Abstract: A locking device is provided that is useful for preventing removal of a hose coupling from engagement on a valve. The locking device comprises two clamping members hingedly joined together at one end by an interlocking joint. When in a closed position, the clamping members have a first passage for receipt of the body of the valve and a second passage for receipt of the hose coupling on the valve. When the locking device is in place with the valve body in the first passage and the hose coupling in the second passage, the clamping members are locked together at the end remote from the interlocking joint to prevent the removal of the coupling from the valve.