How is a Field Hydrostatic Test Performed? 2

[AWDMIKE]

Aside from identifying a fill, drain, and vent point for any vessel (horizontal or vertical), how is a field hydrostatic test (or field hydrotest for search engines) performed in terms of how the water is filled?

Some of the questions I have are a bit scattered, but not having been part of a field hydrostatic test in my career I'm not sure of any of the specifics. Any help would be appreciated.

Is the water taken from a fire system?

Is the water typically treated before it's used inside equipment or piping? I understand the limits on chlorides and why that's important.

What size lines are typically available in plants/refineries for water? For reference I know that most domestic water supply lines are 3/4" but the branch lines may be 1/2". I can't imagine anyone would sit around while a 1/2" or even 5/8" system under 40-80 psig was used to fill a large vessel, but I could be wrong.

I suppose if the vessel is small enough, treated water could be brought via truck, is this ever done?

Are the fill points usually at some midpoint / midelevation of the vessel?

Are the fill points usually something like a coupling welded to a blind flange, which is then bolted to an available nozzle flange?

I'm assuming as many of the process nozzles are blinded so as to prevent water getting to places where you don't want it to go, but I suppose you could test some of the attached piping assuming the test pressure in the piping was acceptable.

Thanks for any help anyone can offer. I went looking for a field hydrostatic test procedure (only for my edification, not for actual use) but haven't found one yet.

 

[MFJewell]

A lot of what you do will depend on the facility requirements and will be unique to the application. For example, I used to work at a nuke plant, and we could not use fire service water for anything other than fire service. In the fossil power gen side, it was used for almost everything but fire service.

My experience has been to either use raw water if it is clean enough (usually from local municipality, well water, or clarified river/lake water) or use treated water if required and the site has a large treated water storage tank to supply it. Any connecting piping to the vessel that is not desired to be filled is valved out. Fill point will typically be an existing water line and my experience is that they usually come in at the top.

I am currently doing a project that is similar to building field fabricated, open top tanks (we are relining sumps with 316L SS). I plan to hydrotest using the normal make up water line (6") that can be fed from either the city or from one of our wells. The makeup lines comes in at the top of the sumps.

 

[LittleInch]

AWD MIKE

An awful ot of your questions are in the realms of "it depends".

It depends on the quality and availability of water, the internals of the vessel you're testing, the water disposal issues, if any, what the isolation available is, is the vessel new, repaired, annual test?

So here goes:
Is the water taken from a fire system?
Can be if there's no other option. Some refineries etc don't mind, others act like you've asked them to sacrifice their first born

Is the water typically treated before it's used inside equipment or piping? I understand the limits on chlorides and why that's important.
Typically no unless there is a good reason. Beware of MIC corrosion in hot climates and if water gets left inside for anything more than a couple of days

What size lines are typically available in plants/refineries for water? For reference I know that most domestic water supply lines are 3/4" but the branch lines may be 1/2". I can't imagine anyone would sit around while a 1/2" or even 5/8" system under 40-80 psig was used to fill a large vessel, but I could be wrong.
No that's an issue alright - 4" or 6" mains are usually available, but that's sometimes why you try and use the FW ring main.

I suppose if the vessel is small enough, treated water could be brought via truck, is this ever done?
Yes, many a time, especially if you're using De-min water or treated water. Also as you will be filling from a pump this can reduce the time a lot

Are the fill points usually at some midpoint / midelevation of the vessel?
I would normally go for the lowest possible location. Reduces splashing and foaming and just drives the air out from the top and fills evenly.

Are the fill points usually something like a coupling welded to a blind flange, which is then bolted to an available nozzle flange?
Correct, usually with a valve in between so it doesn't all pour out when you disconnect the hose....

I'm assuming as many of the process nozzles are blinded so as to prevent water getting to places where you don't want it to go, but I suppose you could test some of the attached piping assuming the test pressure in the piping was acceptable.

Yes, but then you need to drain it and the pipework needs to be able to vent to get the air out. Not normally a good idea and vessels often come with spectacle blinds and similar to positively isolate the vessel for inspection and testing.


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