Machine Safety

Pre-Start Warning Unit Code 2629

The Conflow Code 2629 - Pre Start Warning Unit interrupts the electrical pilot circuit of a coal cutting machine so that the drive motor cannot start until a predetermined time has elapsed following the starting of the dust suppression water.

The device has been designed to provide a positive safety measure to eliminate accidents in the vicinity of the cutting drums of mineral cutting machinery. It does this by utilising dust suppression water sprays to drive anyone working in the danger zone clear of the cutting drum.

These water sprays operate for a fixed time (7 seconds, within the pressure parameters 10-70 bar) before the pilot circuit is made and the cutting drum starts to rotate. The standard unit is a pressure switch with a built in time delay.

A flow switch can be added to cover situations where all the warning sprays may be blocked and no other machine safety system has been specified.

Typical Applications

  • To prevent mineral cutting machines from operating unless dust suppression water is spraying for a warning period prior to start up


  • 3/8" BSP water connections
  • Maximum working pressure 70 bar
  • Provides 7 second delay between attainment of hydraulic pressure and switching off electrical circuit
  • Electrical switch rating: - 250Vac @ 5A : - 30Vdc @ 5A
  • FLP Approved unit. Cert # 03ATEX1537