Cleaver-Brooks - Complete Boiler Room Solutions

Emphasize Code Compliancy in Steam Boiler Outlet Piping

Tip Sheet: October 2017

Key Facts

  • Adhere to the ASME Code for components that directly connect to the boiler
  • When selecting the pipe, valves and fittings in a high-pressure steam application, the pressure and temperature of the steam must be tolerated by the device
  • When two valves are installed, a drain line and valve must be placed between them, freely discharging to a safe point

For safety reasons, manufacturers of steam boilers must follow ASME Section I of the Boiler and Pressure Vessel Code. While there is strict adherence to this part of code, typically the same emphasis is not given to the piping system that connects the boiler to the load. This piping system is considered an extension of the boiler, and therefore it requires as much attention to detail as the selection of pipe, fittings and valves that comprise a system. 

The ASME Boiler and Pressure Vessel Code addresses the components that directly connect to the boiler, called the boiler proper. There are many details in the ASME Code, but generally boiler proper ends at the first valve of any connection to the boiler. The ASME Code that applies to the piping and components beyond the first valve is B31.1.

Here are some key requirements of ASME Code B31.1:

1. When selecting the pipe, valves and fittings in a high-pressure steam application, both the pressure and temperature of the steam must be tolerated by the device. 

2. Therefore, the pipe, valves and fittings must have a pressure rating of at least the lowest set safety valve pressure on the boiler and a temperature rating comfortably above that saturation temperature. 

3. Paragraph 104.5.1 of B31.1 addresses flanges, both slip-on and weld-neck type. Slip-on flanges can be applied up to 24" nominal pipe size, but only on pressure classes of 150 and 300#. All other conditions require weld-neck flanges. 

4. If a high-pressure boiler has a manway allowing access, and a steam connection to a common boiler steam header, it shall have two steam valves off the boiler outlet piping.

5. These valves must have a pressure/temperature rating as described in item #2 and be of the rising-stem style (or have a position indicator) to allow visual detection of is open or closed position. 

6. When two valves are installed, a drain line and valve must be placed between them, freely discharging to a safe point.

7. Often a non-return valve is used as one of the two and is placed between the other stop valve and the boiler outlet connection. This for servicing of the non-return valve, if needed. Also, the non-return valve is used for automatically cutting the boiler into the main upon the boiler achieving adequate pressure.

Safety is a critical factor when installing and operating a boiler. Ongoing training of operating and supervisory personnel is essential and highly recommended. To sign up for an upcoming training session, visit cleaverbrooks.com/training.

For more information about Boiler Steam Supply Piping Basics, watch this recorded webinar. To learn more about best boiler room practices, visit cleaverbrooks.com/techtips or consult your local Cleaver-Brooks representative at cleaverbrooks.com/reps.