Estop vs Stop

A bit off topic but I'm sure this thread will have many opinions.
I'm pretty clear on the Estop vs Stop for machine safety, by machine I'm thinking CNC, presses...manufacturing type equipment. Where I struggle is in petrochemical, where we have pumps and fans. It seems we use Estops where it should just be a Stop circuit. I may be splitting hairs, but when you have 300HP compressor that coast to a stop all you really need is a Stop (category 0) per NFPA 79? So here is my question to the thread Estop vs Stop on non machine safety applications? Looking forward the replies.

Hi!

Without being an expert on regulations, from my dealings with (petro)chemical installations, they are often set up as high redundancy/ fault tolerant in stead of fail safe. It is often crucial that an installation does NOT stop in case of emergency, because a stop would be a higher risk.

I know that is not a complete answer, but it might be part of the picture.

All motion

The way I was taught was that an "e-stop" was for emergency use and must stop all motion ASAP, but does not have to shut down blowers or other external devices.
A "stop" will stop the machine where it is needed to be for a safe shut down.

My experience is on upstream (wellpads, multiphase pumping stations, test separators). In this area I see 3 different ways to stop a process:

a) Stop (normal stop): the system receives a request from the operator and starts a controlled stop of the process.

b) Shutdown: the system detected a fault and starts a controlled stop of the process. Sometimes the stop steps are the same of Normal Stop, sometimes is a shorter version.

c) ESD (emergency shutdown): the system or the operator detected a critic fault and will stop the process as fast as possible.

Normally we have 3 pushbutton on the field: Start, Stop and ESD. Start and Stop could be part of the HMI screens.

In normal conditions, you'd expect that any process is stopped only using Normal Stop. If the alarm philosophy is well designed and implemented, the operator is able to modify the process in the case of receiving an alarm. However, if something can't be controlled, you always have a Shutdown to deal with the situation without affect the equipments, pipelines, etc.

ESD is a particular condition. We are trying to preserve the security of the people, enviroment and devices (just in that order). For that reason, the red mushroom pushbuttons are reserverd to ESD function and the personnel is trained to use them only under extreme situations.