What Is a Concrete Conveyor?

Concrete conveying pump, also known as concrete pump, consists of pump body and conveying pipe. It is a machine that uses pressure to continuously transport concrete along the pipeline. It is mainly used in building construction, bridge and tunnel construction. It is mainly divided into gate valve concrete pump and S valve concrete pump. The other is a pump truck which is composed of a pump body mounted on a car chassis and equipped with a retractable or flexing cloth rod.

(1) The operator and relevant equipment management personnel should read the instruction manual carefully, master its structural principles, use and maintenance, and relevant knowledge of pumping concrete; when using and operating the concrete pump, it should be implemented in strict accordance with the instruction manual. Since it takes a process for the operator to fully grasp the mechanical properties, the instruction manual should be provided at random. At the same time, special operating points should be formulated according to the instruction manual to achieve effective control of some variable factors in the pumping technology, such as the position of the pump and the layout of the pipeline. (2) The ground supporting the concrete pump should be flat and solid; the whole machine should be placed horizontally, and it should not be tilted during work. The outriggers should be able to support the whole machine stably and be locked or fixed reliably. The position of the pump should be convenient for the concrete mixer truck to enter and exit the concrete hopper and feed the hopper, and it should also be considered to be beneficial for pumping the distribution pipe and reducing the pumping pressure loss. At the same time, it needs to be close to the pouring site, and convenient for power supply and water supply. (3) Piping should be carried out according to the characteristics of the construction site and the concrete pouring plan. When piping design, check whether the horizontal conversion distance of the pipeline is compatible with the pumping distance of the concrete pump. When piping, shorten the length of the pipeline as much as possible, and use fewer bends and hoses. The laying of pipelines should be convenient for pipeline cleaning, troubleshooting and disassembly. When the new pipe and the old pipe are mixed, the new pipe should be arranged at a place with a higher pumping pressure. During the piping process, a simple pipe layout diagram should be drawn to list the specifications and quantities of various fittings, pipe clips, bends and hoses, and provide a list. (4) When vertical upward piping is required, as the height increases, that is, the potential energy increases, there is a tendency for the concrete to flow back. Therefore, a certain length of horizontal pipeline should be laid between the concrete pump and the vertical piping to ensure sufficient resistance to the concrete. Reflux. When pumping concrete for high-rise buildings, pipes need to be piped up vertically. At this time, the length of the ground horizontal pipe should not be less than 1/4 of the length of the vertical pipe. If the water pipe of the required length cannot be placed due to site constraints, a bend or hose can be used instead. (5) In the concrete pumping process, as the pumping pressure increases, the pumping impact force will force the pipe to move back and forth, which not only consumes the pumping pressure, but also the connection between the pump pipe is in shock and intermittent The tensioned state can cause premature damage to the pipe clamp and the rubber ring, and the cement slurry to overflow, so the pump must be fixed. (6) After the concrete pump is connected to the conveying pipe, a comprehensive inspection shall be carried out in accordance with the instructions of the concrete pump operation manual. After 10 minutes of no-load operation, check whether each mechanism or system works normally. (7) During construction in the hot season, it is advisable to cover the concrete conveying pipe with wet straw bag, wet cover cloth, etc. to avoid direct sunlight, which can prevent the concrete from being blocked due to excessive slump loss. (8) When carrying out concrete pumping construction in winter in severe cold areas, appropriate thermal insulation measures should be taken. It is advisable to use thermal insulation materials to wrap the concrete delivery pipe to prevent the concrete in the pipe from being frozen. ^[1]

The concrete conveying pipe shall be piped according to the characteristics of the project and construction site and the concrete pouring plan. The length of the pipeline should be shortened, and fewer elbows and hoses should be used. The laying of the conveying pipe shall ensure safe construction, which is convenient for cleaning the pipeline, troubleshooting and assembling and disassembling and repairing. In the same pipeline, concrete conveying pipes with the same pipe diameter should be used; when new and 1-day pipe sections are used at the same time, the new pipe should be arranged at the place where the pumping pressure is greater; the pipeline should be arranged horizontally and vertically. A simple pipe layout diagram should be drawn, listing the specifications and quantities of various pipe fittings, pipe connection rings, elbows, etc., and a spare parts list proposed. The concrete conveying pipe should be selected according to the maximum size of coarse aggregate, the type of concrete pump, the conveying distance of the concrete output, and the difficulty of conveying. The conveying pipe should have strength suitable for the pumping conditions. Use pipe sections without cracks, bumps, and bends. The joints of the conveying pipe should be tight, have sufficient strength, and can be quickly disassembled. When the minimum pipe diameter is 100mm, the maximum particle size of the coarse aggregate cannot exceed 25mm, and when the minimum pipe diameter is 125mm, the maximum particle size cannot exceed 40mm. When piping vertically upwards, the length of the ground horizontal pipe should not be less than a quarter of the length of the vertical pipe, and should not be less than 15m, or follow the regulations in the product manual. A stop valve should be set at the root of the conveying pipe at 3 ~ 6m from the Y-shaped pipe outlet of the concrete pump to prevent the concrete mixture from flowing back. When pumping underground structures, the axis of the horizontal pipe above the ground should be perpendicular to the axis of the Y-shaped pipe outlet. When the pipe is inclined downward, an exhaust valve should be set at the upper end of the inclined pipe; when the height difference is greater than 20m, a horizontal pipe with a length of 5 times the height difference should be set at the lower end of the inclined pipe; if conditions are restricted, an elbow or ring pipe can be added To meet the 5 times height difference length requirement. The fixing of the concrete conveying pipe shall not be directly supported on the steel bars, formwork and embedded parts. The horizontal pipe should be fixed at intervals with a bracket, a table mat, a spreader, etc., in order to eliminate pipe blocking, assembly and disassembly, and cleaning the pipe; vertical The pipe should be fixed in place at the top hole of the wall and column or floor with embedded parts. On the walls and columns, each section of pipe shall have at least one fixing point, and shall be fixed at the reserved holes on each floor. The bend at the lower end of the vertical pipe should not be used as a support point for the upper pipe. A steel support should be provided to support the weight of the vertical pipe. When the vertical pipe is fixed on the scaffold, the scaffold can be reinforced as required. No slurry shall leak at the pipe joint clamp. In hot seasons, wet concrete, warm grass bags, etc. should be used to cover the concrete pipe to avoid sunlight. For construction in the cold season, it is advisable to use thermal insulation materials to wrap the concrete pipe in Kunming to prevent the concrete in the pipe from being frozen and to ensure the temperature of the concrete in the mold. When the horizontal conveying distance is more than 200m, the vertical conveying distance is more than 40m, the conveying pipe is vertically downward or the horizontal pipe is arranged in front of the inclined pipe. Process, it is better to use a large diameter concrete pipe and a long tapered pipe, and less bends and hoses. When the conveying height exceeds the maximum conveying distance of the concrete pump, the relay pump (subsequent pump) can be used for pumping. In addition, the distribution equipment should be selected according to the engineering structure characteristics, construction technology, distribution requirements, and piping conditions. The distribution equipment should be arranged according to the structural plane size, piping conditions and the length of the distribution rod, and it should be able to cover the entire structural plane and be able to distribute the material uniformly and quickly. The distribution equipment should be installed firmly and stably. ^[1]

In terms of foreign body plugging management , plugging pipes are most likely to occur when three large stones meet and get stuck in the same section. At this time, the section is mostly occupied by stones and the flowable area is small. Generally, the maximum particle size of the stone and the inner diameter of the pipe d: D <1: 3 (Note: This item is specified in the Procedures, according to the conveying height and the type of stone, 1: 2.5 1: 5) A grid is set on the hopper of the machine to prevent mixing of ultra-large stones. Poor proportion of concrete. In poorly proportioned concrete mixtures, where the pressure gradient is large, moisture will penetrate through the aggregate gap, causing aggregates to aggregate and cause plugging. It often occurs in pipeline bending, diameter reduction, and soft layout of pipelines. In addition, when the water-cement ratio of the concrete is too large, it is easy to segregate, causing the mortar to separate from the aggregate and blocking the pipe. It is more common in the long-distance horizontal pumping of the "segregation" pipe and the lower end of the vertical down pipe. . When the amount of cement is too small and the sand rate is too low, the concrete is poor in workability and difficult to deform. The frictional resistance in the pipeline increases, and it is very easy to block the pipe. When the concrete slump is too low (below 80mm), the pumping resistance increases significantly, making pumping impossible. The particle size of the sand is unreasonable. When the content of fine sand passing through the 0.315mm sieve is small, even if other technical specifications of the concrete meet the requirements, the pipe will be blocked. Because these fine sands play a ball-like role in the concrete, they can reduce the friction between the pipe wall and the concrete, improve the flowability of the concrete, increase the cohesion and water retention, and have a great impact on the pumpability of the concrete. Therefore, it is stipulated in JGJ / T10-95 "Concrete Pumping Construction Technical Regulations" that the sand passing through the 0.315mm sieve should not be less than 15%. ^[1]

Location of easy-to-clog pumps and troubleshooting methods

Blockage at the dispensing valve outlet

The discharge port is blocked, usually the pumping system is suddenly interrupted, and there is abnormal noise, the equipment has strong vibration, but there is no corresponding vibration in the pipeline.

Remedy: Pour cement slurry into the hopper, and repeatedly start the pump in the forward and reverse directions to force the passage to open. If you don't dare to do this, you can only remove it manually, remove the connecting pipe, and remove the debris in the valve. ^[1]

(1) Avoid 90 as much as possible when installing and designing piping. And S-curved. Try not to use pump pipes with obvious pits to reduce the resistance to pump concrete and prevent blockages. The pump tube should be checked frequently. If the pump tube is worn in one direction, the tube should be replaced in time. If the thickness of the pump tube is too thin, it should be replaced with a new one in time to prevent the pump tube from bursting or due to replacement of the pump. Tube blocking caused by long tube time. (2) In order to ensure the continuity of the pumped concrete operation and the quality of the concrete pouring, the interval time during the operation should not be too long to prevent clogging. If the interval is long for some reason, you should start the pump or reverse and forward pump several times every 20 minutes, and if necessary, play a circulating pump to prevent blockage. (3) The pumpable concrete should meet the pumpability requirements, and the pumping concrete mix ratio should be determined by test pump if necessary. First, the ratio of the maximum particle size of the coarse aggregate to the diameter of the conveying pipe should be determined. 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; the pumping height is 100m In the above case, it should be between 1: 4 and 1: 5. The content of needle-like particles should not be greater than 10%. 3.3.2 For different pumping heights, the slump of concrete for pumps can be selected as shown in Table 1. ^[1]

(1) The towing concrete pump can be towed by motor vehicles, but it is not allowed to carry any cargo, and the towing speed must not exceed 8km / h;

(2) The pressure of each safety valve of the hydraulic system of the concrete pump shall meet the requirements of the instructions, and the user shall not adjust or change it;

(3) Construction of concrete pumps in cold seasons must have anti-freezing measures;

(4) During construction in hot season, the concrete pump should prevent the oil temperature from becoming too high. When the temperature reaches 70 , it should stop running or take other measures to reduce the temperature;

(5) After the concrete is pumped, the hopper, S valve, concrete cylinder and conveying pipeline should be cleaned in time. After the pump is cleaned, release the pressure of the accumulator and cut off the power. The switches should be in the stop or open position.

(6) Workers are not allowed to climb or ride on the transportation pipeline, and they should be absolutely avoided when working at high altitudes;

(7) Before pumping the concrete, the pump should be pumped back several times to reduce the pressure in the conveying pipe to avoid accidents;

(8) Safety and accident prevention devices shall be provided at the construction site. Such as: instructions and warning signs, fences, metal baffles, etc., set the necessary working area (not less than 1 meter) around the pump, non-operators must not enter without permission. Regularly replace the conveying pipeline within three meters from the operator, which must be fastened and shielded with wooden boards or metal partitions;

(9) It is strictly forbidden to operate when the vacuum gauge reading is greater than 0.04Mpa, otherwise the main oil pump may be damaged;

(10) The use, installation and wiring of electrical control boxes must be performed by professionals;

(11) The concrete in the hopper of the concrete pump must be higher than the mixing shaft to avoid concrete splashing due to the intake of air;

(12) When the pumping operation is completed, when the transfer pump receives the outriggers, the rear outriggers are retracted first, the support wheel is lowered, and then the front outriggers are retracted;

(13) Operators (pumpers of concrete pumps) shall record the working conditions of concrete pumps as required.

(14) The concrete pump should be properly fixed before use. Support the four feet to make the tire off the ground, or remove the tire. Check the support of the hopper and chute on the top of the pump to ensure stability and reliability. Pay special attention to casualties caused by the pump overturning!

(15) When pumping, pay attention to concrete splashing or other objects entering the eyes and causing eye injury!

(16) The concrete pump power supply wiring must be provided with a leakage protection switch. It should always be checked whether the electrical components are working properly and the cable is damaged to prevent electric shock from causing injury or death!

(17) To ensure the reliable connection of the transportation pipeline, regular inspection and maintenance, to prevent injuries caused by pipe jams, pipeline bursts or blockages!

(18) It is forbidden to open the hydraulic pipe joint or loosen the hydraulic flange bolts when the hydraulic system is not unloaded. High-pressure hydraulic oil injection can cause great damage! (19) When the pump is working, it is strictly forbidden to reach into areas with moving parts such as hoppers, water tanks, reversing oil cylinders, etc., and stop operation when inspection is required! ^[1]

After the concrete is pumped, the conveying pipelines, pumps, cleaning, maintenance and other finishing work should be cleaned immediately. (1) Cleaning of conveying pipelines Air-cleaning work steps of conveying pipelines a. The pipeline should be equipped with a stop valve and a stop plate should be inserted to prevent the concrete in the pipe from tilting vertically or upward. b. Take out some concrete from the mouth of the first straight pipe, and connect the air-wash joint. The joint should be filled with a sponge ball soaked in water, and the joint should be equipped with an exhaust valve and compressed air hose. c. Install a safety cover at the end of the pipeline to prevent concrete spray from hurting people. d. Open the compressed air inlet valve slowly, so that the compressed air will push out the sponge ball and concrete. If the pipeline is equipped with a check valve, it should be opened in the open position before opening the air valve. e. When the concrete in the pipeline has been completely emptied, and the sponge ball has been shot immediately, the air washing is completed. At this time, the compressed air inlet valve should be closed, and then various pipe fittings should be removed. Precautions for air washing:-The pressure of compressed air must not be higher than 0.7MPa. The air valve should not be opened at once, but it should be opened-closed-opened. Observe carefully. It can only be opened when the concrete can flow out smoothly. If you find that the purge does not move, you should first close the intake valve, then slowly open the exhaust valve to deflate, and then try to clean in stages. -In the case of segmental purge, first blow off a section of pipe near the discharge end, then connect the blown pipe to the unpurged section and purge the remaining part. -During air washing, personnel should not approach the outlet of the discharge pipe, sharp turns of the pipe (if 90 ° curve) and compressed air pipe joints. ^[1]

The pipeline washing process is as follows: a. Pump the fine stone concrete in the hopper as much as possible before the end of pumping. b. The back pump moves a few times to release the pressure in the pipeline and cut off the power. c. Open the first section of reducer and discharge door, and completely remove the residual concrete in the hopper, the distribution valve box and the reducer. d. Take out some concrete from the mouth of the first straight pipe, insert it into a sponge ball soaked with water, and fill the soaked cement bag paper in front of the sponge ball. e. Connect the reducer and close the discharge door. f. Fill the hopper directly with water. g. Pumping. ^[1]