As part of the suite of standards replacing Australian Standard AS1677, some key changes have come about with the introduction of AS/NZS 5149.2. Julian Parker, executive VP of operations for Henry Technologies explains the amendments with safety device systems.
The focus is as much on refrigeration containment and reporting releases, as it is on protection for over pressure. Safety device system selection is based on the energy contained in the system which could be released catastrophically in a fire or other over pressure situation; therefore it is critical to get the sizing and application of the safety device system correct.
A typical safety device system compliant to AS/NZS 5149.2 consists of the following devices:
Rupture Disc: – Comprising a hermetically sealed membrane within a body which is threaded to attach to a system and accept a safety device. The rupture disc will burst at a predetermined pressure, equal to the set pressure of the safety valve setting; it will also contain an access port to accept a tell-tale gauge, or pressure sensor to indicate discharge pressure has been reached. A good quality product will ensure no nuisance emissions and lost gas, whilst protecting the system from over pressure.
Safety Valve: – An automatic mechanical device which lifts and discharges a specified volumetric flow rate at the set pressure stamped on the valve body. It should be correctly sized for the energy contained within the system to be protected. Safety valves may be ASME Section VIII div 1 or CE compliant, but must comply with AS/NZS 1200.
Three Way Valve: – A change over valve capable of allowing replacement of individual valves, without shutting down the system for maintenance. It is imperative that this valve has very low dynamic pressure drop and is matched with the Safety valve capacity to prevent choking of the valve.
Henry Technologies is a leading manufacturer and supplier of refrigeration components, with an emphasis on oil management, pressure vessels and safety devices. With manufacturing facilities and operating subsidiaries in the USA, UK, Australia, China & Singapore, Henry Technologies markets its products globally to leading OEM’s, wholesalers and contractors.