Hydrostatic Test Pipe Laydown Procedure 1

[Yash23]

Hi everyone!

I'm from piping design section and I'm currently doing a hydrotest diagram. My problem is that I dont really have any site experience for me to be very confident in providing test limits. I do know know that common test limits are where there is material and class break. In some cases where control valves are to be removed from the line for hydrotesting, some guys with site experience says that they usually provide removable spool at that area, they also said that they usually combine a couple of test limits into 1 hydrotest package.

My question here actually is how do they do it on site. Do they erect the piping comlpetely first as per design or they do hydrotest once a certain test limit has been completed? How do they do it in pipes running long through piperack? In cases where control valves, are to be removed from line, which is the better option to provide removable spool or use a blind flange and separate the line into two test sections?

Thanks!

 

[SnTMan]

Might try the Piping Forum forum378

Regards,

Mike

 

[weldstan]

First, the test limits are indicated on marked up P&IDs and if needed the piping isos are included in the test package to further define the boundaries.
The equipment (control valves/pumps, etc.) to be removed from the test due to potential damage are defined by Engineering or the Owner.
Dummy spools may be used in place of equipment or pipe blinds can be used to isolate equipment. Flanged joints are recommended for equipment that will be removed.
Valves are often left in place or the pipe system is tested up to the valve(s) in the closed position.

 

[Yash23]

Hi Weldstan!

Thanks for the reply, I understand what your saying but I didnt really get the answer I needed in terms of how do they do it in site?

SntMan,
This is actually my first post and I might have been posted it in the wrong section, can this thread be moved?

 

[weldstan]

That's how we do it during construction at the site.

 

[RossABQ]

In my experience, they test as much at once as possible, in the final erected position. You want to do it only after all attachments for gauges, supports, drains, etc, have been completed (where welding is involved). Usually there is a 3rd party inspector involved and there is a cost to getting him out to witness the tests. He may be from the underwriter, the state/city/county, or an owner's representative.

 

[Duwe6]

What RossABQ said. Further, it is usual to test thru in-line valves; hydro spool-pieces are a pain. Thus there will be some backing leakage at these valves. DO NOT allow the fitters to adjust that packing for hydro pressures; if they do, the valve will be almost impossible to operate, and over half of the packing's useful life will be gone. Let 'em weep, keep the water off the welds, and make sure you have enough pump volume to keep up with these weeps & seeps. Big system hydro's are indeed the way to go, saves overall time. But the actual day that you hydro an entire system tends to get 'interesting' -- like when we did the entire Main Steam system throughout the turbine building and on over to the Stop Valves going into the reactor at St. Lucie #2. Running backwards into the Stop Valves, plus incidental valve packing, there was a combined leakage of almost 300 gpm.