Introduction to Plot Plan

A plot plan is an engineering diagram which shows schematically the equipment layout, the position of roads, buildings and other constructions inside an industrial plant with their dimensions and distances in between. This blog post gives you a basic introduction to plot plan.

Plot plans are considered key documents to projects and are normally initiated in the pre-contract, conceptual and development stages of a proposal.

After the contract is awarded for engineering, plot plans are developed at a rather rapid pace with very limited information. This early stage plot plan usually is very limited in detail, containing only enough dimensional data to define the outer limits of the available property selected for plant development. Located within the boundaries of the available property, rough equipment sizes and shapes are pictorially positioned. along with anticipated pipe rack configurations, structure shape and rough sizes. The plot plan at this level of detail is then used for constructability evaluation and is normally submitted to the client for approval.

Once approved by the client, almost every group including Engineering, Scheduling, Construction, Operations, Cost Control, Estimating and Material Control use the plot plan as a pictorial reference for their work. At this point, the plot plan becomes a universal document used by all groups to interface with one another and the client.

Development of the plot plan in the very early stages is usually accomplished through the use of preliminary project design data, approximate equipment sizes and a process flow diagram to establish rough sketches. These sketches are used to determine structure configuration and relative equipment positioning.

The plot plan is a dynamic document, evolving through the life of a job. Some of the more common names and descriptions used during this evolution process are as follows:

Proposal Plot Plan – used to establish the basis of bid work.
Overall Plot Plan – a small scale depiction of utility, storage, and loading facilities as associated with the process plant.
Sectional Plot Plans – the overall plot plan broken into manageable size drawings.
Planning Plot Plan – an agreed-upon arrangement which usually starts the work of most groups that rely on equipment positioning.
Production Plot Plan – an update of the planning plot plan after enough study work has been completed to establish firm location of equipment. This plot plan is the basis for beginning detailed design work
Construction Plot Plan – releases the constructor to begin activities related to equipment location, such as roads, pile driving, underground piping, foundations, etc. It is the single document containing all equipment, structure and road locations.
Final or “As Built” Plot Plan – a plot plan normally provided by the responsible engineering company that reflects the completed project as constructed. This plot plan is maintained by the client for future expansion work requirements or other business needs. Plot plans are also used to assure proper operator and maintenance access while maintaining engineering economy. Plot plans are used for operational needs such as training and emergency access, as well as facilitating insurance ratings. Major Roles of a Plot Plan
This drawing serves as reference for the following
Designers that develop plot plans are usually persons that can do development type work using original thought and utilizing minimal process, utility and equipment information. The plot plan designer must also know the functions of engineering, construction, operations and maintenance in order to envision and anticipate mechanical problems and emergencies that may occur in the future.
In addition to depicting relative and specific positioning of equipment, plot plans help in the establishment of support facilities and are used to determine the most cost-effective construction sequence and methods.

Battery limits of the plants
Location of all major equipment’s coming inside the B\L including structures and roads.
Construction of civil foundation at site.
Serves as a master document for various engineering departments to proceed with detailed engineering activities. During the engineering and construction phases of a job, many owners use the plot plan as a basis for evaluating the level of completeness of agreed upon work. The document thus becomes a measuring device for progress payments. Climatic considerations also play a major role in plot plan development. Extreme sun exposure in desert areas or near the equator may require shelters to protect operators and maintenance personnel from high temperatures. Conversely, special considerations must be given to plants located where extreme cold, ice or snow may be prevalent. Under the most extreme conditions, many equipment items requiring frequent visits by personnel are enclosed by heated shelters. These shelters are sometimes connected by tunnels suitable for human passage. In many cases, plant utilities are run within the confines of these tunnels to guard against freeze-up and to conserve energy for producing utilities streams. Plot plan economy is directly linked to the ability to develop process modules. Process modules can then be related to actual plot plan configurations and in some cases integration of equipment items can eliminate the need for interconnecting piping.
The level of talent required to develop plot plans and the interaction of the plot designer with process and equipment personnel often result in new and innovative equipment integrations and configurations.
Economy of Plot Plans
Prevailing winds and tower and structure heights must be considered in developing a plot plan. Although wind direction is never constant, prevailing wind is used as a basis to evaluate safety within the client’s complex, as well as the safety of neighbors should a spill, release or fire occur. Tower and structure height and their positioning are major considerations, especially when units are located near airports or in flight paths.
Plot plans are essential for obtaining permits and determining environmental and personnel safety. They are the key documents used in assessing fire protection.

Input Data

Contour map of the plant area and absolute elevation from mean sea level.
Conceptual plot plan.
Equipment list & data sheets.
Preliminary equipment details\drawings.
Preliminary civil drawings for buildings & structures.
Preliminary layouts of the following, where required.
1. Pump House
2. Compressor House
3. MCC & Sub Station
4. Control Room
Specific requirements from client, if any.

Output Data

The Plot Plan drawing in the standard A1 sheet.

Site or Overall Plot Plan

The Site or Overall Plot Plan shall indicate the projection of a facility in outline in the over all field.. The plans shall be made as an ‘overlay’ of existing topographical drawings and shall indicate the location of the plant base co-ordinate in true Northing and Easting

This single drawing shall indicate the entire plant area highlighting the following.

Various individual plants, storage farms etc. with their boundary co-ordinates & grade elevations
Well locations
Both intra and inter-field pipelines shall be shown
Relation between grade elevation and mean sea level
Grid lines set to suit the scale of drawing ( normally in steps of 50 M )
Roads with centerline coordinates & width, boundary walls ( where required )
Geographical north, plant north, wind direction
Existing plant details ( if required ) for corelation
General indication of major pipe bridges and if required, existing pipe bridges.
Boundary coordinates. for Plant Areas with designation.
Any other detail required by client for an overall view of the entire area.

Key Plan for Plot Plans

The key plan for plot plans shall be made as an overlay of the overall plot plan and shall indicate a logical grid covering the full area of an overall plot plan with a projection of all relevant plot drawings, indicated with sequential sheet numbers.

Plot Plans

When the scale of the overall plot plan is 1:1000 and more, the unit plot plan is drawn to a scale of 1:250 or smaller to indicate the location of all equipment’s along with the location table.

Plot Plans shall indicate:

Scale of the drawing shall be selected so that smallest equipment coming in the plant will have a minimum dimensions 5 mm x 5 mm in the drawing
Fences and gates; Escape routes shall be clearly indicated.
Buildings, with indication of doors. They shall be represented with centerline coordinates of the columns along with size of columns. Non-plant buildings shall be represented by outside dimensions to scale. Location of non-plant building shall be defined by co-ordinates of outer edges.
All main equipment (including skid mounted units)
Package items & assemblies, skid mounted consoles etc. shall be represented by outside dimensions \ base plate dimensions to scale with location of the same defined by co-ordinates of centerlines \ supports edges and support elevation
Storage tanks and vertical vessels shall be represented by out side diameter circle to scale. The location shall be defined by coordinates of vertical centerline (in both horizontal directions)
Horizontal vessels and heat exchangers shall be represented by outside dimensions to scale, and location defined by co-ordinates of longitudinal centerline of the vessel, fixed support and elevation.
Pumps shall be shown with baseplate outline, and co-ordinates of the pump discharge flange.
Compressor shall be represented showing base plate dimensions to scale, and location defined by co-ordinates of casing centerline\discharge nozzle or exhaust nozzle in case of turbine driven machine, and support elevation.
For rotating equipment’s, the representation shall be updated to indicate the plinth area of foundation
Similar equipment’s with same designation number, and suffixes added to distinguish standby etc. shall be arranged chronologically from top to bottom and from left to right respectively (e.g. Pump P1011 A shall be on top and P1011 B on bottom and so on)
Pipe rack main supports.
Pipe bridges shall be detailed with typical cross sectional views showing deck elevations. Area reserved for electrical and instrument cable trays shall be clearly marked on the sectional views. Top elevation of the beam for supporting pipes also shall be indicated in the sectional view.
Sterile areas around flares, vents and burn pits by means of a discontinuous line with an arrow and text stating ‘Sterile Area Limit’.
All major operating platforms, walkways and stairs.
Benchmarks indicating co-ordinates and elevation. Finished grade elevation shall be shown on the drawing in a box. The relation of this grade elevation with respect to mean sea level may be given in the notes Note: Grade elevation 100000 shown in the drawing corresponds to absolute elevation of 50.5 meters above mean sea level.
e.g. GRADE EL 100000.
True north and Plant north with included angle at the right hand top corner
Prevailing wind direction.
Earthling and cathodic protection wells.
Bund walls.
List of main equipment indicated on the plot plan in a location table, with description (as in the PEFS/ P&ID & equipment list). This table shall be spaced preferably on the right hand side of the drawing. If the table cannot be spaced in the same drawing a separate drg. may be drawn for this purpose
Cross-references to the Key Plan, Foundation Location Plan and Site Plan.
Eye wash\safety showers & utility station shall be represented using symbols and shall be given clearly in the legend.
All roads and access ways inside battery limits shall be shown on the plot plan with centerline/ edge co-ordinates/ width of road.
Maintenance spaces, drop areas, tube pull out areas etc. as required shall be clearly demarked in the plot plan. The space reserved for these shall be crossed diagonally
Over head crane, monorails, EOT cranes etc. shall be indicated suitably
All abbreviation and symbols used in the drawing shall be clearly described in the legend for the drawing

Introduction to Plot Plan