Common failure analysis of the hottest gate valve

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Analysis of common faults of gate valve concrete pump

gate valve concrete pump has strong adaptability to concrete with different grading and quality, and has a wide range of users in the market. However, due to its special structure, it often has many faults different from S-tube valve pump. This paper introduces the common faults in its working process and analyzes the causes and treatment methods

1. The slide valve oil cylinder is obviously in place twice during lifting

during the pumping process, the sealing of the inlet and outlet is achieved by the close contact between the ram and the valve seat, and the ram cannot be in place at one time, resulting in the failure to complete the sealing in time. When the ram does not rise in place, the pumping has begun to reverse, causing part of the concrete to return to the hopper from the suction port, so that the concrete can not form a normal pumping state in the delivery pipe, and pipe blockage will occur when repeated for many times

this phenomenon is caused by the piston or valve rod encountering too much resistance when the slide valve cylinder is near the end of its stroke. There are two possible reasons: one is that the buffer of the oil cylinder is too strong, and the other is that the valve rod of the gate valve is stuck. The sticking of the valve stem is usually caused by the damage of its surface. The more common is that the sand in the concrete marks irregular axial grooves on the valve stem

buffering principle of slide valve cylinder: in the middle of the end face of the cylinder seat at the upper end of the slide valve cylinder is the oil inlet (return) cavity, around which there are two groups of damping holes (usually two in a group), each of which is connected to a cone valve with spring, and at the end of the cylinder piston, there is a protruding shaft head. When the cylinder rod is lifted close to the end of the stroke, the shaft head enters the volume cavity of the cylinder seat, at this time, the oil return circuit is closed, and the oil return pressure increases instantly; At the same time, the pressure oil pushes the cone valve through the damping hole to form a new oil return circuit with high back pressure, which slows down the speed of the valve rod and achieves the purpose of cushioning

a user once reported that his ram valve pump often had one ram in place twice. After disassembling the slide valve cylinder, no problem was found in the inspection of all components. After blowing air into the damping hole on the valve seat, it was found that three of the four small holes leading to the oil return chamber were blocked. Further inspection found that the small holes were filled with oil stains with solid particles, while the four damping holes of the other slide valve cylinder were normal. After dredging and cleaning the blocked hole, reassemble it for pumping, and the slide valve oil cylinder works normally

from the above phenomena, it can be seen that the cleanliness of the hydraulic system of the concrete pump has an important impact on its working performance. In the process of parts manufacturing, assembly and machine maintenance, iron filings, fibers and other sundries must be prevented from entering the hydraulic system as far as possible

2. Early damage of slide valve stem

after a new gate valve pump degrades the sensitivity of the dial pointer of the tensile testing machine for a period of time, irregular axial grooves will appear on the valve stem. The depth and degree of wear of the grooves are different in all parts of the valve stem. The parts in contact with concrete will wear faster, but there will be no axial grooves

at this time, the working resistance of the slide valve is generally large, and the ram is difficult to complete the sealing task. Disassemble the slide valve and check it. It is found that the valve stem seal has been seriously damaged and there is a large amount of concrete mortar at the sealing pair. At this time, the valve stem, seal and even the whole set of slide valve must be replaced immediately

the main reason for this kind of failure is poor lubrication. There are two reasons for this: first, such as the failure of the lubricating pump, the blockage of the distributor, the blockage of the lubricating pipeline or the poor quality of the lubricating grease; The second is that the operator can strictly abide by the operating procedures. Start the machine and idle for several minutes before starting pumping each time. It can work normally only after the lubricating grease overflows from the sealing pair; After pumping, the concrete in the hopper shall be cleaned in time, and then the machine shall be operated empty for a few minutes, and the cement mortar at the seal of the slide valve guide rod shall be extruded by the pressure of lubricating grease

good lubrication is an extremely important factor to ensure the normal operation of the gate valve and prolong its service life

3. The slide valve oil cylinder is not working properly

when the ram valve pump is working, sometimes the slide valve stroke is shortened or the ram slides automatically, resulting in the serious consequences of decreased pumping capacity or even no pumping at all

for the shortening of the slide valve stroke, the movement may be blocked due to the clamping of the valve rod, so that the ram cannot reach the end point, but the probability of this situation is small; However, the leakage in the slide valve cylinder causes the channeling of the high and low pressure chamber, which is more likely to shorten the stroke of the slide valve cylinder. Especially in midsummer, the ambient temperature is high, the hydraulic oil temperature rises rapidly when the machine is working, the oil viscosity decreases, and the piston sealing effect decreases seriously, resulting in internal leakage, and the high-pressure oil enters the low-pressure chamber, resulting in a shortened stroke. Therefore, when the concrete pump works, liquid 2. Compared with the old electro-hydraulic servo pressure testing machine, this testing machine has the following advantages: the pressure oil temperature should be controlled below 60 ℃

when the ram at the upper end suddenly slides down during the operation of the pump, in addition to the internal leakage of the slide valve cylinder, it is very likely that the cylinder piston has a problem. One user's HBT60 ram valve found that the ram on one side fell slowly during the gap between waiting for materials during the working process, and the inspection system was normal. The author suggested that it dismantle and inspect the slide valve cylinder after the work was completed. As a result, it was found that the cylinder piston had been damaged and fell off, and everything was normal after replacement

4. The pumping is weak and the discharge is reduced

after the ram valve works for a period of time, especially when the long-term high-precision, sensitive and fast servo electromechanical control system breaks through the pressure pumping work, the seal at the RAM will wear rapidly. When the ram and valve seat wear to the limit gap, there will be slurry leakage, that is, the ram on the high-pressure pumping side cannot completely seal the hopper cavity and concrete cylinder cavity, Causing the high-pressure concrete part to return to the hopper; In the ordinary protection of hydraulic universal testing machine, we should pay attention to the following problems: the ram on the suction side of concrete samples and iron filings and other parts can not completely seal the Y-shaped tube cavity and the concrete cylinder cavity, so that the high-pressure concrete part entering the Y-shaped tube is pumped back to the concrete cylinder. Both of these conditions will greatly reduce the amount of concrete pumped out and seriously reduce the working efficiency of the pump

at this time, after the machine is completed, repair the ram or valve seat according to the clearance requirements of the instruction manual and grind it smooth, otherwise the complete set of slide valves must be replaced

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