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Gasket Installation & FRP Flanges

Gasket Installation & FRP Flanges

mkkessel

(Materials)

(OP)

7 Sep 11 16:17

I am researching gasket installation on FRP piping and vessels and my search results have typically lead back to the vessel/piping or flange manufacturer. I'm curious if there's any empirical data on FG or FRP flanges that details maximum allowable stress? I've also been cautioned in vessel applications that the ability of the flange to accept stresses applied by sealing a joint are often secondary due to the relative strength of the neck coming from the vessel. If anyone has experience with written procedures on gasket installation in FG or FRP applications, it would be most helpful.  

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RE: Gasket Installation & FRP Flanges

StevenHPerry

(Mechanical)

8 Sep 11 13:34

With FG and FRP you aren't exactly dealing with high pressure situations.  Throw in a full face gasket, make sure you got washers under the nuts, tighten by the usual pattern (i.e. skip around, don't go in a circle), and give it a go.

I would err on the under-tightened side and tighten joints as necessary during a hydrotest to achieve a seal, assuming that cleaning up the water would be less of a pain than replacing a fractured flange.

Is it really absolutely critical that you have a written procedure and achieve a seal on the first try?

I'm not understanding the full problem here I suppose, but I'll venture an answer since no one else has.With FG and FRP you aren't exactly dealing with high pressure situations. Throw in a full face gasket, make sure you got washers under the nuts, tighten by the usual pattern (i.e. skip around, don't go in a circle), and give it a go.I would err on the under-tightened side and tighten joints as necessary during a hydrotest to achieve a seal, assuming that cleaning up the water would be less of a pain than replacing a fractured flange.Is it really absolutely critical that you have a written procedure and achieve a seal on the first try?

- Steve Perry
http://www.linkedin.com/in/stevenhperry
This post is designed to provide accurate and authoritative information in regard to the subject matter covered.  It is offered with the understanding that the author is not engaged in rendering engineering or other professional service.  If you need help, get help, and PAY FOR IT.

RE: Gasket Installation & FRP Flanges

MikeHalloran

(Mechanical)

8 Sep 11 14:51

My first choice for termination is a simple nipple, reinforced internally against crushing by a bonded stainless liner, joined to the remainder of the system by a silicone 'hump hose', with triple stainless hose clamps.

My second choice for termination, where flanged joints are required by a class society, are FRP/steel plate swivel flanges, and flanged rubber compensators.  The flange bolts are tightened just enough to stop leakage, and silicone or polyurethane sealant is often used on the flange faces to further minimize the torque required.

In both cases, the goal is to minimize the possibility of moment loads from pipe movement being transferred to the (relatively thin) FRP shell through the termination.  

 

I'm a little familiar with FRP marine mufflers.My first choice for termination is a simple nipple, reinforced internally against crushing by a bonded stainless liner, joined to the remainder of the system by a silicone 'hump hose', with triple stainless hose clamps.My second choice for termination, where flanged joints are required by a class society, are FRP/steel plate swivel flanges, and flanged rubber compensators. The flange bolts are tightened just enough to stop leakage, and silicone or polyurethane sealant is often used on the flange faces to further minimize the torque required.In both cases, the goal is to minimize the possibility of moment loads from pipe movement being transferred to the (relatively thin) FRP shell through the termination.

Mike Halloran
Pembroke Pines, FL, USA

RE: Gasket Installation & FRP Flanges

jdarco

(Chemical)

8 Sep 11 18:29

The piping/flange manufacturer should have installation procedures for their flanges, but Mr. Perry pretty much has it right.  Full face gaskets, typicslly a "softer" material (EPDM, Viton, Red Rubber), 1/8" or 1/4" thick, washers under the bolt/nuts (that is important).

Most piping/flange manufacturers will have a maximum bolt torque to acheive a seal.

RE: Gasket Installation & FRP Flanges

mkkessel

(Materials)

(OP)

9 Sep 11 20:15

Thanks for all. further research shows that ASME RTP-1 provides guidelines for material selection and installation. However manufacturers recommendations vary from this. None of the documentation I've found suggests the use of expanded PTFE, which is widely used in the field, although having much higher sealing stresses than the 60-70 durometer elastomers on the RTP-1 spec.

The purpose of this inquiry is/was to develop a series of guidelines for use of expanded PTFE in FRP and fiberglass flange applications. The physical properties and sealing characteristics of the material are well-known. Without some guidance on stress tolerances for FRP or FG flanges, the potential for catastrophic damage to vessels or systems is very real. So is the possibility of litigation resting with the gasket material manufacturer if this kind of failure occurs.
    

RE: Gasket Installation & FRP Flanges

StevenHPerry

(Mechanical)

9 Sep 11 21:10

Quote:

So is the possibility of litigation resting with the gasket material manufacturer if this kind of failure occurs.

Not likely.  You'll get the cost of the gasket back, but that's going to be close to the limit of liability from any reputable gasket manufacturer.

Just start easy and tighten only as necessary.

A major FGD OEM uses a combination of split steel backing rings and steel spacers as field remedies whenever they get stuck with with a lap joint or raised face flange mating to an FRP flange.  Keep the full face FRP flange from being sprung like a raised face.

Downgrading your bolts might be an option too.  Pick one that will yield before you crack a flange.  Perhaps A307-B instead of your normal A193s.

Not likely. You'll get the cost of the gasket back, but that's going to be close to the limit of liability from any reputable gasket manufacturer.Just start easy and tighten only as necessary.A major FGD OEM uses a combination of split steel backing rings and steel spacers as field remedies whenever they get stuck with with a lap joint or raised face flange mating to an FRP flange. Keep the full face FRP flange from being sprung like a raised face.Downgrading your bolts might be an option too. Pick one that will yield before you crack a flange. Perhaps A307-B instead of your normal A193s.

- Steve Perry
http://www.linkedin.com/in/stevenhperry
This post is designed to provide accurate and authoritative information in regard to the subject matter covered.  It is offered with the understanding that the author is not engaged in rendering engineering or other professional service.  If you need help, get help, and PAY FOR IT.

RE: Gasket Installation & FRP Flanges

Duwe6

(Industrial)

12 Sep 11 11:57

Sorry, but the flange stress introduced using an A307 Gr.B bolt and a standard washer will exceed the breaking stress of a typical FRP flange long before the bolt fails.

Please don't ask how I know this ugly fact.

RE: Gasket Installation & FRP Flanges

donf

(Chemical)

12 Sep 11 13:21

While I can't answer your specific question, here's something you should consider:

http://vsptechnologies.com/wp-content/uploads//04/vsp_opra_brochure_rev-6-.pdf

donf

mkkessel,While I can't answer your specific question, here's something you should consider:donf

RE: Gasket Installation & FRP Flanges

rconner

(Civil/Environmental)

12 Sep 11 23:51

Further to the astute revelation of Duwe6, in partial explanation flanges have been designed and applied most commonly in the last several decades in general with metallic materials that are much stiffer, less vicoelastic and stronger than the polymers/plastics (that have understandably exhibited relatively more problems).

The goal or guidance "tightened just enough to stop leakage", though certainly well-meaning, is however in itself neither specific nor measurable, and furthermore may be of questionable practical value in the real world or field environment.   

 

RE: Gasket Installation & FRP Flanges

Duwe6

(Industrial)

13 Sep 11 11:38

Most [all?] FRP manufacturers have recommended torque values.  They may be a bit low, but these values are guaranteed to not ruin your flange.  Read the torque carefully, as a lot of the values are inch-lbs, not ft-lbs.

RE: Gasket Installation & FRP Flanges

mkkessel

(Materials)

(OP)

13 Sep 11 12:03

Again thanks to all. Further research shows that ASME RTP-1 is most likely the prevailing document in this area. Two classes of FRP construction are considered. One has a maximum stress value of PSI and the other PSI. Torque recommendations do not exceed 40 ft/lbs. To a gasket material manufacturer these are extremely low figures.

Not only is the low available gasket load an issue with FRP/FG, but bolt stress, both initial and residual are called into question.

Given the limitations set up in RTP-1, gaskets must be highly conformable, and seat under extremely light bolt loads. It should also have excellent recovery characteristics, as residual tension in the fasteners is minimal. For materials other than low durometer elastomers, such as expanded PTFE, this has meant utilizing surface area reduction of the gasket itself to comply with the low load requirements.

90% of all gasket failure is related to things other than material selection. For purposes of making material recommendations, it is imperative to work backward from failure modes to do so. In this case design limitations and field installation practices are the driving forces to develop this recommendation.  

RE: Gasket Installation & FRP Flanges

StevenHPerry

(Mechanical)

13 Sep 11 13:36

Assembling low pressure flange joints doesn't even approach a scientific process in my mind.  The pipe is already fit, the welds (or equivalent) are already made.  I just send a bolting crew (foreman and a few helpers) out to drop in a gasket and tighten the bolts using a standard wrench.  Once they claim they're done, I may or may not ping a few bolts before turning the hydro crew loose.  If a joint leaks, the bolt crew gets to try again.

High pressure and/or critical joints are another story.

By some of the descriptions indicated here, I wonder if engineers are expecting skilled labor using torque wrenches, tensioners, etc to assemble

every

flanged joint to precisely the torque specified by an engineer.  Is this really the norm?

I suppose I need to recalibrate my way of thinking...Assembling low pressure flange joints doesn't even approach a scientific process in my mind. The pipe is already fit, the welds (or equivalent) are already made. I just send a bolting crew (foreman and a few helpers) out to drop in a gasket and tighten the bolts using a standard wrench. Once they claim they're done, I may or may not ping a few bolts before turning the hydro crew loose. If a joint leaks, the bolt crew gets to try again.High pressure and/or critical joints are another story.By some of the descriptions indicated here, I wonder if engineers are expecting skilled labor using torque wrenches, tensioners, etc to assembleflanged joint to precisely the torque specified by an engineer. Is this really the norm?

For more GRP flange connectionsinformation, please contact us. We will provide professional answers.

- Steve Perry
http://www.linkedin.com/in/stevenhperry
This post is designed to provide accurate and authoritative information in regard to the subject matter covered.  It is offered with the understanding that the author is not engaged in rendering engineering or other professional service.  If you need help, get help, and PAY FOR IT.

RE: Gasket Installation & FRP Flanges

Duwe6

(Industrial)

14 Sep 11 08:18

Torquing is the norm on FRP flanges, at least until the pipefitters develop a "feel" for the correct, very low torque.  Any pipefitter with a 12-inch crescent wrench can overtorque and destroy FRP flanges on lines up to 6"NPS.  I've seen the aftermath.

I agree that this is not the Design Engineer's problem, and that it belongs to the Field Engineer, the Pipe Supt., and Quality Control.  The problem is that our "Leaner, meaner, faster" management eliminated the QC guy, the Pipe Supt. is also filling in for at least one foreman, ahd Mr. Design Engineer is also expected to act as the Field Engineer.

Thus I highly recommend that the required torque values be prominently placed on the drawing(s) the pipefitters will be working to.  Mr. Engineer has the resources to easily research the recommended torques.  Mr. Pipefitter doesn't, and when he guesses, he guesses too high on FRP flanges.

 

RE: Gasket Installation & FRP Flanges

Hello000

(Materials)

16 Sep 11 06:25

Recently i have done project with FRP/RTR lines upto 36 inches with pressure ranges from 10 bar to 27 bar. You shall follow only FRP/RTR flange manufacturer procedure for bolt tightening. For each flange size, manufacturer provides Torque increment & final torque value. You can get this table from manufacturer. Gasket material & type shall also be as per flange manufacturer recommendation. You can refer to guidelines available on manufacturer sites. Some of the good manufacturer are Bondstrand / Ameron / Aminatit, Future Pipe etc.

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The Difference Between a Raised Face and Flat Face Flange

The difference between a raised face and a flat face flange is that the raised face has a raised area that surrounds the pipe bore and the flat face flange doesn&#;t. These are two of the most commonly used types of flange faces. They can both be sealed with one of two different types of gaskets, the ring type and the full-face gasket. This post will provide some details on the raised face flange, the flat face flange, and the two types of gaskets used with them.

Raised Face Flange

The raised face is the most common flange face type used. It&#;s called a raised face because it has a raised surface above the bolting circle where the gasket is placed. Sealing this type of flange face is accomplished by compressing a soft, flat, or semi-metallic gasket between mating flanges in the raised area of the flanges.

Raised face (RF) flanges are common in process plant applications but can be used in almost all applications. They are suitable for use in high and low temperatures and pressures. The purpose of the RF flange is to focus more pressure on the smaller gasket area, which increases the pressure containment capabilities of the joint.

Flanges are sized according to pressure ratings. The higher the pressure rating of the RF flange, the bigger the flange diameter, the number of bolts it requires, and the thicker both the flange itself and the raised face are.

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Flat Face Flange

Flat face (FF) flanges are similar to the RF flanges, but they do not have the raised area like the RF flange. Instead, the whole surface is flat. That means that the gasket used with the FF flange has full contact with the whole surface where two flanges are mated. The gaskets for FF flanges are typically made from non-metallic materials like Viton (a brand of fluoroelastomer) or EPDM (ethylene-propylene diene monomer); it&#;s uncommon for them to be metallic.

The purpose of the FF flange is to avoid the bending moment that is put on the flange as the bolts are torqued. Some flange materials can easily break at this time, such as cast iron and fiberglass. FF flanges eliminate this problem.

Generally speaking, flat face flanges are used in less arduous applications, like low-pressure water piping. They are commonly used in low temperature and pressure environments such as pump suctions or water treatment flanges.

At Commercial Filtration Supply, we carry a variety of simplex and duplex models that are constructed with flat face flange connections (found here and here). Contact us to learn more about how we can help you find exactly what you need.

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Gaskets to Seal Flanges

Sealing raised face or flat face flanges allows for two different types of gasket shape, the full-face and the ring-type. It&#;s important to know which type is best for your application and to understand the measurements you will need to know when you buy them.

Ring Type Gasket

The rig type gasket can be used for both the RF and FF flanges. It sits around the pipe bore and inside of the flange bolts, and in the RF flange, it is positioned on the raised surface. The ring type gasket is a drop-in gasket, which means it can be installed without taking apart the whole joint. It also requires less material and cutting than a full-face gasket, though it can be harder to clamp into position.

The measurements you need to know for ring type gaskets are the ID (the inside diameter or pipe bore size), the OD (the outside diameter), and the thickness of the gasket.

Full-Face Gasket

The full-face gasket is typically used with flat face flanges but can also be used with RF flanges. It sits on the raised flange faces but has the same outside diameter of the flange. For that reason, it has to have holes for the bolts securing the flanges to pass through. This makes aligning the gasket easier, but it does mean that the entire joint has to be taken apart for installation. The full-face gasket is better at stopping dirt from getting into the joint because it extends all the way out to the OD.

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How to Choose an RF or FF Flange

Choosing the right type of flange face is important, especially when the application is high pressure or temperature. In those situations, it&#;s best to use an RF flange, as they are designed to withstand more demanding environments. The FF flange is better for operations that are lower pressure and temperature and in systems where cast iron, fiberglass, or other materials that may break as the bolts are torqued are being used.

If you want to learn more, please visit our website FRP flange fittings.