When working on process equipment, a machine, or a piping system, the last thing you want is for the components to suddenly come to life. That's why the Occupational Safety and Health Administration, or OSHA, is a staunch advocate of lockout/tagout practices and procedures. Lockout/tagout is about shutting off or isolating equipment so it can be worked on safely. It's good practice even when not required, and valves have an important part to play.
Here we'll discuss what lockout/tagout means and how it's applied, particularly with regard to valves. For specific references to OSHA requirements, we suggest visiting the OSHA website, perhaps starting with Publication 3120 “”
OSHA describes lockout/tagout as a way of avoiding a sudden, unexpected, or uncontrolled release of energy. The idea is to keep anyone from turning on the power to a machine or piece of equipment while someone else is working on it. ( provides specifics.)
This is usually done by fitting a padlock to the switch or valve. The padlock goes on in a way that prevents switch activation or valve operation. The person working on the machine keeps hold of the key, and the equipment is said to be “locked out.”
The “tagout” part refers to a tag or note added to the switch or valve along with the padlock. This will say when the equipment was locked out and who has the key.
Locking out valves
Electrical switchgear often comes with an eyelet or loop and hasp that a padlock can be threaded through to fix the lever in the “off” position. This kind of feature is unusual in valves though, perhaps because it's not needed in all situations. Instead, valves are locked out by fitting some kind of cover over the body that stops it from being turned.
With ball and butterfly valves, the handle usually indicates if it's open or closed. (Open, it points in the direction of flow; closed, it's perpendicular.) Other fluid control devices, such as globe valves, use handles rather than levers, which makes it harder to tell if they're open or closed.
While there may be occasions when you'd want to lock a valve open, far more often, the requirement is to keep it closed. One approach is just to fit a cover around the valve and lock it in place. Another is to use a device that fits over the handle and prevents it being turned. Whichever you adopt, the critical step to remember is to lock it in place and take the key away.
Always prudent, not always required
If you've ever experienced someone turning on the water while you're working on a faucet, you'll know surprises aren't always a good thing. Lockout/tagout prevents those kinds of surprises, along with others far more serious. When you want to know a valve will stay closed, use an appropriate lockout device. It's good practice even when not OSHA-mandated.