The diaphragm metering pump is the pump in the category of positive displacement type pump. The name diaphragm means the use of a membrane for transferring the fluid from a source to the end-user. Metering means the fluid to be measured in volumetric quantity and then discharged into the closed system. Diaphragm metering pumps work against the backpressure of closed pressurized systems like reactors, vessels, and drums.
Diaphragm metering pumps are used to dose the ingredients, reactants, additives, and catalysts into the closed pressurized systems. They dose the fluid into the system at high pressure and with high volumetric accuracy. Diaphragms, used in these pumps could be of polymer material like Teflon or metallic. Multi-layer diaphragms are much stronger than single diaphragms and are used for a longer useful life without failure in the diaphragm.
Diaphragm metering pumps have a cavity made in the diaphragm head of the pump. Small capacity diaphragm pumps use a Teflon diaphragm. This Teflon diaphragm is fitted between the diaphragm plate and the diaphragm head. On one side of the diaphragm, there is the fluid to be pumped. On the opposite side of the diaphragm, there is the hydraulic oil that builds the pressure on the diaphragm with the movement of the plunger fitted in the pump. This oil pressure acts on the diaphragm and therefore the deflection in the diaphragm takes place.
During the backward motion of the plunger, the diaphragm gets deflected in the backward direction and therefore the vacuum is created in the pump diaphragm head cavity and the fluid to be handled is sucked into the pump head cavity. The forwarding motion of the plunger oil pressure acts on the diaphragm hence deflection takes place in the forward direction and the fluid inside the diaphragm cavity is pushed out through the discharge valve of the pump. This backward and forward deflection of the diaphragm pumps the fluid to the system where it is required to be fed.
Diaphragm pumps parts:
(1) Liquid End
(2) Power End
The liquid end has the following parts:
(1) Diaphragm head
(2) Diaphragm plate
(3) Suction valve assembly
(4) Discharge valve assembly
(5) hydraulic oil cylinder
(6) oil replenishing chamber
(7) oil safety valve
(8) oil compensating valve
(10) plunger packings.
Power end has parts:
(2) worm shaft
(3) N- crank, it’s the standard mechanism used by the varied pump manufacturers to create the
eccentricity to vary the stroke length of the pump from zero to a hundred percent
(4) pump frame filled with oil have an oil gauge
(5) oil drain valve
(6) Stroke length adjustment system either manual or a servo motor
DIAPHRAGM METERING PUMPS:
Diaphragm metering pumps are used to handle fluids containing fine slurry particles. These pumps are used to handle fluids that are hazardous to the atmosphere and unsafe for living beings. Fluid handled by diaphragm pumps is corrosive, obnoxious, inflammable, and precious. Diaphragm metering pumps are used to inject the fluids in closed pressurized systems at high pressure with high volumetric accuracy. They are mainly used in chemical, petrochemical, refineries, and R and D set up’s where contamination in the process fluid is not permissible.