The pig launchers and receivers were designed for a coal-bed methane gas production facility in Colorado. They are equipped with an integral safety locking system which works on the principle of mechanical key interlocking (transfer of keys). This system avoids serious injuries from human error and insures safety of personnel.
One starter key per launcher/receiver is kept in a box located in the control room. Each lock is executed with two keys. When the first valve is opened with this starter key, it releases the second key. This key is transferred to next valve which releases second key from that valve and so on and so forth. This process guides the operator through the specified sequence for opening and closing valves with unique a key for each step.