9.1 SYSTEM DESCRIPTION
The Heat Store is fitted with a Nitrogen Blanket System as a protection against corrosion and to provide a system for the detection of closed circuit leakage.
The system comprises the following components:
(i) Pressure switch.
(ii) Warning light actuated by the pressure switch on falling closed circuit pressure.
(iii) Second stage pressure regulator set to 50 kPa.
(iv) 10 mm internal copper pipe work, fittings and valves.
(vi) Nitrogen pressure regulator - set to 100 kPa
(vii) Flexible hose to connect from the regulator to the brass nipple located on the side of the Heat Store below the electrical control cubicle.
9.2 PRINCIPLE OF OPERATION
The system is designed to maintain a minimum positive pressure of 50 kPa within the Heat Store.
The primary regulator fitted to the nitrogen bottle reduces the pressure to 100 kPa and the second stage regulator supplied with the Heat Store further reduces the pressure to 50 kPa. The in-line pressure switch monitors the line pressure between these two regulators.
In the event of a leak within the closed circuit, nitrogen from the gas bottle will enter the Heat Store to replace the fluid or nitrogen lost through the leakage. This prevents oxygen entering the closed circuit through the point of leakage.
If a leak is allowed to continue unchecked, the nitrogen bottle will be depleted and the loss of pressure detected by the pressure switch. When the pressure falls below 30 kPa the pressure switch activates the external warning light and an electrical control circuit relay that will turn OFF and lock out the closed circuit circulating pump.
When the indicator light is illuminated the entire system must be checked for leakage and all leaks repaired immediately. The fluid level of the closed circuit must be re-established and the nitrogen bottle replaced before the system can be restarted.
Failure to repair a leak or replace the nitrogen bottle can result in internal closed circuit system corrosion.