What is a Pressure Vessel, and how is it defined?

They are industrial equipment designed for accumulation or process, which, given their construction characteristics, can be designed to withstand certain internal and/or external pressures. The design spectrum is very wide, from very low temperatures that work close to minimum levels for metals to high levels and throughout their pressure range.

Within what is known as subject or pressure devices there are many types and many industries that use them. The most common, to name a few, are: liquid separators, free water, economizers, liquid receivers, separators in general, hydraulic storage tank, filters, among others. Taking into account the variety and versatility in the market, it is to be imagined that there are different sizes, diameters, lengths and thicknesses depending on the manufacturing material. The most common construction materials are carbon steel and stainless steel, depending exclusively on the service. For example, work with food or highly corrosive fluids, water with contaminants or gas with carbon dioxide content are usually made of stainless steel. While, in other cases, due to the cost-benefit ratio, carbon steels are chosen. Taking into account the type of service, both internal and external coating tasks can be carried out or, what is known as "

cladding”, being able to manufacture a team entirely in carbon steel and attaching a “cladding" stainless steel.

The most common shapes of the envelope or body found on the market are: cylinders, spheres or cones. While the ends, in the case of cylindrical enclosures, elliptical, hemispherical, conical or flat heads are usually used, constituting the most frequent designs in the industry.

Some standard containers and others designed by ASME are offered on the market, with ASME VIII being the mother standard for this case. However, many times, more than one standard is used for its design and there are several organizations authorized to manage the authoritative codes, such as the American Society of Mechanical Engineers and the Union Pressure Equipment Directive European.

At a minimum, a device with these characteristics of having a connection for the entrance and another for the fluid outlet, other connections for the necessary instrumentation and for security measures added. In general, these teams have PSV or PRD (for its acronym in English: “Pressure Safety Valve" either "Pressure Relief Device”) what is known as safety valve and relief devices.

In addition, depending on the use, they have alternative discharge outlets or drains in the lower area and vents in the upper area. Likewise, in relation to the inspection codes that apply for their evaluation of remaining life and aptitude for service, the Containers have inspection nozzles and "manhole" or passage of man, mouth used for inspection, maintenance and cleaning of the unit.

This type of asset is subjected to extensive quality tests, from hydraulic pressure tests or tests hydrostatic, to evaluation of the quality of the materials, analysis of welds and the efficiency of board.

Classification

There are different ways of classifying the containers, since by their use we can divide them according to whether they are solely for storage or have a specific function in the process. On the other hand, if we classify them by their shape, broadly speaking, we have horizontal, vertical and spherical containers.

Storage containers are used to have a certain stock in the event of an unscheduled plant stoppage or to carry out maintenance tasks on a certain line. Typical case are the famous "zeppelin", for its typical shape. This equipment is often sought for its storage to be limited to certain values, since, if it is a flammable product, its fire load can be high.

On the other hand, in the case of process vessels, there is a very wide range of typologies ranging from heat exchangers, distillation towers, fractionation columns, reactors to separators liquids.

In the case of the shape of the container, when one speaks of "spheres" given its cylindrical shape, one speaks of equipment designed, for the most part, for storage. In the refinery industry, you can see this equipment for the storage of natural gas, butane or hydrogen. Instead, both horizontal and vertical cylindrical bodies are used for processing. The horizontal position equipment is mounted on saddles while the vertical equipment is mounted on legs or tubes and skirts.