Shotcrete pumps are one of the most important components in a mechanized concrete spraying system, and they are designed to ensure a continuous flow of concrete.
A continuous concrete flow is of vital importance to guarantee a homogeneous shotcrete application, to be able to ensure the required quality and layer thickness, as well as reducing rebound.
A double-piston concrete pumps is made up of the following components:
Hydraulic system: open or closed
In a closed hydraulic oil system, the pump works when it needs to transmit energy, but does not generate flow when it is resting: this system offers greater energy efficiency and reduced component wear.
Above all, a closed circuit implies a shorter response time as it requires significantly less hydraulic oil than an open system, which renders it more efficient as the amount of flow is reduced.
Drive cylinders: generate pressure into concrete cylinders
Drive cylinders receive the hydraulic oil flow created by the hydraulic pump, and in turn push the concrete cylinders, providing the speed and thrust needed to pump concrete.
Concrete cylinders: suck concrete from the hopper
Concrete cylinders are in charge of pushing concrete through the pipes: they work in a synchronous alternative manner, so that while one is pushing concrete, the other one is sucking and vice-versa. This change is regulated by electromagnetic or hydraulic sensors, depending on the system.
The size of the cylinders will determine the number of strokes required to fulfill the theoretical output. For instance, a Putzmeister SPM 500 Wetkret machine is able to produce a maximum theoretical output of 30 m/h with 21 strokes.
Greater filling ratio will reduce the number of total strokes required to push concrete, thereby reducing energy consumption and cutting down on the wear of the system at large. In addition, there are fewer cuts in the total flow of concrete, and you can save time.
S-tube allows for constant flow of concrete
The oscillating S-tube shifts alternatively between each of the two concrete cylinders on one side, linking to the pipe delivery system on the other: its function is to toggle between them to keep a constant flow of concrete.
The concrete goes through the S-tube into a pipe designed to constrain the diameter of the concrete column in order to increase the hydraulic pressure, which causes a great deal of friction wear. Given the high level of abrasion, it’s vital for the S-tube to be built in wear-resistant materials.
Water box: cools down the system
The water box cools down both the drive and concrete cylinders to ensure an optimal working temperature. In addition, it must be easily accessible to double-up as an inspection and maintenance element, since any potential residue will point towards possible leaks. Experts recommend checking the water’s transparency daily.
Agitator in the hopper: maintains the concrete’s fluidity
Concrete is poured into the hopper through a grill, and the agitator maintains the fluidity of the mix, avoiding sedimentation.
Grill with vibrator
The hopper is covered with a grill with a vibrator that helps the concrete flow. The grill is a key security element that helps keep out any extraneous elements that could damage the equipment (big stones, chunks of brick…)
It’s obligatory to feature both mechanical as well as electric security components in order to prevent operators from reaching into the hopper while the pump is active.
- Food & Agriculture Organisation of the United Nations, “Sistema Hidráulico” in Parámetros de Comparación de Motores Agrícolas, p2-5, accessed 29/04/16, http://www.fao.org/3/a-ah927s/ah927s06.pdf
- Victor Yepes, Universitat Politècnica de València Blogs, published 13/03/15, accessed 29/04/16, http://victoryepes.blogs.upv.es/2015/03/13/bomba-de-tubo-o-trompa-oscilante-para-hormigon/