Learn more about Positive Displacement Pumps and their types

 What Positive Displacement Pumps do?

With each pumping part revolution, positive displacement pumps displace a known amount of liquid. This is accomplished by trapping liquid between the pumping parts and a fixed case. Gears, lobes, rotary pistons, vanes, and screws are some of the pumping elements used. 

Positive displacement pumps, unlike centrifugal pumps, provide the same flow at any given speed regardless of discharge pressure. Because these pumps do not have a shut-off head like centrifugal pumps, they must not be run against a closed valve on the discharge side of the pump. 

A positive displacement pump running against a closed discharge valve will continue to produce flow until the pressure in the discharge line increases to the point where the discharge line breaks or the pump is badly damaged or both.

As a result, a relief or safety valve on the pump's discharge side is absolutely essential. Internal or exterior relief valves are available. Internal relief or safety valves are often supplied by the pump manufacturer.

Types of Positive Displacement Pumps:

1.Reciprocating Positive Displacement Pumps

The back-and-forth movement (strokes) of a piston, plunger, or diaphragm in a Reciprocating Positive Displacement pump is what makes it operate. These cycles are referred to as reciprocation.

The volume of fluid moved by a piston pump is determined by the cylinder volume, whereas the volume of fluid moved by a plunger pump is determined by the plunger size. In general, a plunger pump seal is easier to maintain since it is stationary at the top of the pump cylinder, whereas a seal around a piston moves up and down inside the pump chamber regularly.

A diaphragm pump employs a flexible membrane rather than a piston or plunger to move fluid. The capacity of the pumping chamber is expanded by extending the diaphragm, and fluid is sucked into the pump. Diaphragm pumps are hermetically sealed devices, making them excellent for pumping hazardous substances.

2.Rotary Positive Displacement Pumps

Instead of the backward and forward motion of reciprocating pumps, rotary positive displacement pumps employ the motions of spinning cogs or gears to move fluids. The revolving element provides suction at the pump intake by forming a liquid seal with the pump casing. Fluid is pulled into the pump and contained inside the teeth of its spinning cogs or gears before being discharged. 

The gear pump is the most basic type of rotary positive displacement pump. There are two types of gear pumps: exterior and internal.

What are the primary characteristics and advantages of a positive displacement pump?

Positive displacement and centrifugal pumps are the two primary types of pumps. Centrifugal pumps have higher flow rates and may operate with lower viscosity liquids. In certain chemical facilities, centrifugal pumps will account for 90% of the pumps in operation. On the other hand, positive displacement pumps are chosen for a variety of applications. They can, for example, handle greater viscosity fluids and operate at greater pressures and lower flows more efficiently. They are also more precise when metering is a crucial factor.

What are the most common uses for positive displacement pumps?

Positive displacement pumps are frequently used to pump high viscosity fluids such as oil, paints, resins, and foodstuffs. They are preferred in any application requiring precise dosing or high-pressure output. Because, unlike centrifugal pumps, the output of a positive displacement pump is not impacted by pressure, they are often favored in situations where the supply is irregular. The majority of them are self-priming.

To conclude:

A positive displacement pump moves a fluid by periodically enclosing a set volume with seals or valves and mechanically pushing it through the system. Pistons, screws, gears, lobes, diaphragms, or vanes can drive the pumping motion, which is cyclic. 

Positive displacement pumps are favoured for applications requiring very viscous fluids such as thick oils and slurries, particularly at high pressures, for complicated feeds such as emulsions, edibles, or biological fluids, and for precision dosing.

Fluorolined Equipments Pvt. Ltd. are known to be the best Horizontal Pump Manufacturers in the industry. So, whether it’s Positive Displacement Pumps or Chemical Process Pumps, they have solutions for all your industry needs.