jimhokie
Mechanical
- Feb 16, 2005
- 50
I have a question about an orifice flowmeter installation being used to verify a pump is putting out its design flow and head. It has a 2.68" orifice in a 4" pipe, with 58" of straight pipe upstream and 15.75" straight pipe downstream. The question deals with the first downstream fitting: a spec flange with a 1.93" orifice prior to discharging into a tank. The pressure upstream of the flowmeter (pump discharge) is about 700 psi with a flow of ~80F water at supposedly about 2000 gpm. Can the downstream spec flange orifice be interfering with the DP across the flowmeter orifice and throwing off the flowrate measured by the orifice flowmeter? The DP across the flowmeter should be about 150psi for 2000 gpm, but it's only 135 psi corresponding to about 1875 gpm. I'm thinking the flowmeter is not indicating correctly as opposed to the pump not operating on its normal curve. I'm far from a flowmeter expert beyond knowing you want at least 10D or more straight pipe upstream and at least 5D downstream. But could an even smaller orifice in close proximity downstream of the flowmeter throw it off?
