(1) Pumpability of concrete. The pumped concrete should meet the pumpability requirements, and if necessary, the proportion of pumped concrete should be determined by test pumping.

   ① The ratio of the maximum diameter of coarse aggregate to the diameter of the conveying pipe should be: when the pumping height is below 50m, it should not be greater than 1: 3 for gravel and 1: 2.5 for pebbles; when the pumping height is 50 ～ 100m It should be in the range of 1: 3 ～ 1: 4; when the pumping height is above 100m, it should be between 1: 4 ～ 1: 5. The content of needle-like particles should not be greater than 10%.

   ② For different pumping heights, the slump of pumped concrete can be selected as shown in the table.

    Pumping height (m) 30 or less 30 ～ 60 60 ～ 100 100 or more

    Slump (m) 100 ～ 140 140 ～ 160 160 ～ 180 180 ～ 200

   ③ The water-cement ratio of pumped concrete should be (0.4 ～ 0.6): 1.

   ④ The sand content of pumped concrete should be 38% to 45%. Fine aggregate should be medium sand. The amount of sand passing through the 0.315m sieve should not be less than 15%.

   ⑤ The minimum cement content in the pumped concrete is 300kg / m³.

(2) After the concrete pump is started, pump an appropriate amount of water to wet the parts of the concrete pump that are in direct contact with the concrete such as the hopper, concrete cylinder and conveying pipe. After pumping water, use one of the following methods to lubricate the above parts: pump the cement slurry; pump the cement mortar of 1: 2; pump the cement mortar with a distribution ratio other than coarse aggregate.

   The cement slurry or cement mortar used for lubrication should be dispersed and not concentrated in the same place.

(3) When starting pumping, the concrete pump should be running at a slow and uniform speed, and then gradually accelerated. At the same time, the pressure of the concrete pump and the working condition of each system should be observed, and the normal speed pumping can be performed after each system works normally.

(4) The concrete pumping work should be performed as continuously as possible. The piston of the concrete cylinder should be kept running at the maximum stroke in order to maximize the effectiveness of the concrete pump and make the concrete cylinder wear uniform in the length direction.

(5) If the pressure of the concrete pump is too high and unstable, the oil temperature will rise. When the conveying pipe has obvious vibration and pumping difficulties, it shall not be forced to pump, and the cause shall be immediately investigated and eliminated. You can bend the pipe by first hitting the pipe with a mallet. Conical tubes and other parts, and slow pumping or reverse pumping to prevent clogging.

(6) When blockage occurs, the following methods should be adopted to eliminate:

   ① Repeat the reverse pump and forward pump operation, gradually suck out the concrete and return it to the hopper, and then re-pump after stirring.

   ② Use a mallet to tap and other methods to find out the blockage. After the concrete is loosened, repeat the reverse pump and forward pump operation to eliminate the blockage.

   ③ When the above two methods are not effective, the blockage site should be disassembled after the concrete is depressurized, and the blockage should be discharged and pumped again.

(7) The pumped concrete should be ready-mixed concrete, and a mixing station can also be set up on the site to supply pumped concrete, but manual-mixed concrete should not be pumped. The supplied concrete should be strictly controlled, and the change of slump should be paid attention to at all times. The concrete that does not meet the pumping requirements is not allowed to enter the pump to ensure the effective operation of the concrete pump.

(8) A sieve should be set on the concrete pump hopper, and a special person should be set to monitor the feed to avoid blockage caused by the excessively large diameter aggregate or foreign matter entering.

(9) When pumping, the concrete volume in the hopper must not be lower than the position of the mixing shaft to avoid air entering the pump pipe and causing pipeline vibration.

(10) When the concrete pumping process needs a terminal, the interruption time should not exceed 1h. The reverse pump and forward pump should be operated every 5-10 minutes to prevent the pipeline from being blocked due to concrete bleeding or excessive slump loss.

(11) After the pumping is completed, the hopper and the conveying pipe system must be cleaned carefully. If the residual concrete in the concrete cylinder is not cleaned, it will solidify on the cylinder wall. When the piston runs again, the sealing surface of the piston will directly bear the impact of the solidified concrete on the cylinder wall, which will cause the piston to be partially peeled off. This kind of damage is different from the normal wear of the piston seal. The sealing surface cannot compensate for itself under the pressure, resulting in slurry leakage or air suction, causing pumping weakness and blockage.

(12) When the concrete is poorly pumpable or the concrete is bleeding and segregated and it is difficult to pump, the mix ratio, concrete pump, piping and pumping process should be studied immediately, and corresponding measures should be taken to solve it.