by Equipment layout is developed as the course of the detailed engineering phase by the designer considering the location of the equipment and supporting facilities within the process operating plant. Various factors to be considered to develop the equipment layout and the are discussed below.
Plant Layout Specification – This document in the project highlights spacing requirements for equipments and access widths and elevation clearances for operator and maintenance access.
Economic Piping – Major portion of the piping within most process units is used to interconnect equipment and support controls between equipment. To minimize the cost of this bulk material, equipment should be located in process sequence and close enough to suit safety needs, access requirements and piping flexibility. The layout to be subdivided into smaller groups of process related equipment. These groups of related equipment and controls that function as a subsystem within the main process unit. The components within the subsystems should be arranged to suit the most economic piping runs and the whole assembly should be positioned within the plot area to provide the most economic interconnection between related process subsystems.
Process requirements – Equipment often must be located in a specific position to support the plant process operation. The plant layout designer must be familiar with the process because the process flow diagram rarely indicates this information. It is recommended that the designer discuss these requirements with the process engineer before proceeding with the plant arrangement.
Common operation – Equipment that requires continuous operator attention or shares common utility and maintenance facilities should be located in the same area.
Layout space availability – Generally most new process units are built within an existing facility in which a piece of land is dedicated to the new operation. Older process units which undergone many expansions have less space for the new facility. This can be a problem for inline horizontal arrangement of equipments and so vertical arrangement of equipments in an elevated structure is a good option.
Equipment sizes – All types of equipments within the process units would be the same size. But normally a plant layout designer struggles to place a large piece of equipment into an area so in these situations the designer should place these items first and plan the remainder of the unit around them.
The plant layout designer must make provisions for operator and maintenance access. The designer should review the items of equipment that are included in the process and plan for their operation and maintenance requirements. For example, Shell and tube exchangers require space for bundle removal and rotating equipment needs space for drive and casing removal.
Underground facilities – Depending upon the soil conditions the foundations for the equipments are either piled or spread footings. Spread footing foundations require more space than piled foundations and care should be taken to locate equipment so that enough space exists between equipment for the foundations of larger equipments. Depending upon the project specification instrument and electrical cables can be located above or below ground level. Underground piping is another factor to consider for fixing the equipment layout. All these factors determines the required plot space, and it is recommended that the plant layout designer finalize what facilities are to be positioned below ground before proceeding with the equipment arrangements.
Climate conditions – Weather conditions could influence the location of equipments. For cold climates equipments should be housed. The wind can influence the location of such equipments as furnaces, compressors, control housed, cooling towers and stacks. Furnaces or other fired equipments should be located on the prevailing or upward of the wind direction of that so as not to allow flammable vapors to reach the equipments.
Pipe racks – In the process plant the central pipe racks system that acts as the main artery of the unit supporting process interconnection, feeds, product and utility piping, instrument and electrical cables and air coolers and drums. Usually the pipe rack is made of structural steel, either single level or multilevel to suit the width and capacity of the unit it is serving. The pipe racks bays width spaced normally 6000 mm. The width is determined by such factors as the quantity of piping and cabling to be carried on the main run of the pipe rack, the equipment and access ways located beneath the pipe rack or the equipment supported above the pipe rack. The layout that results in the most economical design should be chosen.
In pipe racks normally 20% future space to be considered for each level. The pipe rack width can be adequately sized on the basis of approximate line sizing, utility piping and insulation requirements by the plant layout engineer. The bottom support elevation of the main pipe rack is finalized by the maintenance and access ways and piping clearance beneath the pipe rack.
Pipe rack configurations are done by the equipment layout, site conditions and client requirements and plant economy. Based upon the project requirement and the pipe racks can be in T, L, or U shaped. Changes of direction in pipe racks must be accommodated by changes in elevation and are usually spaced about the midpoint of the main pipe rack elevations to suit required clearances.
Roads, access ways and paving – For maintenance and safety the principal access to and from most process units is by auxiliary roads. Normally the unit battery limits should be positioned 15000 mm from the center line of the main plant roads. This allows adequate space for drainage and fire fighting facilities and avoids obstructing roads when such items as heat exchanger tube bundles are removed. Clearance to be provided according to project specification and should be provided over roads and access ways for mobile equipment access.
Buildings – Control rooms, substations, analyzer houses and operating shelters to be located within the process unit areas. Control rooms and substations are usually located at the edge of the unit adjacent to plant road 15000 mm from the operating equipment. Analyzer houses and operator shelters should be located next to the equipment that they service.
