Pressure Vessel Training Definitions and Questions

Provide a definition for pressure vessels

Pressure vessels are a type of a closed process container designed to hold liquids, gases, or both. In some cases, pressure vessels can also contain solids. OSHA 1910.106(a) identifies a pressure vessel as a “storage tank or vessels which has been designed to operate at pressures above 15 psig.”

Explain pressure vessel design requirements.

Must be pressure tested before put in service, Repairs or modifications must be performed to the ASME code requirements, each pressure vessel must have a name plate securely affixed in a conspicuous place on the vessel.

Identify the basic components of a pressure vessel.

Nozzles, Heads, Shell, and Manway

List the factors that influence the selection of construction materials.

Strength of the material, resistance to deterioration due to corrosion, ability of the material to withstand conditions that cause brittle fracture, a potentially catastrophic condition in which the material fractures or cracks under stress

Surge Drum

Cylindrical vessel placed in a process to absorb fluctuations in the process stream pressure or flow

Separator

A category or pressure vessels that promote the separation of mixtures which can be any combination of liquids, gases, and solids

Settler

A type of separator that allows more time for a mixture to separate, known as retention time.

Flash Drum

Cylindrical vessels that are a type of liquid-gas separator and operate on the principle of partial vaporization. A common use is to recover low pressure steam from condensate.

Distillation Column

A column that promotes the separation of a mixture of two or more hydrocarbons by their boiling point temperatures. This is done by the application and removal of heat.

Fractionating Column

Performs a complex distillation process carried out in a tall tower that contains series of trays. Exchanges heat and mass between the liquid and vapor to perform multiple distillations, providing a more precise degree of separation.

Vacuum Distillation Tower

A vessel for performing distillation at a reduced pressure, typically below atmospheric pressure.

Contactor

A vertical tower that is designed to allow maximum contact between two immiscible (will not mix) fluids to remove impurities form the product stream.

Reactor

A vessel used for containing and controlling a chemical reaction. The reaction typically converts or cracks a low value hydrocarbon into a higher value usable product. The reactor’s design configuration, shape, size, and specifications are specific to the nature of the reaction and the reaction conditions.

Filter

Filter trap and remove fine solid particles from a process stream and improves downstream operation by preventing fouling and reduces equipment maintenance.

Distributors

Evenly distributes the product stream across the vessel. Breaks up the product stream into smaller particles to help with liquid-vapor separation.

Inlet Diverter

Breaks up the inlet stream flowing into a vessel to minimize the agitation of the process fluid in the vessel.

Demister Pad

Prevents small droplets of entrained liquid from exiting the vessel with the vapor. The pad causes the entrained liquids to collect and form into larger drops that fall.

Packing

A bulk of small objects shaped n such a way to increase the surface area in a tower, causing better contact between the process fluids.

Weirs

Vertical dams that divide a vessel into compartments. Weirs hold a constant level of liquid in a certain portion of the vessel to allow a skimming action to occur across the top of the liquid.

Baffles

Partial plates which cause the fluids to flow in a zigzag pattern through a vessel. This creates turbulence in the flow. This turbulence promotes more contact between the fluids.

Trays

Horizontal plates that cause contact between two different fluids. Trays retain a liquid level, which is contacted with a gas or vapor stream. Holes or perforations in the tray allow lighter vapors to bubble through the liquid.

Bubble Caps

A device installed on bubble cap trays to enhance the contact between liquids and vapors. The bubble cap forces the vapors that are flowing up through the liquid on the tray.

Downcomers

Downspouts that direct the liquid down a tower from tray to tray. They are typically staggered down the tower.

What is the most common shape of a pressure vessel?

Cylindrical

Entrainment

Occurs when droplets of heavy liquid are carried up with vapors.

Catalyst

A catalyst is a substance that promotes and enhances a chemical reaction but is not consumed by the reaction. Catalysts are usually in the form of a fluidized solid or a liquid and are specific to the desired reaction.

Fixed-Bed Reactors

Solid catalyst is held in place, and the reactant (product) flows over the catalyst to promote the reaction

Nozzle

A cylindrical component that penetrates the vessel heads and or shell. Nozzles are typically flanged to allow for the process piping to be attached.

Manway

A large type of nozzle that allows access to the inside of the vessel

Shell

Body of the pressure vessel

Head

The end cap that closes the vessel and prevents the contents from escaping.