How should a twin-screw pump deal with this situation?
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The plant plans to pump oil from the tank to supply the production units, and a twin-screw pump has been selected for this purpose. Question: If there are fluctuations in the equipment and the flow rate needs to be reduced by closing valves, how should the oil supply party respond? The pump does not have a design for remote shutdown or other control mechanisms; it can only be started and stopped manually.
More people are welcome to participate in discussions in the process area; this topic might be better discussed in the storage and transportation section, so I’ll help you switch there
What oil is used for feeding with twin-screw pumps? Is crude oil fed to the atmospheric and vacuum distillation units? If not, a regular centrifugal pump will be sufficient. Double-screw pumps cannot be regulated using valves; if flow fluctuations need to be controlled, a bypass circuit for backflow should be installed. And it features a tank-based circulation system; if circulation is carried out before or after the pump, the oil temperature rises too quickly, which can easily lead to cavitation.
1. The flow rate of a twin-screw pump remains relatively constant; a intermediate tank is generally used in the feeding system to regulate the flow rate. 2. If there is no intermediate tank, a bypass line should be installed; however, it is difficult to achieve automatic matching. Should a flow meter and control valve also be added at the pump outlet? But this would result in high costs as well ； Or add an inverter motor ； 3. Determine whether the screw pump takes heavy oil into consideration.
1. The unit has a 50-cubic-meter buffer tank, and the pump has a flow rate of 90 cubic meters per hour; this capacity is not very effective. 2. The pump is designed with a bypass valve, but it is not automatic; manual operation makes it difficult to keep up with the fluctuations in the device’s operation. I also thought about adding variable frequency drive, but that would require additional investment.
A twin-screw pump must have its flow rate reduced by using an outlet return flow; it cannot have its outlet closed directly like a centrifugal pump. A 50-liter buffer tank for return flow control will work for now. If enough time passes, the reflux can only be directed back into the storage tank. If you don’t want to install an inverter on the pump, this is the only feasible method. A dedicated person must be on duty to adjust the opening degree of the return valve at the pump outlet.
The screw pump is a pump with fixed characteristics; its flow rate cannot be changed, and backflow can only be achieved through a bypass
A self-acting control valve can be installed; as the flow rate decreases, the pressure at the pump outlet increases, which in turn pushes the control valve open and allows the fluid to return to the storage tank
With a dual return line, one of them is equipped with a self-acting safety control valve, while the other is fitted with an easy-to-operate gate valve for manual control.
Screw pumps cannot use an outlet valve to control flow; instead, a bypass valve must be used for manual adjustment and control. In addition, safety valves must be installed at the inlet and outlet of the pipeline to allow for emergency pressure relief in case of crises, thereby preventing damage to the pumps due to excessive pressure
Our usual approach is to use backflow control; as for whether to use a control valve or a self-acting control valve, that depends on your requirements