Plot Plan Design

The various process plants we come across are Petroleum refineries, Petrochemical complexes. Fertilizer plants, and Chemicals and Pharmaceutical plants, which need special attention due to the nature of the materials and products handled in those plants. All these plants involve various facilities such as raw material storage; intermediate and finished product storage, Process units and Control rooms; Flare System, Raw material/Product loading and unloading facilities; Utilities generation and distribution; Waste water treatment facilities; Non plant facilities such as Administration Buildings, Canteen, Workshops, Laboratory, Security arrangements, Vehicle Parking space, Stores, Fire station, and Township. Space allocation need to be provided to accommodate all these facilities.

In order to minimize the risks, certain norms are developed and practiced with respect to space Allocations & relative locations and some specified distances are to be taken care of while a plant is designed. Many times, existing plants are modified to increase the capacity by change/addition of certain equipment whereas the original space designs may not be sufficiently cater for such changes. This also calls for a detailed analysis of the space allocation and consideration of any new additions. Generally, the basis of keeping specific inter distances depends on the lessons learnt during the past years from accidents which occurred in various plants throughout the world. Accordingly, the specified minimum distances and the specified relative locations are undergoing a continuous updation as new datas are generated and experiences increase. A few of the major points to be born in mind while venturing into plant layouts are explained here.

Equipment Layout

When Process flow sheets and major equipment dimensions (e.g. Equipment list) are available. Piping Engineer should first develop a one-plane elevation of all Equipment to scale and relatively locate to fulfill process requirements. He should keep good Margins for nozzle lengths, bends, valves, slopes and distances between equipment, etc. While locating the equipment. He must as well think of structural/concrete beam depths, Monorails, pipe-ways, cable trays, lighting, etc. while deciding the floor elevation. This one-plane elevation view should be discussed internally and then with PE group who will Check relative locations & elevations of equipment. Routing of major & critical process lines Should also be discussed at this stage. After deciding floor elevations and number of floors, Work can start on preliminary arrangement drawings which should show each floor plan as Well as elevation views at different sections.

Piping Layout

The arrangement of piping is probably the most important consideration affecting the layout of petroleum, petrochemical and similar types of plants. The following in general, is the order of importance in which piping systems should be considered.

• Alloy piping or special materials
• Large bore piping or lined pipe.
• Low temperature pipe or other piping requiring thick and expensive insulation.
• Major headers for utilities or auxiliaries.
• The routing of lines involving temperature where expansion and contraction necessitates flexibility which should preferably be inherent in the layout. Pipe shall be arranged in an orderly manner and routed as direct as possible.

Study piping

After a basic equipment layout has been developed, piping study drawings shall be made for units which have sufficient size and scope to warrant further investigation of equipment arrangements, pipe rack widths and the like. For units or areas which obviously do not require extensive study due to simplicity of piping involved, the piping layout may be started directly which will eventually be issued as construction drawings. Responsibility for determining whether study drawings are required and the extent, to which they are to be carried, shall rest with Project Piping Engineer. The study drawings are intended to serve the following purposes:

• To confirm equipment locations for review, comments and/or early approval by various Concerned departments on the plant layout.
• As a basic guide to making model, constructions drawings and isometrics.
• To help minimize interferences by showing the structural, instrumentation and electrical groups the intended piping and equipment arrangements.
• To enable the analysis of line expansions and supporting systems.
• To enable the analysis of line expansions and supporting systems.
• To enable other concerned departments i.e. Pressure vessel, Civil, Structural, Electrical, Heat Exchanger, Process Departments to develop their work/check their requirements.

In general, study drawings consist of plans, elevations (where necessary) showing unit piping arrangement fulfilling all conditions laid down in P&ID manifold locations, platform, elevations, Instrumentation etc. And schematic routing diagram of piping on the racks. They will also indicate special requirements like monorails for exchanger bundle pulling or catalyst loading etc. Piping Studies are prepared as line diagrams to form the basis of General Arrangement Drawings and the details shown in the case of piping general arrangement drawings for construction are not shown to that extent such as control valve manifolds are shown as a block, only important elevations and arrangements are shown etc.

Pipe rack Design

The piperack general arrangement is finalised during the development of overall plot plan. The exact width of the piperack, numbers of levels and elevations, the access and maintenance platforms are finalised during piperack piping study. Normally, the piperack piping study, with its structural and platform requirements is the first priority item for detail engineering of a process unit. The piperack may be an integral part of a process unit located in the middle of the unit or it may be an arterial part connecting several services of other process unit. The following data and drawings are required to be studied before starting the detailed design of piperack piping study:

• Unit Plot Plan / Overall Plot Plan
• Piping and Instrumentation diagrams
• Plant layout specification
• Client specification
• Material of construction
• Fireproofing requirements

Tank Farm Design

Tankfarm consisting of a group of tanks shall be carried out keeping the following basic points in consideration. Grouping of tanks,

• Specification of the content.
• Capacity of tanks
• Nature of hazard
  • fire
  • toxic
  • explosive
  • corrosive
  • bulk handling
    • loading
    • unloading
• Statutory distance
• Requirement of Dykewall or curbing
• Dykewall height or curb height calculation
• Location of Pumps
  • inside dyke area
  • outside dyke area
• Approach to tank nozzles with valve
• Approach to tank roof
• Drainage of dyke area - Sump and pump
• Road around tankfarm
• Fire hydrant / monitor requirement
• Underground system connected to specific system of treatment / dispos

Stress Analysis

Flexibility Analysis is a subject which is more talked about and less understood. Flexibility Analysis is done on the Piping System to study the behavior of the same, when it changes the temperature from ambient / installed to operating, so as to arrive at the most economical layout. There are mainly three sets of conditions which define the minimum acceptable flexibility on a piping configuration. They are :

• The maximum allowable stress range in the system.
• The limiting values offer stress and moments which the system is permitted to impose on the equipment to which it is connected.
• The maximum allowable stress on the supporting structure

When piping is connected to strain sensitive equipments, the flexibility required to satisfy the acceptable limits of forces and moments overrides that required to satisfy the maximum stress range conditions and overstressing of supporting structure

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Isometrics

Tendering & final MTO Calculation