Duct taping spiral wound gasket 6

[henderrj]

I have a client who is covering the seeling surfaces of spiral wound gaskets, as well as the sealing surfaces of flange faces, with duct tape.

He recently switched from paper gaskets to spiral wound. Once he did, his customers started complaining, due to the flange faces having scratches, so he began wrapping them in duct tape to alleviate the scratching. (I think he is compressing the gaskets all the way on their first use, which would cause the circular scratch marks).

I understand that this is incorrect, and a safety concern. I've been trying to find articles about accidents due to this issue, but haven't had any luck. Have any of you seen anyone do this in the past, or have a good story to tell about it?

 

[pennpiper]

Henderrj
Go ask the experts:

http://flexitallic.com/

Sometimes its possible to do all the right things and still get bad results

 

[jte]

Might as well save a few dollars and cut out some cardboard gaskets and wrap those with duct tape.

Seriously, if coining the flange face is a concern (or is it really scratching?), then he's over tightening the crud out of the flanges. Use less torque and see if he gets a better seal (without the tape).

Or, he could try one of the other experts' products such as a CMG type like this one which is less likely to coin the sealing surfaces. But even with these, try a lower preload.

 

[georgeverghese]

Are these flanges flat face or raised face? I've seen spiral wound gaskets being used only on RF flanges and not on FF flanges.

 

[henderrj]

RF flanges. He said he had a leak with paper gaskets, and would never use them again. I told him that taping the spiral wounds was much less safe than using paper correctly.

I think he's probably bottoming out the spiral wounds on the first use, which would take a lot of torque. I'm pretty confident that that's the real issue causing the damage. The damage issue aside, i'm looking for something to help him understand that the duct tape is interfering with the proper design and use of a spiral wound.

I've looked on Flexitallic's website, i didn't see anything regarding this particular issue

 

[miningman]

Tell the client to watch the Red Green show, and then imagine how he is going to respond to questioning at a coroner's inquest.

 

[DSB123]

He would not have a leg to stand on in an inquiry after a fatal accident due to this heath-robinson approach to flange sealing

 

[LittleInch]

Well I agree it sounds rather odd, but we need a few more facts here before going off the deep end.

We don't know:

Fluid contents
Flange sizes
Flange rating
Flange material
Max operating pressure
Any issues with leakage

Some strange items for me - What fluids can be contained using "paper gaskets". That's not a term I'm used to
"his customers started complaining, due to the flange faces having scratches" - What is the flange material? Alumininium? Plastic? I don't know many steel flanges which would get scratched by a gasket.

Why this apparent make and break - "on their first use" - implies re-use of gaskets which is not normally recommended (though I recognise it is commonplace).

Ultimately, as long as the gasket seals then it is doing it's job. Using duct tape is not a great idea, but in B 16.5 all it says is
"The user is responsible for selection of gasket materials that will withstand the expected bolt loading without injurious crushing and that are suitable for the service conditions"

We don't have that information, only guesswork.


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[pennpiper]

"Looked at Flexitallic's website, and didn't see anything regarding this particular issue"
You missed it! It's called "Contact Information" Call or Email their Technical Support for help.

Sometimes its possible to do all the right things and still get bad results

 

[TenPenny]

I don't even understand the point of a paper gasket. What application would call for paper gaskets?

 

[JJPellin]

In two places, you used the phrase "on the first use." We would not consider a spiral wound gasket to be reusable. They would be compressed one time. If the flange was opened up for any reason, the gasket would be replaced with a new one. If they want to repeatedly reuse gaskets, I would expect them to have leakage problems. I don't understand the term scratching. The flange faces normally have a phonograph finish, which is desirable. How do you see circular scratches on a phonograph finish? We regularly use "paper" gaskets in raised face flanges. This is common on fabricated skids such as lube oil skids for large compressor trains. We would prefer to convert these to spiral wound gaskets. But, in many cases, the piping was custom bent with the flat gaskets and would have to be modified to make room for the thicker spiral wound gaskets.

In any case, I would never allow anyone to wrap a gasket in duct tape. I have wrapped spiral wound head gaskets on certain pumps with Teflon tape to solve chronic leakage. But, never on a pipe flange.


Johnny Pellin

 

[henderrj]

Fluid contents,flange sizing, rating, material, max operating pressure, and issues with leakage aren't really applicable to the discussion, but these were water, 2-6", 150-300#, SA-105, 900PSI, no leakage (off the top of my head, its been a few weeks).

Paper gaskets are compressed and treated paper, like a really hard cardboard. To my knowledge, theyre only used for lower pressures. They're a cheaper alternative, but noone really uses them.

In my background (Navy) spiral wound gaskets were reused. Basically, they were inspected to ensure X amount of graphite was still visible above the metal ring on both sides, and that there were no visible signs of damage. Once the gaskets failed that inspection, they were replaced. Granted, that may have been tribal knowledge. Now that I think about it, I don't remember seeing a procedure for that.

These particular gaskets are being used for hydrostatic testing on ASME pressure vessels, so B16.5 doesn't really apply. The B16.5 piping is installed on location, after the test, by the client's customer (usually), when my involvment in the job has ended. That's why I'm asking for personal experiences and information from the manufacturer, instead of B16.5 information.

By "scratches" i mean that the metal on the flange face has been indented, by some method. These particular "scratches" have a depth less than the depth of the phonographic grooves, but deeper than the surface of the flange. Phonographic grooves, by design, are not perfectly concentric, and neither are the "scratches", so the "scratches" are visible. I think the flange is being over-torqued to the point that the outer metal ring on the spiral wound is being compressed into the flange face material, causing the "scratches".

The point im trying to drive home to the client is that spiral wound gaskets are designed to be used without duct tape, and the duct tape is detrimental to their safe use. With the tape present, the graphite will not be able to fully compress into the phonographic grooves, meaning that the duct tape is the only blockage in the path of the leak. The spiral wound is rated, by design, to withold certain pressures. With the duct tape, i have no idea what pressures it can safely contain.

 

[NBrink]

I'd have him check out blue garlock for hydrotests (or whatever equivalent rubber bound fiber gaskets they can find)

As far as the duct tape, if they're doing this on austenitic stainless steel vessels, I've seen chloride cracking caused by adhesive from duct tape. If I bought a vessel and had a nozzle crack in service because a fabricator had put duct tape on the flanges, I'd be all sorts of upset.

Can't really think of a way to quantify the effect of duct tape on a spiral wound though. Just a bad idea in general it seems...

Nathan Brink

 

[henderrj]

I havent heard of blue garloc before, ill let him know.

I didnt think about austenitic, but thats a very good point. Almost all jobs here are carbon steel, but every once in awhile somebody wants different material.

I think the lack of responses about actual real-world experiences with the duct tape speaks volumes. Noone ive asked in person has ever seen anyone try it either. Maybe that will be enough to sway him.

Thank you all for your replies, i appreciate your time.

 

[DSB123]

duct tape on a spiral wound gasket could prevent the spiral windings from working properly. Uner bolt loading the spiral "V" of the winding closes up and having a tape stuck to the outer edge could affect this. Duct tape on any flange face/gasket is incorrect and I would reject the flanged joint every time!!

 

[LittleInch]

henderrj,

FYI, the flanges on an ASME VIII pressure vessel are almost certainly ASME B 16.5 flanges. B16.5 is a flange specification, not a piping spec hence "B 16.5 piping" is incorrect.

Still don't know what you mean by "scratches" as they sound completely insignificant if the depth is less than the grooves.

Ultimately the gasket won't fail because of the tape, but might leak a bit and could encourage over tightening of bolts, but it sounds like you have that problem any way.

As this is for hydrotesting, not sure why they're using spiral wound.

Get him to solve the root cause issue - these scratches - and then the issue goes away.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[moltenmetal]

Spiral wound gaskets can be and are re-used numerous times, unless they have become damaged due to excessive or uneven compression or have come unspooled. Whether or not you want to take that risk depends on the hazards of the service and the ease with which a gasket can be replaced.

When testing vessels, we hydrotest with the type of gasket specified by the client in any large flanges, to ensure that there are no leaks at flange faces. We rarely do large piping (beyond 12") so we aren't as fussy when hydrotesting pipe.

We've never noticed spiral wound gaskets causing damage to flange faces. Quite the opposite- we find that they sometimes seal flanges that leak with other kinds of gaskets (i.e. sheet grafoil).

Corrugated metal gaskets are an alternative, up to 300# class (these usually can't be re-used but offer no risk of marring your flanges), as are fibre composition gaskets like Garlock BlueGard (for low temperautre services only). Composition gaskets are not blow-out proof, but that won't likely be a problem if you're using them for hydrotesting.

 

[bimr]

Spiral wound gaskets are manufactured according to ASME B16.20 standards. Use of the duct tape is a violation of the standard.

Use of duct tape will reduce the friction between the gasket and flange and may result in leaks.

http://europeansealing.com/uploads/...-FSA-Guidelines-Flange-Gaskets-009_98_ENG.pdf

"Spiral-wound designs have layers of V-shaped metal and gasket material wound to create a gasket. They also have a centering ring on either the inside diameter or outside diameter of the gasket, or both. Under load, the V-shaped metal in the spiral compresses, sealing the process.

Maintenance procedures must account for the gasket types in use. Because the flange load permanently compresses the metal in the gasket, a second use often leads to process leaks. Treat spiral-wound gaskets as single-use items; procedures to prevent reuse must be in place."

http://www.chemicalprocessing.com/articles/2004/111/

One would doubt that any gasket manufacturer will state that gaskets may be reused.

http://www.garlock.com/en/technical-information/frequently-asked-questions/faq-reuseofgaskets/

 

[donf]

I agree with not using duct tape as part of the sealing mechanism. I've also seen situations where the high chlorides present in the adhesive of certain types of tapes can cause problems. In one case, electric heat tape was secured to stainless steel piping. The combination of heat, tensile forces and the chlorides in the tape resulted in leaks everywhere tape was used.

There are a number of gasket designs/materials options other than "paper" (compressed fiber) and spiral wound. Get the advice of a reputable gasket supplier and remember that the gasket is but one part of the assembly. Be sure you're using the right fasteners and assembly procedure.

donf

 

[MessyJessy]

It sounds like your client does not know what they're doing, so you need to tell them what to do.

1. Tell them not to cover the sealing surfaces (raised face) or the gasket with duct tape.

2. Ask them what the hell they're torqueing the flange to. The flange face should not be getting damaged, yet it is. Which seems to indicate over-torqueing as others have said. Are they torqueing to dry torque values but using thread lubricant?

3. On the subject of re-using gaskets.... Although gaskets can be re-used, it is best practice to use a gasket only once. (Gaskets are cheap, accidents and incidents and shutdowns are not.)

If this is a shop job where all they're doing is pressure testing a vessel or pipe spool and then sending it out, I can see it being acceptable to re-use gaskets for low pressure tests. As long as those gaskets stay in the shop.

For high pressure tests or permanent installation in the plant, they should use new gaskets.