Position indicating lights may be required for the EBV and for the manual bypass valve (if there is one). Locate these lights in the field, in the control house, or in both places.
If position lights are required, there should be at least two lights: one for the open position and one for the closed position. Locate the lights next to their switches.
For position lights located in the field, be sure to shade the lights from the sun so that the operator can see if the lights are on or off. Push-to-test lights are useful, allowing the operator to check the bulbs.
There are two conventions for specifying which of the lights is red and which is green:
1. The green light indicates the normal position, and the red light indicates the abnormal position (the position the valve will be in during the emergency), or
2. The green light indicates that the valve is open, and the red light indicates that the valve is closed.
The engineer should ask the operating representative which convention is followed by the particular facility.