Leak pressure testing EN 378-2

[sider]

Can somebody clarify a little setting of a pressure testing based on standard EN 378-2? So, currently the heat pump units (R410A) we need to test have HP switch set on 40 bars, and safety valve on 41,5 bar (+- 3% opening, so possibly it is opened on 40,2 and 42,7 bar respectively). We are testing on 40 bars, and in the last months we had some issues with safety valves failing. From my understanding, EN 378 states that leak pressure test must be conducted on pressure equal or less then MWP. The MWP on the old units was set on 40 bars, however new units don't have MWP stated. How would you approach this issue? For me there are few question I would like to clarify?

1. If the MWP is not stated, do we need to use the table where we get MWP from saturation temperatures?
2. Can we remove the safety valve during testing?
3. Is the main point of EN 378 leak pressure testing to test the unit in the whole max range to the setting of HP?
4. Is it weird to you that settings of HP and safety relief are so close?

Thanks in advance

 

[sider]

anybody ?

 

[BenMacier]

First stop using acronyms you don't define : HP = Heat Pump = High Pressure?
In your case of high pressure switch set at 40 bar to switch off the heat pump, the safety pressure relief valve is set just above it to discharge over pressure and prevent catastrophic failure of the pump circuit.



* Finding a solution is great * Knowing how to implement it is fantastic * Believing it is the only one and best is naive ?

 

[sider]

Hi Ben,

thanks for the feedback.

I understand the principle behind the pressure relief, however, shouldn't there be more pressure difference between a setting of a high-pressure switch and pressure relief? In this case, the high-pressure switch will give a warning on 40 bars, and immediately after that (for the lower tolerance range of pressure relief at 40.3 bars) will be a discharge of refrigerant (in case pressure rises a little bit more).

But besides that, how do you define pressure for leak testing?

 

[BenMacier]

EN 378-2 defines up to 3 methods to perform the pressure resistance test. Each method has a different test pressure: 1.43x or 3x or 2x service pressure.
For the pressure limit devices (safety relief valves), the device has to be set below or equal to 1x service pressure, and open at a pressure below or equal to 1.1x service pressure.
So in your case, you have 40 bar service pressure, the safety device is set at 1x 40 bar = 40 bar and the relief valve at 1.1x 40 bar = 40.4 bar (maybe there is 0.1 bar tolerance)

* Finding a solution is great * Knowing how to implement it is fantastic * Believing it is the only one and best is naive ?