Process Equipment Design ChE 311

University of KhartoumFaculty of EngineeringDept. of Chemical Engineering

Factors Influencing the design of Vessels• Industrial process is the transformation of raw

materials to final products through chemical and

physical operations.

Factors Influencing the design of Vessels• These processes require treatment & storing of big

quantities in different types of containers / vessels

depending on:

a) Material status inside vessel.

b) Its chemical and physical properties.

c) Type of operation to be carried out.

Factors Influencing the design of Vessels• There are many factors affecting vessels design:

1. Selection of the Type of the Vessel.

2. Methods of Fabrication.

3. Types of Criteria in Vessel Design.

4. Economic Considerations.

1. Selection of the Type of the Vessel.

• The first step in vessel design is the selection of the appropriate vessel type to intended operation.

• Main factors affecting the selection:a) Vessel function and location.b) Nature of fluid.c) Operating Temperature & Pressure.d) Storing or Production Capacity.

1. Selection of the Type of the Vessel.

• Vessels can be classified according to:a) Functional Service.b) Temp. & pressure service.c) Material of construction.d) Geometry of the vessel.

1. Selection of the Type of the Vessel.

• Most of common vessels are classified according to its geometry as follows:A. Open Vessels.B. Closed Vessels:

i. Flat-bottomed, vertical, cylindrical tanks.ii. Cylindrical vertical and horizontal vessels

with formed ends.iii. Spherical and modified spherical vessels.

1. Selection of the Type of the Vessel.

• General Guidelines in current use of common vessels:

Big volumes of non-hazardous , cheap liquids such as brine and other aqueous solutions stored in ponds.

1. Selection of the Type of the Vessel.

• General Guidelines in current use of common vessels:

Big volumes of non-hazardous , valuable liquids stored in steel, wood or concrete vessels.

1. Selection of the Type of the Vessel.

• General Guidelines in current use of common vessels:

Toxic, Flammable, Gaseous or high pressure fluids require closed system.

1. Selection of the Type of the Vessel.

• General Guidelines in current use of common vessels:

Fluids under atmospheric pressure stored in flat-bottomed cylindrical tanks with conical heads.

1. Selection of the Type of the Vessel.

• General Guidelines in current use of common vessels:

Spherical and Spheroids used for storing under high pressure where big volumes in required.

For small volumes cylindrical tanks with formed heads are more economical.

1. Selection of the Type of the Vessel.

• Open Vessels. It’s cheaper than covered or closed vessels of the same

volume and construction. It’s used as:

a) Storage tanks.b) Vats in batch operations where materials may be mixed

and blended.c) Settling tanks.d) Decanterse) Chemical reactors, f) Etc.

1. Selection of the Type of the Vessel.

• Open Vessels.Ponds are the cheapest type of open vessels

and it’s used to store very big volumes of aqueous solutions.

Large circular tanks made from steel or reinforced concrete used as settling tanks.

Small open vessels used as storages and mixing tanks during the operation.

1. Selection of the Type of the Vessel.

• Open Vessels.Ponds are the cheapest type of open vessels

and it’s used to store very big volumes of aqueous solutions.

Large circular tanks made from steel or reinforced concrete used as settling tanks.

Small open vessels used as storages and mixing tanks during the operation.

1. Selection of the Type of the Vessel.

• Closed Vessels.It’s used to store Toxic, Flammable, Gaseous &

Dangerous chemicals such as acid and caustic.

It’s also used in Petroleum and Petrochemical industries because the combustible nature of its products.

1. Selection of the Type of the Vessel.

• Closed Vessels.(Cylindrical vessels with flat bottoms and conical or

domed roofs):The most economical design for closed vessels

operate at atmospheric pressure is Cylindrical vessels with flat bottoms and conical roofs.

Cylindrical vessels with flat bottoms and conical roofs are provided with “breather” or vent which permit expansion and contraction of fluids as a result of temperature and pressure fluctuation.

1. Selection of the Type of the Vessel.

• Closed Vessels.(Cylindrical vessels with flat bottoms and conical or domed

roofs):Tanks up to 24 ft diameter are covered with self-

supporting roofs.Tanks with lager diameter up to 48 ft require at least on

central column as support.Tanks with diameter larger than 48 ft are usually designed

with multiple column support or floating roof with rises and falls with the level of liquid inside the vessel.

1. Selection of the Type of the Vessel.

• Closed Vessels.(Cylindrical vessels with flat bottoms and conical

or domed roofs):Cylindrical vessels with flat bottoms and domed

roofs are used to store fluids under pressure from 2.5 – 15 lb per sq. in.

These vessels normally design with smaller diameter and greater height for the same capacity of that with cone roofed

1. Selection of the Type of the Vessel.

• Closed Vessels.(Cylindrical vessels with formed ends): It’s used when liquid vapour pressure requires stronger design. Normally vessel diameter less than 12 ft. Field erected vessels dimensions may exceed 35 ft diameter

and 200 ft height. Formed ends include:

o Hemi-sphericalo Elliptical – dished.o Standard dished.o Conical

1. Selection of the Type of the Vessel.

• Closed Vessels.(Spherical & modified spherical vessels): It’s used for medium pressures.For large volumes under medium pressure

spherical vessels are more economical.For high pressure cylindrical vessels are more

economical.Small cylindrical vessels are more economical

than spherical vessels.