What is a Triplex Pump?

Triplex (Pump): A reciprocating pump design that utilizes three separate drive rods to drive the pumps plungers or pistons.

Triplex pumps are available in both single and double-action designs. However, single-action is much more common. Their design uses three drive rods, each at a 120 degree offset around the crankshaft. A single-acting triplex contains the fewest drive rods in a positive displacement pump where the flow does not reach zero anywhere in the crankshaft rotation.

Triplex Flow Characteristics

Triplex pumps are the first simplex pump to never fully reach a zero flow in the pump’s cycle. However, pulsations are still present within the pump’s flow rate. The flow rate will vary between 82% and 107% of the average flow. For example, if pumping at a flow rate of 100 gallons per minute, the flow will vary between 82 GPM and 107 GPM three times per crankshaft revolution.

A triplex pump also is the first reciprocating pump design in which the crankshaft design begins to alter the flow velocity. The peak velocity of each flow does not take place at 90-degree increments. The skewed maximum flow rate is caused by the geometry conditions of the crankshaft and arm. The result creates an additional, smaller pressure pulsation which can be seen by the combined flow line above.

The flow rate produced by the pump will fluctuate from 82% of average, increase to 107%, decrease to 100%, increase back to 107%, before returning to 82%. This process takes place three times in every crankshaft rotation. The change may not seem significant, but running the pump at 100 RPM will result in this fluctuation 5 times per second. Careful attention should be given to the design of the surrounding system to prevent damage from pulsations and vibration.

Triplex Pump Example Applications

Triplex pumps are routinely used for low to medium flow applications such as:

• Drilling Mud

• Secondary Recovery

• Hot Oil

• Coal Slurry

• Lean Oil Circulation

• Water Jetting

• Metering Pump

• Hydraulic Fracturing

• Water Flooding

• CO2 Injection

• Steam

• Amine Circulation

• Descaling

• Hydrostatic Testing

• Hydrocarbon Condensate

• Salt Water Disposal

• Well Service

• Bauxite Slurry

• Food Homogenizing

• Cement

• Reverse Osmosis

• Crude Oil Transfer

• Drilling Mud

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