How do you use Car Seals for locking valves?

We're interested in feedback from readers of this blog on why they use car seals. In our experience there's a couple of common applications for using car seals for sealing valves. For example:

Sprinkler System Water Supply. For obvious reasons, continuity of water supply is essential for fixed fire fighting systems. The water supply valves will be set in the open position and sealed with a car seal.

PSV (Safety Relief Valve) Isolation Block Valves. Valves upstream and downstream of a safety relief valve can be 'car sealed open' or 'car sealed closed'. For process safety reasons, a safety relief valve must be kept onstream at all times. By sealing the valves around the PSV, this status is assured. If the PSV must be taken off-line for maintenance, a spare relief valve must be brought onstream. (Sometimes, valve interlocks are used to provide control in this critical application.).

Aside from these two applications, car seals may be used for random locking of valves to prevent inadvertent or unauthorized tampering.

We'd be interested to learn of your experiences. How do you use car seals for locking valves?