The purpose of the Nitrogen Purging system is to reduce the oxygen level in the mill-housing during the size reduction process, thus reducing the risk of an explosion. The system consists of a solenoid valve, flow control valve, pressure switch and pressure gauge. These components are linked together using a small bore stainless steel pipework and assembled in an IP65 stainless steel enclosure.
Typically the N2 purging enclosure is affixed to the machine at a point suitable for the customer to connect the supply of nitrogen. The valve and the switch are wired into the Uni-Mill control panel, and connected to the E/Stop circuit. The stainless tubing is routed neatly round the machine to a final connection in the impeller housing. As an additional safety measure, a dedicated oxygen analyser control system can be used to monitor the presence of oxygen in the mill, shutting the system down in case of malfunction / absence of nitrogen (this can initiate an alarm).
Sequence of Operation for Nitrogen Purging:
1. Press start button on the control panel and the solenoid valve opens, Nitrogen enters the machine, at the same time a timer is activated inside the mill control panel. The machine will not start until the timer, which is adjustable, switches on. The purpose of the delay is to allow for complete purging of the Uni-Mill housing.
2. The pressure switch monitors the presence (flow) of Nitrogen into the mill housing.
3. Providing the pressure switch is ‘made’ and the timer has switched on, the machine will start. If the Nitrogen runs out, or is switched off during production the machine will stop.
A warning lamp can be fitted to the control panel which will illuminate when the pressure switch is not made.