How To Write A Plant Operating Manual
Most Process Engineers, specially the senior process engineers are
required to write a plant operating manual for a new greenfield project
during their career. Mind you, this is quite different from updating an
existing operating manual for a brownfield project where the scope of
the project is modification and debottlenecking. Updation of an existing
operating manual is a simpler exercise compared to writing a new
operating manual where you follow the format of the existing operating
manual and only provide an addendum to the existing operating manual
related to the scope of the project.
The real challenge lies in
writing a new operating manual and that is where the experience of the
process engineer comes into fore.
In this blog entry I have
tried to put across general guidelines on preparing a plant operating
manual based on my experience of writing a few of them. These guidelines
are generic in nature and do not subscribe to any company philosophy
for writing an operating manual.
Let us begin the exercise with what are the basic minimum requirements to start writing an operating manual
Following input documents are required during preparation of Operating Manual:
a. Basis of Design – Process Description
b. Process & Utility Flow Diagrams (PFDs and UFDs)
c. Piping & Instrument Diagrams (P&ID’s)
d. Deatiled process description from "Technology Licensor" for proprietary processes if applicable
e.
Operating and Miantenance manuals of vendor equipment and packages
(e.g. Instrument Air Package, Compressor Systems, Pumps, Water Treatment
Plants, Fired Heaters etc.)
f. Function logic narrative provided by Instrumentation
Procedure:
Operating Manual is generally a Microsoft Word document.
Structure:
The Operating Manual is a structured document with a particular narrative style. The following is the sequence of the document:
- Coversheet with project title and document name i.e. Operating Manual
- 1
st sheet with project title, document name i.e. Operating Manual
- List of Contents which includes:
. Abbreviations and Definitions
. Introduction which provides an overview of the project
. Process & Utility System Description
. Process Control and Automation
. Equipment Description
. Start-Up Procedure
. Normal Operating Procedure
. Shutdown Procedure
. Health, Safety & Environment (HSE)
. Appendices
Abbreviations & Definitiions:
The abbreviations and definitions of terms used in the entire document are summarized here.
Introduction:
This section provides the brief overview of the project which includes the purpose of the facility and what it contains.
Process & Utility System Description:
This
section describes in detail the overall facility. The narrative should
be in such a manner that the description is in the correct sequence of
the process for easy understanding. Utility systems which supplement the
main process should be described as a separate sub-section. Wherever
possible, process description should be supplemented by simple sketches
showing the major equipment and process control for a particular unit
operation. This enhances the understanding of the process.
Process Control & Automation:
This
section provides the description of the overall controls required for
the safe, reliable and uninterrupted operation of the plant / unit. This
could include flow, pressure, temperature and level control of the
plant / unit for the smooth operation of the plant / unit. Controls
required for start-up, planned shutdown and to change plant / unit
capacity should be mentioned. High and Low alarms for process operating
parameters are also described in this section.
Plant
section-wise or unit-wise control systems should be addressed in a
sequential manner in order to explain the process control in continuity.
All
process safety and shutdown interlocks, automation provided for
emergency shutdown of entire plant or unit of the plant should be
described in this section. An example of an emergency shutdown could be
the description of the Fire and Gas Monitoring system which initiates
the plant or unit shutdown.
Tag numbers of instruments used for process control and automation should be mentioned for sake of clarity.
Equipment Description:
This
section provides the functional description of the individual equipment
or group of equipment which form a unit operation in the overall
context of the entire facility. Description could include operating and
design conditions for the individual equipment.
Providing tag nos. for the equipment is recommended.
Wherever possible, sketches are recommended for the sake of clarity.
Start-up Procedure:
This section provides the description of the start-up procedure for the plant / unit under consideration:
The
first sub-section of this section should address the readiness of the
plant to be started-up. By readiness it is meant that the plant / unit
is ready to accept the process or utility fluid, raw materials or
reactants. This requires that the commissioning check-lists prepared for
the plant / unit are ticked off and signed off by the start-up team. A
list of the check-lists may be provided in this section which have been
signed-off to indicate readiness.
The second sub-section should
address the start-up of the utility systems prior to the start-up of
the main process. Utility systems could include charging up headers for
instrument air, cooling water, inert gas for blanketing / purging etc.
The
third sub-section should address the start-up of the main process. This
section should describe the valves (manual or automated) and
instruments to be lined up for introducing the process fluid (e.g.
hydrocarbons, chemicals) into the equipment or equipments (e.g. piping,
vessels, tanks, reactors) of the plant / unit being started up.
Wherever applicable, reference of vendor documents for any equipment / package unit should be provided in this section.
Normal Operating Procedure:
This
section provides the description of the normal operation of the plant /
unit and indicates the parameters to be monitored for maintaining the
product quality and operational reliability of the plant / unit.
Operating
parameters should be mentioned for a particular equipment or unit or
the entire plant in this section. Sketches describing the normal
operation are recommended for the sake of clarity. Field logging and
maintaining history records of critical process parameters from the DCS
or SCADA need to be mentioned in this section. Requirements of manning a
particular plant section or unit should be mentioned in this section
including field monitoring intervals by operating personnel for a
particular equipment or unit.
While describing any operation it
is recommended that equipment, instrument and line tag nos. be mentioned
for the sake of clarity.
Shutdown Procedure:
This section provides the description of the shutdown procedures to stop the operation of the plant.
The
first sub-section of this section deals with normal shutdown due to
either scheduled maintenance and / or inspection or modification /
de-bottlenecking of the plant. In this sub-section, description should
be provided for planned reduction / removal of inventory of the process
fluids from the equipment or unit to be shutdown. This would include
stoppage of fresh feed, gradual reduction of plant / unit throughput to
minimise off-specification product and final draining and purging of the
equipment / unit for the purpose of complete emptying prior to handing
over for maintenance / inspection or modifications / de-bottlenecking.
The
second sub-section deals with emergency shutdown procedures due to any
emergency such as an external fire, water flooding, earth quake, loss of
containment of process fluid (gas or liquid leak) etc. In this section
description should be provided for the methods for isolation of
equipment or unit due to either manual initiation or automatic
initiation of an emergency. Manual initiation is emergency initiated by
the operator of the plant / unit whereas automatic initiation is
emergency initiated by automatic detection of an emergency such as
detection of fire or gas leak by an automated Fire & Gas detection
system.
Usage of tag nos. for equipment, valves and instruments while providing the shutdown procedure description is recommended.
Health, Safety & Environment:
This section describes the HSE aspects of the facility that need to be considered.
Health:
This
sub-section relates to the health of the people and working in the
plant or living in the vicinity of the plant whose health should be a
concern for the management of the plant. This should also address the
health and well being of animals and other living organisms present in
the vicinity of the plant, for e.g. marine life in any water body which
would be effected by the operations of the plant.
In this
sub-section a brief description of toxicity of the chemicals used in the
plant / unit, acceptable noise levels for humans and other animals,
magnitude of injuries due to fire and explosion, first aid measures for
treating injuries etc. should be provided.
Safety:
This
sub-section relates to the safe start-up, operation and shutdown of the
plant during its entire lifetime. This section should address the
normal hazards those are encountered in day-to-day operations of the
plant. This section should also address the safety measures available to
prevent any accident.
Some of the normal hazards could be loss
of containment of any hazardous fluid due to overflow, leak or rupture,
static electricity build-up, accidental fall from heights, burns due to
exposure to hot surfaces, exposure to toxic fluids while collecting
samples and piling up of flammable solid waste (wood, paper, cloth
etc.).
Description of safety measures should include:
- Special operating procedures for activities like sample collection and regular maintenance of rotating machinery
- Issuance of work permits for hot work and vessel entry
- Usage of personal protective equipment (hard hats, safety shoes, eye goggles, ear muffs, breathing apparatus etc.)
- Provision of field sign boards indicating the type of hazard
- Regular house-keeping
- Emergency evacuation procedures
Environment:
This
sub-section describes the limits for discharge of hazardous solid,
liquid and gaseous effluents to the environment based on local laws and
regulations and procedures for compliance to them.
Appendices:
The
appendices should preferably include the list of Process & Utility
Flow Diagrams (PFDs / UFDs), Piping & Instrument Diagrams
(P&IDs), Cause and Effect Diagrams (CEDs) and reference vendor
documents, table for Alarm / Trip setpoints and lubrication schedule.
The above mentioned guidelines should help a process engineer to get started on a plant operating manual.
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