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Introduction to the working principle of Nuoguan NORGREN pressure reducing valve

NORGREN pressure reducing valve is an essential accessory for pneumatic regulating valve. Its main function is to decompress and stabilize the pressure of the air source to a fixed value, so that the regulating valve can obtain stable air source power for adjustment. NORGREN pressure reducing valve can be divided into membrane type, spring diaphragm type, piston type, lever type and bellows type according to the structure; it can be divided into single seat type and double seat type according to the number of valve seats; It is positive and negative.
NORGREN pressure reducing valve failure phenomenon: unstable pressure fluctuation
NORGREN pressure reducing valve failure analysis:
1. Air is mixed into the oil. Damping holes are sometimes blocked
3. The roundness of the spool and the valve body exceeds the specified limit, causing the valve to become stuck
4. The spring is deformed or stuck in the spool, making the slide move difficult or the spring is too soft
5. The steel ball is not round, the steel ball is not well matched with the valve seat or the poppet valve is not installed correctly.
NORGREN pressure reducing valve elimination method:
1. Eliminate air in oil
2. Cleaning damping
3. Grinding valve hole and slide valve
4. Replacement spring
5. Replace the steel ball or disassemble the cone valve to adjust
Fault phenomenon: secondary pressure rise is not high
NORGREN pressure reducing valve failure analysis:
1. External leakage
2. Poor valve and valve seat contact
Method of exclusion:
1. Replace seals, tighten screws, and ensure torque uniformity
2. Repair or replacement
Failure phenomenon: no reduction
Pressure effect
Failure analysis:
1. The drain port is blocked; the drain pipe is connected to the return pipe and has a return pressure
2. The main spool is in the fully open position
Method of exclusion:
1. The drain pipe must be separated from the return pipe and returned to the tank separately
2. Repair and replace parts. Check oil quality
The function principle of the NORGREN pressure reducing valve is to reduce the water pressure by the local resistance of the flow passage in the valve to the water flow. The range of the water pressure drop is automatically adjusted by the pressure difference between the inlet and outlet of the membrane or the piston connected to the valve flap. The principle of constant pressure reduction is to use the water pressure ratio control of the floating piston in the valve body, and the pressure reduction ratio at the inlet and outlet ends is inversely proportional to the ratio of the piston area on the inlet and outlet sides. The pressure reducing valve works smoothly without vibration; there is no spring in the valve body, so there is no spring corrosion and metal fatigue failure; the sealing performance is good and does not leak, so the pressure is reduced (when the water flows) and the static pressure is reduced (the flow rate is 0 o'clock); especially during decompression without affecting water flow.
Basic performance of NORGREN pressure reducing valve (1) Pressure regulating range: It refers to the adjustable range of the pressure reducing valve output pressure P2, within which the specified accuracy is required. The pressure regulation range is mainly related to the stiffness of the pressure regulating spring.
(2) Pressure characteristics: It refers to the characteristic that the output pressure fluctuates due to input pressure fluctuation when the flow rate g is constant. The smaller the output pressure fluctuation, the better the characteristics of the pressure reducing valve. The output pressure must be lower than the input pressure setting to substantially not change with the input pressure.
(3) Flow characteristics: It refers to the input pressure timing, and the output pressure changes with the change of the output flow g. When the flow rate g changes, the smaller the change in the output pressure, the better. Generally, the lower the output pressure, the smaller the fluctuation with the output flow.
NORGREN pressure reducing valve is a valve that adjusts the inlet pressure to a certain required outlet pressure and relies on the energy of the medium itself to make the outlet pressure automatically stabilize. From the point of view of fluid mechanics, the pressure reducing valve is a throttling element whose local resistance can be changed, that is, by changing the throttling area, the flow velocity and the kinetic energy of the fluid are changed, resulting in different pressure loss, thereby achieving the purpose of decompression. Then, relying on the adjustment of the control and regulation system, the fluctuation of the post-valve pressure is balanced with the spring force, so that the post-valve pressure remains constant within a certain error range.
NORGREN pressure reducing valve common fault
(1) The outlet pressure is almost equal to the inlet pressure, no decompression
This failure phenomenon is manifested as: the inlet and outlet pressures of the pressure reducing valve are nearly equal, and the outlet pressure does not change with the rotation adjustment of the pressure regulating handle. The causes and troubleshooting methods are as follows.
1Because there is a burr on the edge of the main valve core or the hole of the valve body, or there is dirt in the gap between the main valve core and the valve body hole, or the tolerance of the main valve core or valve hole is too poor. The hydraulic clamp is generated, and the main spool is stuck at the position of the maximum opening (max). Since the opening is large, the oil is not decompressed. At this time, according to the above situation, the method of deburring, cleaning and repairing the valve hole and the accuracy of the valve core can be respectively excluded.
2 Because the main valve core and the valve hole are too tightly fitted, or the valve hole or the valve core is assembled during assembly, the valve core is stuck at the maximum opening position, and a reasonable gap can be selected at this time. J-type pressure reducing valve with clearance is generally 0. 007 ~ 0.015mm, can be properly polished before the valve hole, and then with the valve core.
3 The main spool has short damper hole or valve seat hole blockage, and the automatic adjustment function is lost. The main valve spring force pushes the main valve to the maximum opening degree, which becomes straight through and the inlet pressure is equal to the outlet pressure. Available 1. Omm wire or blown through the orifice with compressed air and cleaned and assembled.
4 pairs of J-type pressure reducing valve, the damping member with damping hole is pressed into the main valve core, and may be flushed out due to insufficient interference during use. After flushing out, the pressure between the oil inlet chamber and the oil outlet chamber is equal (no damping), and the upper and lower force areas of the valve core are equal, but the oil outlet chamber has a spring, so the main spool is always at the maximum opening position, so that the outlet The pressure is equal to the inlet pressure. At this point, the damper with a slightly larger outer diameter needs to be reworked and re-pressed into the main spool.
5JF type pressure reducing valve, the oil drain 孑L is blocked by the oil plug at the factory. When the oil plug is not unscrewed and used, the main valve core upper chamber (spring chamber) is trapped of oil, causing the main spool to be at the maximum opening without decompression. The J-tube valve is the same. J-type plate valves can also occur if the L-port is not connected to the oil pool when the mounting plate is designed.
6 pairs of J-tube valves, it is easy to install the wrong direction of the valve cover (wrong 90 or 180) during the disassembly, so that the outer drain port is blocked, the oil can not be drained, resulting in the same trapped oil phenomenon, so that the main valve top Maximum opening without decompression. Install the bonnet assembly direction when repairing.
7 pairs of JF type pressure reducing valve, when the top cover is installed in the wrong direction, the output oil hole will be connected with the oil drain hole, so that no decompression is required, and care must be taken.
(2) The outlet pressure is very low, even if the pressure regulating hand wheel is tightened, the pressure will not rise.
1 The pressure-reducing valve inlet and outlet ports are reversed: the plate-type valve is designed incorrectly for the mounting plate, and the pipe-type valve is incorrectly taken over. The inlet and outlet ports of the J-type pressure reducing valve are just the opposite of the inlet and outlet ports of the Y-type relief valve. When using the user, please pay attention to the stamps (Pl, P2, L, etc.) that are printed near the oil port on the valve, or consult the hydraulic component catalog, and do not design wrong and wrong.
2 The inlet pressure is too low. After the orifice is throttled, the pressure output from the outlet is lower. At this time, the cause of the low inlet pressure (such as the relief valve failure) should be ascertained.
3 The downstream circuit load of the pressure reducing valve is too small. The pressure cannot be established. At this time, it can be considered to solve the problem by connecting the throttle valve in series downstream of the pressure reducing valve.
4The pilot valve (cone valve) and the valve seat mating surface are in poor contact due to dirt retention, and are not tightly closed; or the pilot cone valve is severely scratched, the valve seat fits 孑L out of round, and there is a gap, resulting in a pilot spool Not in close contact with the seat hole.
5 When removing the repair, the leaking poppet or poppet valve is not installed in the seat hole. In this regard, the assembly or closeness of the poppet valve can be checked.
6 The long orifice on the main spool is blocked by dirt. As shown in Figure 3-21, the oil in the P2 chamber cannot flow into the main valve spring chamber through the long orifice e. The feedback pressure of the outlet chamber P2 is not transmitted to the pilot cone. On the valve, the pilot valve loses its regulation of the main valve outlet pressure. After the orifice is blocked, the main valve P. The cavity loses the effect of the oil pressure p3, so that the main valve becomes a direct-acting slide valve with a weak spring force (only the main valve balance spring), so when the pressure at the oil outlet is very low, the balance spring can be overcome. The force reduces the orifice of the pressure reducing valve to a small ymin, so that the inlet port pressure p1 is greatly reduced to p2 through the ymin orifice, so that the pressure at the outlet port does not come up. The long orifice should be made smooth.
7The pilot valve spring (pressure regulating spring) is misfitted into a soft spring, or the permanent deformation or breakage due to spring fatigue causes the p2 pressure to be low, and can only be adjusted to a certain low value, which is much lower than this. The maximum regulated pressure of the pressure reducing valve.
8 The pressure regulating handle is not properly screwed due to thread strain or effective depth, so the pressure cannot be adjusted to the maximum.
9 The sealing between the bonnet and the valve body is poor, and the oil leaks seriously. The cause may be that the O-ring is missing or damaged, the compression screw is not tightened, and the end face flatness error occurs when the bonnet is processed. Generally, it is convex and concave.
10 The main spool is stuck at a small opening position due to dirt, burrs, etc., so that the outlet pressure is low. Can be cleaned and deburred.
(3) Not regulated, the pressure is large, sometimes it is noisy
According to the relevant standards, the pressure relief of the J-type pressure reducing valve is o. lMPa, JF type is o. 3MPa, exceeding this standard, the pressure is large and the voltage is not regulated.
Type 1J and JF type pressure reducing valves are pilot type, and the pilot valve and the relief valve are common. Therefore, the reason for the large pressure swing and the elimination method can be referred to the relevant part of the relief valve.
2 When the pressure reducing valve is used under the rated flow rate, the main valve oscillation phenomenon often occurs, so that the pressure reducing valve is not regulated. At this time, the pressure at the outlet port is increased, the pressure is reduced, and the pressure is gradually increased and then stepped down. Be sure to use a pressure reducing valve that fits the model specifications.
3 The back pressure of the oil drain port L is large, and the pressure swing is large and unregulated. The drain pipe should be separately returned to the oil.
4 spring deformation or poor stiffness (poor heat treatment), resulting in large pressure fluctuations, can replace the qualified spring.

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