The diaphragm pump is an important part of bead mill operation, and its quality often directly affects the efficiency of the whole line. Here is an overview.
The diaphragm pump, also called a control pump, was developed in the 1970s by adding a diaphragm chamber to the reciprocating piston pump. It is a relatively new type of transfer machine. Unlike ordinary pumps, it acts as an actuator: it receives control signals and changes fluid flow using power such as compressed air, electric drive or hydraulic fluid.
Its core structure consists of the drive section and the diaphragm cylinder head. Hydraulic, pneumatic or electric drive draws in and discharges the medium, which is completely isolated from the drive parts, so it can transfer corrosive liquids, liquids containing particles and high-viscosity, volatile, flammable or toxic liquids completely.
By the power used by the actuator, diaphragm pumps are pneumatic (driven by compressed air), electric (driven by electricity) or electro-hydraulic (driven by the pressure of a liquid such as oil). Bead mill lines mainly use pneumatic and electric pumps.
Pneumatic diaphragm pumps are made in plastic, aluminium alloy, cast iron and stainless steel. Driven by compressed air, they are positive-displacement pumps in which reciprocating deformation of the diaphragm changes the chamber volume, similar in principle to a plunger pump.
Depending on the medium, diaphragms are made of nitrile rubber, neoprene, fluororubber, PTFE or other materials to meet different needs, and pumps are installed in many special applications to transfer media that conventional pumps cannot handle, with satisfactory results.
Features of pneumatic diaphragm pumps
(1) The pump does not overheat and emits no harmful gases.
(2) No electrical sparks.
(3) Not easily blocked.
(4) Minimal agitation of the material, suitable for unstable substances.
(5) Adjustable flow, for example with a throttle valve at the outlet.
(6) Self-priming.
(7) Can run dry without danger.
(8) Can operate submerged.
(9) Handles a very wide range of fluids, from low to high viscosity and from corrosive to thick.
(10) No complex control system, cables or fuses.
(11) Small, light and easy to move.
(12) No lubrication needed, so maintenance is simple and there is no contamination from drips.
(13) Efficiency stays high and does not fall with wear.
(14) Uses energy fully; when the outlet is closed the pump stops automatically.
(15) No dynamic seals, so maintenance is easy and leaks are avoided; no dead point during operation.
In an electric diaphragm pump, the motor drives the diaphragms on the left and right plungers back and forth through a reducer. Four check ball valves in the two pump chambers open and close alternately as the diaphragms move and the chamber volume changes, continuously drawing in and discharging liquid.
Features of electric diaphragm pumps
(1) No priming needed, with self-priming lift of more than 7 m.
(2) Good passage: particles and slurries below 10 mm in diameter pass through easily.
(3) The diaphragm separates the medium from the drive, so there is no external leakage; with no shaft seal, service life is much longer.
(4) Small and light: a planetary cycloidal drive makes the pump compact, about half the size and weight of comparable pumps.
(5) Wetted parts can be cast iron, stainless steel or rubber-lined as required, and motors can be standard, explosion-proof or variable-speed.
With its distinctive design and core advantages, the diaphragm pump is an indispensable transfer specialist in bead mill lines. As materials science and drive technology advance, diaphragm pumps will become safer, more efficient and more environmentally friendly for many more industries.