Plant layout design plays an important part in the design and engineering phases of nay industrial facility.

The Plant Layout Designer is skilled primarily in the development of equipment arrangements and piping layouts for process industries. Process facilities must be designed and engineered within extremely short schedules while adhering to maintenance, safety, and quality standards; moreover, the design must take constructability, economics, and operations into account. Although the tools to achieve these goals are changing from pencil and paper to computer graphics terminals, the responsibilities of the plant layout designer remains the same.

The Plant Layout Designer must develop layout documents during the conceptual and study phases of a project. The skills needed include:

· Common sense and the ability to reason.

· Knowledge of what a particular plant is designed to do

· A general understanding of how process equipment is maintained and operated

· The ability to generate a safe, comprehensive layout within a specified time and with consideration toward constructability and cost effectiveness

· Creativity

· Sufficient experience to avoid reinventing the wheel

· Knowledge of the principal roles of other design and engineering groups and the ability to use input from these other disciplines

· The ability to resolve unclear or questionable data

· Willingness to compromise in the best interest of the project

· The ability to generate clear and concise documents

· The ability to defend designs when challenged

Principal Functions

The principal functions of the plant layout designer include the conceptual and preliminary development of process unit plot plans, sometimes referred to as equipment arrangements; the routing of major above and below grade piping systems, and the layout of equipment and its associated infrastructure.

Project Input Data

Although there is a vast amount of input data throughout the life of a project, the data basically falls into three distinct categories.

1. Project design data – is supplied by the client or project engineering

2. Vendor data – pertains to equipment and specialty bulk items

3. Internally generated engineering data


AG Above ground

ANSI American National Standards Institute

ASME American Society of Mechanical Engineers

BBP Bottom of BasePlate

BL Battery Limit

£ Centreline

EL Elevation

IRI Industrial Risk Insurers

N North

OD Outside Diameter


NFPA National Fire Protection Association

NPSH Net Positive Suction Head

OSHA Operational Safety and Health Act

PFD Process Flow Diagram

P&ID Piping and Instrumentation Diagram

TL Tangent Line

TOS Top Of Steel

TYP Typical

UG UnderGround

Codes and Standards

ANSI/ASME B31-3 Chemical Plant and Petroleum Refinery Piping

ANSI/ASME B31-4 Petroleum Piping

ANSI/ASME B31-8 Gas Transmission Pipeline

NFPA 30 Tank Storage

NFPA 58 Liquified Petroleum Gas Storage and Handling

NFPA 59A Liquefied Natural Gas Storage and Handling

OSHA 1910-24 Fixed Stairs

OSHA 1910-27 Fixed Ladders


Process Flow Diagram : This document schematically shows all major equipment items within a plant and how they are linked together by piping, ducts and conveyors. It shows equipment numbers, flow rates, and operating pressures and temperatures and is used to prepare the mechanical flow diagrams. It is also used to prepare conceptual and preliminary plot plans.

Equipment List : An itemized accounting list by class of all equipment to be used on a project, this document gives the equipment item numbers and the descriptions and is generally furnished by the client or project engineering.

Piping and Instrumentation Diagrams : These documents schematically show all process, utility, and auxiliary equipment as well as piping, valving, speciality items, instrumentation and insulation and heat tracing requirements.

Piping Specification: This document lists the type of materials to be used for pipes, valves and fittings for each commodity in the plant.

Line run: This is the physical route a pipe takes between any two points as set by the plant layout designer.

Planning Study or layout drawing: This is an orthographic piping plan. This drawing shows all equipment in a given area to scale and includes major process and utility piping systems, significant valving and instruments.

Heat tracing: Equipments, instruments and piping systems require extremely applied heat. This heat may be applied by electrical tracing leads attached to the item or line or through a small bore pipe or tubing that carries steam or other heating media.

Inline: Refers to a component that is placed either inside or between a pair of flanges as opposed to one attached to a piece of pipe or equipment.

Header Block valves: These valves isolate branch lines that are not usually provided with permanent access for plant operations personnel.

Header: This line is the primary source of a commodity used by numerous pieces of equipment or service points in a plant.

Branch: The individual piping leads between headers and users

Maintenance: Equipment and its components require routine maintenance for continued reliability and safe operation. A plant layout designer must provide unobstructed space for service equipment and personnel to access and remove components without removing unrelated equipment and piping.

Operation : Valves, instruments and many types of equipment require frequent attention for operation. These items must be accessible without impairing the safety of personnel.

Safety: The layout of any facility must enable plant personnel to exit a potentially hazardous area without injury.

Cost effective: A cost effective design is the result of a balanced consideration of initial cost, safety and the long term effects of a design in operations and maintenance.

Gravity Flow: When pockets must be avoided in a given piping system, the line is labeled ‘gravity flow’ on the piping and instrumentation diagram.

Open systems: An open system is one in which the contents of a line are discharged and not recovered.

Closed systems; A closed system is one in which the contents of a relief systems or steam trap condensates are recovered.

Flexibility: Every piping arrangement must be sufficiently flexible to allow each line to thermally expand or contract without overstressing the pipe or equipment.

Pipe Supports: The steel members attached to a pipe to hold it in place during operation. Some typical pipe supports are a) Pipe Shoes b) Spring Supports c) Trunnions and dummy legs d) Brackets.

Constructibility : Spending additional time and effort during the engineering phase of a project is often justified if it reduces initial construction staff time or decreases the potential for costly rework on piping layouts.


Specification means the constraints under which a component should be designed and manufactured.

Specifications encourage uniformity and improve quality. Ignorance or failure to comply with the guidelines set could affect the quality of the design.

Components of a Specification

Modifications: Any revisions, exceptions, or addenda to the specifications should be highlighted in the project documentation.


Operator Access – the space required between components or pairs of components to permit walking, operating valves, viewing instruments, climbing ladders or stairs and safely exiting the unit in an emergency.

Maintenance Access – the space required to service equipment in place or remove the unit equipment or portions of equipment for off-site repair.

Equipment Arrangement : General plant arrangement must be consistent with prevailing atmospheric and site conditions as well as with local codes and regulations. Equipment must be grouped within common process areas to suit independent operation and shutdown. Equipment within process and off-site areas must be arranged to accommodate operational and maintenance access and to meet safety requirements.