Have you considered a portable actuator? There are some innovative systems on the market now designed to take the hard-work out of turning valve wheels. Plus they have the added advantage of being completely portable, meaning one actuator can be used on many valves around the site.
I'm not sure...
Good advice from MiketheEngineer regarding calling OSHA.
The scenario you described should be fine. The isolation lock can be retained close by the isolating switch on a chain or lanyard along with a Danger Tag.
If more than one worker is involved in the blade change, then each one should add...
We could be getting distracted by terms here. 'Car Seal' derives from a device used to 'seal' closed a freight car on the railroads. Nowadays, cargo containers travelling across borders will often be sealed in the same way to provide evidence of tampering with the cargo. This simple seal device...
Sometimes there is double relief, i.e. two PSV's on the vessel. Valve interlocks fitted to the upstream block valves can ensure that the spare relief valve is brought onstream before the other is isolated, thereby ensuring a spare path to relief is always maintained.http://www.valvelockout.co.uk