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Hydrostatic Test Pressure

08/05/2013 11:06 PM

Dear all,

I encountered there are two hydrostatic test pressure standard in our M&E field for cold water system, which as follows :

i) Hydrostatic test for 2 hours

ii) Hydrostatic test for 24 hours

Anyone can advise me what the suppose test pressure which differentiate these two test ?

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#1

Re: Hydrostatic Test Pressure

08/05/2013 11:30 PM

Yes.

Maybe it's not pressure.

One is a two hour test. The other is a 24 hour test.

I don't have a clue myself.

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#2

Re: Hydrostatic Test Pressure

08/05/2013 11:43 PM

The test pressure for (i) is probably higher than for (ii), but we don't have access to your standard and thus cannot read the whole thing for ourselves.

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#3

Re: Hydrostatic Test Pressure

08/05/2013 11:57 PM

Actually we don't have a clear standard. Everyone saying different test pressure. This make me feel that I need to know whether there is a standard practice for all these requirements.

Please advise.

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#4
In reply to #3

Re: Hydrostatic Test Pressure

08/06/2013 12:06 AM

I doubt very highly that there is any widespread standard for this. Indeed, it is the first time I have heard of such a thing on a mere cold water system.

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#5

Re: Hydrostatic Test Pressure

08/06/2013 1:37 AM

Just to get that straight even so it was mentioned before.

Test pressure has to be given in a pressure unit as in [bar], [psi], [atm] or whatever.

All you have is a TIME over which has to be pressure tested which will not tell you the least bit what pressure has to be applied.

A test over 24 hours is as good as a 2 hours test if you can wait that long. So unless you have better arguments the standard should be 24 hours.

What is the working pressure of the system?

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#7
In reply to #5

Re: Hydrostatic Test Pressure

08/06/2013 3:30 AM

The working pressure differ for different height of buildings or external water transfer system. Here, just general discussion.

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#6

Re: Hydrostatic Test Pressure

08/06/2013 2:59 AM

Here, the local council requires a static pressure test of the house plumbing (except the water heater itself) for 24 hours.

Filled with water and loaded at around 8 atm pressure and requires less than a certain drop in that time. (The drop allows for thermal changes in pipe diameter and maybe some pressure relaxation in seals but definately no leaks.

The use of a 2 hour test might be a preliminary done by the plumber before requesting the "observed" test by the council or regulating authority.

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#8

Re: Hydrostatic Test Pressure

08/06/2013 3:39 AM

Actually I am doubt because in NFPA, the standard only called for 200 psi or (150% design pressure + 50 psi) whichever is higher for a 2 hours test.

But in cold water system in our area, most of the application are having pressure much more less than the pressurized fire protection system. There must a reason the 2 hours test is accepted worldwide but not 24 hours. So, why must we have 24 hours test ?

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#9
In reply to #8

Re: Hydrostatic Test Pressure

08/06/2013 3:54 AM

How would any of us know? Please ask whoever is requiring your test(s).

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#11
In reply to #8

Re: Hydrostatic Test Pressure

08/06/2013 5:18 AM

M&E field, NFPA its all a bit cryptic.

maybe you should give us all the information that you have.

Is your cold water system for a high rise building? if teh water pressure varies is this because of the height of the building? What is the building code?

I would accept a 24 hours test when only 2 hours was required, but I would not do it the other way around. Is there something you want to share of your information so we can answer your general question?

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#15
In reply to #11

Re: Hydrostatic Test Pressure

08/06/2013 7:54 PM

Actually, our building code does not have clear definition on this. So every consultant might have their own requirement (sometimes) on the test pressure and duration.

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#13
In reply to #8

Re: Hydrostatic Test Pressure

08/06/2013 5:57 PM

What will you "cold water system" be used for?

The testing requirements for a hose bib used for watering a plant will be different than for a fire sprinkler system protecting a nuclear power plant.

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#14
In reply to #13

Re: Hydrostatic Test Pressure

08/06/2013 7:49 PM

Our cold water system is for buildings like banglo, high rise etc. Mainly plumbing works.

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#10

Re: Hydrostatic Test Pressure

08/06/2013 5:15 AM

Hydrostatic pressure test is carried out for two reason A) To check the status of material, like any leakage/any cracks or any defect in the material B) Or to acertain the further life of material. Reason of 24hrs. to check the state of material at day and night varying tempratures and the changes occur due to change in temp. weather that material is able to hold stresses under changing temp. /pressures at that particular test pressure. Further I have no idea but it may be decided on the past experiences that failure of material/system will occur within 24hrs. due to stress if material is weak otherwise it will withstand

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#12

Re: Hydrostatic Test Pressure

08/06/2013 4:45 PM

The 2 hour test is too short in duration to show evidence of minor leaks. Leaks which would cause damage over time. 24 hours allow time for the piping to show evidence of even small leaks. Leaks that may not even cause damage in a enclosed wall. That may provide moisture for bacteria to grow.

There is also some added stress to the pipe. Fractures may occur that may not show evidence of a leak in 2 hours. With the 24 hour test it gives the stress fracture time to grow and show up as a leak.

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#16

Re: Hydrostatic Test Pressure

08/06/2013 11:17 PM

2 hrs for pipework (normally 30 mins for ANSI B31.3)

24 hours for any open tanks in the system.

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#17

Re: Hydrostatic Test Pressure

08/13/2013 6:03 PM

2 hour will give you the rated test pressure.

24 hour test will indicate whether there were any small leaks in the test vessel, separation of stay-bolts, deformation of walls, marginally weak welds, etc.

Which one to use? depends what you want to test for.

Good Luck, Old Salt

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