Emergency Stop Circuit at a Diesel/Petrol Service Station

In accordance with the design, construction and maintenance standards imposed by the Country and the Client.

Presumably there are other designs that can be cloned and modified rather than starting with a blank piece of paper and a pencil (rhetorical question - NNTR)? Why re-invent the proverbial wheel?

I would consider a main circuit breaker with a shunt trip feature.

What stinking idiot thinks that that is off-topic?

It depends on the country and local electrical standards and codes, regardless you will need a qualified electrician (or similar) to install and sign off on it.

Based on petrol stations here in New Zealand, it is common to use standard industrial e-stops to do the isolation including at least two - one next to the counter inside for staff to use and one outside on the wall for people to use in an emergency.

As for what they isolate, well the pumps would be a good start and anything else in the area that could be a potential ignition source (overhead lights, signs, etc), HOWEVER be careful about disconnecting ALL power as you may have some safety or communication systems that may need to be kept alive in the event of an emergency (evacuation lighting, fire alarm call out system, emergency fire suppression systems, alarms, etc for example - country and site dependent of course).

Do you have access to your local standards and regulations, or an approved company electrician that would know how to install this system correctly (and legally) to meet your local standards?

Good answer! As a mechanical engineer in the USA, I would refer to NEC (NFPA 70) and find out in Article 514.11 what is required for circuit disconnects. Industrial E-stops installed to meet requirements of the authority having jurisdiction would be the starting point of my design.

Remember, if you do it right, this isn't rocket science. If you don't do it right, it could become rocket science.

If you are doing an estop you should incorporate a safety relay to monitor the stop circuit. As per posting by jack of all trades you need to isolate power going to the forecourt including power, lights communication cables for console etc. You can group these and any other circuits through there own contactor and leave any needed circuits on seperate breakers etc

Very Important to remember:

You are dealing with explosive vapors.The vapors are heavier than air.All installations must meet Class1,Div1 regulations, and all conduits leaving or entering the area must be potted to prevent fumes from migrating.All wiring, including neutrals, must be disconnected at the same time at the breaker panel.

This is not a job for an ad-hoc electrician.Get a qualified company that has license and insurance to do this,otherwise, make sure your liability and life insurance premiums are paid up.