Nevada Administrative Code
Chapter 455C - Boilers, Elevators and Pressure Vessels
BOILERS AND PRESSURE VESSELS
Boilers
Section 455C.264 - Stop valves and check valves

1. Each outlet for steam from a boiler, except connections for a safety valve and water column, must be fitted with a stop valve that is located as close as practicable to the boiler.

2. If a stop valve is so located that water can accumulate, ample drains must be provided. The drainage must be piped to a safe location and must not be discharged on the top of the boiler or its setting.

3. If boilers provided with manholes are connected to a common steam main, the connection for steam from each boiler must be fitted with two stop valves having an ample free-blow drain between them. The discharge of the drain must be visible to the operator while manipulating the valves and must be piped clear of the boiler setting. The stop valves must consist of one automatic nonreturn valve set next to the boiler and a second valve of the outside-screw-and-yoke type.

4. If any part of a heating system may be closed off from the remainder of the system by closing a steam stop valve, there must be a check valve in the condensate return line from that part of the system.