Process of low-flow protection pipeline
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This post was last edited by Clouds of flowing water shine on 2017-12-28 at 14:32. In HG/T 20570.18-95 \"Valve Installation\", section 1.9.7 Low-flow protection piping: Centrifugal pumps operate with very low efficiency under conditions of low flow, or may not even function at all; therefore, low-flow protection piping is required. (1) Since the pump may operate in the short term at a flow rate of less than 20% of its rated value, a bypass equipped with a flow-limiting orifice plate should be installed without a valve; the size of this orifice plate should ensure that the flow rate through the pump remains at least 20% of the rated value (or as specified by the pump’s operating curve). When flashing may occur as the liquid passes through the bypass orifice plate, the bypass pipe should lead back to the liquid suction device upstream of the pump, with the orifice plate placed close to this device, as shown in Figure 1. (2) Since the pump may operate for extended periods at less than 40% of its rated flow rate, a bypass or manual valve equipped with a orifice control valve should be provided. (3) When the pump operates at low flow rates for an extended period, the bypass pipe should return to the suction device upstream of the pump. In Figure 1, the orifice plate bypass is located after the pump outlet shut-off valve; however, according to the piping documentation, the orifice plate bypass is situated before the pump outlet shut-off valve, with a valve installed in front of the orifice plate. Which one is more reasonable? For a pump with one in service and one as backup, how should the low-flow protection pipeline system be set up?
This post was last edited by Liushui Zhiyun shine on 2017-12-28 at 14:38. In the SH3122-2013 Standards for the Process Pipeline Design of Refining Units, it’s another way of expressing it; I’m stunned.
Figure 1 shows that the return pipeline does not perform well behind the outlet valve. The other two differences don’t seem significant
The SH3122-2013 Standard for the Design of Process Piping in Refining Units is more reasonable, facilitating the removal of orifice plates
For a pump with one in service and one as backup, how should the low-flow protection pipeline system be set up?
The flow control orifice plate can serve to reduce pressure; in cases of high head pressures, it can protect the valve and minimize the pressure difference
This post was last edited by Liushui Zhiyun shine on 2018-1-6 at 10:40. Page 173 of the \"Petroleum and Chemical Engineering Design Manual (Revised Edition)_ Volume 4 _ Process and System Design\" seems to explain things in a simpler manner.