Valve bakseat test and nameplate details

[gafoorkti]

Gents, I need your advice.

We have received 8" Gate valves without backseat tested and no details found on the nameplate. Upon completion of our inspection, the subject valve has been rejected and conveyed our discrepancy report to local vendor.

Now, vendor clarifies that the valve is supplied from stock and
also there is no back seat test report available and proposes to carry out this test at some other contractor's valve workshop. Regarding nameplate he is going to prepare one nameplate with all details by his own.

Please advise me if can we accept above offer.

Thanks and Regards

 

[gerhardl]

It seems clear that the valves supplied do not meet your specifications. Although you have not given all details it seems that you require a backseat test (which I presume is dropthight or near dropthight) both ways with zero pressure one side and x bar (operwtion pressure ?) in the opposite direction, tested for both sides.

Anyway:

That the valves are supplied not meeting your standards could indicate, but not necessarily:

Valves generally of poor quality
The producers fabricating procedures, QA and repeatabillity in fabricating process poor, weak or actually generally not satisfying your demands
Valves not fabricated to correct engineering standards or for correct pressure or pressure class
Supplier: as producer
Great variation in quality from valve to valve (accuracy)

(Also note that some constructions of gatevalves (especially knife-gate valves) are dropthight in one direction only, requiring pressure from the fluid to keep gate thight agains seat sealing. This construction tends to leak at low pressures even with correct pressure direction.)

If you can nullify above statements, have references from long-term users of the exact valve, and get a guarantee (bank guarantee) from the supplier for changing to better standard valves if valves fail within a certain periode, are satisfied with the detailed test procedure suggested, a paid third-part surveyance when testing is included, and consequences if valves fail ore have an unexpected short lifetime are moderate, etc. etc. you could of course consider.

The key question is as always: who bears the cost if anything goes wrong, and is that party willing to take both the cost and the risk involved?

There is no reason to take an extra risk or cost if some other party have made a mistake. Normal trade rules and contracts will place the responsibillity and cost where it belongs.

 

[gafoorkti]

Detaisl are as follow:

Gate Valve 8" class 150, Testing requirement as per API 598.

Manufacturer carried out only Body and seat leak test and we have reviewed the test results found to be acceptable. However as per API 598 back seat test is also required which is not carried out as per test certificate result.

Please let me know wheather code allows conducting missed out pressure test at independent contractor's workshop.
or should we return back to original manufacturer?

Regards

 

[gafoorkti]

I am still waiting for response.

Regards

 

[JohnGP]

Hi gafoorkti,

Presumably the valves have the back seat feature, which necessitates the manufacturer to perform the backseat test. For testing location, the standard says:

Pressure tests shall be performed by the valve manufacturer at the valve manufacturer's plant or at a facility mutually agreeable to both the manufacturer and purchaser.

It seems though your valve vendor has taken it upon themselves to complete the testing. While this is not what the standard has in mind, if the vendor is going to stand by the test results, then having the tests performed at an independent facility should confirm whether or not the valves fully comply with the standard. I would want to witness the test though, if they were my valves.

Cheers,
John

 

[gafoorkti]

John, thanks for your input regarding back seat test. Can you please give some details on "Nameplate discrepancy".