MODULE 1:
BASIC DESIGN CONCEPTS OF INDUSTRIAL PLANT SYSTEMS AND EQUIPMENT
Overview of Module
The study of design concepts of Industrial Plant Systems and Equipment is the first
procedure in any industrial or manufacturing plant operation. This module provides the
tools to study the layout, facilities, and equipment required for operation.
General Design Considerations
Developing a full-plant design involves considering several different factors, such as:
a. Plant location
b. The site and plant layout
c. Plant operation and control
d. Utility
e. Storage system
f. disposal of waste
g. Health and safety protocols
h. Handling of materials (will be discussed in the following chapters)
a- Plant Location and Site Selection
The final plant's geographical location can tremendously affect the progress of an
industrial venture. In deciding the plant's site, considerable care must be exercised,
and several factors must be considered. The plant should primarily be located where
the lowest cost of production and distribution can be obtained. Still, other
considerations are also important, such as room for expansion and the right living
conditions for plant and local community activities.
The significant factors in the selection of most plant sites are:
➢ Marketing Area
For materials manufactured in bulk quantities, such as cement, mineral acids, and
fertilizers, where the product's cost per metric ton is relatively low and the shipping
cost is a Large Fraction of the selling price, It should be sold at the plant near the
primary market. This factor is far less relevant for low-volume production and highpriced goods such as pharmaceuticals.
➢ Raw Materials
Often the site location will be determined by the availability and price of suitable raw
materials. Plants processing bulk chemicals are best located near the primary raw
material source as long as the shipping product costs are no higher than the shipping
feed costs. On the other hand, oil refineries tend to be located near major population
centers, as an oil refinery produces several grades of fuel that are expensive to ship
separately.
➢ Transportation Facilities
An overriding consideration in site selection is transporting materials and products to
and from the factory. If practicable, a location close to at least two significant modes
of transportation should be selected: road, rail, waterway (canal or river), or maritime
port. Road transport is increasingly being used and is ideal from a central warehouse
for local distribution. Rail transport is typically cheaper for transporting bulk chemicals
over long distances. Air transport is easy and effective for transporting staff and
necessary equipment and materials, and consideration should be given to the
location's proximity to a major airport.
➢ Availability of Labors
It will take labor to build the plant and its operation. Skilled construction workers are
typically brought in from outside the site area. Still, there should be a sufficient pool of
locally available unskilled labor, and jobs suitable for training to run the factory. The
maintenance of the plant would involve professional craft workers such as
electricians, welders, and pipe fitters. When determining the availability and suitability
of local labor for recruitment and training, attention must be given to local labor laws,
trade union rules, and discriminatory practices.
➢ Water supply
Chemical processes usually need significant quantities of water for cooling, washing,
producing steam, and as raw material, and the plant must be located near a good
source of water quality. Process water can be collected from a river or wells or
purchased from a local authority.
➢ Energy Availability (power and fuel)
Most industrial plants have high power and steam requirements; fuel is typically
needed to supply those utilities. Power and energy can also be combined as one of the
main factors when selecting a plant site. If the plant needs large amounts of coal or
oil, the position near a fuel supply source may be necessary for economic activity.
Local power costs can help to decide whether power is to be purchased or generated
by itself.
All sites need electric power. Electrochemical processes (for example, the
manufacture of chlorine or the smelting of aluminum) need vast amounts of energy
and must be located near a cheap power source.
A competitively priced fuel must be available on-site for steam and power generation.
➢ Climate
Adverse weather conditions will increase costs at the site. Low temperatures require
additional insulation and particular heating for fittings and pipe runs. Locations subject
to high winds (cyclone/hurricane zones) or earthquakes require more robust
structures. The plant machinery will need strong protection from corrosive
environments.
Site layout and plant layout
➢ Site Layout
In providing the most efficient movement of materials and staff around the site, the
process units and ancillary buildings should be laid out. Hazardous facilities have to
be within a reasonable distance from other buildings. Future expansion of the site also
needs to be considered. In addition to the central processing units (buildings), the
ancillary buildings and facilities available at a site include:
1. Storage for raw materials and products: tank farms and warehouses;
2. Maintenance workshops;
3. Stores for maintenance and operating supplies;
4. Laboratories for process quality control;
5. Fire stations and other emergency services;
6. Utilities;
7. Effluent disposal plant: wastewater treatment, solid and or liquid waste
collection;
8. Offices for general administration;
9. Canteens and other amenity buildings, such as medical centers;
10. Parking lots.
When the preliminary site layout is roughed out, the process units are typically first
sited and configured to provide a seamless material flow across the different
processing stages, from raw material to final product storage. Process units are
usually spaced at least 30 m apart; destructive processes can require greater spacing.
It should then be determined where the main ancillary buildings are situated. They
should be designed in such a way as to reduce personnel's time commuting between
buildings. Administration offices and laboratories should be far away from potentially
dangerous procedures where a relatively large number of people would be employed.
Control rooms are usually adjacent to the processing units, but those with potentially
hazardous processes can need to be situated at a more certain radius.
The primary process unit sitting defines the layout of the plant avenues, pipe alleys,
and drains. Access roads are required for the construction, operation, and
maintenance of each building.
Some guidelines (notes) about the layout:
· Utilities should be positioned to have the most economical pipeline run to and from
process units.
The cooling towers should be positioned, so that the condensate spray plume drifts
away from the plant area and adjacent properties under the prevailing wind.
· The main storage areas between the loading and unloading facilities and the process
units that they support should be stored.
· Storage tanks containing hazardous materials should be situated from the site
boundary at least 70 m (200 ft).
Plant Layout
A processing unit's cost-effective construction and operation would depend on how
well the plant and equipment defined on the process flow sheet are laid.
The arrangement of the significant equipment products always follows the sequence
given on the flow sheet of the process: with the columns and vessels arranged in rows
and ancillary equipment, such as heat exchangers and pumps, placed outside.
The key considerations to consider when making the layout of the plants are:
1. Economic considerations: construction and operating costs;
2. The process requirements;
3. The convenience of operation;
4. The convenience of maintenance;
5. Safety;
6. Future expansion;
1. Economic considerations: The costs of construction and service.
Construction costs can be reduced by following a configuration offering the shortest
connecting pipe between the equipment and the smallest amount of structural
steelwork; however, this would not be the best operational and maintenance
arrangement.
2. Process Requirements
One example of the need to consider process considerations is the need to raise the
base of columns to provide a pump or the operating head for a thermosiphon reboiler
with the requisite net positive suction head.
3. Operation
Equipment that requires regular attention from the operator should be conveniently
located in the control room. Valves, sample points, and instruments should be placed
in suitable locations and heights. There must be ample workspace and headroom for
easy access to the equipment. If the equipment is likely to require repair, adequate
space must be allocated to access the lifting equipment.
4. Maintenance
Heat exchangers need to be placed to allow quick removal of the tube bundles for
cleaning and tube replacement. Vessels requiring regular catalyst replacement or
packaging should be placed outside buildings. Equipment requiring maintenance
dismantling, such as compressors and large pumps, should be undercover.
5. Safety
Blast walls can be sufficient to separate potentially dangerous devices and minimize
the impact of an explosion. The process buildings must have at least two escape
routes for operators from each floor.
6. Installation extension
Equipment should be positioned in such a way as to be easily connected with any
potential process expansion. Space should be left on pipe racks for future uses, and
service pipes should be over-dimensioned to allow for future requirements.
When the configuration of the main pieces of equipment has been determined, it is
possible to draw plan and elevation drawings and to undertake the design of the
structural steelwork and foundations.
Plant operation and control
The methods that will be used for plant operation and control helps determine many
of the design variables in the design of an industrial plant. The complexity of the
instrumentation, for example, maybe a factor in selecting the type of process and
setting the labor requirements.
Utilities
The word utility is used for the ancillary services required to operate any manufacturing
operation. These facilities are usually delivered from a central facility at the site and
include:
1. Electricity;
2. Steam for process heating;
3. Cooling water;
4. Water for general use;
5. Demineralized water;
6. Refrigeration;
7. Compressed air;
8. Inert-gas supplies;
Electricity
The power needed for electrochemical processes, motor drives, lighting, and general
use may be produced on-site but, more generally, would be bought from the local
supply company.
Steam
Process heating steam is typically produced using the most economical fuel in water
tube boilers.
Cooling water
Natural and forced cooling towers generally provide the cooling water required at a
site unless water can be drawn from a suitable river or lake in appropriate quantities.
Seawater, or brackish water, may be used in coastal areas, but it would require more
costly construction materials for heat exchangers when used directly. The minimum
temperature reachable by cooling water depends on the local atmosphere. If the
ambient temperature and humidity are high, then a method of cooling water is less
efficient, and either air coolers or refrigeration are used.
Demineralized Water
Demineralized water, from which an exchange of ions extracted all minerals, is used
where pure water is required for process use and as water for boiler feed. Mixed and
multi-bed ion exchange units are used, with one resin transforming the cations into
hydrogen and the other extracting the anions. Water can be created with less than 1
part per million dissolved solids.
Refrigeration
Refrigeration is needed for processes requiring temperatures below those which can
be obtained economically with cooling water. Vapor compression machines are
usually used for refrigeration.
Compressed air ( instrument air )
Compressed air is needed for general use, and pneumatic controllers are generally
used to control chemical plants. We use single-stage or two-stage rotary and
reciprocating compressors. Instrument air shall be dry and clean (oil-free).
Inert Gases
Large quantities of inert gas are needed for the inert blanketing of tanks, and this will
usually be supplied from a central facility for purging. Nitrogen is generally used and
can be produced on-site at an air liquefaction plant (membrane system) or obtained in
tankers as a liquid.
Storage
Storage facilities are required for:
➢ Raw materials
➢ Intermediate products
➢ Final products
➢ Recycle materials
➢ Off-grade materials
➢ Fuels
A storage tank is a container for compressed gas (gas tanks) or liquid storage. The
word "pool" originally meant "artificial lake" and originated in India.
Storage tanks are available in several forms: vertical and horizontal cylindrical; open
and closed top; flat bottom; cone at the bottom. Big tanks tend to be upright or rounded
(transition from vertical side wall to low profile to more easily withstand hydraulic and
hydrostatic liquid pressure).
Choice of storage tanks
Tanks for a specific fluid are selected according to the substance's flash-point fixed
roof tanks, and floating roof tanks are available, typically in refineries and particularly
in liquid fuels.
• Fixed roof tanks
Usually, cone roofs, dome roofs, and umbrella roofs are used for very high flash point
liquids (e.g., oil, water, bitumen, etc.). These are sealed to prevent the clogging of some
materials within the tanks, where steam coils provide the heat. Dome roof tanks are
designed for tanks with a slightly higher storage pressure than atmospheric ones (
e.g., slop oil).
Advantages of fixed roof tank:
Easy and cheap to build.
Disadvantages:
Material loss due to vapor escape.
• Floating roof tanks
The floating roof tanks are designed to store volatile liquids to reduce the loss of
valuable vapors and the hazard of accumulating hazardous vapors under a fixed roof.
Floating roof tanks are commonly divided into floating roof tanks on the outside
(usually called floating roof tanks: FR tanks) and floating roof forms inside (IFR Tanks).
IFR tanks are used for low-flash liquids (for example, ATF, MS, ethanol). These tanks
are cone roof tanks with a floating roof (steel disc) inside, which is going up and down
along with the liquid volume. This floating roof traps fuel vapor at a low-flash point.
They are covered by floating-legged roofs on which they stand.
FR tanks do not have a fixed roof but a floating one (it is open at the top). Medium
flash point liquids, such as naphtha, kerosene, diesel, crude oil, etc., are contained in
these tanks.
Advantages of floating roof tanks:
1. Reduce material losses and air pollution.
2. Reduce fire and explosion risk due to minimal vapor space.
Disadvantages:
1. High price.
Construction Materials Used For Storage Tanks
Although steel remains one of the tanks' most common options, other materials are
growing in popularity, such as:
1. GRP (Glass Reinforced Plastics)
2. Thermoplastic
3. Polyethylene
4. FRP (Fiberglass Reinforced Plastics)
They offer lower construction costs and excellent chemical resistance, particularly for
specialty chemical storage.
Tank Wall Thickness
The tank wall must withstand the following:
1. The hydrostatic pressure of the liquid
2. Wind loading
The minimum wall thickness required to resist the hydrostatic pressure can be
calculated from the equation:
where
Tt: tank thickness required at depth HL, mm;
HL: liquid depth, m;
ρL: liquid density, kg/m3;
E: joint efficiency (if applicable);
g: gravitational acceleration, 9.81 m/s2;
St: maximum allowable stress for tank material, N/mm2;
Dt: tank diameter, m.
Important Note:
Since most liquids can spill, evaporate, or fill even the smallest gap, careful attention
must be given to their safe and secure handling. This attention typically includes
creating a bundling or containment dike around the tank so that any leakage can be
controlled safely. In some cases, this field is known as the tank farm.
Tank failures
There have been some glaring flaws in storage tanks' designs. Might attribute these
shortcomings to the following:
1. Inferior design and construction, with a wall unsuitable to withstand the daily
load of material.
2. Before use, the tank was not tested by filling it with water and was severely
riveted.
3. With the corrosion issue, storage tanks must be protected (e.g., cathodic
protection).
4. Defective welding or using substandard steel.
But storage tanks also present another, oddly, problem when empty. If used to carry
oil or oil products such as gasoline, the atmosphere in the tanks can be highly
explosive as hydrocarbons fill the vacuum. If new welding operations are initiated,
sparks will quickly ignite the contents, with the welders getting catastrophic results.
This problem can be solved using an inert gas blanket to prevent volatile atmospheres
from building up from residues.
Waste disposal
For several chemical plants, the disposal of waste is a serious issue. Processproduced materials that can not be recycled or sold as by-products must be disposed
of as waste. In certain situations, the concentration of the waste stream before it is
sent to final disposal needs extra care.