Did you know that the "mechanical pressing-in of the hose by external forces" is the most frequent cause for premature wearing of concrete pump hoses? This is the result discovered by an internal Putzmeister examination of the causes of failure of concrete delivery hoses of type SK 65.

• Regularly check the outer layer of your hoses for damage
• Lay the hoses with widest possible radius so as to avoid unnecessary friction. Never bend the hoses!
• When cleaning, pay special attention that no concrete residue remains in the delivery hose.
• Only PM hoses are to be used as they can endure the prescribed operating and testing pressures, and are especially wear-resistant.

Most of the concrete pump operators are perhaps unaware of the fact that a delivery hose, resp. end hose is similar in design to a car tyre. For the concrete pump hose, too, the pressure body consists of a steel wire fabric. And where the car type has a tread, a thick layer of rubber protects the delivery hose from damage.

What happens then when you drive too fast with a car tyre against the kerb? The tread can be damaged and, what is worse, the fabric of the tyre could damaged but remaining at first not noticeable. This is exactly what happens in principle to the concrete pump hose if, for example, a heavy machine drives over the hose line by mistake or if the hose rubs against a sharp steel edge when pumping concrete. A few job sites later, when this has long been forgotten, a defective end hose suddenly comes to light and nobody knows the reason why. The hose has simply just not "forgotten" the rough treatment.

The direct effect of force on the fabric is not the only decisive factor here. Once the external skin has been damaged, moisture and oxygen come into contact with the steel fabric and rust starts eating the steel wires within the shortest of time.

Just how hard-going work on a job-site is for the hose nozzles which have been forcibly torn out. As an explanation for this one must be aware of the fact that concrete which has dried out in the hose can connect up with the rubber. This means that the next time that the hose is used that not only the concrete residue but also a whole piece of the hose itself is torn out at the same time. As insufficient cleaning is low down in the "Charts of breakdown reasons" it may count as proven that pump operators are really good at cleaning.

A further cause often mentioned for premature hose wearing is the incorrect laying of a delivery hose. A hose line which is laid with radii too tight immediately behind the pressure connection, leads to rubbing on one side within a short period of time. If the hose is bent during pumping, then just a few cubic metres of concrete throughput are sufficient to finally destroy the delivery hose completely.

Finally, we feel obliged to mention the fact that three of the hoses examined had manufacturing faults which meant that they failed due to the tread. This low number of material faults speaks well for the extensive quality safety measures which Putzmeister has been carrying out extensively now for years in cooperation with its suppliers.