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Rupture Disc: Definition, Types, Components, Selection, Sizing, Advantages, Installation

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

Rupture discs are the second most commonly used pressure relief (protection) devices after safety valves (PSV/PRV) in industrial applications. Rupture Disk is basically a non-reclosing type of pressure relief safety device that protects equipment or system during overpressure situations or potentially damaging vacuum conditions. A rupture disc is also popular as a pressure safety disc, bursting disc, or burst diaphragm.  It consists of

  • a one-time-use membrane that ruptures at a pre-decided pressure difference between the inlet and outlet of the device (i.e, defined breaking point), either positive or vacuum, thus releasing the pressure
  • and a disc holder.

The major objective of the rupture disc (Fig. 1) installation in piping or pipeline systems is to optimally protect and minimize the downtime of the system/plant. As the rupture disc is a one-time-use device. So, it has to be replaced after the burst. Rupture Discs are frequently used for over-pressure protection in chemical, petrochemical, oil & gas, and sanitary applications.

Rupture Disk Materials

Rupture disks can be constructed from any materials that the process fluid permits. Industrial rupture discs are normally constructed from the following materials:

Rupture disks are widely accepted and used in industry and are normally available from 3 mm to 1200 mm sizes.

Advantages of Rupture Disc over Pressure Safety valve (PSV)

The major advantage of rupture disc compared to electronic, pneumatic, or spring-loaded safety systems are

  • the failsafe performance of rupture discs.
  • economical.
  • high reliability to prevent unnecessary downtime of the system.
  • simple design with no moving parts.
  • Provide both overpressure protection and depressurizing.
  • leak tightness.
  • Reduced fugitive emissions – no simmering or leakage prior to bursting.
  • react quickly enough to relieve the excess pressure quickly.
  • lightweight.
  • used for both gas and liquid handling application.
  • no additional maintenance cost for each rupture disc per service.
  • Greater sensitivity to temperature.
  • Protect against rapid pressure rise caused by heat exchanger tube ruptures, runaway reactions, or internal deflagrations.
Typical Rupture Disc for Industrial Application
Fig. 1: Typical Rupture Disc for Industrial Application

Disadvantages of Rupture Disc

However, there are a few drawbacks of rupture disks as well. These are

  • not possible to test before application.
  • can degrade with age or due to corrosion.
  • need replacement every time it ruptures. So, a shutdown may be required to refit.
  • care to be exercised during installation not to damage the rupture disc.
  • improper bolt torque during installation may also affect the disc burst pressure.
  • Greater sensitivity to mechanical damage.

Design of Rupture Disc

The Rupture Disc or Rupture Disk consists of one or more flat or domed layers and generally, are round or square in shape. The rupture element of the disc is equipped with breaking points that are normally created by means of lasers. These breaking points can be made of simple cuts or even special geometries. A rupture disk is normally actuated thermally or mechanically. A safety factor should be used regardless of the disk design.

Rupture Disc types

Depending on the applications and suitability, rupture discs can be of different types. They are mostly made of metals or plastics (Inconel, Hastelloy, or Tantalum, plastic liners such as PTFE or FEP.). Domed rupture discs are of two types

  • having the dome towards the process (reverse-acting rupture disc) enabling very high operating pressures and operating pressure ratio.
  • or having the dome away from the process (forward-acting rupture disc).
    • Forward-acting composite disc
    • Forward-acting solid metal disc
    • Forward-acting scored metal disc
    • Graphite disc

Difference Between Reverse-Acting Rupture Disc and Forward-Acting Rupture Disc

The major differences between the above-mentioned rupture disk types are tabulated below:

Reverse-Acting Rupture Disc (Fig. 2)Forward-Acting Rupture Disc (Fig. 3)
The convex side of the dome faces the process mediaThe concave side of the dome faces the process media
Functions when the pressure creates an instability in the dome, resulting in reversal, or buckling, of the dome. They are designed to act in compression.Functions when the weakest portion of the disc exceeds its tensile strength. They are designed to act in tension.
Possess longer cycle life and generated stresses are compressive. Hence, less crack propagation.lower cycle life due to the generation of tensile stresses that promotes crack propagation.
Domes are typically supported on the outlet side to prevent movement of the dome prior to reversal.Normally not supported.
CostlyComparatively cheaper
Table 1: Rupture Disc-Reverse Acting vs Forward Acting
Reverse-Acting Rupture Disc
Fig. 2: Working of Reverse Acting Rupture Disk
Forward-Acting Rupture Disc
Fig. 3: Working of Forward-Acting Rupture Disc

Installation Methodology

A Rupture disc can be installed

  • directly between flanges, or
  • inserted into a rupture disc holder, which is then mounted between flanges.

Refer to Fig. 4 below which shows one of the standard rupture disc installations.

Installation of Rupture Disc
Fig. 4: Installation of Rupture Disc

How do you select a Rupture Disc?

Rupture discs are not standardized products. hence, various parameters need to be considered for the optimal selection of the right device. Some of those parameters for the proper selection of a rupture disc are:

  • Line operating parameters.
  • Pipe size (The diameter of the rupture discs is specified matching the diameter of pipes or flanges as the nominal pipe size DN or NPS (Nominal Pipe Size).
  • Burst or set pressure (The pressure at which the rupture disc opens. It is selected in such a manner, that the rupture disc opens before there is any system damage. It is normally, above the working pressure during normal operation and below the maximum allowable working pressure) and corresponding temperature.
  • Burst tolerance: Defines the tolerance around the defined burst/set pressure at which the rupture disc opens. For example, If a ruptured disc has a burst tolerance of +/-10%, and the defined burst pressure is 10 bar, the rupture disc will open between 9 bar and 11 bar.
  • Permissible overpressure or vacuum pressure
  • Process medium
  • Vacuum resistance
  • Pulsation
  • Necessary vent area, or required flow rate
  • Phase Application: Gas-only rupture discs should be used for gaseous medium only.
  • Rupture Disc Operating ratio: This is the pressure at which the rupture disk can be operated with prolonged service life. Depending on the construction method and materials used, Rupture disks have a maximum operating ratio of about 50 to 95%. So, rupture disk selection must consider this ratio for proper working.

Components of a Rupture Disc

The main components of a rupture disk are:

  • Rupture Disks
  • Rupture Disc Holders
  • Alarm system to transfer the signal for rupture disc opening
  • Heat Shield
  • Baffle Plates

Sizing a Rupture Disc

Rupture Disc Sizing for a particular application is done following the standard methodologies described in ASME Section VIII Div. 1, API RP520, API RP 521, and Crane TP-410. Three basic methodologies are followed for sizing rupture disc devices. They are:

  • Coefficient of Discharge Method (Kd)
  • Resistance to Flow Method (Kr) and
  • Combination Capacity Method

Co-efficient of Discharge Method of Rupture Disc Sizing

In the coefficient of discharge model, The rupture disk is considered as a relief valve, and the flow area is estimated using relief valve formulas with a fixed coefficient of discharge, “Kd” of 0.62. In order to use this method for rupture disc sizing, the following four conditions must be met:

  • The rupture disk has to be installed within 8 pipe diameters of the equipment or the overpressure source.
  • The rupture disk discharge pipe should be limited to 5 pipe diameters.
  • The rupture disk discharge should be directed to the atmosphere.
  • The inlet and outlet piping is at least the same nominal pipe size as the rupture disk.

This is popularly known as the “8 and 5 rule”. A typical sketch of the “8 & 5” rule for rupture disc sizing is provided in fig. 5 below:

Co-efficient of Discharge method for rupture Disc Sizing
Fig. 5: Co-efficient of Discharge method for rupture Disc Sizing

The flow area calculated is known as the Minimum Net Flow Area (MNFA). This is the rupture disk’s minimum cross-sectional area needed to meet the required flow. The rupture disc manufacturer publishes the actual Net Flow Area (NFA) for each model and size. For the selected rupture disk the NFA should be greater than or equal to MNFA.

Resistance to Flow Method of Rupture Disc Sizing

The Resistance to Flow Method analyzes the flow capacity of the relief piping and accounts for the frictional losses of the relief piping and all components. Such losses normally include nozzle entrances and exits, elbows, tees, reducers, valves, and the rupture disk. The rupture disk is also considered a piping component and its contribution to the overall frictional loss is determined.

A factor Kr that represents the velocity head loss due to the rupture disc device is determined experimentally in flow laboratories by the manufacturer for their line of products and is certified per ASME Section VIII, Division 13. This Kr accounts for the holder and the bursting characteristics of the disk. API RP521 recommends using a Kr of 1.5. However, ASME Section VIII, Division 13 states that a Kr of 2.4 shall be used. ASME PTC25 provides standardized test methods to measure the Kr of rupture disc devices. By quantifying this performance characteristic, rupture disc devices may be selected.

Where do you use a Rupture Disc?

The following picture (Fig. 6) below shows three main cases of rupture disc applications.

Application of Rupture Disc as Primary and Secondary Relief
Fig. 6: Application of Rupture Disc as Primary and Secondary Relief

Rupture Disc as Primary Relief

A rupture disc can be used as another pressure relief device to protect a vessel of the piping system from overpressure. In the following cases, they can be preferred as a primary relief option over pressure relief devices:

  • When the pressure rise is so large and rapid that extremely fast-acting is required to prevent catastrophic failure. A relief valve (PSV/PRV) can still be installed in parallel to protect against other relieving scenarios.
  • When the relieving fluids may impede the proper operation of the pressure relief valve.
  • The use of a ruptured disc as primary relief is attractive if the relieving fluids are non-toxic, non-hazardous, and the system stop and the loss of fluids is not an issue.
  • When the vessel has no permanent supply connection, and to protect the vessel against exposure to fire or other sources of heat. This is usually the case with storage vessels for non-refrigerated liquefied compressible gases at ambient temperatures.

Rupture Disc as Secondary Relief Device

  • As stated earlier, rupture discs and pressure relief valves can be used in parallel. In such a configuration, the design considers a double jeopardy scenario and gives protection with both the vessel overpressure and the pressure relief valve failure.
  • If the process involves exothermic reactions where abnormally high and uncontrollable pressure conditions arise, parallel installation of a Rupture disc and PRV is recommended.

Combination of a Rupture Disc and Pressure Relief Valve

The combined use of a ruptured disc along with pressure relief valves is becoming more popular within industries nowadays. There are two potential possibilities:

  • rupture disc upstream (inlet) of the relief valve.
  • rupture disc downstream (outlet) of the relief valve. 

Rupture disc at the inlet of Pressure Relief Valve

The process benefits of installing a Rupture disc upstream of PRV/PSV are the following:

  • It ensures positive sealing of the system.
  • It protects the PSV/PRV from fluids containing solids, that may plug/damage the valve.
  • It provides protection of the valve from corrosion and thus reduces valve maintenance.
  • It allows in-situ testing and calibration of the safety valve.
Rupture Disc
Fig. 7: Rupture Disc

Rupture Disc at the outlet of the Pressure Relief Valve

A rupture disc can also be installed on the downstream side of the pressure relief valve for the purpose of protecting the valve from the atmospheric downstream fluids. If the relief fluids are vented in the common header vented media can result in either corrosion or polymerization. In such cases, the Rupture disc would isolate the vented media from the relief valve.

Rupture discs can also be used upstream as well as downstream of Pressure relief devices.

Few more Resources for you..

Routing Of Flare And Relief Valve Piping: An article
Various types of pressure relieving devices required for individual protection of pressure vessels in process plants
Modeling Relief Valve (Pressure Safety Valve) Thrust force
Stress Analysis of PSV connected Piping Systems Using Caesar II

Details about Intergraph Smart Licensing Platform for Caesar II (PDF)

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

Have you seen the message displayed in your Caesar II dashboard whenever you open your Caesar II Program saying “CAESAR II will no longer respond to HASP keys after May 31, 2020.” as shown in Fig. 1

Yes, you got it right. Intergraph, i.e Hexagon is changing their licensing system from HASP (Hardware Lock) or SPLM (Smart Plant License Manager) Licensing to Intergraph Smart Licensing (ISL) from June 1st, 2020 onwards. Hence, if your current licensing is on the HASP Key platform, you must transition it to smart licensing.

Caesar II Warning for ISL Transition
Fig. 1: Caesar II Warning for ISL Transition

What is Intergraph Smart Licensing?

Intergraph Smart Licensing or ISL, in short, is the next-generation cloud server-based advanced software licensing product from Hexagon PPM.

Smart Licensing Cloud contains servers with license keys. The cloud servers with license keys will be connected to a website portal. This portal will be accessible from a browser with the help of an internet connection. License administrators will be able to use the portal for setting up the configurations and generating license keys. Smart Licensing Client is basically a small application that has to be installed on each client computer where a licensed application is running. A configuration connection info (.cci) file will be used to connect the client computer to the cloud for licensing. Once you open the Smart Licensing Client, you can easily view, change, update settings and check whether licenses are in or out.

Details about Intergraph Smart Licensing Platform

Advantages of ISL

As per Hexagon PPM, ISL will offer many benefits with respect to the earlier system like

  • It will be very easy to install, use and administration.
  • It is expected to reduce your costs as it will eliminate the requirement of maintaining the license server.
  • the risk of losing the expensive hardware locks will be eliminated.
  • As the ISL will be through the internet, so one can work from anywhere without the geographical limitation of the office.
  • In Smart Licensing Client, one can change projects and settings as and when required.
  • It may support offline working as well

Comparison between SPLM and ISL

Smart Licensing, ISL provides more features and enhanced usage reporting. Refer to the following table that compares features in the previous licensing solution and the current licensing solution.

SPLM vs ISL
Table 1: SPLM vs ISL

ISL Webinar

There is a recorded webinar by Hexagon regarding the background of Smart Licensing and steps to follow for changing your current licensing into a Smart Licensing system. Refer to the webinar to understand more details about ISL.

Major discussion points of the webinar

In this online webinar You will learn about:

  • The Transitioning from SPLM or ESL (dongles) to ISL
  • The new solution rollout of the ISL

About the Presenter

Geoff Blumber, Technical Sales Manager – Hexagon PPM: As the Technical Sales Manager at Hexagon PPM, Mr. Geoff Blumber is aligning the people and resources to deliver the right solutions to the right people at the right time.

Bryan Stuckey, CADWorx Technical Manager – Hexagon PPM:  Mr. Bryan Stuckey who serves the role of CADWorx Technical Manager joined Hexagon PPM in March 2013. He has huge experience with multiple 3D platforms ranging from software administration to modeling. He provides end-user technical support, product testing, and training/presentation support for CADWorx Plant Design Suite.

How to Register for the Webinar?

To Register and view this webinar click here and submit your details.

Few more Resources for you..

Stress Analysis using Caesar II
Stress Analysis using Start-Prof
Piping Stress Analysis Basics

Details about Spectacle Blind and Spacers

Written by Anup Kumar Dey in Engineering Materials,Mechanical,Piping Design Basics,Piping Interface

What is a Spectacle blind and Spacer?

Spectacle blinds and Spacers are pressure-retaining devices used in the piping/pipeline industry to temporarily or permanently blind (shut) or isolate part of the piping or pipeline system.

  • A spectacle blind is a forged product and a combination of a flange spade and a ring spacer in one single product.
  • One end of the spectacle blind will have an opening that allows fluid flow through the pipe during operation and the other end is made solid to block flow during isolation or maintenance time.
  • One can simply rotate the spectacle blind by 180 degrees to close or open the fluid flow through the piping system.
  • However, when there is space constraint, Flange spades and ring spacers can be used as separate products.
  • As one of the two discs is always outside the pipe, one can easily understand if the blind is in an open or closed position.

As it looks like the numeric number Eight or a pair of eyeglasses, a Spectacle blind (Fig. 1 & 2) is also known as a figure 8 blind or figure 8 spectacle blind.

Design Code and Standards for Spectacle Blind

ASME B16.48 is the governing code for spectacle blind design. This specification provides the dimensions, pressure-temperature ratings, materials, marking, dimensional tolerances, and testing requirements of the Spectacle blind. In general, Blinds are available in sizes NPS 1/2 – NPS 24, and these are installed between ASME B16.5 piping flanges in the 150, 300, 600, 900, 1500, and 2500 Pressure Classes. They are manufactured from steel plates and are available in forged material grades like ASTM A105 (high-temperature carbon), A350 (low-temperature carbon), and ASTM A182 grades (alloy, stainless steel, duplex).

Bigger size spectacle blinds with a diameter of>24 NPS are also available, but these are custom-made. Spectacle blinds of Carbon steel Material are normally manufactured from a single piece of steel, whereas alloy / stainless steel blinds can be produced by welding more pieces together.

Various spectacle blind standards used in industrial applications are:

  • ANSI/ASME Standard: ANSI B16.5, ANSI B16.47, MSS SP44, ANSI B16.36, ANSI B16.48
  • DIN Standards for Spectacle blind: DIN 2527, DIN 2566, DIN 2573, DIN 2576, DIN 2641, DIN 2642, DIN 2655, DIN 2656, DIN 2627, DIN 2628, DIN 2629, DIN 2631, DIN 2632, DIN 2633, DIN 2634, DIN 2635, DIN 2636, DIN 2637, DIN 2638, DIN 2673
  • BS Standards for Spectacle Bild and Spacer: BS 4504, BS 4504, BS1 560, BS 10

Definition of Terms used with Spectacle Blind

Ring Spacer or Spacer Ring or Paddle Blank or Paddle Spacer

Spacer Rings are made to match the pipe ID with the same thickness as the “single-blind” that it replaces.  During the installation of spacers, the flange and associated piping should be pulled together and a “ring spacer” has to be installed to fill the gap. Normally, a handle is attached to the blank by welding.

Single/ Line Blind or Blank or Spacer Blind or Flange Spade or Paddle Blind

Single-blind is a positive shut-off device that is generally installed along with a valve so as to prevent accidental flow. In general, they fit inside the bolt circle of mating flanges. However, Plastic, Fiberglass, and Cast Iron, are bolted. Single blinds use standard gaskets.

To differentiate between a spacer and blind in the installed line, the handle of the blank is made solid whereas a formed eye or drilled hole is made for the spacer.

Spectacle Blind

A combination of a ring spacer and a single-blind is used as a spectacle blind. As required they are rotated to serve the purpose. When spectacle blinds become too heavy, a pair of paddle blank and paddle spacer is used instead of a single spectacle blind.

Spectacle Blind and Spacer
Fig. 1: Spectacle Blind and Spacer

Test (Hydrotest/Pneumatic Test/Service Test) Blank

During leakage testing, test blanks are used. Test blanks are specifically designed blanks and used only for testing purposes for the test duration.

Vapor Blind

Similar to a “single-blind”, Vapor Blinds are positive sealing devices used for preventing vapor leakage into a pipeline or vessel. Generally, they are thinner compared to single-blind and normally 1/8″ to 5/16″ (3-8mm) thick.

Jack Screw Flanges

For larger-size blinds, Jack Screw Flange is required. Jackscrew help in spreading the flanges and replacing the spacer/blind or turning of spectacle blind.

Use of Spectacle Blind, Spades, and Spacers

As Spectacle Blind, Spades and Spacers belong to the family of pipeline isolation devices, and they are used to provide flexibility during operation and maintenance. Hence, it is required to consider this during the design of the Piping system. Blanks are normally installed in a horizontal line. On average, spectacle blinds are installed on the following

  • At inlets and outlets of rotary and static equipment
  • In bypass line
  • At the unit battery limit
  • Where double isolation is required for high-pressure lines.
Spectacle Blind is installed position
Fig. 2: Spectacle Blind is installed position

Spectacle blinds in Piping Material Specification (PMS)

In the PMS following details need to be clearly specified for spectacle blinds:

Common Spectacle blinds are available in the following facing types

  • Raised Face (for high-pressure applications)
  • Flat face (for low-pressure applications)
  • Male and Female Ring-Joint Blanks (used in conjunction with ring-joint gaskets)

Materials of Spectacle Blind and Spacers

Spectacle blinds and spacers are manufactured from various materials as listed below:

  • Carbon Steel Spectacle Blind: ASTM A105.
  • Stainless Steel: ASTM A182 F304, F304L, F304H, F316, F316L, F316Ti, F310, F310S, F321, F321H, F317, F347, F347H, F904L.
  • Alloy Steel: ASTM A182 F1, F11, F22, F5, F9, F91.
  • Duplex Stainless Steel Spectacle blind: UNS S31803, UNS S32750
  • Nickel Alloys: Monel 400 & 500, Inconel 600 & 625, Incoloy 800, 825, Hastelloy C22, C276.
  • Copper Alloys: Copper, Brass & Gunmetal.

Symbols of Spectacle blinds

The following spectacle blind symbol is used in P&ID to denote spectacle blind.

Spectacle Blind Symbol
Fig. 4: Spectacle blind Symbol

Difference between Spectacle Blind and Spade and Spacers

Spade and Spacer combinedly are comparable to Spectacle Blind. So, a spectacle blind is the combined form of a spade and spacer. For larger pipe sizes the weight of the spectacle blind becomes too heavy. So sometimes, as the requirement arises, a spade or spacer is used. The word “SPADE” or “SPACER” are stamped on the handle of the spade or spacer to clearly indicate what is installed in the line.

In the installed position the handles of the spade and spacers are visible from the outside. The common handle configurations are provided below in Fig. 5

Spade handle Configurations
Fig. 5: Spade handle Configurations

Few important Considerations for Spectacle blinds

  • Spectacle blinds must be accessible from grade, platform, or if below 4500 mm by a portable ladder, or temporary scaffolding.
  • The proper weight of the Spectacle blind needs to be considered during pipe stress analysis when near the equipment nozzles.

Few more Resources for you…

“Pipe Coupling”-A short Introduction for the piping professionals
A Literature on Piping Nipples for piping and plumbing industry
Piping Elbows and Bends: A useful detailed literature for piping engineers
Reducers used in Piping Industry: A short literature
Tee Connection: A short literature for piping engineers
Difference between Stub-in and Stub-on Piping Connection

What are Insulating Gaskets? Their Types, Components, Applications, Installation

Written by Anup Kumar Dey in Engineering Materials,Mechanical,Piping Design Basics,Piping Interface

What is Flange Insulation Gasket Kit?

The most common problematic area for a Piping/Pipeline System design is flanges. So we have to be doubly sure to seal it properly to prevent flange leakage. At the same time, It must also be insulated cathodically so that stray currents which are known behind the undue corrosion and eventual metallic breakdown be prevented. Insulating gasket sets or Flange insulation kits play an important role in such cases.

  • They are designed for electrically insulating the flanges.
  • They act as an insulator between dissimilar metallic flanges.
  • Also, they are used to isolate sections of pipework (dissimilar metals) electrically in the cathodic protection systems; thus preventing the electrostatic charge flow along the pipelines as they remove the possibility of galvanic cell system creation.

Major Applications of Insulating Gasket Kit

Insulating gasket kits can be used in all such places where galvanic corrosion protection and electrical insulation are needed. Common Application areas are piping/pipeline systems with seawater environments, offshore installations, chemical installations, oil refinery pipelines, etc.

Components of Flange Insulation Gasket Kit

Each flange insulation Kit (Refer to Fig. 1) constitutes of

  • one central flat or oval section gasket,
  • one insulation sleeve per bolt and
  • two insulating steel washers per bolt and
  • two plated steel washers per bolt.

All these components are produced using special materials possessing chemical stability, dielectric properties, and low water absorption so that the purpose is solved. The full sets are packed individually and labeled clearly mentioning the flange size, rating, type, and material combination. Insulation kits are generally available upto 24 inches, but custom-made higher nominal sizes can be produced on the requirement.

Insulating Gasket Kit
Fig. 1: Components of Flange Insulating gasket Kit

Assembling of the flange insulation gasket kit components

The polyethylene insulating sleeve and the mounting stud are the main components of the insulating gasket kit. Contrary to the conventional nut and bolt system of flanged joints, the insulation kit uses a stud with a washer and nut on each end of the flange joint. The insulating sleeve is then inserted into the bolt holes using one insulator on each side of the flange. So, Two insulators per bolt hole are inserted into the flange. Then the mounting stud is inserted into the insulating sleeves until threads on each end of the stud are visible outside of the flange. A flat steel washer is slid onto the stud at each end, and a nut is threaded onto each end of the stud and tightened.

As a nut is tightened on each end of the stud, the flange insulation kit becomes much stronger than the typical nut-and-bolt type connection. In the traditional manner of nut-bolt tightening, all of the clamping force is applied to the single set of threads on the bolt while in the case of a double-ended stud such as in a flange insulation kit, the clamping force is divided equally between the threads on each end of the stud as well as inside both nuts. The stud is protected and insulated from any electric charge and corrosion. This creates a flanged connection that will not corrode or fail due to a chemical reaction between two dissimilar metals.

Types of Flange Insulating Gaskets

Four major types of gasket isolation kits are available in the market those are designated as F, E, D, & O. Each type of flange kit fits flanges with a specific type of flange face (RF, FF, RTJ).

F Type Gasket

Type F type gaskets are produced to fit the raised face flanges. The inside diameter of the bolt-hole circle is made slightly smaller than the external diameter of the gasket which assures automatic positioning of the gasket. To avoid the accumulation of foreign materials, Special band protectors can be used for the joint assembly to strengthen the cathodic isolation further.  These are manufactured from 1/8″ thick fabric-based phenolic sheets either without coating or a with a nitrile rubber coating on the two faces. Type F gaskets are also available in non-asbestos fibers with high isolation capacity.

E Type gasket

In full-face type, Type “E” Gaskets, the outside diameter of the gasket matches the external diameter of the flanges. So the gasket completely covers the whole flange surface.  There are produced with precision-located bolt holes and are easy to position in the center. This design will prevent foreign material accumulation between the flange faces and thus enhances the isolation properties of the kit. Type E flange insulation kits are available in phenolic, neoprene-faced phenolic, and high-temperature materials.

D Type Gasket

Type “D” Gaskets are manufactured to fit into the ring groove of RTJ flanges (style R, RX, and BX). They are available in medium weave reinforced phenolic and other materials are sized to ANSI specifications available in a basic oval as well as an octagonal shape. This type of gasket is known as an “API ring joint”.

O Type gasket

Type O Gaskets are extra special as they feature an additional sealing element on both sides of the device, generally, PTFE, Nitrile, or Viton Rubber, and are available in both ring and full-face designs (type E and F).

Insulating gasket Material

  • All materials should be selected to assure long-term effective sealing and electrical insulation of the flanged joints.
  • To take advantage of the best characteristics, sometimes, gaskets are made with combinations of materials.

Normal Gasket materials are G3, G7, Nitrile-Face, Plain Phenolic, G10, Neoprene-faced Phenolic, Klinger, Teflon, Durlon, etc. Popular Sleeve materials are Phenolic, Mylar, Polyethylene, Minlon, or Nomex.  Common washer materials are Phenolic, Steel, G7, G3,  or G10 available as a single washer and sleeve kit, a one-piece washer kit, a double washer kit, or a one-piece double washer kit (Minlon)

Sleeves and Washers of Flange Insulation Gasket Kits

One-piece sleeves and washers

One-piece sleeves and washers are available molded from acetal resin. They should generally be used as single washer sets since they are molded to specific lengths and are in many instances longer than the thickness of a single flange. They are available for bolt diameters of ½” to 1-1/2″ (12.7 mm to 38.1 mm), and are limited to applications where the flange temperature does not exceed +180^oF (+80^oC).

A special feature is a washer centering ring that positions the steel washer on the unit properly to avoid uneven pressures on the washers.

Insulating Washers

Standard insulating washers are made of high-strength phenolic and provide tough, positive insulation at temperatures of +3000F ( +1500C). They are available for bolt sizes from ½” (12.7 mm) through 3 ½” (88.9 mm) and are made to fit over the insulating sleeves. Fiberglass reinforced high temperature phenolic insulating washers are available on special order in the same sizes as the standard insulating washers

Insulating Sleeves

Insulating sleeves are available in Mylar, polyethylene, phenolic, and Nomex. They are through 3-1/2″ (88.9 mm) and are designed to fit easily over the flange bolts, and may be used with standard-sized bolts and bolt holes even with some misalignment. Insulating sleeves are used with separate insulating washers and have a standard wall thickness of 1/32″ (0.79 mm). They are available for standard American bolt sizes from ½” (12.7 mm) to 3 ½” (88.9 mm), as well as metric bolt sizes from 12 mm and larger.

Steel Washers

Steel washers are designed to fit over the insulating sleeve or retainer ring on the one-piece sleeves and washers. The outside diameter is sized to fit within the bolt facing on ANSI standard flanges. They are of 1/8″ (3.2 mm) thick plated hot-rolled steel. Pyrox insulating sleeves and washers are also available.

Flange Insulation Gasket Kit Installation procedure

The Gasket ID (inside diameter) is normally made slightly smaller than the flange ID. While installing ensure that the gasket is properly centered over the bore. It will prevent the build-up of foreign material between the flange faces during pigging.  

Single washer insulating sets are recommended for underground flanges. This should be installed on the unprotected side of the flange, which will provide cathodic protection for the studs as well as the nuts. For above-ground flanges, It is suggested to use Double washers for ease in testing.  

The use of alignment pins is always suggested which will ensure proper alignment of flanges and gaskets. The size of each Pin shall be a minimum of 3/32″ (2.38 mm) larger than the bolt.  

A diagram showing a recommended bolt tightening sequence is normally supplied with each insulating gasket set.

Common Vendors for Insulating Gasket Kits

Common vendors who manufacture and supply insulating gaskets are

  • PSI
  • Pikotek
  • Central Plastics
  • Garlock
  • Trojan
  • Lemons
  • Advanced Products and Systems

Information needed for Ordering Flange Insulating Kits

To order an insulating gasket kit, the following information needs to be provided:

  • Flange Specification (ANSI/ASME, DIN, API, MSS SP44, BSI, AWWA Standard)
  • Nominal Pipe Size, Pressure Rating, and Bore Size
  • Operating Pressure, Temperature, and Media
  • Gasket type (D/E/F/O)
  • Required Seal Material
  • Isolating Sleeve Material
  • Isolating Washer Material
  • Metal Washer Material
  • Quantity

Few more Resources for you…
Methods for Checking Flange Leakage
Guidelines on selection of various types of Flanges
Few points on Gaskets for leak Proof Flanged joints
PROCEDURE FOR FLANGE-BOLT TIGHTENING OF VARIOUS SIZES OF FLANGES
Functions of Gaskets for leak-proof Flanged joints

Reference

Guidelines for Modeling and Supporting of Large Diameter Pipes / Pipelines

Written by Anup Kumar Dey in Piping Supports

During the course of pipe stress analysis, we find a few lines in any complex project to have a very large diameter. Caesar II Support Modeling of such pipes always creates confusion on whether to consider radial thermal growth or to be modeled as centreline supporting. There is still confusion among several engineering organizations and the design approach varies. In this article, We will discuss pipe support modeling in Caesar-II, support selection, its detailing & functionality. In this article, Pipes /Pipelines having a diameter of more than 24’’ are considered large-diameter pipes.

Support Modeling Philosophy in Caesar II

Up to 24’’ pipe size, support shall be modeled at the centerline of the pipe i.e. the radial expansion of the pipe shall be neglected & support shall be assumed to be acting at the center of the pipe as shown in Fig. 1

For the Large diameter bare pipes (>26″ NB), the Stress Engineer shall model a rigid element from the center of the pipe to the bottom of the pipe up to the supporting point considering the pipe radial expansion as shown in Fig. 1.

Pipe Support Modeling for bare pipes at Caesar II
Fig. 1: Pipe Support Modeling for bare pipes at Caesar II

For Large diameter insulated pipes, the temperature gradient and the actual point of action of guide and resting can also be fed as shown in Fig. 2.

Pipe Support modeling for large diameter insulated pipes at Caesar II
Fig. 2: Pipe Support modeling for large-diameter insulated pipes at Caesar II

The stress engineer shall decide whether to provide the reinforcing pad or not at the support point (trunnion type) in the following cases:-

  • If the slope of the piping is more than 15˚, the Stress engineer shall decide whether to use a reinforcement pad or not, depending upon pipe size, support load, support function (Line Stop/Guide), unsupported pipe span, etc. Refer to Fig. 3 for an illustration.
Use of R.F. Pad for Sloped Lines > 15˚
Fig. 3: Use of R.F. Pad for Sloped Lines > 15˚

The reinforcement pad at the Directional Anchors or line stops for large pipes shall be used as shown in Fig. 4 below.

Requirement of RF Pad for Supporting large diameter pipe
Fig. 4: Requirement of RF Pad for Supporting large diameter pipe
  • Irrespective of any size, the stress engineer shall provide a reinforcement pad for higher loads on the support based on the trunnion check calculation.
  • RF pad shall be provided at all support for thin pipes. The pipe shall be considered a thin-walled pipe if  D/T> 96, where D is the outer diameter of the pipe and t is its thickness.
  • Wear Pad shall be used at all support locations in case of uninsulated large pipes

For large-diameter pipes, two or more bottom-type springs may be used as shown in Fig. 5, Fig. 6, and Fig. 7.

Illustration of Two Bottom Springs used for Large pipes
Fig. 5: Illustration of Two Bottom Springs used for Large pipes (Note: Provide stiffener plate if the shoe base plate extension is large)
Illustrating Four Bottom Type Springs used at one Supporting Location with guide for Large Pipes
Fig. 6: Illustrating Four Bottom Type Springs used at one Supporting Location with a guide for Large Pipes
Illustration of Four Bottom Type Springs used for Large pipes
Fig. 7: Illustration of Four Bottom Type Springs used for Large pipes

For large diameter pipes, it’s better to avoid single lug support due to the tendency of ovalization of the pipe because of Self-weight. Supporting shall be done using a pipe clamp or two trunnions having two different clamps instead of a single lug as shown in Fig.8.

Use of clamps for supporting Large Pipes
Fig. 8: Use of clamps for supporting Large Pipes

Approach for Caesar Modeling Vs Actual Supporting

Generally, the following points are to be taken care of while converting Caesar II modeling into practical support. Depending upon supporting and practical function of the support we should revisit our Caesar II support modeling.

Supporting for guide modeled with zero gaps

Guide modeling & supporting for Large Pipes
Fig. 9: Guide modeling & supporting for Large Pipes

Supporting a guide with resting

Modeling & supporting of Guide with resting for Large Pipes
Fig. 10: Modeling & supporting of Guide with resting for Large Pipes

These are a few standards practices. These may vary from one consultancy to another. Please provide your input in the comments section.

Few more articles related to piping supports for you..

Supporting of Piping Systems: Few Guidelines
A Brief Description of Sway Brace, Strut and Snubber (Dynamic Restraints) for pipe supporting for process industries
Co-Efficient of Friction for pipe supporting during Stress Analysis using Caesar II
Supporting of Dual Insulated Piping System
Purpose of Pipe Supports
Pipe Support Span for Aboveground Piping

Online Course on Pipe Support Engineering

If you want to learn more details about pipe support engineering then the following online course is a must for you:

Recorded Webinar on Expansion Joints in CAESAR II

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

Expansion Joints are one of the critical devices that piping stress engineers use in piping systems having less flexibility. But it becomes quite a headache to choose the right kind of expansion bellow and then model it exactly considering all real configurations. Whether to choose a tied one? or whether to consider the thrust force? Such questions always arise in our mind and most of the time remain unanswered simply because there are very little literature and description available for modeling and analysis of systems considering expansion joints.

So now we all have a chance to learn from the experts and clarify our doubts. Thanks to the Caesar II owner company, Hexagon PPM who has arranged a webinar on 25th February 2020 at 10:00 AM CST as per the below-mentioned details.

Expansion Joints in Caesar II
Expansion Joints in Caesar II

Webinar Details

Date and time: February 25th, 2020 at 10.00 AM CST (Please convert to your local time and mark it on the calendar else you may miss it)

Main Focus Points of the Webinar

This webinar will briefly throw light on the following points:

  • Various ways of expansion joint inclusion in the piping system.
  • Different types of expansion joint assemblies are available.
  • Selecting the appropriate expansion joint assembly.
  • Using the Caesar II Expansion Joint Modeler.
  • Zero-Length expansion joint.
  • Complex, Detailed Expansion bellow Model
  • Evaluating the joint

About the Presenter

David Diehl, P.E.: With more than 30 years of engineering and technical support experience is the Director of Training for CADWorx & Analysis Solutions – Hexagon PPM. He is the lead instructor for CAESAR II and the principal author of the CAESAR II online training course. He also served as a Director for the Society of Piping Engineers and Designers (SPED) for 16 years and currently, he is Chair of the B31.3 Process Piping Committee. 

How to Register

To register and view this webinar simply click here and submit your details to book your seat.

Few more Resources for you…

Design Considerations for a Piping System with an Expansion Bellow
Piping Stress Analysis using Caesar II
Piping Stress Analysis Basics
Piping Stress Analysis using Start-Prof