Failure of pressure washer

A member has reported an incident in which a Karcher HDS1195 pressure washer failed when a technician was conducting a test run after maintenance. The model involved was a portable unit designed for domestic and industrial use, and was three years old. A technician had completed the replacement of an electrical switch, and was checking that the switch was working correctly. On successful completion of the tests, the unit was powered up to ensure it was fully operational. The technician saw water emerging from the nozzle of the cleaning gun, and proceeded to shut down power to the washer. As this was done, there was a loud bang and the hatch for the boiler was blown off into the air. The technician received two small cuts to the face and minor droplet burns to the right arm.

Following investigation, the following was revealed:

• A pressure relief valve, designed to prevent system overpressure, was found to be corroded and unserviceable;
• A switch, designed to regulate the boiler, was also found to be defective. As a result, overpressure within the system caused the heating coil to rupture, and the escaping water and steam blew the hatch off the boiler unit and into the air.

The following recommendations were:

• A thorough inspection of similar portable pressure washing devices, particularly those using a heating system, would be beneficial;
• Portable pressure washing devices should be part of the planned maintenance schedule.