No matter their size, pressure vessels share a standard design template that allows them to effectively regulate pressure and temperature, and carry out a range of functions. A number of important internal and external components are present in each pressure vessel design. This article briefly explains the more common components in turn and the role it plays.
The outer body of a metal pressure vessel constitutes several different components:
- Shell: Usually a series of welded plates rolled and joined together along a horizontal or vertical axis. The shell is arguably the most important part of the pressure vessel as it maintains pressure and keeps potentially dangerous hydraulic fluids contained. Most pressure vessel shells are cylindrical in shape. Smaller vessel shells can be made from pipe.
- Inlet/outlet nozzles: The shell is penetrated by inlet and outlet nozzles at various points to allow the circulation of fluids. The nozzles are usually a combination of a machined flange and a piece of pipe designed to match the pressure rating. Alternative designs include self-reinforced single piece nozzles, small couplings, manways and specialist nozzles combining some form of dispersion device which might be a simple distributor pipe with various holes or a complex system of plates and plates.
- Supports: Various support components carry the weight of the vessel and reduce stress on the shell. Horizontal pressure vessels use two or more saddle supports, which are shaped components strategically positioned to bear the load of the vessel and components. Vertically orientated pressure vessels might use skirt supports – essentially a full or partial cylinder with a welded base plate. Alternatives include legs usually three or four in number welded near the base of the vessel and brackets where the vessel is not upheld at ground level but is braced and restrained from a superstructure.
Pressure vessels contain a range of internal components, which vary based on the function of the vessel. These can include:
- Internal or external supports: Large pressure vessels and reactors may include a network of supporting beams and rings, connected to the pressure vessel wall to prevent buckling or bulging.
- Internal walls: Walls might divide the pressure vessel into two or more chambers, each with ingress and egress points. For additional safety, some pressure vessels may feature a complete inner shell to preserve integrity in the event of emergency decompression or leakage.
- Vapour demister pad: In some pressure vessels a wire mesh demister plate usually circular is installed below the vapour outlet nozzle. The purpose is to lower the temperature of superheated vapour rising from the inlet diffuser and to encourage condensation into liquid form.
- Baffle plates: Baffles are used to divide pressure vessel chambers into smaller compartments or to act as internal weirs in order to direct the flow of pressurised fluids in the most efficient manner.
- Vortex breakers: These components are positioned on the inside of outlet nozzles to prevent the formation of a vortex as liquids or gases are drained away from the vessel. Foam and wave breakers play a similar function in preventing turbulence inside pressure vessels.
- Trays: Usually seen in columns or reactor vessels used for mass transfer – meaning stream, phase, fraction or component movement from one part to another, e.g. in distillation, separation and extraction.
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At Vessco we design and manufacture large, specialist pressure vessels for the heavy industrial manufacturing, nuclear power, water, chemical and oil and gas sectors. Each vessel is designed to meet specific operational requirements, with individual components crafted to maximise safety and efficiency. To discuss your project with one of our engineers, please call +44 (0) 1656 750 262 or email email@example.com.