Mich. Admin. Code R. 408.4217 - Safety valve discharge pipes
Rule 217. No valves of any description shall be placed between the safety valve and the boiler nor on the escape pipe between the safety valve and the atmosphere. When an escape pipe is used, it shall be full size of the safety valve discharge and fitted with an open drain to prevent water lodging in the upper part of the safety valve or escape pipe. When an elbow is placed on a safety valve escape pipe, it shall be located close to the safety valve outlet and the escape pipe shall be anchored and supported securely. All safety valve discharges shall be so located or piped as to be carried clear from walkways or platforms used for access to main stop valves of boilers or steam headers.
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