TESTING VALVES 1

[kali_0142]

HI SIRS.
TODAY I TESTED THE VALVES AS PER API598.
VALVE 800 CLASS, TESTED THE VALVE IN VENTIL TEST BENCH.
FOR BODY TEST,205 BAR HIGH PRESSURE HYDRO.
RESULTS:NO VISIBLE LEAKAGE AS MENTIONING ACCEPTANCE CRITERIA.
BUT LITTLE PRESSURE DROP HAPPENS 0.4 BAR(WILL NOT SHOWN IN VISIBLE). THIS LEAK IS ACCEPTABLE OR NOT.
PLEASE JUSTIFY.

 

[Danlap]

Hi,

Not sure why your CAPS LOCK is always on. Most people consider this gesture as shouting.
Also not really clear about following:
- Valve type? Gate/globe/ball/check/Plug
- just to be sure. Is this Body or Seat test?? For body test, is your valve half or partially open? and does the gland / stem seal is tightened?
- Is this soft seated (not common, but then again, I am not sure) or metal seated? Soft seated means no visible leakage
- How do you check visually not leaking?? Is this two clamp testing bench or one clamp (standard safety valve used) test bench - only hydraulically clamped on one side
- How do you equalize pressure prior starting the timer?

Horizontal position seat and closure testing testing. Difference is that seat testing valve is in close position. My example below is for seat testing, but the philosophy remain similar for closure testing
Not so good way: close valve with full thrust – fill up (one side of) valve with water – boost the pressure until reach testing pressure – close the needle / regulator valve – start the timer
Better way: fill the bottom cavity with water – close valve – fill up valve with water – boost the pressure up to testing pressure – close the needle / regulator valve - wait 5-10 minutes until no pressure drop – start timer
This way will ensure a) “all cavities” already filled by water (minimum false reading induced by air escape) and b) the instrument reading already adjusted by the environmental temperature and humidity. I cannot really explain this but using Ventil in tropical country and now Europe under same behavior, sometimes show some deviation.
For vertical position, more or less the same. For old school inspector, this is preferable since blind flange can mounted on the top side and after valve filled up with water (both A and B side) and connect the pipet on the blind flange then we can see the droplets built up. If there is any

In general, if this is seat test for metal to metal it should be acceptable. 0,4 bar over 5 – 15 minutes period is minimum. Under the assumption that all are calibrated, can only imagine that the pressure is not yet “equalized” once you start the timer.
But if this is body test, aside from the possibility the pressure is not yet equalized, there is also a possibility of leak point(s) that one may not notice. Can be due to one of the following: hydraulic clamp not providing consistent sufficient force; gland is not tightened; some joint (body to bonnet / body to body) is not tight or damage gasket.
If your water reservoir is nearby and "drying" the leakage path surface was not performed, it can lead to bias visual inspection as well

regards,
MR

https://nosuchvalve.com

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

http://www.eng-tips.com/faqs.cfm?&rat1=2&fid=376

 

[kali_0142]

THANKS SIR.
I tested the valve 15 sec only because according to API 598 BELOW 2 INCH 15 SEC TIME DURATION.
And yah my valve metal to metal.