Concrete pump plugging the reasons and preventive measures:
1, improper operation likely to cause blockage:
1.1 operator energy is not focused
Pump operators should focus on pumping construction, always pay attention to the pressure gauge readings, once the pressure gauge reading suddenly increased, should immediately anti-pump trip 2-3, then the pump, plugging can be ruled out . If you have carried out the anti-pump (positive pump several operating cycles, has not ruled out plugging pipe, pipe should be promptly demolished cleaning, or plugging will be more serious.
1.2 improper selection of pumping speed
Pumping, the choice of speed is the key, the operator can not blindly map fast, sometimes speed is not up. When pumping for the first time, due to the pipeline resistance larger, at this time should be low-speed pumping, pumping normal, may be appropriate to increase the pumping speed. When there is a sign of tube plugging or slump of a particular vehicle, it should be pumped at low speed to eliminate the tube plugging in the bud.
1.3 excess material control is not appropriate
Pumping, the operator must keep track of excess material in the hopper, the remaining material should not be lower than the mixing shaft, if the remaining material is too little, extremely easy to inhale the air, leading to blockage. Hopper material can not pile too much, should be lower than the fence, in order to timely clean up the coarse aggregate and large aggregate. When the slump of a car concrete is small, the remaining material may be lower than the stirring shaft and controlled above the "S" pipe or the suction port to reduce stirring resistance, wobbling resistance and suction resistance. This method is only applicable to "S" valve series concrete pump.
1.4 When the concrete slump is too small to take improper measures When a bucket of concrete found slump is very small, can not pump, the concrete should be promptly let go from the bottom of the hopper, if the covet effort, forced pumping can easily lead to blockage . Avoid mixing water in the hopper.
1.5 downtime is too long
Shutdown should be every 5 ~ 10min (depending on the specific time of the day temperature, concrete slump, concrete initial setting time may be) to prevent the pump tube. For downtime is too long, has been the initial setting of concrete, should not continue to pump.
1.6 pipe is not cleaned
The last pumping is completed, the pipe is not cleaned, will cause the next pumping blockage. So every time after pumping must be in accordance with the rules of the pipeline cleaning.
2, pipe connection caused by the plugging:
Pipe connection error can easily lead to plugging. Take over the following principles should be followed:
Pipe layout should be the shortest distance, the minimum elbow and the largest elbow to pipe, minimize the transmission resistance, also reduces the possibility of tube plugging.
Pump outlet cone Department, not directly connected to the elbow, at least 5mm or more straight pipe access, and then elbow.
Pumping midway takeover, you can only add one at a time, and the application of water to lubricate the inner wall of the pipe, and exhaust the air side, otherwise easily lead to plugging.
Vertical downward pipe, outlet should be equipped with anti-segregation device to prevent plugging.
When pumping at high level, the length of the horizontal pipe should not be less than 15% of the length of the vertical pipe, and the horizontal pipe should be connected to the pipe stop valve. Shutdown time exceeds 5min, shut-off valve should be closed to prevent concrete backflow, leading to plugging. 90-degree bend from horizontal to vertical bending, bending radius should be greater than 500mm.
3, segregation of concrete or mortar caused by the plugging:
Concrete or mortar with water, easily lead to segregation. Sometimes when pumping mortar, plugging phenomenon occurs because the mortar and water in the pipe after direct contact with the mortar segregation caused by the precautionary approach is: after the pump water wet pipe, the lowest point of the pipe from the pipe joints Loosen the rest of the water to let go, or after the pump, before pumping mortar, put a sponge ball, the mortar and water separated.
Pumping is completed cleaning the pipeline, but also into a sponge ball, the water and concrete separation, otherwise easily lead to plugging.
4, caused by local leakage tube plugging:
Leakage of mortar, on the one hand affect the quality of concrete, on the other hand after the slip, will lead to the slump of concrete and pumping pressure loss, resulting in blockage. Leakage of the main reasons for the following:
4.1 pipeline joints tight seal
Transmission pipeline joints lax seal, tube card loose or damaged seal leakage of plasma. At this point you should fasten the tube card or replace the seal.
4.2 The gap between the glass plate and the cutting ring is too large
Glasses and cutting ring wear serious, the gap between the two become larger. When the clearance is greater than% -, the adjusting bolt should be used to narrow the gap between the lens plate and the cutting ring. If the clearance can not be adjusted, the worn part should be replaced immediately. This method is only applicable to "S" valve series concrete pump.
4.3 concrete piston wear serious
The operator should always observe the water tank is turbid, with or without mortar, once found that water has turbidity or water in the mortar, indicating that the concrete piston has been worn, then the piston should be replaced promptly, otherwise it will result in leakage and pressure loss caused by plugging Tube, while also exacerbating the wear and tear of the piston and delivery cylinder.
4.4 Due to the serious wear and tear caused by concrete delivery tank leakage
If, after each change of piston, the water in the water tank becomes turbid quickly and the piston is good, then the transfer cylinder is worn and the transfer cylinder needs to be replaced.
5, non-qualified pump concrete blockage caused by:
The concrete used for pumping must comply with the requirements of pumping concrete. Not all concrete can be pumped. Non-qualified pumping concrete will aggravate the wear of the pump and often cause blockages and squibs.
5.1 Concrete slump is too large or too small
The size of concrete slump directly reflects the fluidity of concrete, the transport resistance of concrete decreases with the increase of slump. Pumped concrete slump generally in the range of 8 ~ 18cm, for long-distance and high-altitude pumping generally need to strictly control the 15cm or so. Slump is too small, will increase the delivery pressure, aggravate the equipment wear and tear, and lead to blockage. Slump is too large, under high pressure concrete segregation caused by blocking tube.
5.2 Sand content is too small, coarse aggregate gradation unreasonable
According to the sources, the fine aggregate can be divided into river sand, artificial sand (ie, mechanism sand), sea sand and mountain sand. Among them, the river pumpability is the best and the pumpability of mechanism sand is the worst. Fine aggregate by particle size can be divided into: coarse sand, medium sand, fine sand, which can pump the best in sand.
According to the shape of coarse aggregate can be divided into: pebbles, gravel. Pebble pumpability is better than gravel. The maximum aggregate size of the pipeline and the minimum diameter also has a relationship, the largest pebble particle size should be less than 1/3 diameter, the maximum size of the gravel should be less than 1/4 diameter, otherwise it is easy to cause blockage.
Due to the different materials, fine aggregate content (ie, sand content), coarse aggregate gradation there is an optimal value. Under normal circumstances, the sand content should not be too low, should be greater than 40%, the content of large-size coarse aggregate should not be too high. Reasonable choice of sand content and determine the aggregate gradation, to improve pumping performance of concrete and prevent plugging is essential.
5.3 too little or too much cement
Cement in the pumping of concrete, from the role of bonding and lubrication, while cement has good water retention properties, so that concrete is not easy to bleeding during the pumping process, the amount of cement there is an optimal value, if the amount of cement is too small, will be Seriously affect the inhalation of concrete performance, while increasing the pumping resistance, poor water retention of concrete, easy bleeding, segregation and plugging occurred. Under normal circumstances, the content of cement per cubic meter of concrete should be greater than 320Kg, but not too large, too much cement, will increase the viscosity of concrete, resulting in increased transport resistance.
In addition the amount of cement and the shape of the aggregate is also related to the aggregate surface area, the need to wrap the slurry should be more, accordingly, the greater the content of cement. Therefore, a reasonable determination of the amount of cement, to improve the pumpability of concrete, prevention of plugging is also very important.
5.4 The choice of additives is not reasonable
Many types of additives, such as: air entrainer, water reducer, superplasticizer, retarder, pumping agent, etc., according to the strength of concrete and cement varieties, a reasonable choice of admixture, to improve the concrete Pumping performance plays a very important role. Unreasonable admixtures will make the concrete pumpability and fluidity worse, leading to blockage.
6, too little mortar or unqualified due to blocking the tube:
6.1 mortar dosage too little
Because the first pumping, mixing host, concrete truck mixing tank, hopper, pipes and so on to absorb part of the mortar, if the amount of mortar is too small, it will lead to some of the pipeline did not get lubrication, leading to blockage. Correct amount of mortar should be calculated according to 0.5m3 mortar per 200m pipeline, mixing mortar about about 0.3m3, such as mixing tank of main engine, hopper and concrete truck. Therefore, before pumping must calculate the amount of mortar. Too little mortar plugging tube, too much mortar will affect the quality of concrete or unnecessary waste.
6.2 mortar mix failed
Mortar mix is ​​also crucial. 1: 2 cement mortar (1 part cement / 2 parts mortar) when the pipe length is less than 150m, 1: 1 cement mortar (1 part cement / 1 part mortar), cement Too little dosage can cause blockage.
7, the temperature change caused by the plugging:
High temperatures in summer, the pipeline in strong sunlight, concrete is easy to dehydration, leading to plugging pipe, so the pipe should be covered with wet bag or other cooling supplies. Insulation measures should be taken in winter to ensure that the concrete temperature.
8, Summary:
The above is a summary of several common causes of plugging and preventive measures, in the actual production process, due to changes in external conditions, resulting in blocked tube often more than these reasons. However, as long as we operate in strict accordance with the rules and regulations, and take preventive measures, we will continue to accumulate experiences and lessons from each blockage and we will surely minimize the possibility of blockage.
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