When accurate dispensing of liquids, chemicals or other substances into a process or system is needed, metering pumps are there putting in yeoman’s work. Often taken for granted, metering pumps are utilized in several different industries where their tremendous accuracy and detail can be seen in products used in our everyday lives. This article explores the common types and applications of metering pumps.
What is a Metering Pump?
Metering pumps, also known as dosing pumps, are positive displacement pumps that are designed to deliver specific, small amounts of liquid with calculated flow control. Metering pumps are known for their consistently high level of accuracy and leak-free liquid containment, which in turn make them a great choice for pumping a wide range of chemicals including acids, bases, corrosives, viscous liquids, and slurries. The construction of a metering pump varies, but generally they have a pump head, motor, and either an electronic or manual adjustment mechanism.
Common Types of Metering Pumps
Diaphragm Metering Pumps
Diaphragm metering pumps use a flexible diaphragm that is repeatedly compressed and depressed to move fluid into and out of the pumping chamber. When the diaphragm expands, the suction created draws liquid into the inlet. When the fluid chamber is full, the diaphragm compresses and the fluid is expelled. To confirm flow continues in only one direction diaphragm metering pumps often have inlet and outlet valves. Diaphragm metering pumps can be fitted with variable frequency drives (VFDs) that provide even greater dosing accuracy and reduces the chance of operator error, pumping inaccuracies and chance of leakage. The fact that diaphragm metering pumps are sealless and have several chemical resistant material options available allow them to handle a variety of liquids, including slurries, bases and acids. There are different types of diaphragm metering pumps, including a solenoid diaphragm metering pump and a hydraulic metering diaphragm pump.
A solenoid diaphragm metering pump provides precise chemical dosing and is used in several industries, including wastewater treatment, pharmaceuticals and agriculture. The pump operates by using a solenoid to control the motion of a diaphragm that pumps the chemical solution. The solenoid creates a magnetic field when an electrical current passes through it. The magnetic field moves the diaphragm back and forth and that motion pushes the chemical media through the pump. A solenoid metering pump is typically equipped with several safety features such as a pressure relief valve and leak detection system to prevent over-pressurization and chemical spills.
A hydraulic diaphragm metering pump is a type of positive displacement pump that uses a flexible diaphragm that is actuated by a hydraulic system to pump fluids. A piston or plunger is used to create pressure on one side of the diaphragm, causing the diaphragm to flex, creating vacuum on the opposite side of the diaphragm. This draws the liquid into the pump’s inlet and when the diaphragm flexes back to its original position the fluid is pushed out through the outlet valve. Like other metering pumps, hydraulic diaphragm metering pumps provide accurate dosing of liquids even at low flow rates. Hydraulic metering diaphragm pumps can be constructed out of several different chemical resistant plastics and elastomers to be compatible with a wide range of chemicals and fluids. They are commonly utilized for several applications, including in the chemical processing, water treatment and food and beverage industries.
Piston Metering Pumps
A piston metering pump is a type of positive displacement pump that uses a piston to displace fluid in the reservoir chamber. The pump’s flow rate and dispense amount is determined by the stroke rate and internal volume of fluid in the pumping chamber. Piston pumps work with the piston or plunger moving downward, which opens the inlet valve and creates suction allowing liquid to enter. The piston then moves upward c
losing the inlet valve. The inlet valve being closed pressuriz
es the liquid and discharges the liquid out of the cylinder. Piston pumps are capable of handling liquids of varying viscosities, temperatures and pressures making them versatile for a wide variety of applications.
Common applications piston metering pumps are used in are in chemical processing, oil and gas and water treatment.