instruments and components connected to process and utility lines or equipment via small (maximum DN 50 or 2 in) primary isolation valves. They are subjected to the pressures of the piping systems or equipment on which they are installed.

Typical examples of online instruments are impulse line components, transmitters, pressure gauges, mono-flange assemblies, analyzer sampling systems, etc.

Offline instruments:

Off-line instruments are considered to be all instruments and components, which are not in direct, contact with any process medium or which are not connected to any process/utility line or equipment

Typical examples of offline instruments are thermocouples, resistance elements, bi-metallic thermometers in thermowell, signal converters, local receiving indicators, etc.

Piping-Instrumentation Interface Salient Points

Some general points which need to be remembered are mentioned below:

Datasheets for ESD valves if not standardized the Plant ESD valve datasheet must be given to C&A
Material details for the control valves, Nuts, Bolts, and Gaskets should be considered by piping. Flanges as per ASME B 16.5
A process-to-instrument valve unit is a means of interfacing between process piping and instrumentation systems.
Instrument specifications apply downstream the last joint of the last process to the instrument valve or valve assembly, defined for the instrument connection in the mechanical piping class.
The philosophy is to use single-block valves up to Class 600 and a double block for Class 900 and above.
If the pipe is insulated, then the design shall incorporate an “over the insulation design” or mount the transmitter remotely.

Flow Instruments:

Flow meters measure the flow. There are various types of flowmeters that can be used in a piping system. Click here to learn more details about flowmeters and their types and applications.

1. Coriolis Flowmeter:

Should be installed on the downside In Liquid Service and upside in Gas service
Flow direction should be marked on vendor drawings
Orientation should be shared with C&A.

2. Vortex / Ultrasonic Flowmeter / Restriction orifice (Fig. 3)

Straight lengths should be maintained.
Tappings on the straight length should be avoided

3. Flow Transmitters / Restriction orifice (Fig. 4)

Break at the isolation valve ( DBB /SBB).
The end connection ( instrument side) should be discussed. ( generally threaded)

Analytical Instruments

1. Red Eye Meter (BSW meter-Fig. 5)

Orientation is to be ensured in such a way that the instrument is always flooded.
Flow direction should be marked on vendor drawings
Orientation should be shared with C&A

Pressure Instruments

Pressure instruments measure the pressure difference. They are popularly known as Pressure gauges or Pressure Transmitters. Click here to learn more about pressure-measuring instruments.

Pressure Gauge / Pressure Transmitter-Break at the isolation valve ( DBB /SBB).

Level Instruments

Level instruments are also known as Level Gauges or Level transmitters. Click here to learn more about Level gauges. The main points related to the piping-instrumentation interface for level gauges or level transmitters are:

Break at the Isolation valve
Drain / Vent valve under the piping scope
Level gauge drawings by piping
Transmitter details by C&A

Temperature instruments

Temperature instruments measure the temperature. Thermowells are the most widely used temperature-measuring instruments in the piping industry. Click here to know details about thermo-wells. The instrument-piping interface’s salient points are:

Scope break at the flange.
Gaskets, studs, bolts by piping

API 610 Pumps vs ANSI / ASME B73.1 Centrifugal Pumps

Written by Ankur Srivastava in Mechanical,Process

ANSI Pump and API Pump are two types of Centrifugal pump styles that are used in Chemical Plants, Refineries, and Oil and Gas Industries. They have some distinct differences. This article will compare the major features of both these pumps.

What is an API Pump?

An API Pump is a special type of centrifugal pump that meets the design, inspection, and testing criteria specified by the American Petroleum Institute’s API-610 standard for pumps. In Refineries and Petrochemical Industries, mostly API pumps are used as they provide very good operating experience in handling hydrocarbons (oil, gasoline, Natural gas, and petroleum products) due to their robust design. Generally, They come in many different forms employing a number of pumping mechanisms. Traditionally API pumps are considered very conservative (stringent) and costly.

What is an ANSI Pump?

ANSI Pumps are a type of horizontal, single-stage, end suction centrifugal pump that has an overhung impeller and back pull-out. This type of pump is designed based on the ASME B73.1 standard. Due to their low cost, they are popularly used in chemical industries, refineries, and industrial and mining applications for comparatively less temperature pressure applications. The main advantage of ANSI pumps is their interchangeability across manufacturers and brands.

ANSI Pump vs API Pump

Compared to an API pump, the typical ANSI pump has the following characteristics:

Criteria	API Pump	ANSI Pump
Design Code	API 610	ASME/ANSI B 73.1
Pump Casing	Thick Casing, more corrosion allowance. In general, designed for 750 PSIG at 500℉.	Thinner Casing, less corrosion allowance. Normally designed for 300 PSIG at 300℉.
Nozzle Load	More sensitive to pipe-induced stresses, ANSI pumps allow reduced permissible nozzle load	More sensitive to pipe-induced stresses, hence ANSI pumps allow reduced permissible nozzle load
Stuffing Box Size	API pumps have a large Stuffing Box.	Smaller stuffing box size. Unless a large bore option is chosen, an ANSI pump may not be able to accommodate the optimum mechanical seal for a given service.
Impeller Design	API pumps feature closed impellers with replaceable wear rings.	ANSI pump impellers are designed and manufactured without wear rings. Many ANSI pump impellers are open or semi-open
Mounting Option	Normally, API pumps are center-line mounted	Generally, ANSI pumps are foot-mounted.
Application	API pumps are suitable for heavy-duty, much higher temperatures, and pressures	ANSI pumps are usually not suitable for moving thicker and/or viscous fluids. Moderate duty application.
Reliability	API pumps are highly reliable	The reliability of ANSI pumps is comparatively less.
Cost	High	Comparatively less

Difference Between API Pump and ANSI Pump

Refer to the attached sketch. In foot-mounted pumps, casing heat tends to be conducted into the mounting surfaces and thermal growth will be noticeable. It is generally easier to maintain the alignment of API pumps since their supports are surrounded by the typically moderate-temperature ambient environment.

Choosing Pump Type: API or ANSI

The decision on API vs. ANSI construction is experience-based and is not governed by governmental or regulatory agencies. However, experienced machinery specialists have their own likes and dislikes based on the experience gathered by them over their long years in the machinery field.

Many highly experienced and reliability-focused machinery engineers would prefer to use pumps designed and constructed according to API 610 for toxic, flammable, or explosion-proof services at on-site locations in close proximity to furnaces and boilers in some of the conditions (rules-of-thumb) that are listed below:

Head exceeds 106.6 m (350 ft)
The temperature of pumpage exceeds 149°C (300°F) on pumps with discharge flange sizes larger than 4 inches or 177°C (350°F) on pumps with a 4-inch discharge flange size or less.
Driver horsepower exceeds 74 kW (100 hp)
Suction pressure in excess of 516 kPag (75 psig)
Rated flow exceeds flow at best efficiency point (BEP)
Pump speed in excess of 3600 rpm.

The author mentions that there have been exceptions made where deviations from the rules-of-thumb were minor, or in situations where the pump manufacturer was able to demonstrate considerable experience with ANSI pumps under the same, or even more adverse conditions.

Finally, the author gives his opinion on choosing either API or ANSI pumps based on the following:

Conventional Wisdom: API-compliant pumps are always a better choice than ANSI or ISO pumps

Fact: Unless flammable, toxic or explosion-prone liquids are involved, many carefully selected, properly installed, operated and maintained ANSI or ISO pumps may represent an uncompromising and satisfactory choice.

The above comparison that is provided in the article is referenced from Heinz P. Bloch’s book “Pump User’s Handbook Life Extension” co-authored with Allan R. Budris.

Few more useful resources for you.

Pump Suction Intake Design with Sample Calculation
Pumps & Pumping Systems: A basic presentation
Stress Analysis of Water Pump Station Piping using Flexible Sleeve Coupling
Types of Pumps used in Process Plants
Cause and Effect of Pump Cavitation

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