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Managing Technical Information Exchange With Process Equipment / Package Vendors

Written by Ankur Srivastava in Process

Who is an Equipment Manufacturer?

A manufacturer produces/fabricates and/or assembles the pieces of equipment parts for the end-user. A manufacturer may not assemble the equipment pieces. Many a time, a third party who conforms to the assembly requirements of the equipment pieces as specified by the manufacturer does the assembling. Many experienced engineers use the acronym “OEM” which stands for “Original Equipment Manufacturer”.

Who is an Equipment Vendor?

An equipment vendor could mean a party like a manufacturer, an assembler, a trader, or a combination of the above. The term Vendor is mostly used in process industries by the most experienced engineers.

Where does all this begin?

It all starts when a piece of particular equipment is required for a specific chemical process plant and for a given chemical manufacturing process.

How does it appear as information in the first place?

The equipment information is represented in a “ PFD (Process Flow Diagram)” in the initial stages. In the next step, the equipment qualifies the function the equipment in terms such as exact type, capacity, power requirement (rotary equipment), the material of construction,  operating and design conditions (pressure/temperature), properties of the process material entering/leaving the equipment, compliance to statutory requirements (if any), HSE requirements and any special considerations.

A Process Engineer captures the above-mentioned information in a “Process Datasheet”.

The third step is the preparation of a specification or material requisition (MR) mentioning further details for the requirement that need to be fulfilled.

Other information that must be a part of a specification could be as follows:

  • International / Company Standards based on which the equipment should be designed and manufactured.
  • Quantity and type of Vendor Documentation in terms of the number of paper / electronic documents
  • Requirements of Spares and consumables during commissioning and operation of the equipment
  • Material testing and test certification requirements
  • Guidelines and standards for Inspection and testing of the completed equipment.
  • Packing and Shipping Instructions
  • Site Information for equipment storage, erection, and commissioning, if any
  • Erection / Commissioning / Operation / Maintenance instructions
  • Lubrication Schedule

Depending on the type of equipment and project-specific requirements, There could be many more.

Managing Technical Information Exchange With Vendor

Now let us discuss how to improve the communication with the vendor to expedite the procurement of the equipment as required or suited for the particular application and in a timely manner. Please note that the emphasis is on the suitability of the equipment for a particular function and an adjective such as “best” has not been used to describe the equipment.

Provide Specific Information

Avoid providing data in a wide range as no equipment can perform well over a wide data range. So always study the subject and arrive at precise data and parameters for the equipment. Without proper data, It is difficult for the vendor to come up with a suitable equipment design. The operating or rating case of the equipment should be known beforehand.

Fill the Equipment datasheet

The datasheet should be filled with the appropriate information as much as possible. A thorough analysis must be conducted beforehand of what information can provide and what cannot. Inform the vendor to provide only the equipment-specific relevant information that is necessary for the selection of the equipment.

Managing Technical Information Exchange With Process Equipment Package Vendors

Do not waste time by asking for Proprietary Design parameters

You will be simply wasting your time if asking for design information related to any proprietary design. It is always preferable to agree with the vendor to provide performance guarantees for a proprietary design. However, do your homework to be sure about what the vendor is claiming to be a proprietary design, is really a proprietary item, and not something that is an open design.

Don’t provide incomplete or incorrect information

Incomplete or incorrect information can lead to the wrong equipment selection and can be disastrous. It will be allowing the vendor to escape from his contractual obligations for the performance guarantee of the equipment.

One of the most common examples of this would be the selection of a wastewater treatment plant. Incomplete or wrong chemical and biological analysis of the influent wastewater would certainly lead to the selection of the wrong treatment unit or units. This would be specifically true when the specifications of the discharged effluent from the treatment plant are very stringent and there are practically no margins on the discharged effluent quality as specified by regulatory authorities.

It also gives the vendor the excuse of escaping from the performance guarantee clause of the contract by proving that the influent water quality is not correct or incomplete for his specific design. In a nutshell, wastewater analysis in terms of multiple samples over a spread of time would be the ideal way to ensure that the treatment plant selected gives the optimum performance in terms of the quality of discharged effluent.

One major problem related to providing such data is how to manage this in the case of a grassroots or Greenfield project. This is also manageable. Most reputed vendors maintain an extensive databank of projects they have executed in the past. It is very likely that they would have data related to a similar project executed in the past that could be used for your project. Here my emphasis is on reputed vendors with an extensive portfolio of executed projects.

Raise your concern (if any) immediately

If you find an error in the vendor documents or something which does not fit into the scheme of your plant or unit, Always act promptly to raise queries to the vendor. Keep in mind that the vendor is in the market to do business and earn a profit. So always precisely understand your requirements. Most of the time the vendor would try to sell you something extra which may not be required for your application.

The analogy goes like this:
“I only need a sedan. Why are you trying to sell me a limousine?”

The above-mentioned guidelines should provide insight into the new upcoming engineers (Beginners) on how to effectively communicate with vendors in order to ensure a proper and timely selection of any equipment or package.

Pipe Rack and Rack Piping Design Considerations

Written by Anup Kumar Dey in Piping Design Basics

A pipe rack is the main artery of a processing unit. It connects all equipment with lines that cannot run through adjacent areas. Because it is located in the middle of most plants, the pipe rack must be erected first, before it becomes obstructed by rows of equipment. Pipe racks carry process, and utility piping, and also include instrument and electrical cable trays, as well as equipment mounted over all of these. Fig. 1, shows a typical pipe rack.

This is a small presentation on Pipe Rack and Rack Piping. It will be very helpful for beginners in the piping industry. This article will cover the following points in brief:

  • Data Required for Pipe Rack Development
  • Pipe Rack design criteria
  • Shapes
  • Future Space
  • Width of Pipe Rack
  • Clearance
  • Pipe Rack Loading
  • Rack Piping
  • Positions of Lines (Process & Utilities)
  • Hot Lines & Cold Lines
  • Bigger Size Lines
  • Pipe Spacing
  • Anchor Bay
  • Unit Battery Limit
  • Expansion Loops
  • Pipe Route
  • Trays

What is a Pipe Rack?

A pipe rack is a structural framework designed to support and organize pipes connecting process units and equipment in various industrial and construction settings. Typically constructed from steel and concrete, it holds pipes and instrument cables at an elevated position to facilitate maintenance, prevent damage, and allow for efficient flow and routing of fluids or gases. Pipe racks are commonly used in industries such as oil and gas, chemical processing, and manufacturing, where they help manage the complex network of piping systems essential for operations.

Rack piping design is a very important subject for piping engineers. Designing piping within pipe racks is essential for efficient operation, safety, and meeting regulations. Since the design of the pipe rack structure is closely linked to the rack piping design, both should be considered together.

Data Required for Pipe Rack Design

When designing a pipe rack, we need several documents: the P&ID, Flow Diagram, Plot Plan, Layout Specification, Client Specification, Construction Material details, Fire Protection Requirements, and information about surrounding equipment. The pipe rack design begins with setting the width, spacing, and elevations. After determining these factors, a line routing diagram should be prepared.

The primary data required for the detailed design and development of a pipe rack are:-

Typical pipe rack
Fig. 1: Typical pipe rack

Pipe Rack Design Criteria

Shapes of Pipe Rack

There are various shapes of pipe racks like L/T/U/H/Z. These shapes shall be considered based on the area available.

Future Space Requirement in Pipe Rack

The total width of the pipe rack shall include 25% extra space for future expansion/modification in the unit for rack width up to 16 m and 10% for rack width above 16 m. The future space %age is normally based on client requirements.

Width of the Pipe rack

The width of the rack shall be 6 m, 8 m, or 10 m for single bay and 12 m, 16 m, or 20 m for double bay having 4 tiers maximum. The spacing between pipe rack portals shall be taken as 6m in general. However, it can be increased to 8m depending on the size of the pumps to be housed below the pipe rack.

Clearance criteria in Pipe rack

For units, clearance beneath the pipe rack shall be 4 m minimum both in longitudinal and transverse directions.

For Offsite, clearance beneath the pipe rack shall be 2.2 m minimum both in longitudinal and transverse directions.

Road clearance shall be 7 m for the main road and 5 m for the secondary road.

Rack Width Selection Criteria

Refer to Fig. 2 for details

Rack width selection criteria
Fig. 2: Rack Width selection criteria

Pipe Rack Loading

Pipe rack loads shall be given by the stress group to the Civil & structural discipline for pipe rack design.

  • Sustain Load (Dead Load): Weight of piping, valve, and load insulation
  • Thermal Load: Load by thermal expansion of piping & Reaction force by the internal pressure of expansion bellows
  • Dynamic Load
  • Occasional Loads by the vibration of piping & by wind and earthquake
  • Sustained Load (Live Load): Liquid load for the hydrostatic pressure test

Guidelines for Rack Piping

Position of Lines in a Pipe Rack:

Predominantly process lines are to be kept at a lower tier and, utility & hot process lines are on the upper tier.

Hot Lines & Cold Lines in a Pipe Rack:

Generally, hotlines & cold lines are to be kept at different tiers or at different groups on a tier.

Pipe Spacing inside Pipe rack:

Minimum spacing between adjacent lines shall be decided based on the O.D. of the bigger size flange (minimum rating 300# to be considered), O.D. of the smaller pipe, individual insulation thickness, and additional 25mm clearance. Even if the flange does not appear the minimum spacing shall be based on the above basis only. Actual line spacing, especially at ‘L’ bend and loop locations, shall take care of thermal expansion/thermal contraction/non-expansion of adjacent lines. Non-expansion/thermal contraction may stop the free expansion of the adjacent line at the ‘L’ bend location.

Bigger Size Lines:

Large-size lines (14” and larger) shall be arranged close to the column in order to decrease the bending moment of the beam. Water lines more than 30” shall not be routed over a pipe rack, these shall be routed underground.

Anchor Bay in a Pipe rack

Anchors on the racks are to be provided on the anchor bay if the concept of anchor bay is adopted. Otherwise, the anchor shall be distributed over two to three consecutive bays.

Anchors shall be provided within the unit on all hotlines leaving the unit.

Pipe Route:

Racks shall be designed to give the piping the shortest possible run and to provide clear head rooms over main walkways, secondary walkways, and platforms.

Trays:

Generally, the top tier is to be kept for Electrical cable trays (if not provided in the underground trench) and Instrument cable ducts/trays. Cable tray laying to take care of necessary clearances for the fireproofing of the structure.

Battery Limit (ISBL):

Process lines crossing units (within units or from the unit to the main pipeway) are normally provided with a block valve, spectacle blind, and drain valve. Block valves are to be grouped and locations of block valves in the vertical run of the pipe are preferred. If the block valves have to be located in an overhead pipe-way, staircase access to a platform above the lines shall be provided.

Steps for Pipe Rack Piping

  • The first step is to create a line-routing diagram. This diagram shows all process piping systems on a general arrangement drawing or unit plot plan where the pipe rack is situated.
  • The line-routing diagram is completed using information from the initial P&ID or Process Flow Diagram, including line size, line number, pipe material, and operating temperature.
  • After the routing diagram is finished, determine the rack width, column spacing, road crossing span, and the number of levels and their elevations.
  • Column spacing should be chosen based on the pipe span economics and truss arrangement to handle road crossings or avoid underground obstacles.
  • Design the pipe rack to meet specific plant requirements.
  • Calculate the rack width using a typical cross-section, considering that process lines are usually on the lower levels and utility lines on the top. Instrument and electrical trays may be placed on the utility level or a separate level if space allows.
  • Include extra space for future growth, typically 25 to 30% more in rack width.
  • When flanges or flanged valves are needed on adjacent lines, stagger them to avoid interference.
  • Allow for thermal expansion or contraction by providing sufficient clearance where movement will occur.
  • Establish the clearance of the first line from the structural pipe rack column based on sizes provided by civil or structural engineers.
  • After reviewing all requirements and arrangements, round off dimensions to the nearest whole number. Decide on the width and number of levels, such as a two-tier, 30 ft. wide rack or a three-tier, 20 ft. wide rack.
  • Determine the gap between tiers based on the largest diameter pipeline and branching. Ensure there is no interference from support, insulation, or the size of branches. All branch lines should be arranged aesthetically on a common top of steel (TOS).
  • Finalize the conceptual arrangement of the pipe rack based on these considerations.

Fig. 3 below shows the cross-section of a typical pipe rack:

Cross Section of a Pipe Rack
Fig. 3: Cross Section of a Pipe Rack

Lines Routed in a Pipe Rack

Before starting any pipe rack piping project, it’s crucial to categorize the pipelines. In a pipe rack, pipelines are generally classified into three groups: process lines, relief-line headers, and utility headers.

Process Lines:

  1. Process lines connect nozzles on process equipment that are more than 20 feet apart. Equipment that is closer can be connected directly.
  2. Product lines transport materials from vessels, exchangers, or pumps to storage or headers outside the plant.
  3. Crude or charge lines enter the unit and usually run through the yard before connecting to exchangers, furnaces, or other equipment like holding drums or booster pumps.

Relief-Line Headers:

Relief-line headers include relief lines, blow-down lines, and flare lines. These lines should be self-draining, directing fluids to a knock-out drum, flare stack, or plant boundary. Pocketed systems, which require extra condensate pots and additional instruments, valves, and pumps, are costlier. To avoid pockets, some relief headers are placed on higher elevations, supported by extended pipe rack columns. However, for non-condensing gas systems, self-drainage may not be as critical.

Utility Lines:

Utility lines are divided into two groups:

  1. Utility Headers: These serve the entire plant and include low and high-pressure steam lines, steam condensate lines, plant air, instrument air, and potentially cooling and service water lines.
  2. Utility Lines: These lines serve specific equipment or groups of similar equipment. They include boiler feedwater, smoothing steam, compressor starting air, fuel oil lines, lubricating oil, cooling oil, fuel gas, inert gas, and chemical treatment lines.

For effective condensate collection, steam headers should drain to a steam separator. Branch connections to steam headers are usually placed on top to prevent condensation from reaching the equipment.

Expansion loops in a Pipe Rack

Refer to Fig 4.

Examples of Expansion Loops
Fig. 4: Examples of Expansion Loops

The expansion loop is provided on the high-temperature lines. This information shall be given by the stress group. All the loops shall be located around one column only.

Make lines into a group and install large-size piping and high-temperature piping to the edge of the pipe rack. When necessary to install an expansion loop on the condensate line, do it horizontally to prevent water hammering. But do as above if the horizontal loop is impossible.

To learn the piping stress concepts of pipe rack design, visit the following article: Rack Piping for a Piping Stress Engineer

Types of Pipe Racks

Pipe racks come in various types, each designed to meet specific needs and conditions in industrial settings. Here are some common types:

  • Single-Tier Pipe Racks: These racks have one level and are typically used for smaller installations or where space is limited. They are often used for utility lines or less complex piping systems.
  • Multi-Tier Pipe Racks: These racks feature multiple levels, which allow for the separation of different types of lines (e.g., process lines on lower tiers and utility lines on upper tiers). Multi-tier racks help optimize space and organize complex piping systems.
  • Modular Pipe Racks: Modular racks are pre-fabricated in sections or modules, which can be assembled on-site. This type of rack is flexible and can be easily expanded or reconfigured as needed.

ISBL Pipe Rack vs OSBL Pipe Rack

In industrial piping systems, ISBL (Inside Battery Limits) pipe racks and OSBL (Outside Battery Limits) pipe racks are two key categories that differentiate between the locations and functions of pipe racks within a plant or facility.

ISBL Pipe Racks (Inside Battery Limits):

ISBL pipe racks are located within the battery limits of a processing unit or plant section. These racks are found inside the core area of the facility where the main processing equipment and operations are situated.

They support process lines that are crucial for the internal operations of the plant, such as transporting chemicals, gases, or other materials between equipment like reactors, exchangers, and distillation columns.

ISBL pipe racks are designed to handle more complex piping systems and must accommodate the specific needs of the internal process. They often require careful planning to ensure that they do not obstruct operations or maintenance.

OSBL Pipe Racks (Outside Battery Limits):

OSBL pipe racks are located outside the battery limits of the processing unit or plant section. These racks are found in the peripheral areas of the facility, typically in the utility or service areas.

They support utility lines and other ancillary systems that are not part of the core processing but are essential for overall plant operations. This can include lines for steam, water, electricity, and other utilities that serve the entire facility or connect to external systems.

OSBL pipe racks are generally designed for simpler and less critical piping systems compared to ISBL racks. They often deal with less complex routing and must account for factors like accessibility and integration with the external parts of the plant.

In summary, ISBL pipe racks are integral to the plant’s core processes, while OSBL pipe racks manage supporting utilities and external connections. Each type plays a crucial role in ensuring the efficient operation of the plant.

Pipe Rack Structural Design

The structural design of pipe racks is performed by the civil team using piping loads given by piping stress engineers, equipment loads (Air cooled heat exchanger and others) by mechanical engineers, and cable loads by electrical/instrumentation engineers. If you are interested in learning more details about the structural design, then visit: Design of Structural Steel Pipe Racks

Internal Cleaning of Piping System

Written by Anup Kumar Dey in Maintenance,Pipeline

This article covers the requirements for cleaning (chemically or mechanically), pickling, passivating, and protecting the internal surfaces of new carbon steel and stainless steel piping. Internal cleaning is applicable when requirements are noted on P&IDs and associated piping drawings. Internal cleaning and protection shall be done after installation and pressure testing.

Internal cleaning involves removing corrosion products, mill scale, oils, greases, dirt, organic growth, and organic sediments, primarily to avoid damage to or poor performance of downstream equipment.

Cleaning of equipment, vessels, tanks, and transmission pipelines is not covered by this article.

Field Pipe Cleaning Procedure

The pipe internal cleaning contractor shall analyze the surface contaminants and surface condition and recommend a cleaning procedure for each piping system to the contractor with the following details:

  • Analysis of surface contaminants and surface condition.
  • Review of system metallurgy and evaluation of corrosion risks associated with the cleaning.
  • Options available and recommended for cleaning. Recommendations for degreasing, pickling, neutralizing, passivating and drying should be included.
  • Description of recommended cleaning materials (including quantities, quality, concentration, water quality, etc.) and methods.
  • Corrosion rates of the cleaning solutions on the substrate metals.
  • Corrosion monitoring method.
  • Logistics of cleaning such as batch immersion or continuous circulation, cleaning circuits, etc.
  • Items to be blocked off, disconnected, or removed prior to cleaning.
  • Emissions that may be released during cleaning and methods to protect personnel and the environment.
  • The proposed method of disposing of spent cleaners, equipment to be used and personnel to be involved.
  • Material Safety Data Sheets/Safety Precautions

Internal Cleaning Contractor shall use only materials and process(es) approved by the contractor.

The internal cleaning contractors are solely responsible for all cleaning operations such as supervision, labor, cleaner storage, pumping equipment, filters, holding tanks, hoses, on-site laboratory, analytical testing, and each and every item of expense.

No chemical cleaning, degreasing, etc., shall take place until satisfactory completion of fabrication, heat treatment, examination, and hydro testing (if applicable).

Chemical solutions shall not be introduced into piping systems or equipment unless high-point vents and low-point drains are available to ensure proper filling and complete removal of solutions.

When circulating fluids through an assembled piping system, vessels, exchangers, compressors, etc. shall be positively isolated by blinds. Extreme care shall be exercised to prevent the entry of any cleaning chemicals or vapors into any part of the machinery.

Mechanical/Physical Cleaning of Piping System

Components of piping designated to be chemically cleaned shall be examined before fabrication, and, where necessary, mechanically and/or physically cleaned (e.g. by scraping, wire brushing, blasting with abrasive, steam cleaning, or shot jet cleaning) to remove loose scale, foreign matter, and protective coatings, which may otherwise make satisfactory chemical cleaning impossible, before fabrication commences.

Company-approved procedures shall be used for mechanical/physical cleaning In using mechanical or physical methods, great care shall be taken not to damage the equipment being cleaned.

Following mechanical and/or physical cleaning, the piping shall be inspected to ensure that the internal surfaces are free of weld spatter, grinding debris, abrasives, dust, loose materials, etc. All open ends shall then be temporarily sealed to prevent the ingress of a foreign matter pending the chemical cleaning operation.

Cleaning Agents or Cleaning Materials

Field chemical cleaning materials shall generally be limited to biodegradable detergent cleaners and/or citric acid-based cleaners.

Passivation materials will generally be sodium nitrate or inhibited phosphoric acid. However, other degreasing, pickling, cleaning, or passivation compounds may be submitted for CONTRACTOR/ COMPANY review and approval.

The cleaners shall not contain chemicals such as chromates and lead compounds which could cause soil and groundwater contamination.

The chloride content of stainless steel cleaning solutions shall not exceed 2 ppm.

All cleaning solutions shall be prepared, handled, and used in accordance with the manufacturer’s data sheets and recommendations.

Internal Cleaning Procedures

Cleaning of stainless steel surfaces shall be in accordance with ASTM A380 and testing as per ASTM A967. Piping and equipment manufactured of austenitic materials shall not be allowed to come in contact with solutions containing chlorides such as hydrochloric acid and chemicals containing chlorides as impurities. A compatibility check shall be performed prior to cleaning in order to ensure that Valve seals, Injection Quills, etc. are not damaged by cleaning fluids.

Aluminum, galvanized carbon steel, magnesium, and zinc surfaces shall not be allowed to come in contact with acid-cleaning solutions.

The following items shall be blocked off, disconnected, or removed from the piping system prior to the initiation of cleaning:

  • Bearings Oil Reservoirs and Tanks
  • Cylinders Orifice Parts
  • Filters Plug Cocks
  • Instruments Relief Valves
  • Equipment Screens
  • Special valves and miscellaneous items
  • Items temporarily removed from systems may be replaced by temporary spools whilst the cleaning is in process.
  • Care must be taken that “dead” pockets of the line do not exist in which fluids and debris could accumulate.

Corrosion Monitoring

A corrosion test shall be performed by the Internal Cleaning Contractor on a sample of the cleaning fluid to be used for cleaning. The test duration shall be 24 hours and test coupons shall be the same material as the equipment or system to be cleaned.

From the weight loss of the test coupons, the corrosion rate can be determined, which should not be more than 0.01 mm/24 hours. If higher corrosion rates are measured or if any pitting is observed, the inhibitor shall be replaced and the test repeated until acceptable results are obtained.

The method of monitoring shall be proposed by the Internal Cleaning Contractor for company review and approval.

Corrosion control during chemical cleaning shall be demonstrated by the use of a suitable method(s) of corrosion monitoring including the use of corrosion coupons installed for the total cleaning duration.

Chemical Solution and Rinse Disposal

Following water washing, all spent chemical solutions and rinses shall be completely discharged by draining and flowing out with high-pressure air jets from the lowest points in the system and must be disposed of in an environmentally acceptable manner approved by the company.

If detergent, soda ash solution, rinses, and other liquids are discharged to public waters, these liquid effluents must comply with the applicable state and local discharge regulations, guidelines, and standards.

Before and After Cleaning

If any liquid effluent streams are discharged to a sewer system connected with a sewage treatment plant, they must comply with the applicable state and local pretreatment regulations.

Chemical solution and rinse disposal shall be proposed by the internal cleaning contractor for company review and approval.

Pipe Inspection and Preservation

The piping shall be inspected before and after cleaning to check the effectiveness of the cleaning operations and look for signs of a metal attack.

Externally cleaned surfaces shall be visually examined under a lighting level, including both general and supplementary lighting, of 2700 lux on the surfaces being examined. A lighting level of 1100 lux may be used upon the contractor’s approval. The visual examination shall be supplemented with closed-circuit television cameras, borescopes, mirrors, and other aids, as necessary, to properly examine inaccessible or difficult-to-see surfaces. Lights shall be positioned to prevent glare on the surfaces being examined.

Where visual examination is not practical, a clean, lint-free, white cotton cloth or filter paper moistened (but not saturated) with high-purity isopropyl alcohol (rubbing alcohol) may be rubbed against the surfaces at all openings. The presence of a smudge on the cloth or filter paper is evidence of incomplete cleaning and the cleaning shall be repeated.

The visual examination shall confirm that cleaning solutions are completely removed.

After inspection, cleaned piping shall be filled with nitrogen to 0.35 kg/cm2 g and sealed until plant start-up. The nitrogen pressure shall be checked regularly and topped up as required.

Prior to Nitrogen filling, pipes shall be dried with dry air. During the drying operation, the moisture content of the incoming and outgoing air shall be monitored by the cleaning contractor to ensure the satisfactory completion of the drying operation.

Safety of Pipe Cleaning Personnel

The Internal cleaning contractors are responsible for the health, safety, and well-being of field cleaning personnel and all other parties in the general environment where cleaning operations occur.

The internal cleaning contractors shall employ proper and safe practices for the storage, handling, and disposal of chemicals and spent materials.

Manufacturer’s and governmental safety guidelines, recommendations, and instructions shall be complied with for the prevention of harm or injury to any person before, during, or after these cleaning and pickling activities.

The internal cleaning contractor shall enforce the use of protective clothing and safety accessories such as eye protection, face shields, gloves, and breathing apparatus as required. Internal cleaning contractor’s safety measures shall be submitted to the Company for approval.

The cleaning area shall be closed to unauthorized personnel.

Warning signs shall be posted to forbid smoking, welding, flame cutting, and unauthorized entering of the cleaning area.

During cleaning with acid, adequate venting shall be provided to prevent the accumulation of an explosive gas mixture; special care shall be taken to vent isolated pockets in a safe manner.

Identification of Cleaned Pipe

Cleaned pipe shall be metal tagged in English and the local language to avoid subsequent contamination. The tag shall read “KEEP SEALED UNTIL READY FOR USE. INTERNALLY CLEANED AND PRESSURIZED WITH NITROGEN ON (Date).” Pipe shall not be marked with paint or ink, in lieu of metal tagging.

Click here to know more about the cleaning requirements

Scope of Piping: Inputs and Outputs of Piping Discipline

Written by Anup Kumar Dey in Piping Design Basics

Piping Engineering is not a standalone activity. To successfully finish all engineering aspects piping engineer needs to depend on other disciplines in terms of input and output. While designing a piping system, many inputs are required from other disciplines and at the same time inputs are given to other disciplines too. There are also a few outputs generated by piping that is required for the procurement, erection, and fabrication of the piping system. This article will list a few such inputs and outputs to give the readers an idea in brief.

Inputs to Piping Discipline

  • Requirements from the client: Plot area and location, statutory requirements, special requirements, software to be used, etc.
  • Process licensor: Project design basis, design code, plot plan, PFDs (Process Flow Diagram), P&IDs (Piping and Instrumentation Diagram), PDS (Process Data Sheet), process description, equipment list, line list, site data, licensor, capacity, etc.
  • Process information: Process data sheet showing overall dimensions, supporting arrangement, all nozzles location, size, rating, etc. for equipment.
  • Civil/Structural layout, drawing: Effluent & drain sewer layouts and manhole location.
    Civil drawings (plan and elevation) for the facilities within the unit like the instrumentation control room, electrical substation, and laboratory.
    Pipe racks and technological structure foundation drawings.
    Civil drawings for platforms.
    Tank settlement data. Soil Properties.
  • Instrument drawing:
    Tray width requirement on pipe rack/sleepers.
    Instrumentation hook-up drawing.
    Instruments drawings for control valves, safety valves, inline instruments, etc.
  • Electrical layout:
    Tray width requirement on pipe rack/pipe sleepers and cable trenches width in units/off-site.
    Electrical cable tray layout.
  • Mechanical (Static/Rotary/Package) layout:
    Mechanical datasheets for equipment like columns, vessels, tanks, etc. Layout drawing of package items showing auxiliary equipment.
  • HVAC (Heating, Ventilation, and Air conditioning): Layouts showing the HVAC duct size and the location.
Piping Vs Other Disciplines
Fig. 1: Piping Vs Other Disciplines

Outputs from Piping Discipline:

  • Overall plot plan showing the location of various units, tank farms, offsite, package units, non-plant buildings, roads, culverts, pipe racks, sleepers, etc.
  • PMS (Piping Material Specification)& VMS (Valve Material Specification).
  • Equipment general arrangement drawing/layouts indicating the location of all the equipment within the unit, platforms, ladders, overhead crane elevation, monorail location, and cutouts for piping.
  • Pipe rack general arrangement drawing & structures for equipment support
  • Piping general arrangement drawing/Layouts showing all the piping and equipment.
  • Piping Bill of Materials (BOM) with technical evaluation and technical bid analysis (TBA).
  • Piping stress analysis report for the critical lines.
  • Support loading for critical lines for structure design.
  • A drawing showing the vessel cleat locations for pipe supports and platform/ladder.
  • Layout for underground services.
  • Piping isometrics with the bill of material.
  • Support location plan, support schedule, and pipe support drawings.
  • Purchase specifications for insulation, painting, wrapping, and coating.
  • Material handling study.

Tee Connections in Piping | Equal Tee, Reducing Tee | Piping Tee Dimension

Written by Anup Kumar Dey in Piping Design Basics

Piping Tees are used either for dividing the main fluid flow into two streams or for combining flow from two streams. The term Tee for these types of pipe fittings most probably comes from the resemblance of the English letter Tee.

The main run pipe has often termed a Header and the other as a branch. The branch size may be smaller or equal to the run pipe size but it cannot be larger. Tees having branch size equal to run size are called equal tees & others as unequal tees or reducing tees.

Tees are normally designed based on ASME B16.9 or ASME B16.11. Tee is always normal or perpendicular to the pipe axis and is normally produced by forging.

Types of Piping Tee Connections

Piping tee connections are classified according to the branch size and end connection.

Based on the branch size, there are two types of piping tee connections. They are:

  • Equal Tee, and
  • Reducing Tee

Equal Piping Tee:

When the branch size is equal to the run pipe it is called Equal Tee pipe fitting.

Reducing Piping Tee:

In the case of reducing tee, the branch size is smaller than the run pipe size. there is a limitation to the branch size. It can not be sufficiently smaller. For example, Reducing Tee from 16″ pipe is available up to 6″ branch size. 16″ X 4″ piping tee is not manufactured. Usually reducing piping tee connections are manufactured till a branch pipe size of one size lower than 1/2 the parent pipe size. This rule is valid till 28″.

Equal Tee vs Reducing Tee
Fig. 1: Equal Tee vs Reducing Tee

Based on the pipe end connections, tees are classified as follows:

Socket Welded Tees

  • These are usually forged and used up to 2” run size on services where socket welded connections are permitted.
  • The applicable dimensional standard is ASME B16.11 and material standards including ratings are the same as those for socket-welded elbows.
  • Normal industry practice is to use socket welded tees up to 1 1/2” run size.

Screwed-end Tees

Their use including rating, dimensional, and material standards are the same as applicable to screwed elbows.

Butt welding Tees

  •  The dimensional standard applicable for equal and unequal tees is ANSI B16.9. These are available from 1/2” through 48”.
  • Unequal butt welding tees are available having branches up to one size lower than half run size e.g. If the run size is 8”, unequal tees are available in sizes 8” × 6”, 8” × 5”, 8” × 4” & 8” × 3 1/2”.
  • Applicable Pressure temperature rating and material standards are the same as those for butt-welding elbows.
  • Butt welding tees are usually used for size 2” and above and in smaller sizes for services where the use of socket weld joints is prohibited.

Flanged Tees

Their use including pressure rating, and dimensional & material standards are the same as applicable to flanged elbows.

In normal large-bore pressure piping most often Butt-welded Tee connections are used. The ASME B31.3 (Appendix D) is used to provide a formula for calculating the SIF value at tee connections which Caesar automatically calculates when Tee is defined. From the ASME B31.3-2020 onwards, Appendix D is deleted from the code. Now Stress Intensification and Flexibility factors are to be calculated using the ASME B31J code. The Tee connections are normally defined in Caesar as shown in the attached figure.

Tee modeling in Caesar II
Fig. 2: Tee modeling in Caesar II

For pipeline systems, a special type of tee is used, known as Barred Tee.

Piping Tee Dimensions

Equal Tee Dimension Chart

Refer to the following table (Table-1) for the Tee dimension chart for equal pipe tee as per ASME B16.9

NPS (Inches)Outside Diameter at Bevel (D, mm)Center to End (C, mm)Center to Center (M, mm)
1/221.32525
3/426.72929
133.43838
1 1/442.24848
1 1/248.35757
260.36464
2 1/273.07676
388.98686
3 1/2101.69595
4114.3105105
5141.3124124
6168.3143143
8219.1178178
10273.0216216
12323.8254254
14355.6279279
16406.4305305
18457.0343343
20508.0381381
24610.0432432
26660495495
28711521521
30762559559
32813597597
34864635635
36914673673
38965711711
401016749749
421067762711
441118813762
461168851800
481219889838
Table 1: Equal Pipe Tee Dimensions

Refer to Fig. 3 below to understand the notation used in Table 1 and Table 2.

Equal Tee and Reducing Tee Nomenclatures for Pipe Tee Dimensions
Fig. 3: Equal Tee and Reducing Tee Nomenclatures for Pipe Tee Dimensions

Reducing Piping Tee Dimensions Chart

Refer to Table-2 which provides the reducing Pipe Tee dimensions.

NPS (Inches)Large End Outside Diameter (D, mm)Small End Outside Diameter (d, mm)Center to End (C, mm)Center to Center (M, mm)
1/2 x 3/821.317.12525
1/2 x 1/421.313.72525
3/4 x 1/226.721.32929
3/4 x 3/826.717.12929
1 x 1/233.421.33838
1 x 3/433.426.73838
1 1/4 x 1/242.221.34848
1 1/4 x 3/442.226.74848
1 1/4 x 142.233.44848
1 1/2 x 1/248.321.35757
1 1/2 x 3/448.326.75757
1 1/2 x 148.333.45757
1 1/2 x 1 1/448.342.25757
2 x 3/460.326.76444
2 x 160.333.46451
2 x 1 1/460.342.26457
2 x 1 1/260.348.36460
2 1/2 x 173.033.47657
2 1/2 x 1 1/473.042.27664
2 1/2 x 1 1/273.048.37667
2 1/2 x 273.060.37670
Table 2: Reducing Piping Tee Dimensions

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Difference between Tee and Barred Tee
Smart Tee Model considerations in START-PROF
Inspection & Test, Marking & Colour Coding and Packing Requirements for Pipes & Fittings
Technical requirements for Pipes & Fittings for preparation of Purchase Requisition
Piping Elbows vs Bends: A useful literature for piping engineers

Site Visit Safety Rules: Operating Plant Visit Safety Guidelines

Written by Ankur Srivastava in Health & Safety

Awareness of Safety Rules during a Field Visit (Operating site/Construction Site) is a must. But most of the new designers/engineers working in design consultancy firms are unaware of it. While making a field visit to a chemical process unit whether it be an upstream oil and gas processing installation, a refinery, or a petrochemical plant, safety rules need to be strictly followed. This article explains some basic safety rules for a site visit. Readers can suggest additional points to be taken care of during the field visit.

Carry your own Personal Protective Equipment (PPE)

It is suggested to carry your own personal protective equipment (PPE). Even though these may be available at a few sites but still do not expect the same. Carrying your own PPE has its own advantages like fitment and personal hygiene. It may not be possible to get PPE items of the perfect size and you may not feel comfortable wearing used PPE items.

Complete Mandatory Safety Training prior to Site Visit

Before the field visit, check if there is a requirement to finish some mandatory safety training. If so, attend those before planning for site-visit. For example, a one or two-day course on oil-field safety and Hydrogen Sulfide Safety and exposure protection has to be taken up and a certificate of completion be obtained as a mandatory requirement for many upstream oil and gas companies prior to the field visit.

Check regarding additional Safety Precautions from Plant Operating Staff

It is always better to enquire about the safety precautions of the operating plant from the operating staff. Also, while entering the chemical process unit premises for the first time ensure that the plant operations staff accompanies and guides you. Learn about the layout of the plant and any special safety precautions to be considered from them. Entering an operating area without any awareness of what is around you is dangerous and foolhardy.

Follow Plant Safety Sign Boards thoroughly

Almost all operating plants provide safety signboards inside the plant to make you aware of safety details. So, Lookout for such signboards when walking around the plant or unit.

Be Attentive while walking on elevated platforms

When walking on elevated platforms ensure that you are attentive and looking all around to see where you are landing your feet. Pay attention that your head is not bumping against a beam or piping. Be extra careful as there may be open grates or hatches for maintenance work to avoid a falling accident.

Avoid Touching valves, pipes, or instrument surfaces by Barehand

If you are not authorized, Do not touch valves or instruments with barehand. Without knowing the fluid content in the pipe, If you touch bare pipe or valves, Burning can happen. Even solar radiation on a bare pipe can cause the surface temperature to be high enough to cause 1st-degree burns and blisters.

Seek help from Site operating Staff for Data measurement

Always ask the operating staff to collect the required field data. In case, you are required to take site readings from field instruments ensure that you have a proper foothold and can walk around the instrument without obstruction. Be extra cautious while climbing monkey ladders and do it very carefully and slowly.

Avoid Dehydration

Always keep yourself hydrated and carry water with you. Normally it is required to work in the open sun for quite some time, So make sure that you have taken plenty of fluids before walking around. Dehydration can cause dizziness and lack of focus which could lead to an accident. If you are unwell, it is not advisable to undertake a field visit.

Avoid Removing your PPE

Do not remove your Personal Protective Equipment kit just because you are feeling sweaty and itchy while working in hot and humid conditions in the plant area where PPE is mandatory. In case it is required, take a break in a safe convenient place where you can remove your PPE to recompose yourself before going back to work.

Avoid changing any set points when inside the control room

Do not change any setpoints of the process control instruments while sitting in the control room unless you are both authorized and know the consequences of your actions in terms of the effect on the process.

Know about emergency Exits and Gathering Points beforehand

Before entering the plant premises make sure that you are briefed about the emergency exits and gathering points by the operations staff of the plant. Pay utmost attention to what is being told to you.

No Smoking or Eating inside plant premises

Needless to tell that it is not allowed to smoke and eat in the plant premises except for areas designated for smoking and having food/beverages.

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There could be many other points for a safe field visit and I request the readers to contribute some more points for a safe and successful field visit in the comments section.