BS EN ISO 1266 Leakage rate A vs. rate B
BS EN ISO 1266 Leakage rate A vs. rate B
(OP)
I am involved in a project where Customer specifies globe valve vee-reg type disc for throttling service and additionally requests leakage test complying with BS EN ISO 1266, rate A, i.e., NO VISUALLY DETECTABLE LEAKAGE FOR THE DURATION OF THE TEST. It has been hard to find a vendor to provide rate A, but rate B is not a problem. My opinion is that Customer has a too strict position but I haven't been able to persuade them to accept rate B. Has anyone dealt with such situation?





RE: BS EN ISO 1266 Leakage rate A vs. rate B
It is difficult to find a regulating valve which will also give tight shutoff. I usually install a shutoff valve upstream of the regulator ( typically a soft seated ball valve).
The vee reg valve can the be left in it's throttling postion with no need to readjust when the line comes back on stream.
If we're talking small diameter pipe here ( less than 2" say),
the cost of the extra valve is negligible.
RE: BS EN ISO 1266 Leakage rate A vs. rate B
Thank you for giving me additional arguments to make the customer reconsider such request. In fact we are talking about ND 1", 2" and 3". After all, it sounds me like too severe to request a rate A test for a globe valve.
RE: BS EN ISO 1266 Leakage rate A vs. rate B
Inevitably someone is trying to cut costs and I say that it is false economy.
Metal seated, triple offset butterfly valves might be an exception, but that is not what we are talking about here and whilst they can be a modulating valve I do not believe that they have a fine control capability.
RE: BS EN ISO 1266 Leakage rate A vs. rate B
RE: BS EN ISO 1266 Leakage rate A vs. rate B
please take a look at thread408-150132: "Zero Leakage" conept and EN 1779 std... within this Forum.
P.S.: the right reference is to EN 12266-1 standard
Regards, 'NGL
RE: BS EN ISO 1266 Leakage rate A vs. rate B
RE: BS EN ISO 1266 Leakage rate A vs. rate B
you're wellcome... best wishes for the New Year to you too (and to All the Colleagues in this Forum!)!!
Coming to the post, I agree with PeterIgg's opinion; moreover, about metal seated, triple offset valves, I'd like to add that they may perform well as control valves (i.e. they have a good rangeability) far from completely open and closed positions, more or less between 20° and 70° opening angle (of course it also depends on how fine is the required control and on the positioning system you use...).
With reference to the original question, it should be easy to demonstrate (to those who are willing to consider demonstrations, of course...!) that in practice there's not much difference between "Rate A" [= less than an air bubble or water drop (ml) divided per the minimum test duration (min)] and "Rate B" [= 0.45 ml/min per in of ND or something like that...]... and this difference becomes thinner and thinner as the valve diameter increases.
In addition, the required accuracy would make not feasible - from a metrological (scientific) standpoint - to actually measure and discern such leak rates...
Hope this helps, 'NGL