Industry news

Pipeline pump flow regulation

2021-11-24

Export throttling  

For low and medium RPM pumps, this is one of the most common and inexpensive flow regulation methods.  This method is usually limited to low and medium RPM pumps.  Partial closure of any type of valve on the outlet line will increase the system head, so the system head curve will intersect with the pipe pump head curve at a small flow rate.  Outlet throttling moves the operating point to a lower efficiency point and has a power loss at the throttle.  This may be important for large pump installations, and higher investment regulation methods may be more economically attractive.  Throttling critical dead point may cause the fluid in the pump to overheat, bypass can be used to maintain the necessary minimum flow, or a different means of regulation.  This is very important for pumps dealing with hot water or volatile liquids mentioned earlier.  

Suction throttling  

If sufficient NPSH is available, some power can be saved by throttling in the suction line.  Inlet throttling is often used in jet engine fuel line pumps because outlet throttling can cause liquid to overheat or vaporize.  At very small flows, the impellers of these pumps are only partially filled with liquid, so the flow of the condensate pump is usually controlled by the inundation depth when the input power and temperature rise is about 1/30 of the impeller's full operating level at the outlet throttling 7, which corresponds to the inlet throttling.  Special design can reduce cavitation damage of these pumps to insignificant level, but the energy level is also quite low.  

By-pass adjustment  

The discharge line of the pipeline pump can divert all or part of the flow to the suction inlet of the pump or other appropriate points through the bypass pipe.  The bypass can be equipped with one or more orifice plates and appropriate control valves.  Metering bypass is usually used to reduce the flow of boiler feed pumps, mainly to prevent overheating.  If the bypass rotor pump excess flow, to replace the outlet throttle, can save considerable power.  

Speed setting  

This method minimizes the power required and eliminates overheating during flow regulation.  Steam turbines and internal combustion engines can easily accommodate speed adjustment at little additional cost.  All kinds of mechanical, magnetic, hydraulic gear, as well as DC and AC variable speed motors can be used to adjust speed.  In general, variable-speed motors are too expensive and should be adjusted with adjustable blades only when economic study of special cases justifies it.  

After studying the adjustable guide vane installed in front of the impeller, it is found that this method is effective for the pump regulation when the ratio of revolution =5700(2.086).  Blades produce positive prespin, which reduces pressure head, flow rate and efficiency.  However, the regulation effect of leaf is relatively small.  Adjustable outlet diffusion vanes have been successfully used in large storage pumps in Europe for power generation.  The rotary vane pump with variable pitch is also studied successfully.  Under the condition of constant pressure head and relatively small efficiency loss, a large flow range can be obtained.  However, these methods are too complex and expensive, so their practical application is greatly limited.  

Fill gas  

Supplying air to the inlet of the pipe pump is also a method of regulating flow, which can save some power compared with the outlet throttling.  In general, air is not desired in the liquid being delivered, and there is always a danger that too much air will cause the pump to lose its perfusion head, so this method is rarely used in practice except on rare occasions.