We're presently working on a new 4-way 1/2" NPT ported valve with an internal fixed flow orifice diameter of .438"
and we're performing the above test to find the Cv. Our set up follows that as described by the above subject standard. The problem we're having is that when we test for a 2 delta P we lose almost 40% of the Cv. But yet when use other delta P's for instance 3,4 or 5 the average is within 5% of each other. My questions are:
1. To achieve a 2 delta P we noticed that the needle valve is almost closed and therefore lead us to believe that this device is being measured and not the test component. Is this correct?
2. Is there a rule of thumb as to how big the needle valve should be in relation to the test component?
3. Could NFPA tell me what the industry regards as the standard tolerance for Cv factor. We work with +/- 10%
Thanks In Advance,
and we're performing the above test to find the Cv. Our set up follows that as described by the above subject standard. The problem we're having is that when we test for a 2 delta P we lose almost 40% of the Cv. But yet when use other delta P's for instance 3,4 or 5 the average is within 5% of each other. My questions are:1. To achieve a 2 delta P we noticed that the needle valve is almost closed and therefore lead us to believe that this device is being measured and not the test component. Is this correct?
2. Is there a rule of thumb as to how big the needle valve should be in relation to the test component?
3. Could NFPA tell me what the industry regards as the standard tolerance for Cv factor. We work with +/- 10%
Thanks In Advance,
