ARE THERE GUIDELINES ON HAMMER PEENING FOR LEAK MITIGATION PURPOSES? 5

[Bambie]

At my plant, peening is used to temporarily stop leaks on pressurized metal items.

This includes the following applications:

- closing through-wall cracks & pinholes on pipes
- closing gaps between mating pipe flanges or body/bonnet flanges on valves
- sealing interface gaps between tongue and channel clamps and flanges, and
- closing perimeter seals on bolted sealant injected enclosures.

There is plenty of information on water, laser, UT and shot peening for fatigue enhancement or forming purposes out there, but very little on pneumatic/chisel/hammer peening on pressurized items.

Leak Stopping Service providers that I have approached appear to consider this practice to be a trade secret.

Has anyone encountered guidelines (besides EPRI NP-6523-D) with specific constraints for extent of peening based on materials and applications with a focus on worker safety?

 

[Ron]

The reason you probably can't find any authoritative treatise on the process is that it is not a good practice. It only provides a temporary repair and could be dangerous to the worker doing it if on a pressure vessel or steam.

 

[TugboatEng]

Is this service corrosive at all? Peening a pipe is a recipe for disaster if the leakage is caused by corrosion. You'll punch a hole in it.

If the service temp is low, you can use Loctite 290 to seal cracks, porosity, and pinholes. The equipment would require removal from service.

 

[arunmrao]

Leak Stopping Service providers that I have approached appear to consider this practice to be a trade secret.

Do not be misled by such unscientific claims. Stitch welding for cast iron engine cylinder heads, etc is similarly claimed.

I remember approaching them for swing head of molding machine. They promised the heaven but after fixing it,on the first operation, it cracked.

 

Sounds like one of the reasons we invented codes for building tanks early in the last century.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[TugboatEng]

I can see where someone could mistake a caulking or fullering operating for peening.

 

[Bambie]

Hello,

My apologies for not checking for responses...I didn't expect any.

By the sounds of it, nobody has applied ASME PCC-2 article 202 for weld overlay repair on pressurized systems that approves peening for temporary relief from leaks.

In Ontario, Canada the Ontario Health and Safety Act (OHSA) allows online pressure boundary work such as hot tapping if it is done by experts with specialized training.

Peening is not excluded from these practices and seals very effectively when installing temporary enclosures and clamps over leaking flanges, fittings and pipe.

 

[LittleInch]

Errrr, PCC-2, item 202-4.2.3 states only that you can peen to close off leakage BEFORE then adding weld material to the outside, OR add weld material, peen the gap then add MORE welding. Even this sort of repair is seen in most locations as a VERY short term stop gap before a more comprehensive repair or replacement.

This is not the same as just peening it to close the hole up.

The text is

202-4.2.3 Leakage Repair. All leakage shall be
repaired prior to performing the weld buildup repair.
If sufficient material is available, peening may be used
to close off the leakage and permit seal welding.
Another option is application of a series of overlapping
weld beads immediately adjacent to the leakage. Once
sufficient material is available, peen to close off the
leakage and perform final seal welding

I can only imagine the ontario HSA is based on the same principle. The lack of something being EXCLUDED does not mean that is in INCLUDED. Codes and standards don't normally work that way. There are too many dodgy practices to go round excluding all things - they say this is the way to do it and if you follow it then you have a high chance of doing it safely.

Peeing on its own is not considered a safe or reliable method of stopping leaks.

It's not a "trade secret", it's a dirty secret that some people manage to get away with just long enough to present someone with the invoice and get paid before it leaks again twice as badly.

You should never use it to seal the outside surfaces of a flange as mentioned above.

SO in summary to your question, IMHO, the answer is Yes there are - Don't do it!

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

 

[WKTaylor]

In aerospace, raw castings must be proof pressure tested before peening and/or resin sealing

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[Bambie]

Littleinch,

Which would you say has more pucker power: surface peening or seal welding on thinned pressure retaining material per PCC-2?

 

[LittleInch]

Well as noted above, peening is not an acceptable method of sealing, so seal welding will be needed at some stage, or an external wrap or sleeve or even patch ( a bit old school), but all welded.

These should all be time limited before replacement of the thinned material. IMHO.

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

 

In Ontario, Canada the Ontario Health and Safety Act (OHSA) allows online pressure boundary work such as hot tapping if it is done by experts with specialized training.

Also in Ontario you will need the TSSA to sign off on any temporary disposition of a condition in pressure equipment that does not meet Code. I would not even ask them about peening as a leak repair method.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[0707]

Bambie

As a transitory repair in a safe unpressurized service such as water air or other similar, you can do that, but just as transitory, I do not know of any regulation which accepts that.

luis

 

[Bambie]

I find it odd that most of these responses assume that the use of peening as I have explained it is either illegal or unsafe.

Is it EngTips Forum member policy to berate and malign specialized, non-standard repair methods that are very effective and can be safely applied when the only alternatives are continued production at risk to employees or shutting down production?

LittleInch

By "pucker power" I mean which do you think presents more risk to the worker (causing the bigger pucker).

I would go with seal welding. Localized plastic deformation resulting in the chisel tip punching through would not be as exciting as localized burn-through, vapour formation and molten metal spit back.

 

[0707]

be careful Bambie

luis

 

[WKTaylor]

Bambie…

I find it odd that most of these responses assume that the use of peening as I have explained it is either illegal or unsafe.

Is it EngTips Forum member policy to berate and malign specialized, non-standard repair methods that are very effective and can be safely applied when the only alternatives are continued production at risk to employees or shutting down production?

You have cited a highly non-standard/uncommon/extraordinary 'temporary' repair practice You want E-T engineers to 'bless'... especially [what sounds like] 1-off temp repairs. Would You dare to proof-pressure test these repairs?

You should NEVER get 'lip-service' in any E-T forum with experienced engineers... only honest discussion of safe/sound/proven technical practices, that err for caution/safety... per well-established regulations.

The kind of 'temporary' repair You described is akin to a high-risk battle damage repair for one extra/critical do-or-die combat mission.

War Story as to how critical this can be...
The nephew of a friend of mine was killed in a powerplant accident many years ago. A small group of guys was walking past high pressure steam piping that had not been internally inspected in several years... as per regulations [shut-downs cost money]... when an internally corroded elbow catastrophically failed and shrapnel sprayed the guys... wrong-place... wrong-time... doing their jobs... unaware of any danger. My friend's nephew took a saucer-sized piece of shrapnel to his upper back/shoulders... never knew what hit him. The others lived but all are permanently disabled [shrapnel and steam-burns].

In aviation service engineering I have learned this lesson the hard-way...

"There is nothing more permanent than a temporary fix.” --Russian proverb

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[Bambie]

The one thing this forum has not provided is a 'discussion', just lectures and sad stories.

 

[LittleInch]

I notice you have some previous on peening -

https://www.eng-tips.com/viewthread.cfm?qid=319665

I really don't know why you find it odd that most of us really don't think this is either
a) a good idea or
b) allowed in the codes, standards and rules invented to keep us all as safe as reasonably possible.

To call this a "specialised non standard repair" is pushing it, IMHO.

And that's the essence of Eng-Tips - it is peoples honestly held opinions, based on many decades of experience.

Leaks in plants should not be regarded as "commonplace" where sub standard "repair" techniques are apparently not only allowed but venerated.

This is called normalising failure and I sincerely hope you don't finally manage not to dodge the various bullets which seem to be passing you and your colleagues by.

More pucker power would appear to be working somewhere which permits these sorts of practices.

It took 18 years for the dam to fail in MI recently from initial warnings with action which was ignored by the company, in the most part because they didn't have enough revenue from the power generation to fix the dam and wouldn't shut it down ( drain it) to allow repairs to be made. That should not be a valid excuse.

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

 

The question I never stop asking myself when writing failure analysis reports or weld repair instructions or recommendations in general, all of which normally involve safety to people and/or equipment is:

"Is this statement/conclusion/recommendation supportable by the evidence, by applicable codes, by industry best practices, and is it lawyer-proof?"

It's never unsafe until it is unsafe. I'm not sure what you were expecting from E-T experts but LittleInch has summed it up nicely, and by now you have your answer.

Cheers

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[LittleInch]

Reading this again it looks to me like you're trying all the time to do repairs whilst not stopping operations / de-pressurising or draining down as you "can't stop the process / operation".

This is a falsehood.

Like the dam example, eventually it will all catch up with you and you or your fellow workers have a much higher risk or serious injury or death. You can't keep dodging bullets and not eventually catch one. If the company attitude is production at all costs, then you might find yourself paying the price. The company sure as hell won't.

You might see this as being berated or lectured to, but I've not often seen such poor practice misrepresented as acceptable behaviour in quite some time and for this to be occurring in Ontario is really quite surprising. IMHO.

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