Norgren Collateral

Relief valves Solutions Q&A 21 CONTENTS 7.1 General overview 7.1.1 What types are available? 7.1.2 How do they work? 7.1.3 Are they safety valves? 7.2 Sizing 7.2.1 How do I size a relief valve? 7.2.2 Should the Relief Valve be the same Size as the Regulator? 7.2.3 What is Failure Flow? QUESTIONS 7.1 General overview ? 7.1.1 What types are available? Family Type Repeat- ability Pipe Size Advantages 16-004 Poppet ± 20 1/8" & 1/4" Compact, low capacity V06 Diaphragm ± 10%. 1/8" & 1/4" Brass bodied, liquid service V07 Diaphragm ± 10% 1/8" & 1/4" Miniature Series V72 Diaphragm ± 10% 1/4 & 3/8" Excelon modular & in line mounting V74 Diaphragm ± 10% 3/8-3/4" Excelon modular & in line mounting V64 Integral pilot ± 5% 1/4-3/4" Excellent performance Yoke mounted, fail safe 16-001 Diaphragm ± 10% 3/4" & 1" High relief rates 16-002 External pilot ± 5% 1/2"- 1" Good performance High relief rates ? 7.1.2 How do they work? The inlet port is connected to the system and the valve limits the downstream pressure by exhausting when the system pressure exceeds the preset pressure of the valve. The valve is normally closed, only opening when unusual system conditions prevail. ? 7.1.3 Are they safety valves? No. Safety valves are covered by a variety of national standards. IMI Norgren relief valves are not designed to these standards. 7.2 Sizing ? 7.2.1 How do I size a relief valve? If the relief valve is to be fitted to prevent excess pressure then it needs to be sized to cope with the maximum flow that the system can see - often the output flow capacity of the compressor. The relief valve needs to be able to cope with this flow within acceptable pressure limits. See catalog data sheets for relief flow characteristics. ? 7.2.2 Should the relief valve be the same size as the regulator? Not necessarily. In general the failure flow of a regulator will require use of a relief valve of larger basic size. Detailed graphs are available for sizing - please call Application Engineering. ? 7.2.3 What is failure flow? This is the maximum flow that will pass through a regulator in the event of its total failure. It varies with system pressure and the test results on all IMI Norgren regulators are available from Application Engineering. The failure flow is used for sizing relief valves downstream of regulators. V07 16-004 V06

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