SEM Concrete Placer Pumps
HOW IT WORKS - PUMPING


The SEM pump consists of a main cone into which concrete is filled through an opening at the top, which is manually closed with a self-sealing lid.  Regulated by a control valve, compressed air is fed into the cone through two specially placed nozzles.  The nozzles are positioned so as to create a vortex whereby the concrete is screwed into the pipeline in a continuous flowing action.

The compressed air does not enter the pipeline but remains in the cone.  This ensure a minimum of air consumption.  Each time the concrete has been displaced to the bottom of the chamber, the air is exhausted and the lid automatically opens.  The pump is then ready for recharging.


Schematic SEM concrete pump


When the pipeline has been filled, each new batch fed into the pump will result in the discharge of an equivalent amount from the open end of the pipeline in a smooth, yet rapid flow of concrete (without fear of segregation) when the pump is pressurized.

Cleaning the SEM pump and pipeline at the end of the pour is a simple operation.  A sponge is placed in the outlet of the pump and blown through the pipeline.  This clears the line of all concrete.  The pump is then washed out with water and this water is pumped through the pipeline, cleaning it and discharged to waste. 
HOW IT WORKS - PNEUMATIC PLACING


In certain circumstances it is an advantage to operate the SEM pumps as a pneumatic placer - the most common one being to overcome restrictions on distances and heights.  Used as a pneumatic placer, the application of compressed air is not stopped when the pump is empty but the air is continuously fed into the chamber and will enter the pipeline and convey part of that batch of concrete to the pipe end.  It is a plug flow of concrete traveling through the line at fairly high speeds and with a forceful discharge.

For successful application, the concrete mix needs to be adapted to withstand the plug flow and high speed of travel, with resulting segregation tendencies.  For practical and economical reasons this method of transport is normally only used for underground applications or special work on surface.
CONCRETE PUMPING

Full pipeline - low velocity.
Smooth discharge at pipe end.
Low consumption of compressed air.
PNEUMATIC PLACING

Plug flow - high velocity.
Intermittent and splashy discharge at pipe end.
High consumption of compressed air.


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