Concrete pump

A truck-mounted concrete pump is a mobile pump for conveying concrete. Their field of application is the construction of buildings, bridges or dams. It can be pumped concrete with grain sizes of up to 63 millimeters, the vertical reach of the booms can be up to 100 meters. The truck-mounted concrete pump is legally classified as a self-propelled machine.

A mobile concrete pump is composed of a truck ( chassis), a pumping system and a placing boom. However, there are models which do not have a boom.

• 2.2.1 operation

• 3.1 Structure / Function
• 3.2 Requirements
• 3.3 Wrapping styles
• 3.4 Abstützarten

The invention

Shortcomings when dealing with the conventional casting tower brought in 1927, the engineers Max Giese and Fritz Light on the idea to pump the concrete from concrete mixers directly to point of use. It was especially important to keep the power consumption compared to the casting tower method to a minimum. The reduced water content of the concrete in the pumping process not only saved energy but also let the material quicker and firmer to set. Gravel or crushed stone material were used. Could be pumped up to 38 meters in height and up to distances of 120 meters.

Pumping systems

Piston pumps

As a single-piston pumps concrete pumps are used in Germany since the twenties of the last century. Today mainly come double piston pumps are used, which are hydraulically driven by electric or diesel motors by means of an oil pump. The delivery pistons are hydraulically connected to each other via the drive cylinder and operate in push-pull.

The pump consists of core

• Hydraulic drive cylinder,
• Feed cylinder with feed piston,
• Switched between the water box,
• Concrete hopper with agitator,
• Transfer tube,
• Lever
• Switch cylinder for transfer tube.

Operation

The returning delivery piston of a conveyor cylinder creates a vacuum, the media from the hopper is sucked into the cylinder. Simultaneously, the leading conveying piston pushes the contents of the other feed cylinder through the transfer tube into the delivery line. At the end of the stroke, the pump switches, that is, the diverter swings in front of the other filled conveyor cylinder and the delivery piston reverse their direction of movement.

To clean the pump or to line blockages to solve again the pumps, each machine can also "backwards" pumps. The function of pumping back is reversing the motion of only the delivery piston by a hydraulic pilot valve, while the diverter remains in its position and is moved until reaching the end position of the Umschaltzylindern in the opposite shift position. Piston pump units are called " core pump " pre-assembled and can be mounted as a stationary, construction sites or tunnel concrete pump according to use on chassis as " truck-mounted concrete pump " or to various sub-frame.

The drives for concrete pumps are now carried exclusively hydraulically, with the control versions of each manufacturer are different. Variants are purely hydraulic sequence control, electro-hydraulic sequential control, drives in open and closed hydraulic circuit, one and two- loop controls and free-flow hydraulics. Each system has certain advantages and disadvantages.

Important performance factors are

• Delivery pressure,
• Weight of machine
• Price and
• Complexity of the system.

For these reasons, many variants exist for a long time in parallel. With piston pumps today are pressures in the pumping medium up to 400 bar and flow rates achieved up to 200 m³ / h.

Rotor pumps

The rotary pump is a simple, compact pumping system that works without special concrete slide. The delivery of concrete is caused by rollers which rotate the rotor housing and thereby the delivery hose pinch ( peristaltic pump ). Thus, the rotor pump is the only system on the market, which is a completely dense conveying system when properly adjusted.

Operation

The rotor housing is continuously generated by a vacuum pump under reduced pressure. The higher, atmospheric pressure on the concrete surface in the stirring vessel and the static pressure of the concrete filling the pump tubing directly downstream of the pressure roller up to the full cross-section of concrete on. In the rotor housing of the feed tube ( tube pump ) is compressed by the continuous unwinding of two pressure rollers, which are offset by 180 degrees from each other. The fresh concrete located in front of the pressure roller is thus uniformly pressed into the delivery line. Behind the pressure roller, the hose is directed as a result of the negative pressure in the rotor housing back on and so develops a suction to the feed hopper. To reverse the direction of rotation of the pump rotor drive is reversed. In this way, the rotor absorbs concrete from the delivery line and pumps it back into the hopper.

The rotary pump is driven by an oil hydraulic geared motor, wherein the flow rate may be infinitely variable from zero to a maximum, depending on the speed of the rotor is controlled. The service life and wear cost of this pumping system are almost exclusively dependent on the conditions that affect the pump tubing. The rotor pump system is now estimated to be very environmentally friendly as it operates quietly (no switching noise as piston pumps). It is characterized by a constant speed and smooth running.

In the hopper remains hardly any concrete residue, as well as residual amounts can still be sucked into the delivery hose. In addition to concrete and the pumping of other media such as water, floating floor and Feinstmörtel is possible. The rotor system allows pressures in the pumping medium to a maximum of 30 bar and flow rates up to 60 m³ / h This pumping system is used mainly for truck mixer concrete pumps.

Valve systems / diverter

The heart of a concrete pump in the mechanical part, the concrete gate valve ( diverter ) with different model variants such as flat slide, wedge slide, knee slider, Flapper, pivot tube, S- pipe, trunk, rock slide, delta diverter and CS -transfer tube. Being the only employed pump system, the pump rotor does not require a slide and is not considered here.

Only after prolonged practical use of the different valve systems to all the pros and cons of each system are emerging. In the tube variant of the frictional resistance due to the lower sealing surface is more favorable compared to other rail mountains forming. The seal of a diverter valve to the delivery cylinders or pump output can be performed technically easier and better. The diverter valve is almost completely sealed, so that by means of concrete pumps also easily water can be pumped today. Therefore, concrete pumps are in some large construction sites, even for cleaning the feed line as a water pump use. This is consistent with other slide gate systems, such as the flat slide, only limited feasible.

The requirement of a good concrete slide is primarily tightness, as lead during the pumping process, each gap, especially under high pressure to bleed out of the concrete ( ie water and fine material can be forced out of the concrete mix ) and thereby Betonabsetzern ( encrustation ) can. As a follow bottlenecks in the concrete slide and thus higher pump pressures, limited pumping capacity and, in extreme cases pusher directly to the pump. A further requirement of a good concrete slide is fast By switching between the end positions to possible to have a short flow of concrete demolition during the switching, so that there is a continuous flow of concrete as possible. Further, it is expected of a good concrete slide that he as still as possible, muted, noiseless and vibration-free moves to its new end position despite fast gating. This reduces the overall machine vibration and swaying of the distribution boom during pumping. These demands on modern concrete slides are now dominates safe. An additional important requirement for concrete slide wear resistance, not least for reasons of economy and ease of service. If necessary, the workshop of the operator or a technically skilled machinist without pumping specialists should be able to swap a concrete slide itself. Through new, wear-resistant materials or post-treatment of the slide parts manufacturers are seeking to meet these demands. Since the wear behavior of application criteria such as hardness of the aggregates, flow rate and pressure is highly dependent on a more or less better wear behavior can be identified only on the basis of comparing the flow rates and the site conditions.

Booms

The truck-mounted concrete pump with placing boom is now in many countries, the most widely used concrete pump, placing boom characterizes the structure of the machine. The main criteria for a mobile concrete pump out of the pump power, the kingdom of height or reach of the placing boom, Folding (also called folding kinematics ), number of boom arms, stabilizer spreads and the minimum unfolding.

The market offers a huge range of booms to up to a maximum reach height of around 100 m. The maximum height of the vehicle in the folded state is less than 4 m, the maximum. Width as the chassis 2.50 m. The truck-mounted concrete pump is classified as a self-propelled machine, making them subject to different licensing requirements than the transport traffic. In September 2012, introduced the Chinese manufacturer Zoomlion the largest ever concrete pump in the world: The concrete placing boom of the 101 meter high pump which is mounted on a 7 -axle Scania chassis is divided into seven segments; the top four are made to reduce the weight of carbon fibers.

Design / Function

The individual cantilever arms of a concrete placing boom are made of box construction. They are moved hydraulically. Articulated with large angular ranges found along with a powerful twist movement with large swivel angle is very good flexibility during transport of the concrete at the point of introduction, over obstacles and even through small openings such as windows through. Conveyor and risers usually consist of standardized straight pipe sections and elbows. These are so easy to replace. Standard clamp couplings serve as pivots and spigots. The pipe joint at the end of the mast acts as a brake functions and reduces wear of the end hose. This is suitable bar through his steel cord fabric for concrete pressures up to 85. The support legs of any kind are equipped with hydraulic jacks and provide the necessary stability. The extension or unfolding of the support legs is done depending on the design by hydraulic cylinders or hydraulic motors with chain or cable drive. All movements of the mast done hydraulically.

All mast cylinders have screwed safety valves to protect against overload of the arm and against sagging on rupture of hydraulic lines. The hydraulic oil supply is adjusted so that a plurality of cylinders can be moved. The hydraulic control system can be operated to pump the concrete, or on a portable remote control unit. The operation of the control valve is electrohydraulic. The oil tank of this is integrated in the boom block or run separately. The required power is taken on the vehicle.

Requirements

Since 1982, developments are ongoing to in many-armed booms remote control of the end hose for the machinist to make safer and easier. The goals have always been:

• Simple operation of the mast with a lever without the typical saw-tooth.
• Quiet end hose at each pumping speed.

The resulting control system developed at Putzmeister EBC ( Ergonic Boom Control ) to control and regulate the concrete placing boom is a supplement to the normal boom control. The EBC boom control allows the concrete placing boom to drive with only one joystick. The advantage for the machinist is the simple operation. End hose forward or back, left or right, up or down. For example, a bottom plate to concrete, the height of the end hose is set only once when placed horizontally imputed machine. The descendants of the single mast arms under computer control takes place. The work of the machinist is easier and safer. Another advantage lies in the quiet Endschlauchführung. The building-up of the end hose by driving individual arms and by the vibration excitation of the concrete pump is no longer available due to the computer-controlled damping.

Wrapping styles

Up-to- market folding types are:

• Z-fold
• Overhead roll- fold
• Under overhead roll- fold
• Multi- Z-fold

Good slip properties and mobility of the placing boom are dependent on the combination arm number and type of folding. This contributes significantly to that about a boom extended into the 30- meter class in a hall that is to be brought into working position. A major factor in the use of truck-mounted concrete pumps with placing booms big is the space required for the support. Due to tight site conditions, traffic, etc. are individual concrete pump types can not be used. It is appropriate to provide for predestined machine that can be securely supported at the required reach / height on the available space.

Abstützarten

The following types of support are at market rates, and depending on the size of the placing boom, the space requirement varies fails:

In the narrow support may remain partially collapsed on one side of the support legs. A safety circuit ensures that the boom is stopped before it is moved to the hazardous area, which means the working range of the placing boom is limited depending on the machine to 120 to 180 degrees. The required support surface is substantially reduced, so that it can be carried out on a relatively small support surface today. Today this is often the case, as in this case, for example, only one side of the street is occupied by the concrete pump and the other side of the road remain open to traffic. Booms must not be used as a hoist. They merely serve to carry the filled with concrete delivery line and end hose of a maximum of four meters. The improper use of the placing boom threatens the stability of the entire machine and the steel construction of the boom in case of overload. In addition to acute damage it can cause permanent damage due to overloading, which often occur only after several years. Concrete pump booms are subject to annual, legally prescribed safety review after accident prevention regulations. It is mainly carried out by specialists of the manufacturer works. Booms can be accurately operated with remote proportional control today.

• The swivel range is at least 365 degrees.
• The standard delivery line has 5.5 inch inner diameter, corresponding to 125 mm or 4 inches is equivalent to 100 mm.
• The required maximum oil pressure is about 350 bar and
• The electrical power supply via the trolley is 24 V DC voltage.

For practical operation of a concrete placing boom skill and practice is required especially in multi-member arms; Even if the machine is equipped with computer-aided EBC control, the operator is a complex process. Several movements can be performed simultaneously to avoid during concreting possible rocking of the hanging end hose. Booms are not only built on chassis, but also in the same style, for example in building construction as a stationary boom, on tubular columns with climbing facility or on lattice towers.

The booms then change depending on progress with the building in the height, the technical embodiment of this device corresponds to the booms of truck-mounted concrete pumps. On the market there are also special devices, such as construction rotary distributor which are actuated purely mechanically from the construction site crane on to be concreted surface offset or partially found as wall mounting as well as special equipment as spray arm for the fire service area for a variety of operating conditions.

Others

In the Chernobyl disaster in 1986 put it, a concrete pump in order to spray water for cooling or for deletion in the reactor ruins.

In the Fukushima nuclear disaster put you concrete pumps for various purposes: You were outside of three reactor buildings and injected with their " trunks " by the destroyed roof water into the spent fuel pool. In addition, a concrete pump splashed diluted resin in different buildings in order to bind the radioactive dust there. The power plant operator called the devices "elephant" or " giraffe ".