Working Principle and Fault Analysis of Voltage Regulator

Classification of pressure regulators
1. Direct-acting pressure regulators
Direct-acting pressure regulators are small in size, large in flow, simple in structure, and easy to install, test and repair. It has a wide range of applications and can be divided into high and medium pressure, high and low pressure, medium and medium pressure, medium and low pressure, etc. according to the different inlet and outlet pressures. The disadvantages are large pressure difference, high energy loss, and gasping and jumping at low flow.
According to the structural form, it can be divided into two types: lever type and balanced valve core type:
1.1. The pull rod series pressure regulator transmits the force through the lever, and the outlet pressure of the pressure regulator is set by the adjustment spring. When the downstream flow of the pressure regulator increases, the outlet pressure P2 tends to decrease. At this time, the pressure in the lower chamber of the main regulator decreases, causing the main film to move downward under the action of the adjustment spring; under the action of the lever, the valve stem drives the valve disc to leave the valve port, so that the pressure regulator opens, thereby increasing the flow through the valve port and maintaining the constant downstream pressure. When the downstream flow of the pressure regulator decreases, its action is opposite to the above process until the pressure regulator is closed.

1.2. The action of the diaphragm (M) of the balanced valve core type pressure regulator
is transmitted to the valve (P) through the valve column (S). The outlet pressure is connected to the diaphragm (M) by the pressure sensing tube, and the force generated counteracts the spring (D). The gas pressure of the skin touches the valve to close the valve, while the spring pressure wants to open the valve (failure opens the valve).
When there is no airflow, the spring opens the valve completely. When overpressure occurs, the pressure regulator closes. The valve pad (Q) and the valve (P) are integrated to ensure complete sealing. When the antagonistic effect of the spring and the outlet pressure reaches a balance, the diaphragm-valve column-valve combination remains stationary, and the outlet pressure meets the spring set point. When the flow demand increases, the outlet pressure drops, the effect of the spring is greater than the outlet pressure, and the valve opens until the outlet set pressure is restored. When the outlet pressure increases, the process is reversed.

The inlet pressure acts in the balancing chamber (B) and can accurately and perfectly balance the switch valve (Q) under all operating conditions.

During the adjustment, the shut-off valve should be opened very carefully and slowly in any case to avoid strong airflows that damage the equipment downstream of the regulator.
The steps are as follows:
1. According to the characteristics of the system, a small amount of gas is allowed to flow step by step. Therefore, open the exhaust plug downstream of the regulator. If it is difficult, open the outlet valve a little.
2. Slowly open the inlet valve a little.
3. Reset the shut-off valve (if any)
4. After the outlet pressure stabilizes, first slowly open the inlet valve completely, and then slowly open the outlet valve completely.
The setting is completed during the operation of the regulator. Slightly open the inlet valve and the exhaust nozzle at the outlet of the regulator. Turn the adjuster (L or T) clockwise to increase the pressure, or counterclockwise to reduce the pressure.

Working Principle of Safety Shut-off Valve
When the signal pressure is abnormal and exceeds (overpressure type) or is lower than (pressure loss type) the start pressure setting value of the shut-off valve, the pneumatic diaphragm in the sensor drives the bumper to move, causing the tripping mechanism to operate. Under the action of the closing spring, the main valve disc quickly closes the valve port, thereby protecting downstream equipment such as the pressure regulator and metering instruments.

The working principle of the safety relief valve
is that when the outlet pressure of the pressure regulating cabinet (station) acting on the lower chamber of the main diaphragm rises to the starting pressure of the relief valve, it overcomes the force of the regulating spring and drives the pull rod to move upward. Under the action of the lever, the valve stem moves downward to push the main valve disc open and discharge the gas. When the pressure drops to the starting pressure setting value due to gas discharge, the valve stem moves upward, and the valve disc closes the valve port under the action of the reset spring.

Maintenance of the pressure regulatorA

. Check the pressure regulator for external leakage with a gas alarm instrument (or soap solution). (Note: The residual smell after release may cause the gas alarm instrument to alarm.)
B. Check the closing pressure of the pressure regulator
Slowly close the valve at the outlet of the pressure regulator, connect the pressure gauge to the detection port at the outlet of the pressure regulator, and turn on the switch. Record the closing pressure value after three minutes and check whether it is within the normal range. If the closing pressure of the pressure regulator is normal, there is no need to dismantle the pressure regulator.
C. Clean the outside of the pressure regulator.
D. Clean the inside of the pressure regulator
When the gas medium contains heavy dirt, the inside of the pressure regulator should be regularly repaired and cleaned. According to the gas quality and use, rubber parts that are easy to swell or age, such as valve disc seals, diaphragms, O-rings, etc., should be regularly inspected or replaced every 3 to 6 months to ensure the safety and normal use of gas supply.
When the medium is artificial coal gas, it is recommended that the maintenance cycle be shortened to 1-3 months. The operation management department should adjust the maintenance cycle appropriately according to the gas quality.
E. Before maintenance, the inlet and outlet valves before and after the pressure regulator should be closed to release the pressure; be careful when reinstalling to avoid damaging parts such as valve ports and diaphragms; after assembly, check whether all movable parts can move flexibly; after maintenance and assembly, perform the post-maintenance settings according to the ventilation operation method of the pressure regulator, and use soap solution to check whether there is any external leakage at all connecting and sealing parts.

Common faults and troubleshooting measures for pressure regulators
1. If there is no gas flowing downstream of the pressure regulating valve, it may be:
1) Insufficient inlet flow, no gas flowing through the pilot
2) The filter is clogged   
3) The cut-off device is triggered
4) The pressure regulator membrane is damaged
2. If the outlet pressure of the pressure regulator drops, it may be:
1) Insufficient inlet flow
2) The actual flow exceeds the design flow of the pressure regulator
3) The inlet filter is blocked
4) The spring is broken
5) The signal pipeline from the pilot to the inside of the pressure regulator is blocked or damaged
3. The increase in the outlet pressure of the pressure regulator may be:
1) Wear of gasket or valve seat
2) Dust accumulation on gasket
3) Damage or rupture of membrane
4) Inflexible movement of regulator stem
4. Vibration of regulator
1) Misalignment of pressure pipe connection or failure to meet installation requirements
2) Too low flow
3) Incorrect diameter of valve hole for taking and releasing teeth on pilot
5. Pressure regulator cannot be adjusted to high pressure
1) Pressure regulator valve gasket expands, valve port cannot reach proper opening
2) Pilot adjusting spring deforms, cannot reach design pressure
6. Unstable and panting outlet pressure of regulator
1) Too many impurities in gas
2) Sudden change of gas pressure or flow
3) High outlet pressure, large fluctuation of front pressure Check the regulator
regularly Inspection steps: First, slowly close the outlet valve and check the pressure in the pipeline between the regulator and the outlet valve. If the system operates normally, the outlet pressure will temporarily increase due to closure, and then gradually stabilize. If the outlet pressure continues to increase, it means that the pressure regulating valve port cannot be sealed, causing system abnormality. At this time, the regulator should be closed.