Blow and Pump-Back Safety Alert Updated

This updated Concrete NZ Safety Alert addresses the issue of concrete blow-back and pump-back into the concrete truck mixing bowl, which can be an inherently dangerous procedure unless carefully controlled.

Blow-back uses high air pressure to move residual concrete from the line or boom pump back into the truck mixer or bowl. Air pressure will cause anything inside the pipe to act as a high velocity projectile.

Pump-back is the return of residual concrete to the truck mixer or bowl by either line or boom pumps, excessive pumping pressure creates similar problems to blow-back.

The updated Safety Alert identifies the following four key risks that must be accounted for:

1. High air pressure or pump line pressure and pipe movement during blow-back or pump-back can cause pipe joints to fail and break apart.


2. Concrete in the pipe is subjected to high pressure during blow-back or pump-back and can cause the hose to eject from the concrete bowl or material to rebound and exit the concrete bowl. In both situations there is the potential to cause injury or damage.


3. Climbing a concrete truck ladder while carrying a line pump pipe or trying to manoeuvre a pump line while not having three points of contact creates a high risk of fall from height.


4. Control measures previously deemed as acceptable in both blow-back or pump-back have not been adhered to resulting in injury or damage.

In response to these risks, Concrete NZ strongly advises against the practice of accepting blow-back or pump-back from concrete pumps.

Download the updated Blow-Back and Pump-Back Safety Alert Safety Alert.