Machine Safety

Pre-Start Warning Devices Code 4440 & 4450

The Conflow Code 4440 & 4450 Pre-Start Warning Devices are designed to provide a positive safety measure to eliminate accidents in the vicinity of the cutting drums of coal cutting machinery.

They do this by utilising dust suppression water jets to drive anyone working in the danger zone clear of the cutting drum, whether or not the person is mindful of the risks to which he is exposed. The machine cannot be started until the water jets have been in operation for a predetermined period.

The action of the Pre-Starting Warning Device is that it interrupts the electrical pilot circuit of the machine so that the drive motor cannot start until the predetermined time has elapsed following the turning on of the dust suppression water. This is normally seven seconds. It should be noted that the system is a true pre-start interlock.

Once the pre-start procedure has been completed and the machine is running with no one in the danger zone, the water can be turned off, if so desired e.g. to flit dry or run dry during maintenance checks. Connected in an alternative way, the water must always be flowing for the motor to run.

Typical Applications

  • To provide wet pre-start warning protection for personnel working near cutting drums


  • 1/2" BSP Water connections
  • Maximum working pressure 140 bar
  • Provides both Flow and Pressure switches
  • 4450 version has two flow switches
  • Incorporates a 7 second delay
  • Operating range 10 - 70 bar • FLP APPROVED - Cert. # 03ATEX1537