BS EN 161:2002 pdf download – Automatic shut-off valves for gas burners and gas appliances
6 Construction requirements
6.1 General
6.1.1 Valves shall be designed, manufactured and assembled in such a way that they function correctly when installed and used according to the manufacturer’s instructions.
6.1.2 Valves shall be free from sharp edges and corners that could cause damage, injury or incorrect operation. All parts shall be clean internally and externally. Dismantling and reassembly of valves shall require the use of tools. There shall be no exposed shafts or operating levers that could adversely affect the ability of valves to close.
6.1.3 Holes for screws, pins, etc., which are used for the assembly of parts of the valve or for mounting, shall not penetrate gasways. The wall thickness between these holes and gasways shall be at least 1 mm.
6.1.4 Holes necessary during manufacture which connect gasways to atmosphere but which do not affect the operation of the valve shall be permanently sealed by metallic means. Suitable jointing compounds may additionally be used.
6.1.5 Closure parts, including those of measuring and test points, which may be dismantled for servicing, adjustment or conversion, shall be constructed in such a way that leak-tightness in accordance with 7.7 is achieved mechanically (e.g. metal to metal joints, O-rings) without the use of jointing compounds such as liquids, pastes or tapes. Jointing compounds, where used for permanent assemblies, shall remain effective under normal operating conditions.
6.1.6 Parts which require dismantling, (e.g. for servicing) shall be capable of being dismantled and reassembled using commonly available tools. They shall be constructed or marked in such a way that incorrect reassembly is impossible when following the manufacturer’s instructions. Screwed fastenings which may be removed during servicing shall have metric threads to ISO 262:1998. Self-tapping screws which cut a thread and produce swarf shall not be used for connecting gas-carrying parts or parts which may be removed during servicing. Self-tapping screws which form a thread and do not produce swarf may be used provided that they can be replaced with metric machine screws conforming to ISO 262:1998.
6.1.7 The operation of moving parts, (e.g. diaphragms, bellows) shall not be impaired by other parts.
6.1.8 Soldering or other processes where the jointing material has a melting point below 450 °C after application shall not be used for joining gas-carrying parts except for additional sealing.
6.1.9 Closed position indicator switches, where fitted, shall not impair the correct operation of valves. Adjusters shall be sealed to indicate interference. Any drift of the switch and actuating mechanism from its setting shall not impair correct valve operation.
6.1.10 Flow rates of valves with modulating control shall be adjustable over the full range declared by the manufacturer. If the adjustment of one flow rate affects the setting of any other flow rate, this shall be clearly indicated in the manufacturer’s instructions for setting up. The setting of any flow rate shall require the use of tools and shall be sealed to discourage unauthorized adjustment.
6.2 Materials
6.2.1 General material requirements The quality of materials, the dimensions used and the method of assembling the various parts of the valve shall be such that construction and performance characteristics are safe. Performance characteristics of the valve shall not alter significantly during a reasonable life when installed and used according to the manufacturer’s instructions. Under these circumstances, all components shall withstand any mechanical, chemical, and thermal conditions to which they may be subjected during service.
6.2.2 Zinc alloys Zinc alloys shall only be used for gas-carrying parts of valves up to DN 50 with maximum working pressures up to 200 mbar if of quality ZnAl4 to ISO 301:1981 and if the parts do not exceed a temperature of 80 °C. Where the main inlet or outlet threaded connections are made of zinc alloys, threads shall be external and conform to ISO 228-1:2000.
6.2.3 Housing Parts of the housing which directly or indirectly separate a gas-carrying compartment from atmosphere shall either be made from metallic materials, or shall be such that, on removal or fracture of non-metallic parts other than O-rings, gaskets, seals and diaphragms, no more than 30 dm 3 /h of air escapes at the maximum working pressure, when tested to