- Types and principle of operation of concrete pumps
- Stationary concrete pump
- Concrete pumps
- An important element of a concrete pump is a gate (valve)
- Concrete placing boom
- What concrete mix can a concrete pump pump
- The procedure for working with a concrete pump
- Flushing of the reciprocating concrete pump and concrete pipeline
- Concrete pump rental – selection criteria
More than a century ago, reinforced concrete began to displace the usual wood and brick from construction sites – it was easier to work with this building material, and most importantly, faster. In those days, house-building factories and precast concrete factories were not yet so widespread, and architects and builders, experimenting with monolithic reinforced concrete, faced two problems – the lack of high-quality formwork and a means of conveying concrete to the height of the building. The construction or, more correctly, the assembly of buildings from ready-made reinforced concrete slabs seemed like a good solution – especially this construction technology took root in the USSR. Monolithic construction came to life half a century ago, when a solution appeared how to raise liquid concrete to a height of several tens of meters in a continuous flow – a concrete pump, which took an important place among modern construction equipment.
Types and principle of operation of concrete pumps
They are distinguished by type (hydraulic and mechanical), by pump design (piston and pistonless), stationary or on the basis of a car.
The principle of operation of reciprocating concrete pumps is that the concrete mixture is sucked from the hopper, and the reciprocal movement of the piston, to which the gate knee switches, pushes it into the concrete pipe. Units with a hydraulic (vacuum) drive have a significant advantage – in their operation, the feed rate of the mixture is practically unchanged, because their piston has a long stroke (1500-2500 mm, while the crank-connecting rod has 300-400 mm), which is why the mixture moves along the concrete pipeline evenly and without impulse jumps. Due to this, the resistance to the movement of the mixture in the concrete pipeline is reduced, which allows the use of engines of lower power than in the design of concrete pumps with a mechanical crank drive. Hydraulic concrete pumps are capable of transporting concrete mixture to a great height and distance – compared to a mechanical drive, a hydraulic one creates more pressure in a concrete pipeline.
Piston-driven concrete pumps are susceptible to piston wear due to friction caused by micro-particles of concrete mix and cement laitance penetrating between the walls of the pistons and the piston cylinder. Concrete pumps with a mechanical drive wear out faster than hydraulic ones – a smaller piston stroke reserve forces them to perform more cycles to achieve the required pressure in the concrete pipeline.
Trailed piston concrete pump Concrete Boy 350H
The two-cylinder reciprocating concrete pump is capable of delivering concrete almost continuously – this is provided by alternating strokes of pumping concrete into the cylinders. A single-cylinder concrete pump will work intermittently – the mixture of concrete supplied by it in the concrete pipeline pulsates from maximum to minimum pressure, in accordance with the movement of the piston.
In hydraulic piston concrete pumps, water or mineral oil is used as a filler, in the first version, a pressure of about 5 MPa is achieved, in the second – 10 MPa.
A rotary concrete pump (refers to a non-piston pump) is designed as follows: a body, inside which a rotor is placed with push-pressure rollers fixed on it, covered with rubber around the perimeter. In the rotor housing there is a rubberized hole in which a reinforced rubber hose (D 125 mm) is located – when the rotor rotates, rubber-coated rollers squeeze the hose, moving the concrete mixture along the hose from the receiving hopper to the concrete pipeline. The design of the rotary concrete pump provides a uniform supply of concrete, including hard concrete, plugs in them are quickly eliminated by switching the pump to reverse. However, the performance of rotary concrete pumps is usually low. They are used for small volumes of work – in those areas where the supply and placement of concrete is seriously hampered by frequent reinforcement. The main disadvantage of a rotary concrete pump of any performance is the rapid wear of the hose damaged by the concrete aggregate (especially crushed stone).
Stationary concrete pump
Available in “with chassis” and “without chassis” versions – the “without chassis” unit is usually installed on a flatbed truck or platform for easy transportation.
Stationary concrete pump with diesel engine HBT80C-1818DIII
It should be noted right away that the construction in the form of a trailer “with a chassis” does not mean that it can be transported from one construction site to another by attaching it to a truck – a stationary concrete pump can be mixed in this way only on the construction site. Transportation of a stationary concrete pump “from the chassis” over long distances is carried out only on a platform where it must be loaded / started.
Stationary concrete pumps, depending on the model, are capable of delivering from 5 to 200 m3/ hour to a maximum height of more than 250 m, and with a horizontal position of concrete pipes – at a distance of more than a kilometer. Their design supports two operating modes: concrete supply under high pressure (with low productivity) and low pressure mode, but with higher productivity. This need is due to the fact that when laying concrete pipeline pipes at an acute angle, it is required to develop a higher pressure in the cylinders in order to lift concrete along them. Modes are switched through the control panel of the concrete pump, which can be stationary and remote (the latter is more convenient).
The stationary concrete pump is driven by an electric motor or an internal combustion engine. In the conditions of Russia, the second type of drive is widespread, since at the stage of concrete work, construction sites, as a rule, do not have a sufficient source of electricity..
With their small size, stationary concrete pumps are quite efficient – they work stably, do not require high operating costs. The software of modern units is able to independently select the optimal operating mode (the number of piston strokes, it can also be controlled manually), depending on the stiffness of a given type of concrete and the temperature in the environment. Heating of diesel fuel in the cold season (for a diesel drive), reverse mixing of concrete in the bunker, oil cooling system – the quality capabilities of stationary concrete pumps.
Stationary concrete pumps differ from auto concrete pumps in that they are not equipped with a controlled and movable boom of the concrete pipeline, i.e. their preparation for work in a given concreting area requires manual installation of concrete pipeline pipes. If it is necessary to raise the concrete to a height, the assembled concrete pipeline is lifted to the work site using a crane or attached to the facade of the building being built, and the concrete pump itself is installed in the construction site, allowing free access for automatic mixers.
If a small amount of concreting work is expected, then the use of a stationary concrete pump is not profitable – it is profitable if there is a weekly volume of work or more (you need to bring the concrete pump itself, concrete pipeline pipes, mount them – all this will take time). If the amount of work on concreting is small or the timing of their execution is extremely small, you will need an automobile concrete pump.
Installing a stationary concrete pump on a trailer platform or in a truck body will not provide it with mobility – it can only be transported from place to place. A full-fledged automobile concrete pump is a special structure placed on a truck chassis, often additionally reinforced with a larger number of chassis than the serial version of a truck of this brand has. An important element of the construction of the concrete pump will be the folding boom of the concrete pipeline – consisting of several elbows, it is movable in each of them. The turns and lifts of the boom sections are controlled and allow you to quickly put the pipeline in the required position and start pouring concrete. The length of the concrete pump boom for concrete pumps is different by manufacturer and brand, the standard minimum is 22 m, the largest is 64 m. There are automobile concrete pumps with booms of greater length, but they are produced only for a specific order. The only manufacturer that produces such concrete pumps relatively serially is the Chinese company “Sany”, whose automobile concrete pump “SY5650THB-72” with a boom length of 72 m in 2009 was included in the Guinness records.
Doosan-Daewoo DCP 50X concrete pump truck
In terms of productivity, concrete pumps are inferior to stationary ones due to a less powerful engine – on average, it will be about 130 m3/hour. However, in terms of readiness for work, they have no equal – in half an hour after arriving at the construction site, the automobile concrete pump is completely ready for work! The drive of concrete pumps on a truck chassis is the engine of the truck itself (usually diesel). There are models of concrete pumps with an electric motor – i.e. an independent drive for a concrete pump, not connected to the car engine. Some models of concrete pumps allow you to make up a concrete mixture at the construction site – when loading its components into the hopper. It is permissible to correct the quality of the ready-mixed concrete directly in the bin.
The cost of concrete pumps compared to stationary ones is much higher – the most powerful units with the longest output of the concrete pump boom cost no less than several million rubles.
An important element of a concrete pump is a gate (valve)
It is worth considering carefully: the gate serves to connect with the inlet of the concrete pipeline of one or the other cylinder, for alternately connecting the receiving hopper with the cylinders. In a single-cylinder concrete pump, the gate either blocks the path of the concrete mixture into the concrete pipeline, then opens it – thus, the mixture pressure is created and it literally “shoots” into the concrete pipeline. The current position of the gate is controlled by software from the control unit.
There are three types of gates (valves): C-shaped (Euro designation – BRF), S-shaped (Euro designation – BSF) and rock gate (Euro designation – RL). The gates of the first two types are cast from high-strength steel or cast iron, the rock valve – only from cast iron.
How they look externally: C-valve – curved (slightly), like the letter “C”; The S-valve resembles the Latin letter “S”. The rock valve (a product of the Schwing company (USA)) has a more complex structure – it is a truncated cone, unilaterally “flattened” in the center in the horizontal plane. The non “flattened” end of the rock valve is alternately fed hydraulically to the pistons, each of the two “flattened” sockets – to the concrete pipe. Inside, the rock gate is hollow, between the two sockets (communicating with each other), ribs-thresholds are brought out at the top and bottom – for close contact with the concrete pipeline.
The gate of any of the three types is completed with a set of rubber gaskets and O-rings. What is the best gate (valve) design? They have some specialization – the rock valve is designed for “heavy” and “rough” concrete, which quickly clog the barrel of the S- or S-gate. In general, according to the resistance to blocking the gate barrel with concrete, resistance to hydrodynamic shock, the valves can be arranged in the following order – C-valve, S-valve and rock valve. S-valves lead in terms of reliability, C-valves are easier to operate and maintain, and rock valves have the greatest operating cost savings.
The quality of the concrete pump, by and large, does not depend on the type of gate installed on it – it’s all about reliable isolation of the joints. With increasing pressure, water and air will seep through loose or worn seal rings, concrete deposits will accumulate on the walls of the gate barrel, which will lead to a plug. Therefore, the priority in choosing the type of gate (valve) for a concrete pump will be the availability of consumable spare parts for it in the local market.
Concrete placing boom
This concrete delivery and placement vehicle looks exactly like the boom of a truck-mounted concrete pump, but it is used on its own. It is installed on the ceilings of the object under construction, due to which it has a larger working space – up to 32 m in radius. The concrete distribution boom cannot pump concrete on its own – this is done by a stationary concrete pump connected to the boom by pipes of the concrete pipeline.
There are two types of concrete placing booms – mechanical and hydraulic. The first type consists of hinged special pipes and is able to move only horizontally. The largest radius of coverage of mechanical concrete distribution booms is 10-14 m (in fact, it is slightly larger due to the length of the distribution hose installed on the end elbow). Installation on special outriggers (retractable supports), which raise the mechanical boom to a height of up to 4 m, allows concreting both horizontal and vertical surfaces with its help. Mechanical booms are simple, lightweight (compared to other types of concrete placing booms) and are easy enough to move between concreting areas.
Hydraulic concrete placing booms, in turn, are divided into two types – booms on outriggers and stationary booms..
The first type looks like mechanical booms, which is understandable – hydraulic booms on outriggers are a modification of them, they are similar to the booms of concrete pumps. Their coverage of the working area is from 12-17 m (depending on the specific model), they are controlled remotely (by the control panel) and are able to move with the help of hydraulics in both horizontal and vertical planes. The transfer of hydraulic booms from site to site is carried out by a crane.
The second type of hydraulic concrete placing booms is the most complicated – these booms are much more powerful than those described above and therefore the road. The stationary hydraulic boom has a high performance – its working radius is 24-36 m (from the model). It is possible to carry out concrete work on almost several floors of a building without moving this type of boom, which relieves the load from the tower crane, freeing it for other construction purposes – it is only used to set the boom and dismantle it.
The area of application of concrete placing booms is high-rise buildings, where the booms of concrete pumps cannot reach or their work is impeded by columns or floors. It is especially convenient to deal with hydraulic concrete placing booms – by controlling them with a remote control, you can bring them to the concreting area with the greatest accuracy, making the work process itself easier.
What concrete mix can a concrete pump pump
The mixture that the concrete pump can pump through the concrete pipeline should not contain a filler larger than 30% (for crushed stone) and 40% (for gravel) of the inner diameter of the concrete pipeline pipes (i.e. for a pipe diameter of 125 mm, crushed stone grains should not be larger 37 mm, and gravel – no larger than 50 mm). The grade of the concrete mixture intended for transportation by a concrete pump must be from M-300 and above.
The mobility of the concrete mixture, determined by the draft of the cone, must be within the following limits: for a mechanical drive – 70-140 mm, for a hydraulic drive – 40-120 mm. If this condition is not met, pumping attempts will lead to multiple plugs – in the first case, due to the low mobility of the mixture, in the second, due to stratification into components (lighter water will go faster than the filler). The settlement of the cone in this concrete mixture must be carried out at the construction site, having received a sample from the bunker of the automatic mixer – you can, of course, believe the documentation from the supplier, but if these data do not correspond to the real ones, you will have a piece of paper with numbers and a clogged concrete pipeline.
The procedure for working with a concrete pump
If the concrete pump boom is movable, then for a stationary concrete pump it will have to be mounted, having carefully thought out the order of assembling the concrete pipeline elbows and reliable fasteners when lifting to a height – the concrete supplied is not light and, as the concrete pipeline fills, it can move or tear it off. Therefore, all vertical (distance from the concrete pump at least 9 meters!) And inclined sections of the concrete pipeline must be securely fixed on steel masts, farms or scaffolding.
Concrete pump with boom 70 meters
The line of the concrete pipeline should not contain sharp turns and sharp corners, vertical sections at an angle of 90 degrees – it is better to add knees and increase the length of the concrete pipeline to give the least sharp angle. The rise of the concrete pipeline shaft to a height must be located 10 m from the concrete pump; in front of the vertical section, a needle valve must be built into the barrel to prevent the return of the concrete mixture when the pump is stopped. A reinforced hose (length – usually 4 m) is put on the metal pipe of the concrete pipeline leading to the concreting area – with its help the incoming concrete is distributed over the area.
Before the actual pumping of concrete to the work site and after their completion, two operations are mandatory – pumping the starting mixture and flushing the concrete pump / concrete pipeline. This condition applies to all types of concrete pumps..
The starting mixture for the concrete pump acts as a lubricant; without this, blockage of the concrete pipes is inevitable. There are several options for the starting mix, from classic to more modern:
- Powder of a special composition, packed in bags of 230 gr. Its shell may or may not be water-soluble – carefully read the instructions on the package before using it (it is easier to open and empty only the contents of the package). One 230 gram bag will require 18-19 (according to the instructions) a liter bucket of warm (!) Water (hot in winter). The resulting composition is mixed until the powder is completely dissolved and poured into the bunker of the concrete pump, then pumping is performed. For a 30 m concrete pipeline with a 12 cm pipe diameter, you will need a starting mixture solution based on the contents of one sachet – based on this, the required amount of mixture is calculated for each specific concrete pipeline. Cost 230 gr. packaged starting mixture will average 250 rubles. The powder starting mixture does not affect the characteristics of concrete;
- Manually – you need 150 kg of cement (3 bags) and 200 liters of water. Mixing is carried out in the bunker of a concrete pump, the resulting composition must correspond to the grade of concrete that will be pumped next. The cost of materials and operator’s work (when renting a concrete pump) in this version is about 1,500 rubles;
- Ready-made starting mixture, it is also cement milk. Produced in a concrete plant, requires delivery by a separate auto mixer. It is not cheap – about 8,000 rubles, this price includes delivery by a 5 cube automatic mixer and the cement milk itself, which requires no more than 2 m3.
It will be more correct to accompany the pumping of the starting mixture with a flushing ball made of a sponge, having previously moistened it as part of the starting mixture – its surface will wet most of the inner perimeter of the concrete pipeline. Do not forget to switch the fingers of the needle link-valve to the “open” position before starting, and equip the outlet of the concrete pipeline with a ball catcher. After completing the priming of the starting mixture, switch the needle valve to the “closed” position! So, the main work begins – two automatic mixers with concrete should already be at the construction site. After making sure that the team of workers at the concreting site is ready (using a walkie-talkie), having checked the quality of concrete in the automatic mixer – you need to climb the stairs and look inside the container through the hatch – the operator of the concrete pump gives the driver of the automatic mixer the command to deliver concrete and, after one cubic meter enters the bunker, starts unit.
Checking the quality of concrete in the mixer cylinder consists of assessing whether the mixture contains enough water – it must completely lubricate the concrete pump, this is important! If there is not enough water in the concrete – getting into the bunker, it becomes covered with cracks and falls apart – you need to add water in such an amount that it covers (at least!) The upper bells of the cylinders. The operator must coordinate the rhythm of concrete supply with the driver – after filling the bunker completely, it is necessary to stop the supply of concrete from the automatic mixer, waiting for the bunker to be half empty and only then continue the injection of concrete into it. The goal is to achieve mixing of a new batch of concrete with a concrete pump mixed in the bunker. After that, we increase the speed of concrete delivery and do not reduce it until the mixture comes out at the concreting area (workers will inform by radio) From this moment on, concrete is supplied in a regular manner..
Hydraulic trailed concrete pump
During the operation of the concrete pump, the operator must carefully monitor the readings of the pressure sensor in the hydraulics – after the flow has stabilized, the readings of the sensor should be considered normal and memorized. An increase in pressure in the outwardly normal state of the mixture will inform about its sliding – you need to add water to the hopper without stopping the pump. If it is necessary to stop / start the concrete pump during the working day, the flow should be reduced to reduce the starting water hammer in the system – as soon as the pump enters a normal rhythm, the flow rate can be increased.
Flushing of the reciprocating concrete pump and concrete pipeline
To clean the system from concrete residues you will need: warm water (200 liters for several cleaning cycles); air compressor; flushing link, designed to supply water or compressed air (under pressure not exceeding 10 bar); wash balls and wads in the form of a cylinder. The latter are made of spongy material for the diameter of the concrete pipeline (the price of flushing balls and wads depends on their diameter, on average 450 rubles – a ball and 750 rubles – a wad).
The concrete pipeline must be cleaned immediately after the completion of the last batch of concrete, having prepared everything necessary for this before emptying the last automatic mixer. It is important to constantly keep in touch with the operator at the concreting site – he must inform when only the volume of the mixture contained in the system at the moment remains to be poured. After such a signal, it is necessary to stop the supply of concrete and pour water into the bunker of the concrete pump – the resulting liquid mixture is maintained in the bunker at the lowest possible level, but not so much that air gets into the piston cylinders (air intake will lead to a problem – it will stratify the mixture).
After completing the pouring, the operator of the concreting section gives a signal to the operator of the concrete pump – he switches the operation of the concrete pump to reverse (reverse mode) to reduce the amount of mixture in that part of the concrete pipeline that is located closer to the site of work and to lower the pressure in the concrete pipeline. Then the concrete pipeline is disconnected from the pump and built up with additional sections to reach the area intended for dumping the contents of the concrete pipeline (they must be prepared and assembled to the required length in advance). It is imperative to put on the end pipe that leads the concrete pipeline to the discharge site, the nozzle-catcher of the flushing ball – it can fly out at a decent speed. The operator of the concreting section removes the dispensing hose from his end of the concrete pipeline and installs a blowing nozzle instead of the last elbow, having previously inserted a flushing ball into the concrete pipeline with abundantly moistened water (it is better to combine – first introduce the ball, followed by a wad). The launch of compressed air by the operator of the concreting section and the transfer of the fingers of the needle valve to the “open” position should be performed as simultaneously as possible – the movement of the flushing ball along the concrete pipeline should not stop for a minute. It is better to carry out the flushing operation twice – it is necessary to re-supply water through the concrete pump to the concrete pipeline by switching the needle valve to the “closed” position.
The hopper of the concrete pump is rinsed and cleaned with a stand under the outlet of the drain pan. It is especially convenient if this model is equipped with its own water pump with a hose and a tank for water heated by hot gases from the exhaust pipe – it is easier to flush and remove concrete residues, because no need to think about where to get hot water.
Where do you dispose of concrete residues after flushing the system? You can’t just drop it on the ground – it will seriously damage the soil, because the semi-liquid material will spill over the construction site. There are two options: collecting rinsing residues in a box; dumping the penultimate automatic mixer into the bunker, having previously coordinated this operation with the concrete supplier. In the first option, you need to assemble a square box-formwork from the boards (height 2,000 mm, depth 500 mm), lining it with pvc film 200 microns thick – after washing, its contents can be moved for disposal. The second option: put the discharge hose from the concrete pipeline into the bunker of the automatic mixer, run it in the direction of “loading” and secure it with a chain (otherwise it will jump out and splatter everything), then start the flushing process described above.
Concrete pump rental – selection criteria
If the need for a concrete pump arises only periodically, there is no point in purchasing this expensive unit and wasting time looking for an experienced operator who is hired for a short time. It is more profitable to rent, and not only the mechanism itself, but also the services of its operator – he knows the individual characteristics of this concrete pump better than others. Please note that all operating costs during the rental period will have to be borne by you as a renter – carefully study the list of additional costs and requirements of the lessor!
What should be the starting point when choosing a supplier? Your needs will be determining here:
- Distance to which the concrete mix will be transported.Determining the transportation distance is important not only for concrete pumps with a limited boom length, but also for stationary concrete pumps – based on it, the power of the unit itself is determined, because if it is insufficient, the delivery of the mixture over long distances will be impossible, as they say, physically. In addition, for stationary concrete pumps, you will need a concrete pipeline of a certain length, which should be set by the lessors..
- Total amount of concrete work.With a volume of work up to 1500 m3 a concrete pump capable of delivering 10 m is sufficient3/ h, at 4000 m3 – 20 m3/ h, at 10,000 m3 and above – from 40 m3/ h Here it is important to approach from the standpoint of benefits – the more power of the concrete pump, the higher its rent.
- Ppreferred engine type (electric or diesel).Engine type – operating costs, of course, will be borne by the renter and it is beneficial for him to determine the best source of energy, if there is such a choice.
- Drive type (mechanical or hydraulic).Drive – if you carefully read the material outlined above, then you know that the power of hydraulic-driven concrete pumps is higher than that of mechanical ones. Therefore, renting a pump with a hydraulic drive is more profitable – it is more efficient..
- The period during which this concrete pump is operated.It’s simple – if the unit is dilapidated and worn out, then it will break down more often than work properly. And this is not profitable!
What else do you need to know? It is more profitable to choose the model of a concrete pump that is able to independently stir the mixture in the bunker (vibrating grates may not be enough!) – the road surface on which the automatic mixers follow to the construction site is unlikely to be of high quality – the mixture in the bunker of the automatic mixer will stratify to one degree or another, which will affect both the operation of the concrete pump and the quality of the laid mixture at the work site.
The working 8-hour shift of the rented concrete pump includes about an hour required for pumping the starting mixture and flushing the system after work – i.e. the actual operating time, during which the pump will properly pump the mixture, is 7 hours. If the remoteness of the work site and the layout of the construction site allows, then it is more convenient to rent a concrete pump – it does not have to be moved by special transport, it is not required to rent a concrete pump to it (the average cost of renting a 3-m section is 350 rubles per shift) and it is not necessary to assemble / disassemble it (this will take from 4 to 8 hours).
The average rental price of a concrete pump is 19,000 rubles. for an 8-hour shift (boom length – 32 m, productivity – 90 m3/ h), stationary concrete pump (productivity – 180 m3/ h) – 15,000 rubles. per shift. But – if a large amount of work is expected using concrete distribution booms, then the best option would be a stationary high-power concrete pump capable of supplying the mixture to several work areas at the same time. Before making a final decision, weigh the pros and cons – take your time!