PDA

View Full Version : Pressure Strength Test Duration.







thenewts
07-04-2009, 08:50 PM
Hi all. Regarding a Pressure Strength Test (European Standard, EN 378.) I was wondering what the 'norm' was for how long this should last. I've heard so much conflicting information from severeal hours to a few seconds seconds.

Colin G
07-04-2009, 09:56 PM
In the past i have done either a 15min or in some larger jobs a 30 min test. But for health and safety issues the area usually has to be evacuated for the time of test.

I think it primarily depends on what is stipulated from company's such as zurich.

laf100
07-04-2009, 10:49 PM
As far as I am aware, there is not a stipulated duration, the test is supposed to last for a duration that one feels is suitable for the sytem uder test.

The company I work for have chosen to recommend 15 mins as a min', and 30 mins as a maximum, in theory a total failure (rupture) of a joint/component will occur as soon as it is exposed to the force strength test pressure, and IMHO leaving the system at this pressure for too long could weaken a perfectly good joint/component, and lead to a future leak.
:cool:

Argus
08-04-2009, 09:36 AM
.

There is no easy answer.

What are you pressure testing? Pipe? Vessels? Accessories? It all depends on the equipment in question and there is a logical approach to doing the tests.


Here is a very basic outline - you need to work it out for yourself or seek expert advice.

But first, find out if the product is covered by the directive - if it is read it. If it is a manufactured product, the manufacturer should tell you what category it is in and what modules were used to test it in the factory.

EN 378 (mainly part 2) stipulates the method of obtaining PS and applying it.

In fact parts of it is a harmonised standard (I.E. mandatory) to the EU Pressure Equipment Directive (PED) which is EU law and a CE marking requirement if you are a manufacturer.

The exact methodology is in the requirements of the Directive itself and the guidelines that have been established to apply it for different types of equipment. You use the standard and guidelines to work out which test modules you need to adopt.

Most 'normal ' sized copper piping used at site is below the DN (diameter) limit, but you need to know the category of the products it connects to and the type of connection.

Sorry it sounds difficult and complex - it's meant to be.

The best approach with anything like this is to survey the kit in question, work out what you have to do, then write a detailed method statement that you can use to demonstrate how you did the work. Keep it for any documentation that you provide to sign off your work.

Here's the official EU site with all the official information that you need.

http://ec.europa.eu/enterprise/pressure_equipment/ped/index_en.html


.

thenewts
08-04-2009, 01:30 PM
Many thanks for the information. Just for the record I am testing a short (5 metres) A/C pipe run. 3/4" Suction 1/2" liquid. Pipework test only using 2 mechanical joints (flared unions).

I usually strength test my A/C installs for 30 seconds and then drop the pressure down to the leak test pressure for 24 hours.

I was just interested to find out if there were any definitive guidelines as to the duration of the strength test as I was told by a college tutor it should only be for a few seconds.

I appreciate Argus' point that there is no easy answer. I did read through the manufacturers supplied documentation and there was no specific mention of duration. As Laf says as long as I the engineer can make that judgement and be able to back it up with sound reasoning I think that is good enough.

Afterall - if the manufacturer, client and contractor can't supply me with an answer, who's to say I am wrong.

And like Colin mentions, I do clear the test area :0)

Thanks again - newts.

Tycho
12-04-2009, 02:01 AM
Many thanks for the information. Just for the record I am testing a short (5 metres) A/C pipe run. 3/4" Suction 1/2" liquid. Pipework test only using 2 mechanical joints (flared unions).

I usually strength test my A/C installs for 30 seconds and then drop the pressure down to the leak test pressure for 24 hours.

I was just interested to find out if there were any definitive guidelines as to the duration of the strength test as I was told by a college tutor it should only be for a few seconds.

I appreciate Argus' point that there is no easy answer. I did read through the manufacturers supplied documentation and there was no specific mention of duration. As Laf says as long as I the engineer can make that judgement and be able to back it up with sound reasoning I think that is good enough.

Afterall - if the manufacturer, client and contractor can't supply me with an answer, who's to say I am wrong.

And like Colin mentions, I do clear the test area :0)

Thanks again - newts.

when we do the strength test on our systems (30-45 bar depending on the system) we keep it at top pressure for 5 minutes, cause if the pipes didnt rupture when they reached that pressure, they are not gonna rupture if we leave it there for 24 hours (we have had classification companies making us leave a system at 32 bar for 24 hours and allowing people to work around the system, had it been me, I would have had them sign a paper saying that they were responsible for any injury if any worker stepped on a small pipe, broke it and hurt himself). after the 5 minutes at top pressure, we soap all the welds at 10 and then 2 bar to check for leaks