Locking up

Whether it’s a ball valve, gate valve, plug valve, globe valve or butterfly valve, two factors determine the type of locking device that is needed: method of operation followed by the size of the valveValves often need to be locked, for example to isolate and vent pressure before maintenance engineers enter a vessel, to provide continuity of process operations, or where operation of a number of valves must be carried out in a specific, predetermined sequence.

Whatever the reasons, choosing the right locking device can seem a challenging task, particularly as valves come in a wide range of shapes and sizes

Whether it’s a ball valve, gate valve, plug valve, globe valve or butterfly valve, two factors determine the type of locking device that is needed: method of operation followed by the size of the valve.

For manual, wheel-operated valves, operators can use a wheel-lockout device, similar to those that are manufactured by Master Lock or Brady. They are designed to encapsulate the wheel of the valve, thereby blocking access to the wheel and preventing operation.

Wheel-lockout devices come in a range of five sizes with the largest able to cover a wheel of 350mm (14in) diameter. The wheel cover is secured in place using a safety padlock. Users can choose between four different colours to denote the process medium or perhaps the valve’s positional status.

If the valve wheel is larger than 350mm, it is often worth considering a cable lockout or padlock and chain. These work by threading the cable or chain around the rim of the valve and through the bonnet or perhaps a piece of adjacent pipework or steel work.

Locking a lever-operated valve - ball valve, plug valve, butterfly valve - can be slightly more challenging as they vary greatly from one
The topworks design of the valve is rarely the same and this means that the locking device may not engage securely on the valve. To resolve this, Master Lock’s Seal Tight valve lockout removes the valve lever, locking it away in a pouch, which is wrapped around the body of the valve.
Some valve-locking devices will only lock the valve in a single position, usually the closed position. Other lever lockouts work by attaching to the lever and physically blocking the turning movement of the valve.

With actuated valves, locking off can be quite straightforward. For an electrical actuator, the device will have an on/off switch on board. The switch often has a padlock facility, which is used to secure the switch in the ’off’ position.

For pneumatic or hydraulic actuated valves, blocking the flow of air or oil to the actuator will disable it. This, typically, is done with a small diameter ball valve in the flow line. This valve can then be locked out with one of the lever locking devices described above.