Hydro testing a pipe with a welded flat plate connection 1

[Tricoach]

I'm trying to design a plate connection for a hydrotest of an 8" schedule 80 carbon steel pipe. This pipe will see flows with a pressure up to 900psi coming from a hydraulic cake pump. I do not ever expect the pipe to see pressures higher than 300psi though. However, for some reason, the owner wants me to test the pipe at 1500psi. Extreme I know.

My thought is to fillet weld a flat plate onto the pipe for the one time test.

I was planning to use a 9" x 9" x 1" plate and fillet weld the plate to the pipe.

I have been looking at various equations, but i've been out of school a bit, so i'm having some trouble finding exactly what I want.

How can I be sure that the weld will support the force from the hydrotest?

any suggestions.

thank you.

 

[11echo]

Don't use plate steel! Get a weld cap with the same pipe schedule and weld that on. It would take a standard pipe weld and you could weld a small diameter weld-o-let on the end of the cap for either a vent or a drain, to aid in your hydro-test..

 

[Tricoach]

I've talked with my distributors, and they have really long lead times on the caps I would need. They also are $$$$$$$.

So for time, and cost, I think i'm going to have to go with the plate steel.

 

[dcasto]

a sch 80 end cap is a stock item. Buy 2 A600 sch 80 RFWN flanges and weld one on the line, bolt in a properly sized skillet (use the B31.1 to calc the thickness of a skillet). Run the test Then send the un welded flange back.

 

[Canadieng]

or weld on a 'temporary' flange, perhaps a weldneck - and simply bolt on a blind flange.

 

[rneill]

8" Sch 80 Carbon steel caps should be an inexpensive stock item. All hydrotests I have seen have had caps or flanges welded on for testing purposes.

 

[11echo]

Let me get this straight, you’re putting in a 600# system and they are worried about the cost of afew weld caps!??

 

[jte]

Crud! I thought I'd jump on the bandwagon here... but it seems that a full pen weld to a 1" plate would work. Not sure by how much margin, and there will be some yielding at the inside corner, but good to 1600 psi with no design margin included.

But... a weld cap can't be that expensive. I haven't bought one in a while but maybe on the order of $100? And safe to use without having to hire an engineer to provide backup just in case something goes wrong. Keep in mind my commentary on the suitability of a 1" plate is worth every penny you paid for it if this should land in a courtroom!

jt

 

[Tricoach]

Well in reference to the cap idea. The major problem is the lead time. Apparently my rep needs to get it out of Texas, and it will be 12 weeks. Insane. keep in mind the pressure we are testing to is 1500psi.

However, I have a lead on one from Tenn. So maybe i'll get that. If not I think the plate and weld will work for sure. I've run the calcs a few times over.


thanks for the advice. this was the first time I have ever posted on this, I definitely did not expect to get so much feed back so fast.

 

[MJCronin]

What codes and standards are being used for the design of this piping system?

Is this yet another another piping system being designed using the "whatdoyathink" methodology ?

Test blinds, the required materials, thicknesses etc.. etc are all clearly defined in both ASME B31.1 and B31.3.

If the design pressure is 300 psig then the system test pressure should be 1.5X300 or 450 psig.

Its always a good idea to establish and refer to a set of rules.

With regard to the client's requirement of 1500 psig test pressure....... well... I have always strongly advocated drug testing of all clients in the initial stages of a project.

My opinion only

-MJC

 

[moltenmetal]

8" sch80 butt weld carbon steel pipe caps are a shelf stock item all over North America, and they're not all that expensive.

Don't weld on a piece of plate for that kind of test pressure!

 

[Tricoach]

Well the cake pump which will be supplying the pressure, was tested up to 950psi.

According to the owner the original lines were tested at 1700psi... which I do not believe at all.

so we got them down to accepting a test at 1500psi.

I am working on getting a cap though, so there is a chance it may be simple yet.


the drug test is hilarious by the way.

 

[Tricoach]

Well good news... Think I found a cap that will work, Should get it in by Monday.

 

[Tricoach]

Alright,

Found a bull cap i'm going to use today.

Going to put a weldlet on the cap. then weld the cap to a pipe extention. double groove the other side of the extension pipe, then attach it all to the vic fitting with the test line.

So i'll be able to hydrotest the pipe today after all.


thanks again gor the help.

this forum is great.

 

[rneill]

By the way, since you are testing so much over the design pressure, you would want to check that you are not exceeding 90% of yield stress for any of the components.

 

[Tricoach]

I have checked that, and it is good to go.

 

[vpl]

Tricoach ...

update? Did your test get run? Did everything survive?

Patricia Lougheed

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[Tricoach]

Yes, the test was successful. I ended up testing to 1375 psi, we deemed that good enough. Everything was approved, and the lines are in place and operational.

I didn't even have to duck for cover while it was testing either.