The task of writing chemical plant manual categorized into two. One is for new plants and the other is for plants that already running. For old plants there are already established systems and procedures and for the modifications or revamps additional information has to be added, which is a simple task. But writing the operating manual for new chemical plant is a challenging task though already similar plants are running around the world. Let us will see how to write operation manual for new plants here.

Data Collection and Brainstorming

This is the preliminary task of a process engineer who is involved in preparation of Chemical Plant operation manual. PFD, P& ID, Control System, Process description from Technology provider, Equipment supplier manuals, HAZOP study recommendations, Details of legal/ regulatory requirements, Design Material & Heat balance of Process streams are to be collected before proceeding further. Then a brainstorming session is to be arranged with the colleagues/ superiors to discuss the various activities associated with the task and set Specific Measurable Attainable Relevant Time bound goal to bring up the better manual.

Contents of Chemical Plant Operating Manual

The content of a chemical plant operation manual is simplified into the following topics and the details may be added into appropriate section based on the specific requirements of the plant.
Abbreviations
Design Basis
Overview of the Process
Process Description
Procedures
Safety, Health & Environment Section
Utility and Other Systems
Appendix

Abbreviations

Abbreviations used in the manual are to be consolidated and added in this section for better understanding for beginners.

Design Basis

Design basis of the plant including Plant Capacity, Technology used, Site Climatic Data, Raw Materials, Utility & Product Specifications forms this section in the chemical plant operation manual.

Overview of the Process

Overview of the Manufacturing process with the major equipments or sections involved in sequential manner to be described to get the overall understanding of the chemical plant. Process Flow Diagram (PFD) helps in preparing this section.

Process Description

The detailed process description with Equipments and Control valves associated including tag no’s used with the design parameters and compositions at various streams in a sequential manner forms this section. Process control philosophy for various parameters in the plant like pressure, flow, level & temperature and description of various controllers and control loops available for the process control. Various Trips and Interlocks and reasons for having it along with Emergency Shutdown (ESD) system available in that section is elaborated. Piping & Instrumentation Diagram (P& ID) and Process description from Technology provider will be useful in bringing effective process description of units in the chemical plant.

Procedures

Standard operating Procedures for individual equipment and sections in plant for Normal Operation, Start up and Shutdown and then for total plant are to be established and produced in this section. Procedure for safe isolation of equipment for maintenance jobs shall also be included. This section shall also include Trouble shooting guide for various upsets. Routine schedule with incorporation of lubrication schedule, trial run of equipment, availability check of systems etc. Equipment supplier Manuals, HAZOP study recommendations will help the process engineer for preparing this important section of Chemical Plant Operating manual.

Safety, Health & Environment Section

Safety section provides overview of installed Safety Systems, Fire Fighting Facility and available safety procedures in the chemical plant. It also provides details on Zone classification, Emergency Actions, Hazards. Applicable Work permit systems related to plant like Hot Work, Confined Space Entry and procedure for issuing and authorizing the permits are to be listed for the entrants to understand the systems. Types of Personal Protective Equipment (PPE) available, issue and usage details are to be provided in this section and proper sign boards are also to be made available in plant premises.

Toxicological information of chemicals used in the manufacturing process is to be provided in the chemical plant operation manual. Chemical handling & storage and their first air measures also need to be listed for better understanding of chemical hazards.

Environment section of the Chemical Plant operation manual must contain industry specific disposal limits for various effluents generated in the plant and details on applicable laws & governing bodies.

Utility and Other Systems

Description of various other associated facilities in Chemical Plant like Water Treatment facility, Cooling Towers, Cooling Water system, Deaerators, Boiler & Steam System, Compressed Air System, Inert Gas generation & distribution systems, Effluent treatment facilities, Flare system, Electrical Power Distribution and ESD system is to be prepared and written under this section.

Appendix in Chemical Plant Operation Manual

This section contains the supporting information for better understanding of the Chemical plant operating manual. Normally it contains PFD, P& ID, Alarm & Trip set points, MSDS of Chemicals Handled, Equipment Data sheets & Curves, Further Reading – Vendor Document List etc.

Process engineer can add additional resources in this section based on specific need. One can also create his own structure based on the needs and prepare a better chemical plant operation manual.

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Reciprocating compressor Trips

High Suction Temperature

Due to cooling water failure to inter coolers, valve passing problems, Fouling and Leak in inter coolers suction temperature of the gas will rise. Reciprocating compressor trip is provided for High suction temperature as this will result in damage of the compressor parts.

Low Suction Pressure Trip

In reciprocating compressor handling Hazardous flammable gases like Hydrogen, trip has been provided for low suction pressure. This is to avoid the atmospheric air ingression into the system through leaky flanges or valves which may cause explosion/fire in the discharge of the compressor where the temperature is high. In air compressors this trip is normally not necessary as it takes air from atmosphere.

High Discharge Temperature

High discharge temperature causes polymerization in some applications (like in Polyethylene) which will plug the flow and causes rupture in pipelines. In air compressors ignition of oil will take place at High discharge temperatures.

High Discharge Pressure

High discharge pressure in Reciprocating compressor may result in damage to pipes and machinery. It may also cause personal injury. Reasons for High discharge pressure include control valve malfunctions in consumption or in vent side, valve plate failures due to accumulation of foreign materials etc.

High Separator Level

Liquids are incompressible fluids which occupies space inside the compressor which reduces the mass flow rate of the compressor. Liquid slugging causes stresses which damages compressor connecting rods, piston, crank shaft etc. Therefore trip of the unit has to be provided for High levels in separators in all stages.

High Bearing temperature or High Lube oil Temperature

At High temperatures Lube oil will get deteriorated and increase in viscosity does not form oil film. This results in poor lubrication and causes failure of bearings. So trip for High Lube Oil/ Bearing temperature is provided.

High Vibration

Reciprocating compressors produce pulsations due to intermittent flow. Double acting machines and Pulsation dampeners will reduce the impact due to pulsation. During prolonged operation vibration of the equipment is prone to go high due to damage in internals, change in operating conditions etc. Therefore trip is provided for High Vibration in the reciprocating compressor.

Low Lube Oil Pressure

Adequate Lubrication is necessary for compressor moving parts. Therefore trip of the reciprocating compressor is provided for low lube oil pressure. Starting Interlock bypass timer is provided to bypass the trip during initial startup of the compressor. This time delay will allow the compressor to develop enough lube oil pressure during start of the machine. During normal operation the compressor trips as soon as low pressure is detected.

Cooling Water Failure

Cooling water is supplied to Inter coolers, Lube oil Coolers and Jacketing water coolers. Upsets in water flow will result in any one of the trips discussed here. Any way cooling water failure trip is also provided.

Safety Aspects in Reciprocating Compressor

Discharge Vent

Since Reciprocating compressors are constant volume compressors they keep on delivering the gas at the discharge. Therefore it is necessary to provide the vent in the discharge to avoid over pressurization and other impacts.

Inter stage Relief Valves

Relief valves in inter stage separators are helpful to prevent over pressurization due to Valve plate failures and inter cooler fouling.

Motor Protections

Excitation of Torsional critical speed in reciprocating compressors does not allow variable speed operations. Torsional critical speed is associated with angular or torsional deflection. Therefore in most of the cases driver is electric motor. Normal motor protections like Over Current, Under Voltage, Under Frequency trips are to be incorporated and executed with the help of relays.

Insulation

Thermal insulation has to be provided in the suction and discharge pipelines depending on the temperature. Cold insulation in Refrigeration systems protect the pipelines from corrosion and heat ingression into the system. Discharge pipelines contain gas at high temperature which is prone to cause burns and has to be properly insulated.

Packing Gas Vent

Packing gas vent to safe atmosphere has to be provided to avoid gas contamination with oil in crankcase and Fugitive emission.

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