As a common type of mud pump, the reciprocating piston mud pump is widely used in oil, gas drilling, mining and other industries that require high-pressure fluid delivery. Adjusting its displacement and pressure is the key to ensuring stable pump operation and system efficiency. The following is a detailed explanation of how to adjust the displacement and pressure of a reciprocating piston mud pump from an engineer’s perspective.
Working principle of a reciprocating piston mud pump
The reciprocating piston mud pump achieves the suction and discharge of liquid through the reciprocating motion of the piston in the pump chamber. The piston in the pump chamber is connected to the connecting rod and the crankshaft to complete the periodic reciprocating motion. During the working process, when the piston moves forward, the volume of the pump chamber decreases and the mud is pressed out of the pump body; when the piston returns, the volume of the pump chamber increases and the external mud is sucked into the pump body.
Adjusting the displacement
The displacement of a reciprocating piston pump refers to the volume of mud delivered during each pump working cycle, usually expressed in “liters per minute (L/min)” or “cubic meters per hour (m³/h)”. Adjusting the displacement can be achieved in the following ways:
(1) Adjusting the stroke length of the pump
Changes in the pump chamber capacity: The stroke length of the pump directly affects the volume of the pump chamber, thereby affecting the displacement. The longer the stroke, the greater the amount of mud pumped each time the piston moves. Therefore, adjusting the stroke length of the pump can control the pump’s displacement.
Adjustment method: Some pump designs allow the piston stroke length to be changed by adjusting the piston stroke adjustment bolt or mechanical device.
(2) Adjusting the pump speed
Diesel engine drive and inverter control: The reciprocating speed of the piston (i.e., pump speed) is changed by adjusting the diesel engine speed. The higher the pump speed, the more times the piston reciprocates per unit time, and the greater the displacement.
Frequency converter control: Modern reciprocating mud pumps are usually equipped with frequency converters, which can precisely control the displacement by adjusting the motor speed.
(3) Regulating valves
A regulating valve is usually installed at the discharge end of the pump. By adjusting the opening of the discharge valve, the flow path of the fluid is changed, thereby affecting the displacement.
Close the valve: reduce the flow rate and reduce the displacement;
Fully open the valve: maximum flow rate and increase the displacement.
Regulating pressure
The discharge pressure of a reciprocating piston mud pump refers to the pressure when the pump presses the mud into the pipeline system, usually in “bar” or “megapascal (MPa)”. Regulating pressure usually involves the following aspects:
(1) Regulating pump speed
The relationship between pump speed and pressure: An increase in pump speed will cause an increase in pressure because the reciprocating motion of the piston increases the compression force of the fluid. However, too high a pump speed may cause overpressure in the pipeline system, so it is necessary to balance the relationship between pump speed and pressure.
(2) Regulating the discharge valve
Valve function: The opening of the discharge valve directly affects the pump pressure. Partial closure of the valve will increase the pressure in the pump chamber, thereby increasing the discharge pressure. When the valve is fully closed, the pressure will rise rapidly due to the obstruction of fluid flow; when the valve is fully open, the discharge pressure is low.
(3) System pipeline resistance
The resistance of the pipeline will also affect the discharge pressure of the pump. Longer pipelines or more elbows will increase the resistance of fluid flow, resulting in an increase in discharge pressure. Reasonable design of the pipeline system can reduce resistance and avoid excessive discharge pressure of the pump.
(4) Piston working conditions
Piston sealing performance: The sealing performance of the piston directly affects the pressure of the pump. When the sealing effect is good, it can effectively increase the discharge pressure of the pump and prevent fluid leakage.
Piston friction: The friction between the piston and the pump chamber will also affect the pressure. Excessive friction may cause insufficient pump pressure or reduced efficiency.
Balance between displacement and pressure
In the operation of a reciprocating piston mud pump, water well drilling rig, the displacement and discharge pressure are interrelated, and the two need to be balanced during adjustment. Generally, when the displacement is increased, the discharge pressure may decrease accordingly, because when the mud flow increases, the flow resistance of the pump increases and the pressure decreases. Conversely, when increasing pressure, displacement may be restricted, especially when the pump is heavily loaded.
