What is a Diaphragm Pump?

Diaphragm pumps are actually plug pumps, which use a membrane to separate the liquid to be transported from the movable column and the pump cylinder, thereby protecting the movable column and the pump cylinder. The left part of the diaphragm in contact with the liquid is made of a corrosion-resistant material or coated with a layer of corrosion-resistant material; the right side of the diaphragm is filled with water or oil. ^[1]

Diaphragm pump

Features:

1. No shaft seal, no leakage, and wide flow passage, so it contains particles, high viscosity [viscosity up to 10,000 centipoise], volatile and corrosive media, will not cause environmental pollution and endanger personal safety.

2. There are no rotating parts, and the passing performance is good, allowing the maximum particle diameter to reach 10 mm. There is no shear flow of liquid, and the wear of the pump itself is small. It has little damage to the conveyed material, and can convey sludge and living bodies such as small fish fry.

3. No need to irrigate water, strong self-priming ability, suction range up to 7 meters, dry breathing for a long time without damage to the pump. Once overloaded, the pump will automatically stop. When the load returns to normal, it can automatically start operation. It has a self-protection function (the electric pump does not have this function).

4. The lift of the pneumatic pump reaches 50 meters, the electric pump reaches 30 meters, and the maximum outlet pressure can reach 0.6 MPa.

Abstract: This paper mainly introduces the composition and classification of diaphragm pumps, as well as the selection principles and methods of the types of adjustment rooms, actuators, modes of action, and flow characteristics.

The structure of the diaphragm pump air chamber is generally used to separate the water chamber from the air chamber. After filling the air chamber with compressed air, the pulsation of water in the water chamber is absorbed by the compressed air in the air chamber through the rubber diaphragm. The role of the air chamber is to use the compressibility (or elasticity) of the air to absorb the pulsation of the water from the diaphragm pump and stabilize it. The water flow into the system is basically smooth. However, in order to meet the requirements of basically stable water flow, the air pressure in the gas chamber should be compatible with the water pressure.

Diaphragm pump air chamber inflation method: Before the diaphragm pump runs, inflate the air chamber first, and its air pressure is greater than the working pressure of the pump. Drive the diaphragm pump to adjust the working pressure. At this time, the hose of the pump's water outlet can be shaken violently. Take a needle and deflate at the air nozzle. As the deflation progresses, the jitter of the outlet hose will gradually disappear. After the water outlet hose is stable, stop deflating.

Diaphragm Pump Working Troubleshooting Guide When one or more of the following situations are encountered, this information can be used as a guide to help you develop maintenance measures.

As shown below, there are several abnormal operating conditions described in this guide: A) fast cycle / low flow B) no cycle / slow cycle / irregular cycle C) leakage loss D) noise E) component break

These situations are likely to be encountered during the application of the pump. Each situation can be divided into multiple possible causes. This guide lists the causes of failures and gives the appropriate corrective actions. The meaning of all specific terms in the guide is listed later.

Air valve-copper or stainless steel valve housing is fixed to the pump center body by four bolts.

Piston--Aluminum cylinder is enclosed in air valve to control air flow.

CavitationDue to a decrease or lack of fluid supply to the pump inlet, the pump discharge is below the rated volume. In fact, the liquid chamber is filled with fluid before discharge.

Static Discharge Head-Vertical distance (in feet) from the pump centerline to the free transfer point. Inlet Pressure-The inlet is measured in pounds, including the specific gravity and flow rate of the fluid.

Specific gravity-The ratio of flow to water weight at 68F. 68F water has a specific gravity of 1.0

Static suction lift--the vertical distance from the liquid level to the pump centerline, the pump should be above the liquid level.

Vapor pressure-The pressure of the vapor on all free surfaces of all liquids. In any pump operating system, the operating pressure must not be lower than the vapor pressure, otherwise the formed steam will partially or completely shut off the fluid that is pumped into the pump. Viscosity-Due to the friction inside the fluid, the property of viscosity makes the fluid flow resistance.

Water hammer action-

The water hammer is called a water hammer when the power is suddenly cut off or the valve closes too quickly. Due to the inertia of the pressure water flow, a water shock wave is generated, just like a hammer. The force generated by the water shock wave back and forth can sometimes be large, thereby damaging valves and pumps. "Water hammer effect" means that inside the water pipe, the inner wall of the pipe is smooth and the water flows freely. When the open valve is suddenly closed, the water flow will generate a pressure on the valve and the pipe wall, mainly the valve. Because the pipe wall is smooth, the subsequent water flow is inertial. Under the action, it quickly reaches the maximum and has a damaging effect. This is the "water hammer effect" in hydraulics, which is the positive water hammer. This factor must be considered in the construction of hydraulic pipelines. On the contrary, the closed valve is suddenly opened. Later, water hammer is also called negative water hammer, which also has a certain destructive force, but it is not as big as the former ...

Pneumatic diaphragm pump is a new type of conveying machine, which uses compressed air as the power source, and uses the diaphragm inside the cylinder to move back and forth to do work, so as to achieve the purpose of conveying various media.

Media that can be transported: Pneumatic diaphragm pumps are suitable for transporting various corrosive, granular liquids, as well as high-definition, volatile, flammable, and highly toxic liquids.

Choice of materials:

1. The materials used for the shell are: aluminum alloy, cast iron, stainless steel.

2. The materials used for the diaphragm are: nitrile rubber, neoprene, fluorine rubber, and polytetrafluoroethylene.

Working principle of pneumatic diaphragm pump:

Each of the two symmetrical working chambers of the pump is equipped with an elastic diaphragm. The connecting rod connects the two diaphragms into one body. After the compressed air enters the valve from the air inlet of the pump, it is pushed into the two working chambers. The diaphragm action drives the two diaphragms connected by the connecting rod to move synchronously. At the same time, the gas in the other working chamber is exhausted from the back of the diaphragm. Once the end of the stroke is reached, the gas distribution mechanism automatically introduces compressed air into the other working chamber and pushes the diaphragm to move in the opposite direction. A synchronous reciprocating motion of the two diaphragms is formed. Each working chamber is provided with two one-way ball valves. The reciprocating movement of the diaphragm causes the inner volume of the working chamber to change, forcing the two one-way ball valves to alternately open and close, thereby continuously sucking and discharging liquid.

use:

1. It can pump all kinds of sewage.

2. It can pump various chemical corrosive agents, petroleum, mud, and greasy dirt.

3. A variety of highly toxic, flammable and volatile liquids can be pumped.

4. It can pump all kinds of strong acid, strong alkali and strong corrosive liquid.

5. It can pump various high-temperature liquids, and the highest temperature can withstand 150 .

6. It can be used as the pre-pressure feeding equipment for various solid-liquid separation equipment.

Features of pneumatic diaphragm pump:

1. No need for irrigation and diversion, suction up to 7m, head up to 50m, outlet pressure) 6kgf / CmZ.

2. Good flow performance, allowing the maximum particle diameter to reach 10mm. When pumping mud and impurities, there is little wear on the pump.

3. The head and flow can be adjusted steplessly through the opening of the air valve (the air pressure is adjusted between l-7kgf / cmZ).

4. The pump has no rotating parts and no shaft seal. Due to the reciprocating movement of a pair of diaphragms, various media are pumped. Because the moving parts of the pump are completely separated from the working medium, the conveyed medium will not leak outward, and environmental pollution and personal hazards are avoided.

5. Do not use power supply, can be used in flammable and explosive places, safe and reliable.

6, can be submerged in the medium instead of submersible pumping liquid.

7. When opening and stopping the pump, you only need to open and close the gas valve to operate. The pump will not be damaged even if there is no medium pumping or sudden stop due to unexpected conditions for a long time. Once overloaded, the pump will automatically stop and has self-protection. When the load returns to normal, it can start automatically.

8. Simple structure and few wearing parts. The diaphragm pump has a simple structure and is easy to install and maintain. The pump will not contact the moving parts such as the valve, connecting rod, etc. when transporting the medium, which avoids the corrosion and wear of the parts.

9, can transport more open liquids.

10. No oil lubrication is used, even if idling, it has no effect on the pump. ^[2]