Common faults and causes:
Single Girder Bridge Crane is composed of girder weld by steel plate and I steel, end girder, Electric Hoist and traveling mechanism. The electric hoist runs along the lower flange of the I steel of the girder to accomplish article hoisting. It features light structure and easy installation and maintenance, and is widely used in differenct places or hoisting such as factories, warehouses and material yards, capacity from 1t~20t, span length is 7.5m~22.5m(subject to non-standard design according to user's requirements). The classification group is A3,and the operation ambient temperature is -25℃~+40℃.
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(1) The regulating valve does not operate. The symptoms and causes are as follows:
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a. No signal, no gas source: 1 gas source is not open. 2 Because the water source water freezes in winter, the air duct is blocked or the filter and pressure reducing valve are blocked. 3 compressor failure. 4 gas source manifold leaks.
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b. There is a gas source, no signal: 1 regulator failure. 2 signal tube leaks. 3 Locator bellows leaks. 4 Adjust the mesh diaphragm damage.
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c. The positioner has no air source: 1 the filter is clogged. 2 The pressure reducing valve is faulty. 3 The pipe leaks or is blocked.
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d. The positioner has a gas source, no output: the orifice of the positioner is blocked.
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e. There is signal, no action: 1 valve core falls off, 2 valve core and valve seat are stuck. 3 The stem is bent or broken. 4 valve seat spool freezing or coke block dirt. 5 Actuator springs rust due to long-term use.
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(2) The operation of the regulating valve is unstable, and the fault phenomenon and causes are as follows:
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a. The air source pressure is unstable: 1 The compressor capacity is too small. 2 The pressure reducing valve is faulty.
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b. Signal pressure is unstable: 1 The time constant of the control system (T = RC) is not appropriate. 2 Regulator output is unstable.
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c. The air source pressure is stable and the signal pressure is also stable, but the action of the regulating valve is still unstable: 1 The ball valve of the amplifier in the positioner is not tightly damaged by the dirt, and the output oscillation occurs when the air consumption is particularly increased. 2 The nozzle flaps of the amplifiers in the positioner are not parallel, and the flaps cannot cover the nozzles. 3 output tube, line leakage. 4 The actuator rigidity is too small. 5 The frictional resistance is large in the movement of the valve stem, and there is a blockage in the contact part.