PDA

View Full Version : Now What Pressure do I test to?







Grizzly
20-01-2008, 09:53 PM
For those of us that have to stop and think "now what was the formula" occasionally, refer to the data below!
Grizzly http://www.refrigeration-engineer.com/forums/images/icons/icon14.gif

Brian_UK
20-01-2008, 09:57 PM
Good one, thanks for the reminder.

taz24
20-01-2008, 10:24 PM
For those of us that have to stop and think "now what was the formula" occasionally, refer to the data below!
Grizzly http://www.refrigeration-engineer.com/forums/images/icons/icon14.gif


Hello Grizzly.
I think that document is out of date now.
It was the old British standard 4434 which has now been superseded by EN378. We now test to standing pressure @ 55degc X 1.3 for strength and X1.1 for leak testing.

Cheers taz.

nike123
20-01-2008, 10:44 PM
Good info, no matter of standards!
Thanks Grizly and Taz!;)

Grizzly
20-01-2008, 11:39 PM
Hello Grizzly.
I think that document is out of date now.
It was the old British standard 4434 which has now been superseded by EN378. We now test to standing pressure @ 55degc X 1.3 for strength and X1.1 for leak testing.

Cheers taz.
Taz
Can you give us a bit more info. what is an EN (EUROPEAN SOMETHING?) and does it supersead
A BS. Standard?
Cheers Grizzlyhttp://www.refrigeration-engineer.com/forums/images/icons/icon14.gif

taz24
21-01-2008, 12:01 AM
Taz
Can you give us a bit more info. what is an EN (EUROPEAN SOMETHING?) and does it supersead
A BS. Standard?
Cheers Grizzlyhttp://www.refrigeration-engineer.com/forums/images/icons/icon14.gif


Hello Grizzly the document you have is good the main difference I can see is were it states Max working pressure. that is now designated by the pressure of the refrigerant at 55degc.

BS EN 378-2:2000 referers to

Refrigerating systems, Refrigeration, Refrigerators, Heat pumps, Heat transfer, Safety, Environmental engineering, Operating conditions, Maintenance, Repair, Recycling, Health and safety requirements, Hazards.

It replaces
BS 4434:1995

Cheers taz,

Pooh
21-01-2008, 12:56 AM
However if the equipment manufacturer specifies a different pressure you should always test to that and in the eyes of the law you should be OK if you have followed their instructions, but if you exceed their instructions then you are liable even thou they do not meet EN378 standards.

En378 is not a law just a standard so you do not have to comply with it but if you do not you may be in the C__P big time.

Ian

Josip
21-01-2008, 12:59 AM
Hi, all :)

to find a leak we can see something here:

http://www.acrib.org.uk/MPLUGB71936

and here, but on different way....

http://www.ior.org.uk/ior_/images/pdf/se/Good%20practice%2024%20leak%20tightness%20testing.pdf

....but very little when to make hydraulic and when pneumatic pressure test...

http://www.jlab.org/ehs/manual/EHSbook-389.html

with weird explanation when pneumatic test is permitted...

and F-gas regulation update is here:

http://www.acrib.org.uk/web_images/documents/TRAINING%20AND%20CERT%20LEAFLET.pdf


Best regards, Josip :)

taz24
21-01-2008, 01:16 AM
Hi, all :)

to find a leak we can see something here:

http://www.ior.org.uk/ior_/images/pdf/se/Good%20practice%2024%20leak%20tightness%20testing.pdf

Best regards, Josip :)

This is very informative .
A good document thanks ..


taz.

Peter_1
21-01-2008, 08:19 PM
En378 is not a law just a standard so you do not have to comply with it but if you do not you may be in the C__P big time.

Ian
NE 842/2006 is a law I think and there are also a description how to test.
It may be perhaps not a law but if you have a case which end in court, then a judge will follow the law or standards.

Pooh
21-01-2008, 09:30 PM
Peter
that is what I meant, you can ignore the standards but at your own risk.

Ian

Tony
24-01-2008, 02:14 PM
Hi Taz,


We now test to standing pressure @ 55degc X 1.3 for strength and X1.1 for leak testing.

If you read BS EN 378 the reference to 1.1 ps is the setting for the pressure relief device.

Leak testing is carried out to less than or equal to 1ps (AP)

pendlesteve
24-01-2008, 05:45 PM
EN = European Norm
EN:378 is a standard which lays down minimum requirements for refrigeration & air conditioning systems.
You should distinguish which is the high side & low side of the system then which refrigerant is to be used. Determin the pressure of that refrigerant at 32C for the low side, 43C for the high side of a water cooled system & 55C for an air cooled system. Then multiply by 1.3 for the strength test, 1.1 for the leak test & 0.9 for the setting of the HP switch. Use OFN to perform the tests. Any PRV's must of course be removed during these tests, then refitted before pulling a vacuum of 200 microns (about .25 torr).
Be careful on a heat pump as there is little to the low side. Be very careful as the pressure can be as high as 43 Bar for the high side on a system using R410a.
figures quoted apply to latitudes for the UK

Tony
24-01-2008, 07:19 PM
Hi Pendlesteve,

where do you get 1.1 times for leak test. BS EN 378 clearly states < or = 1 times?

Billy Ray
24-01-2008, 10:19 PM
Good Evening Gentlemen,

A very good civalized debate indeed, very interesting comments.

Your thoughts would be welcome on the following points.

1. How do you 'get round' the issue of pressure testing components within a system which have a lower MWP, i.e evaporators etc. Typically a Searle cooler for instance has a MWP of 21 Bar. How do you pressure test the sytem in entirity should you operate on R404A? Do you disconnect the cooler? This then defeats the objective?

2. Would somebody explain what the system MWP is? Does this relate to 55deg condensing? The H.P setpoint? or the PRV setting.

Thanking in anticipation.

Maybe this is considered differnet in other countries.

Billy Ray (new to posting)

Tony
25-01-2008, 11:26 AM
Hi,


1. How do you 'get round' the issue of pressure testing components within a system which have a lower MWP, i.e evaporators etc. Typically a Searle cooler for instance has a MWP of 21 Bar. How do you pressure test the sytem in entirity should you operate on R404A? Do you disconnect the cooler? This then defeats the objective?

You work out the AP for the LP side (in UK) using 32C saturation pressure for the refrigerant in the system then you work out the AP for the HP side (in UK) using 43C saturation pressure for the refrigerant in the system the if it is a water cooled or evaporative condenser or 55C if it is an air cooled condenser.

So these are your pressures for leak testing if you can test LP and HP separately.

For the strength test you use 1 to 1.3 times AP, but you would not exceed manufacturers test pressures.

Billy Ray
25-01-2008, 10:45 PM
Thanks Tony,

thats understood pressure testing each 1/2 of the system.

i assume from your reply that disconnecting the low side from the high side & pressure testing each section suffices to EN378.

After you reconnect, will a pressure test of the whole system suffice at the lower pressure?

Can you advise on the termniology of 'system MWP'

or is this a mesconception?

Billy Ray

Grizzly
26-01-2008, 12:14 AM
Thanks guys.
Lots of useful info and I am glad to see that all you trainers are not yet to busy to find time to advise. I suspect that you guys will be very busy once things are firmed up come summer!
Those interested might like to comment on my post in the thread " Safety Valve Inspection and Replacement" It's all in a similar vein.
Grizzlyhttp://www.refrigeration-engineer.com/forums/images/icons/icon14.gif

Tony
28-01-2008, 10:44 AM
The MWP (system maximum working pressure) refered to as the AP (allowable pressure) will be set by the manufacturer normally.

However if it is not, BS EN 378 allows you to work out the minimum AP by using 55C or 43C for HP and 32C for LP.

When pressure testing, if it is possible to test LP and HP separately by closing off valves - if you cannot separate LP from HP, you are allowed to test the whole system at 32C. This would be for small systems.

But of course for heat pump systems, you would have to test the whole system at 55C.

Billy Ray
31-01-2008, 12:44 AM
Thanks Tony, that helps.

Another question if i may (as you seem to be 'the man' to answer).

Consider a 10 H.P semi-hermetic condensing unit connected to a DX coil.

This is not a single manufacturers piece of kit, more however a selection of components 'put together by a contractor.

Therfore each component has differnet MWP's.


Would therefore the correct terminology for 'system MWP' be either _

1. PRV set point.

2. H.P switch set point.

Billy Ray

Tony
31-01-2008, 10:16 AM
Billy Ray,

the system MWP would be the manufacturer's MWP of the weakest component in the system.

BS EN 378 sets the PRV set point at 1.1 x that components MWP.

Set the HP switch to cut out at 0.9 x MWP of weakest component on HP side of system.

Billy Ray
31-01-2008, 10:59 PM
Tony,

Thankyou, understood.

Billy Ray