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BFP Recirc Information Sheet
The C600
diffuser is the flanged-plate version of CU Services
LLC's family of high-pressure-drop diffusers. It can
be used individually or as a multi-stage orifice
plate system of two or more units placed in series to
eliminate the damage that is caused by control valve
cavitation or other high-drop stream cavitation. We manufactures diffusers orifices for Pump Spillback and Flow Restriction.
For example, two of the most difficult flow control
problems in a power plant are the control of the
Pump recirculation (pump spillback) and boiler feed pump
warm-up systems. Another example is the boiler blowdown
system.
Because of the high-pressure drops involved with
these high temperature liquid streams, the fluid flashes
and/or cavitates at the exit of the control valve.
This erodes both the control valve and the downstream
piping. In addition the resulting pounding as the fluid
implodes causes unacceptable noise and vibration of the
piping. In some cases, the control valve, the downstream
piping and the hangers must be replaced in a matter of
months.
These diffusers can be used for any flow-restriction
orifice service.
The use of multiple holes causes a shift of the frequency spectrum of the exiting fluid stream to higher frequencies resulting in a noise reduction in the order of 10dBa. The peak frequency scales inversely with the jet diameter ( f a 1/d). Thus, with multiple holes the resulting higher frequency greatly reduces the potential to excite the downstream piping, thus reducing damaging vibrations. A report describing this phenomena is available in the August 2001 issue of Hydrocarbon Processing magazine. The increase in frequency of the exiting fluid stream is f2/f1 a v N where N is the number of holes. For example, for a plate with 24 holes, the peak frequency will be 4.9 times higher than the peak frequency of a single hole passing the same amount of fluid. |
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When multiple plates are used,
each stage is sized to avoid cavitation. |
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Another important benefit of a multi-hole diffuser is that the energy of the discharge jets is dissipated in a much shorter distance than the jet from a single orifice. This would prevent damage to nearby elbows, etc.
One of the most respected hydraulic laboratories in the country has validated the performance of our multistage diffuser design for the pump recirculation system for a nuclear power plant.
The Control Valve should be located upstream of the diffusers. For on/off control situations, the control valve should take approximately 20-30% of the pressure drop and the diffusers take the rest of the drop. For modulating control situations, the control valve should take 60-70% of the pressure drop and the diffusers take the rest of the drop. This will greatly reduce the initial cost and the maintenance cost of the control valve. |
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Failed Steam Trap Damage
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