Periodic Function Test
Testing safety-related functions at defined intervals and with no load. Its scope covers stopping behaviour, response at the range limit, limit switches and direction interlocks. The aim is to prevent a hidden fault from appearing for the first time under load.
Most safety functions are not exercised during normal operation; their faults therefore remain hidden and are only noticed at the moment they are needed. The periodic test exists to reveal these hidden faults.
- Sequence: first operate each channel one by one with no load and verify the correct motion and correct direction. Then trigger the limit switches by hand and confirm that the motion stops.
- Stopping: test the machine's hard-wired emergency stop circuit; verify with no load that motion does not continue when you switch the remote off or move out of range.
- Interlocking: check that the contactors do not pull in together when the forward and reverse commands are given at the same time.
- Records: keep a written record of the test date, the findings and the corrections made.
The test interval is determined by the intensity of use and the risk assessment carried out on the machine; a quick check before each daily shift together with a detailed monthly test is a common arrangement.
Context in which this term is used: Wireless Crane Remote Control Selection Guide