In service testing of Check Valves 2

[desai1]

Group Members,

I want to know about methods for in service testing of Check valves which are connected to pump discharge.

One of the methods i thought was during pump swing operation. This can test check valve functioning. Is there any other method by which we can know wear of condition of hinge pin of swing check valve?

 

[Danlap]

It is virtually almost impossible to determine the hinge pin condition, without actually looking at the valve internal.

X-ray (with any composition)
--> from side (cross sectional circle of pin), the 'ray' have to penetrate body, hinge housing, pin itself. No one knows on what depth the over-clearance exist between the hinge and its housing
--> from front. Exact location of the hinge? Answer same as above.

First have to determine the failure mode (assuming that there are no back flow surge):
1. Are you sure no Differential Pressure (or minimum), when it is deemed to fail? No DP meaning that Check valve supposed to be close
2. When it is close, what is the leakage rate (ISO 5208)? Is it class D, G, or streaming like waterfall? or like most older design, you cannot measure pressure built up between the pump and the check valve.

Some NDE approach:
a. Some Check valve have hinge that are connected to visible bearing from the outside.If this is leaking, then either the hinge, and or sealing is damage. IF NOT

Condition should be applied: Assurance of leaking, Pressure pushes from downstream (backflow) is bigger than upstream, assuming valve is close.
b. Ultrasonic leak detector (subjective measurement by operator), find the area where biggest leak occurs
c. X-ray (Cobalt) on that area
d. Assess the contact between disc and seat. If lucky, you may even see some crack.

If crack visible and valve do close (seat and disc are mating), then that is your failure mode and not the hinge
If gape exist, then most likely either the valve's hinge or some tracing becomes hardened and block the valve from closing.

Shall this is the main pump which working almost all the time, thus Check valve remains Open for a long time. Then it is likely the hinge became fatigue.
If this is a critical pump, mind as well classify the same critical rank for Check valve subjected for periodic maintenance (visual inspection required).

Or else like many recent application in offshore field. Apply API 521, double jeopardy Check valve configuration.

Regards,
MR



Greenfield and Brownfield have one thing in common; Valve(s) is deemed to "run to fail" earlier shall compared to other equipments

 

[gerhardl]

A 'check valve' is a general description and can be found as a multitude of constructions with amultitude of materials, sizes and operational pressures. A swing check valve with hinge pin is actually not an exception. The quality and life expectance of this type of valve is vastly different for different factories and constructional details.

This type of valve can easily be replaced by a high-quality disc check valve, wich is more robust with a much longer lifetime at 'bad' conditions. If trouble with hinge-pins:

Check correct placement and orientation for the valve according to the valve factory specification. If OK and still problems: replace with better quality or disc type valve (Gestra type or other makes), or other constructions


With a general description, the general answer for operational inspection is following:

a) Some check-valve constructions will have the possibillity of adding devices (such as limit switches) to signal if, and when the valve is closed. Weakness: will not show small leakages and general condition.

b) Measurement (continous and track recording if necessary) of pressure in pipeline close after and/or before the checkvalve to track operational behaviour.

c) Pressure switches to signal high or low pressures if relevant or practical for the actual use.

d) Instrumental valves for control connected to the main pipeline, and/or instruments connected to the valves to check if fluid is present or pressure when wanted/at occasions.

e) Flow measurement at suitable places

f) Checking of operational function and results other places upstream or downstream in the process.

g) Visual inspection of outflow behaviour

h) Listening without or with hearing devices for any 'mis-operational' sounds.

Good luck!