1. Improper operation can easily cause pipe blockage
1. The operator is not concentrated
The operator of the delivery pump should concentrate on the pumping construction and pay attention to the reading of the pumping pressure gauge at all times. Once the reading of the pressure gauge suddenly increases, the pump should be reversed for 2 to 3 strokes immediately, and then the pump should be corrected. The blocked pipe can be eliminated . If the reverse pump (forward pump) operation cycle has been carried out and the blocked pipe is still not eliminated, the pipe should be dismantled and cleaned in time, otherwise the blocked pipe will be more serious.
2. Improper selection of pumping speed
When pumping, the choice of speed is very important. Operators can't blindly map fast, and sometimes haste makes waste. When pumping for the first time, due to the high resistance of the pipeline, it should be pumped at a low speed at this time. After the pumping is normal, the pumping speed can be increased appropriately. When there is a sign of pipe blockage or the slump of a certain truck of concrete is small, it should be pumped at a low speed to eliminate the pipe blockage in the bud.
3. Improper control of remaining material
When pumping, the operator must observe the remaining material in the hopper at any time. The remaining material should not be lower than the stirring shaft. If the remaining material is too small, it is easy to suck air and cause pipe blockage. The material in the hopper should not be piled up too much, and should be lower than the guardrail, so as to clean up the coarse aggregate and oversized aggregate in time. When the slump of a certain truck of concrete is small, the remaining material can be lower than the stirring shaft, and controlled above the "S" pipe or the suction port, so as to reduce the stirring resistance, swing resistance and suction resistance. This approach is only applicable to "S" valve series concrete pumps.
4. Improper measures are taken when the concrete slump is too small
When it is found that the slump of a bucket of concrete is very small and cannot be pumped, the concrete should be released from the bottom of the hopper in time. If you want to save trouble, forced pumping will easily cause pipe blockage. Never add water to the hopper and stir.
5. Too much downtime
During shutdown, the pump should be turned on every 5-10 minutes (the specific time depends on the temperature of the day, the slump of concrete, and the initial setting time of concrete) to prevent pipe blockage. It is not advisable to continue pumping the concrete that has been set for too long after the downtime.
6. The pipeline is not cleaned
After the last pumping, the pipeline is not cleaned, which will cause the pipe to be blocked during the next pumping. Therefore, after each pumping, the delivery pipeline must be cleaned according to the operating procedures.
2. Pipe blockage caused by pipe connection
The following principles should be followed when taking over:
(1) The pipeline layout should be arranged according to the shortest distance, the least elbow and the largest elbow, so as to minimize the transmission resistance and reduce the possibility of pipe blockage.
(2) The taper pipe at the pump outlet is not allowed to be directly connected to the bent pipe, at least it should be connected to a straight pipe of 5mm or more, and then connected to the bent pipe.
(3) When connecting pipes in the middle of pumping, only one pipe can be added at a time, and the inner wall of the pipe should be lubricated with water, and the air should be exhausted, otherwise it will easily cause pipe blockage.
(4) For vertically downward pipelines, an anti-segregation device should be installed at the outlet to prevent pipe blockage.
(5) For high-rise pumping, the length of the horizontal pipeline should generally not be less than 15% of the length of the vertical pipeline, and a pipeline stop valve should be connected to the horizontal pipeline. When the shutdown time exceeds 5 minutes, the shut-off valve should be closed to prevent the concrete from flowing back and causing pipe blockage. For 90-degree elbows from horizontal to vertical, the bending radius should be greater than 500mm.
3. Pipe plugging caused by segregation of concrete or mortar
1. When concrete or mortar meets water, it is easy to cause segregation. Sometimes when pumping mortar, pipe plugging occurs, which is caused by segregation of the mortar after direct contact with the water in the pipe. The preventive method is: after the pump is wetted with water, the pipe joint is connected from the lowest point of the pipe. Loosen and drain all the remaining water, or put a sponge ball after pumping water and before pumping the mortar to separate the mortar from the water.
2. When the pipeline is cleaned after pumping, a sponge ball should also be put in to separate the water from the concrete, otherwise it will easily cause pipe blockage.
4. Pipe plugging caused by local slurry leakage
Leakage of the mortar will affect the quality of the concrete on the one hand, and on the other hand, the slump of the concrete will be reduced and the pumping pressure will be lost after the leakage of the mortar, resulting in pipe plugging. The main reasons for leakage are as follows:
1. The joints of the delivery pipeline are not tightly sealed
The joints of the delivery pipeline are not tightly sealed, the pipe clamp is loose or the sealing ring is damaged, resulting in slurry leakage. At this time, the pipe clip should be tightened or the sealing ring should be replaced.
2. The gap between the spectacle plate and the cutting ring is too large
When the spectacle plate and cutting ring are severely worn, the gap between the two becomes larger. The gap between the spectacle plate and the cutting ring must be narrowed by adjusting the special-shaped bolts. If it cannot be adjusted, the worn parts should be replaced immediately. This approach is only applicable to "S" valve series concrete pumps.
3. The concrete piston is severely worn
Operators should always observe whether the water in the water tank is turbid and whether there is mortar. Once the water is found to be turbid or there is mortar in the water, it indicates that the concrete piston has been worn. At this time, the piston should be replaced in time, otherwise it will cause blockage due to slurry leakage and pressure loss. tubes, while increasing wear on the piston and delivery cylinder.
4. Grout leakage caused by severe wear of the concrete delivery cylinder
If the water in the water tank becomes turbid soon after each replacement of the piston, but the piston is fine, it indicates that the delivery cylinder is worn out, and the delivery cylinder needs to be replaced at this time.
5. Pipe plugging caused by unqualified pumped concrete
The concrete used for pumping must meet the requirements of pumping concrete. Not all concrete can be used for pumping. Unqualified pumping concrete will aggravate the wear of the pump, and often cause pipe blockage and bursting.
1. Concrete slump is too large or too small
The size of concrete slump directly reflects the fluidity of concrete, and the conveying resistance of concrete decreases with the increase of slump. The slump of pumped concrete is generally in the range of 8 to 18 cm, and for long-distance and high-height pumping, it generally needs to be strictly controlled at about 15 cm. If the slump is too small, it will increase the delivery pressure, aggravate the wear of the equipment, and cause the pipe to be blocked. If the slump is too large, the concrete is easy to segregate under high pressure and cause pipe plugging.
2. The sand content is too small and the coarse aggregate gradation is unreasonable
(1) Fine aggregate can be divided into river sand, artificial sand (machine-made sand), sea sand, and mountain sand according to the source. Among them, river sand has the best pumpability, and machine-made sand has the worst pumpability. Fine aggregate can be divided into coarse sand, medium sand and fine sand according to particle size, among which medium sand has the best pumpability.
(2) Coarse aggregate can be divided into pebbles and crushed stones according to their shapes. Pebbles are better pumpable than gravel. The maximum particle size of the aggregate is also related to the minimum diameter of the conveying pipeline. The maximum particle size of pebbles should be less than 1/3 of the diameter, and the maximum particle size of gravel should be less than 1/4 of the diameter, otherwise it will easily cause pipe blockage.
(3) Due to different materials, there is an optimal value for the content of fine aggregate (ie sand content) and the gradation of coarse aggregate. Normally, the sand content should not be too low, it should be greater than 40%, and the content of large-size coarse aggregate should not be too high. Reasonable selection of sand content and determination of aggregate gradation are crucial to improving the pumpability of concrete and preventing pipe plugging.
3. Too little or too much cement
(1) Cement plays a role of cementation and lubrication in pumping concrete. At the same time, cement has good water retention performance, so that the concrete is not easy to bleed during the pumping process. There is also an optimal value for the amount of cement. If the amount of cement is too high If it is less, it will seriously affect the suction performance of concrete, and at the same time increase the pumping resistance, the water retention of concrete will deteriorate, and it will be prone to bleeding, segregation and pipe plugging. Generally, the content of cement in each cubic meter of concrete should be more than 320kg, but it should not be too large. If the amount of cement is too large, the viscosity of the concrete will be increased, resulting in an increase in the transportation resistance.
(2) In addition, the amount of cement is also related to the shape of the aggregate. The larger the surface area of the aggregate, the more cement slurry needs to be wrapped, and the correspondingly the greater the cement content. Therefore, it is also very important to determine the amount of cement reasonably to improve the pumpability of concrete and prevent pipe plugging.
4. The selection of admixture is unreasonable
There are many types of admixtures, such as: air-entraining agent, water reducing agent, superplasticizer, retarder, pumping agent, etc., according to the strength requirements of concrete and the variety of cement, admixtures are reasonably selected to improve the strength of concrete. Pumpability plays an important role. Unreasonable admixtures will deteriorate the pumpability and fluidity of concrete, resulting in pipe plugging.
6. Pipe plugging caused by too little mortar or unqualified mix ratio
1. Too little mortar
Because when pumping for the first time, the mixing main engine, concrete delivery vehicle mixing tank, hopper, pipeline, etc. must absorb part of the mortar. If the amount of mortar is too small, some of the delivery pipelines will not be lubricated, resulting in pipe blockage. The correct amount of mortar should be calculated on the basis of about 0.5m3 mortar per 200m pipeline, and about 0.2m3 mortar is needed for the mixing main engine, hopper, concrete delivery truck mixing tank, etc. Therefore, the amount of mortar must be calculated before pumping. Too little mortar is easy to block the pipe, too much mortar will affect the quality of concrete or cause unnecessary waste.
2. The mortar mix ratio is unqualified
The mix ratio of mortar is also critical. When the pipeline length is less than 150m, use 1:2 cement mortar (1 part cement/2 parts mortar); when the pipeline length is greater than 150m, use 1:1 cement mortar (1 part cement/1 part mortar), cement Using too little can also cause clogging.
7. Pipe plugging caused by temperature changes
In summer, the temperature is high, and the concrete is easy to dehydrate under the strong sunlight of the pipeline, which will lead to pipe blockage. Therefore, wet straw bags or other cooling supplies should be added to the pipeline. Insulation measures should be taken in winter to ensure the temperature of the concrete.
The above are some common causes and preventive measures of pipe blockage summarized above. In the actual production process, due to changes in external conditions, there are often more than these reasons for pipe blockage. But as long as we operate strictly according to the operating procedures, prevent the incipient progress, and constantly sum up experience and lessons from each blockage, we will definitely be able to minimize the possibility of blockage