Could you please help me define and highlight the differences between the following documents:

- process description
- process control narratives
- logic description
- operating manual

The way I look at it - and the way we do things where I work - is as follows:

The process description is a narrative that describes the PFDs and P&IDs in words.  For example:

"80/20 TEG/Water mixture at a temperature of 35 C and a pressure of 6000 kPag is injected through the retractable nozzle onto the tubesheet on the inlet end of the gas-gas exchanger E-101..."

The process control narrative describes how the process described is controlled.  For example:

"Rich process glycol from the boot of the low temperature separator V-102 is returned to the regenerator flash gas vessel V-201 via the level control valve / controller / transmitter loop LV/LC/LT-102 which modulates to maintain boot level between (x) mm and (y) mm..."

The logic description basically describes the I/O (input / output) and shutdown key.  For example:

"High level in the low temperature separator V-102 is alarmed at (xx) mm by LAH-102.  Continued level increase to (yy) mm will ultimately cause a Level 1 ESD (block in only) by shutting the gas train inlet emergency shut down valve ESD-102 via a discrete signal from the high level switch LSHH-102..."

The operating manual is an aggregate of the above plus all of the salient vendor data compiled in a set of books.  The operating manual also usually contains narratives about how to warm up, start up, shut down, purge, inspect and maintain the associated equipment and devices.  For example:

"Once the burner on the glycol regenerator has been lit, the process glycol is recirculated through the system with the skid outlet block valve closed and the start-up bypass valve open until the lean glycol temperature measured at TI-201 reaches (xxx) C.  The operator then may open the skid outlet block valve and throttle the start-up bypass valve to pressurize the system prior to admitting gas to the gas train.  As gas flow is established the block valves upstream of the injectors are opened...".

The above narratives, of course, are for illustrative purposes only...I would probably make a dangerous operator so I should stick to my day job.

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