Safety relief valves with threaded connection, can be used for many simple applications. Suitable for gases, vapours and liquids. Specific features and applications: Model 517/518: Saturated steam and hot water, available including Stoomwezen/Lloyd’s Register test certificate on request. Model 527: Including diaphragm, for water, air and other non-aggressive gases. Model 518 – Viton Disc Seal with Disc Lever