Diaphragm metering pump fixed stroke diaphragm pump structure improvement

Diaphragm Metering Pump Fixed Stroke Diaphragm Pump Structure Improvements Diaphragm Metering pumps have the disadvantage that the diaphragm is susceptible to breakage, especially to fixed stroke diaphragm pumps. Once the diaphragm ruptures, the metering fluid and the hydraulic oil system contaminate each other and cause serious losses. By adding auxiliary valve and the use of double-diaphragm with alarm, diaphragm metering pump to run more secure.
First, the diaphragm metering pump structure principle:
Diaphragm metering pumps because of its zero leakage, high measurement accuracy, low noise, widely used in petroleum, chemical, pharmaceutical, textile and other industries. It usually delivers flammable, explosive, highly toxic, highly corrosive and radioactive liquids.
Diaphragm metering pump from the motor, transmission and pump head composition. Through the transmission of motor rotation generated by the piston into the reciprocating motion. When the plunger reciprocates between the two ends of the pump cylinder, the diaphragm is alternately bent to the two sides by the hydraulic oil to complete the working process of suction and discharge.
The mini diaphragm pump head is actually a delivery element that consists of an operator's cab, a hydraulic chamber and a hydraulic tank (Figure 1).

Figure 1 Schematic diagram of the mini hydraulic pump chamber with the metering fluid contact, separated by the diaphragm and the hydraulic chamber. Hydraulic chamber and hydraulic tank by the plunger, dual-function hydraulic valve and built-in charge valve. Dual-function hydraulic valve consists of exhaust valve and pressure relief valve. The exhaust valve is located at the highest point of the hydraulic chamber to eliminate the measurement error caused by the gas gathering in the hydraulic chamber. The relief valve is used to protect the pump. Prevent overpressure.
After the inhalation stroke is completed, the diaphragm presses against the push rod and pushes it to the back dead center. At this time fill valve and hydraulic chamber connectivity. If the vacuum chamber to achieve the set value of the vacuum, fill valve open, the mechanical charge. Hydraulic fluid is filled into the hydraulic chamber from the reservoir to balance the oil drained into the tank by the vent valve and plunger seal.
Second, structural improvements and effects:
1, increase the auxiliary valve:
For fixed-stroke diaphragm pumps, make sure that the diaphragm rests on the back support surface before starting. If placed on the front support surface. After the pump is started, the push rod drives the hydraulic oil to act on the diaphragm and continues to move forward, resulting in excessive stress on the diaphragm, which can easily cause rupture. In order to ensure that the diaphragm is placed on the back support surface before starting the pump, Le Bau GmbH adds an auxiliary valve (Figure 2) to the pump head of the diaphragm pump model G3F / M514ZS, which is mounted on the housing of the hydraulic chamber. Auxiliary valve 0.3 ~ 0.7MPa of air into the auxiliary valve piston below the piston to overcome the spring force upward movement, top open the ball valve, the hydraulic chamber and the hydraulic tank between the communication. Pumping fluid, the operating chamber by measuring the pressure of the fluid to promote the diaphragm back movement, the diaphragm placed in the back support surface, to achieve diaphragm positioning. At the same time, hydraulic oil in the hydraulic chamber is returned to the hydraulic tank through the auxiliary valve.

In addition to the auxiliary valve diaphragm positioning role, there are start-up auxiliary functions. The operating procedures: (1) the pump body fluid, (2) solenoid valve power supply, auxiliary valve open, (3) diaphragm positioning, 60s after the diaphragm pump is allowed to start, (4) diaphragm pump start, delay 60s Auxiliary valve closed. In this way, the auxiliary valve is not closed under the start of the pump, the diaphragm pump started without load, reducing the starting torque. After 60s to start loading. Diaphragm pump to increase the auxiliary valve to ensure that the diaphragm is located in the rear support surface when the pump is started, the diaphragm force evenly to prevent the diaphragm rupture due to excessive stress, effectively protecting the diaphragm, the diaphragm double the service life. By adding auxiliary valve, diaphragm pump to achieve a low load start, reducing the starting current, protecting the motor.
2, the diaphragm into a double membrane with alarm:
If the diaphragm ruptures, the high-pressure metering fluid quickly enters the hydraulic reservoir, damaging the oil seal into the gearbox of the transmission, with very serious consequences. In order to detect the rupture of the diaphragm as soon as possible and to minimize the loss, the German Lewa Company changed the diaphragm to a double diaphragm with alarm. The diaphragm is made of PTFE plastic double diaphragm, two diaphragm attached by hydraulic oil. Diaphragm sandwich with diaphragm damage detection system, if there is a diaphragm rupture, metering fluid or hydraulic oil will enter the diaphragm sandwich, so that the pressure increases, the pressure switch action, the signal sent to the central control room through the sensor, alarm. 

When an alarm occurs, open the test discharge fitting (Fig. 1) and rupture of the diaphragm adjacent to the hydraulic chamber if hydraulic fluid is discharged. If the metering fluid is discharged, the process-side diaphragm ruptures.
Diaphragm changed to double diaphragm, if one of the diaphragm is damaged, the diaphragm leak detection system immediately alarm, another diaphragm can still maintain a day operation. Maintenance personnel have plenty of time to take measures to prevent mixing or leakage of hydraulic fluid with metering fluid to ensure the safety and operating life of the equipment in complex and harsh media conditions.