Emegency Stop - Train Load Out Systems

You could have the first operation trigger a valve that does the second.

Or you could make the first operation require less hydraulic pressure than the second; the hydraulic pressure wouldn't rise fully until the first operation "topped out".

No, not really.

Thanks for the responses guys,

As you know during emergency, Hydraulic System Override PLC control and start to close clamshell and raise chute simultaneously, we lost product and experience downtime to clear spillage. What can be done to follow the same sequence in absence of PLC control? I would assume Solenoid valves are fully opened and not being controlled by PLC anymore, so we cant use any logic to sequentially operate the process.

Make all the solenoids NC.

NC?

Nolo Comprendo

Solenoid Valves Basics.pdf - Process Control and Instrumentation

The first thing to do is write a Control Philosophy, and have it agreed across the business. This document describes how the process is supposed to operate.

Next, the Controls Engineer writes a Functional Design Specification, which gives the level of detail that enables the system to be fully designed. Operator interfaces appear here, including emergency stop sequences as applicable and the detail of failsafe operations.

Once that is agreed across the business, only then does the control system get either built or modified so it complies. Then, when it operates, it will do "exactly what it says on the tin".