4.3　Reciprocating Pumps，Metering Pumps and Rotary Pumps

4.3.1　Reciprocating pumps for petrochemical service shall conform to the current industrial standard SH/T 3141 Technical Specification for Reciprocating Pumps in Petrochemical Industry.

4.3.2　For metering pumps in petrochemical industry，hydraulic diaphragm type metering pump should be selected，and plunger type metering pump may be selected，and they shall conform to the current industrial standard SH/T 3142 Technical Specification for Metering Pumps in Petrochemical Industry.

4.3.3　When the metering pump is used to handle hazardous medium or when the handled streams and hydraulic oil are mixed and subject to reaction，hydraulic double-diaphragm metering pump shall be selected and shall be equipped with alarm device for indicating diaphragm broken.

4.3.4　Rotary pumps for petrochemical service shall conform to the current industrial standard SH/T 3151 Technical Specification for Rotary Pumps in Petrochemical Industry.When rotary pump is used to handle the stream sensitive to shear force，or it is expected that the suspended substances or solids in the solution is not damaged，low shear force rotary pump shall be selected.

4.3.5　Relief valves shall be installed on the outlet piping of reciprocating pump，metering pump and rotary pump.

4.3.6　The reciprocating pump，metering pump and rotary pump shall be capable of continuous operation at the maximum allowable rotated speed and at the outlet pressure that is the setpoint of the Relief valves.

4.3.7　Elastic diaphragm or bladder type accumulators shall be provided at the inlet and outlet of reciprocating pump and metering pump.

4.3.8　The metering pump capacity shall be adjusted by changing the pump stroke or the rotated speed during operation.If required，the metering pump capacity shall be remotely or automatically adjusted.

4.3.9　If the outlet pressure of metering pump is close to inlet pressure，a back pressure valve shall be provided after the pump outlet buffer tank，and the pump outlet pressure shall be at least 0.1MPa higher than inlet pressure.