Once the breakaway torque is determined, the next step is applying a safety factor. Some valve suppliers will give the torque rating with a safety factor already included for the application. However, unless clearly stated, end users and installers should never assume that the safety factor is included. In other instances, vendors may supply a safety factor chart as a reference to be used with the stated valve torques.

If neither of these options are supplied by the manufacturer, then the following safety factors may be used as guidelines:

Type of media

• Wet or lubricating applications — 20 percent

• Dry gas or steam applications — 30 percent

• Viscous or abrasive applications — 50 percent

Type of operation

• On/Off applications — no additional factor

• Proportional applications — 20 percent

Frequency of operation

• Daily — no additional factor

• Weekly — 30 percent

• Monthly — 50 percent

By selecting the appropriate factor from each step and adding them together, a cumulative safety factor can be applied to the breakaway torque.