An overview of the working principle and structure
  
1. Working principle
  
The working principle of the diaphragm pump is shown in Figure 3-1, and the motor (1) drives the crankshaft (2), connecting rod (3) and crosshead (4) through the reducer to convert the rotary motion into linear motion and drive the piston (6) to reciprocate. When the piston (6) moves to the left, the piston (6) drives the hydraulic oil to pull the rubber diaphragm (9) in the diaphragm chamber (10) to the left direction, so that the working chamber volume of the diaphragm chamber (10) increases, and at the same time the discharge valve (11) is closed, and the slurry to be transported opens the feed valve (12) with the help of feeding pressure, enters and fills the diaphragm chamber (10). When the piston (6) moves to the right, close the feed valve (6), and the piston (6) pushes the hydraulic oil to push the rubber diaphragm (9) in the diaphragm chamber (10) to the right, and opens the discharge valve (11) with the help of pressure to transport the slurry to the pipeline.
  
Since the slurry does not contact moving parts such as pistons, the abrasion of these parts is avoided, reducing the number of repairs and operating costs. At the same time, by setting up a sensitive and reliable automatic detection system, the long service life of the rubber diaphragm is guaranteed. The above advantages make reciprocating piston diaphragm pumps ideal equipment for slurry pipeline transportation. The DGMB450/10A diaphragm pump has three diaphragm chambers, each with a 120° initial discharge phase apart, which can make the slurry delivery volume uniform.

(1) Motor (2) Crankshaft (3) Connecting rod (4) Crosshead (5) Oil cylinder (6) Piston (7) Guide rod (8) Probe (9) Rubber diaphragm
(10) Diaphragm chamber (11) Discharge valve (12) Feed valve
Figure 3-1 Working principle diagram of diaphragm pump

2. Structure overview
  
DGMB450/10A diaphragm pump is composed of hydraulic end, power end, hydraulic control system, motor reduction part assembly, electronic control system, flow compensation tank and other components.

(1) Flow compensation tank (2) Hydraulic end (3) Hydraulic control system (4) Electronic control system (5) Power end (6) Motor reduction part mounting
Figure 3-2 Schematic diagram of diaphragm pump structure

2.1 Liquid end
  
The hydraulic end completes the conveying of slurry through the movement of piston, piston rod, rubber diaphragm and opening and closing of the inlet and outlet valves, which is mainly composed of feeding pipe (1), feeding poppet valve box (2), bending pipe (3), diaphragm chamber (4), discharge poppet valve box (5), nitrogen package (6), discharge pipe (7), cavity and cylinder (8), hydraulic end base (9) and other parts. The DGMB450/10A diaphragm pump has three chambers and cylinders, three diaphragm chambers, three infeed poppet valve boxes and three discharge poppet valve boxes at the hydraulic end. The right side of the cavity and cylinder is connected to the power end, and the left side is connected with the diaphragm chamber by bolting the positioning stop; The feeding port of the diaphragm chamber is connected with the inlet poppet valve box by a bend pipe, and the discharge port and the discharge poppet valve box are connected by flange. The feeding pipe and the discharge pipe respectively connect each feed poppet valve valve box and each discharge poppet valve valve box together, and there are two nitrogen packs installed at the discharge pipe part, and a discharge nitrogen package at the discharge pipe, and the slurry is discharged from the discharge port after pressure balancing through the stable pressure air bag in the nitrogen pack.

(1) Feeding pipe (2) Feeding poppet valve box (3) Bending pipe (4) Diaphragm chamber (5) Discharging poppet valve box
(6) Nitrogen package (7) Discharge pipe (8) Cavity and cylinder (9) Hydraulic end base
Figure 3-3 Schematic diagram of the structure of the hydraulic end

2.1.1 Infeed poppet valve box

(1) Valve box body (2) Valve cone (3) Valve seat (4) Valve rubber (5) Valve nut (6) Guide sleeve (7) Valve cover 
(8) Valve spring (9) Valve cone guide
Figure 3-4 Schematic diagram of the structure of the feed poppet valve valve box

The valve cone (2) in the feed poppet valve box is a spring-loaded conical valve structure, and the valve seat (3) is made of wear-resistant alloy steel material and subjected to surface hardening treatment, which is resistant to wear and impact. The mating surface of the valve seat (3) and the valve box (1) is a cone surface, which can ensure that it fits closely and there is no floating phenomenon when subjected to liquid impact. The valve seat (3) and the valve cone (4) on the valve cone (2) are sealed in the form of a cone, and the valve cone (2) is opened and closed by the negative pressure and spring force of the slurry and the gravity of the valve cone to achieve the purpose of feeding and discharging. The valve seat (3) can be disassembled hydraulically by means of the pressure fitting installed on the valve box (1), which is simple and easy. The valve cone guide (9) and the guide sleeve (6) play a guiding role in the up and down movement of the valve cone (2). The valve box (1) is connected with the feed pipe by flange, and its side is designed with a discharge port, which is used to discharge slurry during maintenance.

2.1.2 Discharging poppet valve box

(1) Valve box body (2) Valve cone (3) Valve seat (4) Valve rubber (5) Valve nut (6) Guide sleeve (7) Valve cover 
(8) Cone spring (9) Cone guide
Figure 3-5 Schematic diagram of the structure of the valve box of the discharge poppet valve

The internal parts of the valve cone (2), valve seat (3), valve rubber (4) and other internal parts of the discharge poppet valve valve box are the same as the feed valve box, and the valve box body (1) and the diaphragm chamber are connected by bolts, and its side is designed with a discharge port, and the discharge port is used to discharge slurry during maintenance.
  
2.1.3 Diaphragm chamber

(1) Guide rod (2) Diaphragm cavity (3) Rubber diaphragm (4) Sealing ring (5) Diaphragm chamber cover (6) Shield
Figure 3-6 Schematic diagram of the structure of the diaphragm chamber

The space formed by the combination of the diaphragm cavity (2) and the diaphragm cover (5) is divided into the rubber diaphragm stroke position space (propulsion fluid flow channel) and the slurry flow channel by the rubber diaphragm (3). The slurry flow channel has two openings, the bottom inlet is connected to the feed poppet valve box through the elbow, and the top outlet is connected to the discharge poppet valve box. The rubber diaphragm (3) separates the propellant fluid oil from the slurry, avoiding the mixing of the propellant fluid oil and the slurry to ensure that the moving parts in the cylinder work in the clean oil, thereby prolonging the service life of the piston and the replacement time of wearing parts. The rubber diaphragm is equipped with a guide rod (1), and the diaphragm stroke detection device composed of the guide rod (1) and the oil replenishment signal generator is used to detect the diaphragm stroke position to ensure that the rubber diaphragm (3) works within the optimal working range.
  
2.1.4 Nitrogen packs

(1) Shell (2) Airbag (3) Gland 
Figure 3-7 Schematic diagram of the structure of the nitrogen package

The nitrogen package is mainly composed of shell (1), air bag (2) and gland (3), etc., and is installed in the upper part of the discharge pipe and the discharge pipe. Before the commissioning and operation of the equipment, the nitrogen pack can be pre-filled with nitrogen through the needle throttle valve in the inflation tool and valve device to balance the discharging working pressure and form a discharging pressure compensation system. The inflation pressure values are described in section 2.2.6 of this manual.

Figure 3-8 Schematic diagram of nitrogen-packed gas path

2.1.5 Oil chamber

(1) Support sleeve (2) Cavity (3) Oil replenishment signal device
Figure 3-9 Schematic diagram of oil cavity structure

The cavity (2) and the power end box are positioned through the stop and firmly closed on the power end box. The function of the support sleeve (1) is to support the movement of the guide rod. The function of the make-up oil signal device (3) is to detect the diaphragm stroke position by sending a signal to the PLC.
  
2.1.6 piston cylinder
　　
The piston (1) is mounted on the piston rod (4) and fastened with a nut, moving in a replaceable cylinder liner (2). The piston rod (4) and cylinder liner (2) are made of alloy steel, and the surface is hardened for high wear resistance. Even if the slurry enters the piston cylinder due to rupture of the diaphragm, it will not immediately damage the piston rod (4) and cylinder liner (2). The piston (1) adopts a combined sealing structure, and its sealing ring has the characteristics of high strength, good wear resistance and good oil sealing effect, and at the same time it is also equipped with a lead ring on the piston, which can improve the service life of the piston and cylinder liner.

(1) Piston (2) Cylinder liner (3) Oil cylinder gland (4) Piston rod 
Figure 3-10 Schematic diagram of piston cylinder structure

2.2 Power end

(1) Power end box (2) Clamp (3) Middle rod (4) Crosshead (5) Connecting rod (6) Crankshaft
Figure 3-10 Schematic diagram of the power end structure

The power end box (1) adopts a welded structure, and the stress relief treatment is carried out after welding. The crankshaft (6) is supported and positioned by cylindrical roller bearings, and the adjustment and positioning of the connecting rod (5) is completed automatically. The connecting rod (5) and the crosshead (4) are supported by the pin bearing, and the crosshead (4), the medium rod (3) and the piston rod are pushed to reciprocate linear motion according to the eccentricity. The crosshead (4) slides in the guide plate, and there is sufficient cooling lubricant to ensure that the crosshead (4) works well. The intermediary rod (3) is threaded with the piston rod and locked by the clamp (2), and the piston rod and the inspection holes of the crosshead and guide plate are provided on both sides of the power end box (1) for easy inspection and maintenance. The lid is equipped with an exhaust hole.
  
2.3 Hydraulic Control System
  
The hydraulic control system is mainly composed of diaphragm stroke control system, hydraulic oil tank, lubrication system, flushing system, overpressure protection and exhaust system, valve device and inlet and discharge data reading and collection device, etc., through the normal operation of each system, to ensure the normal operation of the equipment.
  
2.3.1 Diaphragm stroke control system

(1) Flushing oil pump motor unit (2) Check valve (3) Two-position two-way valve group (4) Pneumatic triplet (5) Two-position three-way solenoid valve group
(6) Pressure switch (7) Seismic pressure gauge (8) Accumulator (9) Filter (10) Propulsion liquid oil pump motor unit
Figure 3-11 Schematic diagram of diaphragm stroke control system

After the propulsion fluid oil pump motor unit (10) absorbs oil in the independently installed hydraulic oil tank and is filtered by the mesh filter (9), the hydraulic oil is fed into the two-position two-way valve group (3) and the accumulator (8) respectively through the one-way valve group (2). Accumulator (8) is one of the important components of diaphragm stroke control system, mainly to store energy, stabilize pressure, reduce energy consumption, absorb oil pressure pulse, ease impact and other functions, diaphragm pump using large diameter, threaded connection of capsule accumulator, need to pre-charge nitrogen before use, its pre-charge pressure is 0.3 ~ 0.4MPa.
  
When the amount of oil in the diaphragm chamber is abnormal, the guide rod magnetic ring moving with the diaphragm reciprocating movement to the position of the signal generator, after the signal generator detects the magnetic field line, it will send an oil replenishment or oil discharge signal to the electronic control system PLC, PLC directs the two-bit three-way solenoid valve action, cut off the compressed air to make the two-way valve channel conduction, so that the amount of oil in the diaphragm chamber can be supplemented or excreted, so as to ensure that the volume of propulsion fluid between the piston and the diaphragm is kept within the limit value. After adjusting the amount of propulsion fluid oil, the rubber diaphragm is always in the optimal working range to ensure that the work of conveying slurry can be carried out normally.

A oil drain valve B oil replenishment valve 
(1) Check valve (2) nozzle (3) sealing block (4) valve push rod (5) valve spring (6) small diaphragm
Figure 3-12 Schematic diagram of the structure of a two-position two-way valve

The two-position two-way valve is composed of oil replenishment valve B and oil discharge valve A. The normal state is that the solenoid valve is in an open circuit state, the gas enters the valve, compresses the small diaphragm (6), and closes the valve push rod (4) and nozzle (2). When the oil replenishment action is required, the oil replenishment solenoid valve is closed, the gas is discharged, the sealing block (3) in the oil replenishment valve B rises under the action of spring force, and the oil passes through the nozzle (2) and the check valve (1) after the nozzle mouth is opened, and the diaphragm suction stroke enters the diaphragm cavity, and when the diaphragm discharge stroke, the propellant fluid cannot enter the cylinder because the pressure in the cylinder is greater than the oil pressure of the oil replenishment pipeline of the propulsion fluid system, but due to the action of the check valve (1), the oil cannot overflow from the valve cavity of the oil replenishment valve B. When the oil discharge action is required, the oil discharge solenoid valve is closed, the gas path is cut off, the sealing block (3) in the oil discharge valve A rises under the action of spring force, and the oil is discharged through the nozzle (2) in the diaphragm discharge stroke.
  
2.3.2 Lubrication systems

(1) Oil pump motor unit (2) Seismic pressure gauge (3) Flow indicator (4) Filter
Figure 3-13 Schematic diagram of the lubrication system

The lubrication system provides forced lubrication for crankshaft bearings, crosshead pin bearings, connecting rod bearings, intermediate support bearings, crossheads, guide motion pairs and intermediate rod sealing devices. The pressure gauge (2) on the pipeline can display the lubricating oil pressure, and the flow meter (3) is responsible for providing the lubricating oil flow value to the electronic control system to realize the alarm and shutdown caused by insufficient lubrication flow. In order to ensure the reliable operation of the lubrication system, the double-drum mesh filter (4) should be cleaned regularly.
  
The double-tube mesh filter is composed of two single-barrel filters, which have the characteristics of simple structure and convenient use. When the filter element of one monotube filter is blocked and needs to be cleaned or replaced, there is no need to stop the main engine work, just open the balance valve and turn the directional valve, the other filter can participate in the work, and then replace the blocked filter element. Whether the monotube filter is in the working state can be determined by observing the pointing of the indicator groove, the filter pointed to by the indicator slot is in the working state, and when it is horizontal, it means that both monotube filters are in working state. When the indicator groove cannot be seen, the bleed valve of a single drum filter can be released, and the pressure gauge of the oil circuit where the filter is located can be observed, the pressure gauge display value becomes zero to indicate that it is in use, if the pressure gauge display value does not change, it means that the monotube filter is in a deactivated state and the filter can be cleaned.

Figure 3-14 Schematic diagram of the double-tube mesh filter

2.3.3 Flushing system

(1) Seamless steel pipe (2) Tee joint
Figure 3-15 Schematic diagram of the flushing system

The flushing system uses the flushing oil pump motor unit in the diaphragm stroke control system to suck out the hydraulic oil in the hydraulic tank, flow through the tee joint (2) and related oil pipelines (seamless steel pipe (1)), and continuously flush the piston rod, piston cylinder and plug to play a lubrication and cooling role, and then ensure the good movement of the piston in the piston cylinder.
  
2.3.4 Overpressure protection and exhaust systems 

(1) Accumulator assembly (2) Relief valve (safety valve) (3) Check valve (4) Globe valve
Figure 3-16 Schematic diagram of overpressure protection and exhaust system

The working principle of overpressure protection is: when the slurry discharge pressure of the diaphragm pump reaches or exceeds the maximum working pressure, the main motor will be powered off, because the motor will not stop running immediately under the action of inertia force, and the working pressure will continue to rise; Or when the working pressure switch fails and the discharge pressure continues to rise, if the discharge pressure exceeds the set value of the relief valve (2) (the opening pressure of the relief valve is set to 11.5MPa), the relief valve (2) will automatically open and discharge the propulsion fluid through the return pipe and the relief valve (2) to the hydraulic tank for pressure relief. Therefore, the hydraulic system and other components of the diaphragm pump can be protected from damage due to excessive pressure.
  
The working principle of exhaust is: when there is gas in the diaphragm cavity, manually open the shut-off valve (4), and discharge the gas contained in the propulsion fluid oil back into the oil tank through the check valve (3) and the return pipe. The function of the check valve (3) is to prevent the gas from flowing back.
  
Note: Before each restart of the diaphragm pump, the manual shut-off valve should be opened for exhaust treatment to ensure good operation of the equipment.
  
2.3.5 Hydraulic tanks

(1) Air filter (2) Box cover (3) Box body
Figure 3-17 Schematic diagram of hydraulic oil tank

The hydraulic oil tank is mainly to provide hydraulic oil for the diaphragm stroke control system and flushing system. In order to ensure the cleanliness of the tank, the tank should be cleaned regularly. Clean the tank every three months to six months for initial use, and every other year thereafter.
  
2.4 Motor reducer part assembly

(1) Main motor (2) Elastic column pin tooth coupling (3) Reducer (4) Drum tooth coupling
Figure 3-18 Schematic diagram of motor reducer assembly

The main motor (1) and the reducer (3) are mounted on the base of the split structure. The mounting surface of the base is machined to ensure the concentric alignment of the main motor (1) and the reducer (3), the elastic column pin tooth coupling (2), and the drum tooth coupling (4). The main motor (1) shaft and the reducer (3) input shaft are connected by an elastic column pin tooth coupling (2), and the output shaft of the reducer (3) and the active shaft of the power end are connected by a drum tooth coupling (4) to input the power to the power end. The elastic column pin tooth coupling (2) and drum tooth coupling (4) are equipped with safety guards to ensure safety when the user is approaching.

2.5 Electronic control system

The control items of the electronic control system are: rubber diaphragm working position control, maximum working pressure control, propulsion liquid air pressure control, propulsion liquid oil pressure control; Propulsion liquid oil pump motor, flushing oil pump motor, lubricating oil pump motor, main motor, etc. The above control items are realized by PLC, and the interlocking function between each control system is completed.
  
(1) Conditions (logic and conditions) that must be met at the same time to start the main motor
(1) The propulsion liquid oil pump motor unit is operating normally;
(2) The lubricating oil pump motor unit is operating normally;
(3) The flushing oil pump motor unit is operating normally;
(4) Propulsion fluid air pressure> 0.45MPa;
(5) Working pressure≤ 10MPa;
(6) The service knob is reset.
  
(2) Main motor shutdown control conditions (if one condition is met, it will stop, and it can also be adjusted according to the user's process requirements)
(1) The operation failure of the propulsion liquid oil pump motor unit;
(2) Repair and drain faults;
(3) Lubrication flow≤ 7.8L/min;
(4) Air pressure≤ 0.4MPa;
(5) Working pressure≥ 10.6MPa;
  
(3) Alarm non-stop control conditions
(1) Oil replenishment and discharge alarm;
(2) Working pressure≥ 10.4MPa;
(3) Air pressure≤ 0.45MPa;
(4) Lubrication flow≤ 17.8L/min;
  
The diaphragm position control system consists of a detection unit, a control unit, and an execution unit. Detection unit: the guide rod is driven by the diaphragm to move back and forth and through the action of the complement signal generator, the guide rod position signal is converted into a switching electrical signal and transmitted to the control unit PLC; The execution unit is a two-position three-way electromagnetic directional valve and a two-way valve group in the diaphragm stroke control system, and the PLC issues instructions to the execution unit to control the amount of oil in the diaphragm chamber through oil replenishment and drainage, so as to limit the position of the diaphragm.