CALIFORNIA (formerly known as KOSO) Seismic Gas Shutoff Valves
Operation Principles of CALIFORNIA Valves

1. Stationary post, supporting ball
2. Reacting cylinder
3. Rolling latch (no sliding friction)
4. Soft seat
5. Manual reset
6. Position indicator
7. Window
8. Bonnet

  • The simple design consists of a swing-check valve and an acceleration-sensitive triggering mechanism.
  • The ball is located on a stationary post (item #1) with a seat formed of certain angularity to horizontal. During a violent earthquake, the ball moves & strikes the reacting cylinder (item 2), which causes the CALIFORNIA Valve to close.
  • Note the rolling latch! The latch mechanism automatically resets when subjected to very low amplitude accelerations. The mechanism will not creep in time to an actuating mode.

CALIFORNIA (formerly known as Koso) Valves are earthquake sensitive gas shut-off valves. They are intended to close in the event of a strong earthquake shaking to help prevent gas flow into a structure where earthquake damage may have occurred. These valves reduce the potential for fire or explosion due to the release of natural gas or other fuel gas into structures where gas lines, gas fixtures, or gas appliances may be damaged.

CALIFORNIA Valves utilize a swing-check valve arrangement with an acceleration-sensitive triggering mechanism. The trip mechanism consists of a steel ball that rests on a tapered cup-shaped support. The horizontal motions of an earthquake cause the ball to move from the center of the support, which allows the ball’s mass to act upon the movable pipe of the trip mechanism to actuate the valve and initiate closure.

CALIFORNIA Valves do not use any source of internal or external electrical power. They are designed to remain closed until manually reset. These valves are intended to be mounted in the gas line upstream or downstream of the gas-line pressure regulator and gas meter outside the structure. CALIFORNIA Valves are not intended to replace manual shut-off valves installed in the gas service line.

Springs assist the valve’s disc to close, and gas pressure assists in holding the disc in the closed position. The trip mechanism is factory set and sealed. A sight glass combined with an open/closed indicator that has green (i.e., open) and red (i.e, closed) bars enables the valve’s position to be easily and quickly determined.