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  • Nadirsha Shahabudeen

Brief note on Pressure Vessel inspection

As pressure vessels are meant for challenging conditions of environment the way of inspection must be spotless. A decision on inspection not taken seriously creates havoc in the whole structure. The things to be taken into account are that are instructed by ASME standards.

For an outsider every pressure vessel seems similar but it tend to change in accordance with the application. Every pressure vessels are similar in shape with rounded edges or are spherical. These shapes are desirable because it avoid stress raisers. The common accompaniments of a pressure vessel include a pressure gauge, fusible plug and pressure switch, which are equipped to control the compressor and to turn off when pressure is at max. In a pressure vessel there are manhole, hand hole or sight hole for general cleaning and inspection purposes. Some pressure vessels would have a condensate drain to release the moisture, depending on the material moisture trapped in the tank can cause corrosion or pitting.

As pressure vessels are meant for challenging conditions of environment the way of inspection must be spotless. A decision on inspection not taken seriously creates havoc in the whole structure. The things to be taken into account are that are instructed by ASME standards.

There are two kinds of inspections they can be internal and external. Internal inspection is conducted when the pressure vessel is not working. This kind of inspection includes identifying wear and tear and corrosion around components such as vessel connections, welded nozzles and seams. In the case of external inspection, it is done while the vessel is under operation. This inspection includes Inlet piping, vessel connection and outlet piping.

The frequency of the inspection depends on the functional operation of the vessel. For instance vessels that store hazardous content may require a regular inspection than that contains safer fluids. Heating boilers may require external inspection once in every three years, also vacuum vessels requires inspection every five years.

Inspection is not merely external and internal there are different types of pressure tests such as

  • Hydrostatic tests: Hydrostatic testing is a type of pressure test in which the components is completely filled with water, removing the air contained within the unit, and pressurizing the system up to 1.5 times the design pressure limit of the unit. This is one of the way in which vessels such as boilers and fuel tanks are tested for their leaks.

  • Pneumatic Tests; The pneumatic strength test uses air, or an inert gas medium such as nitrogen, to pressurize the system to 110% of its designed pressure limit. The purpose of pneumatic strength testing is to verify that a system may be safely subjected to its maximum operating pressure by testing it beyond its designed pressure limit. Pneumatic tests are only allowed on vessels in which water filling is prohibited.

  • Leak Tests: The leak tests can locate leaks, verify performance and confirm the strength and durability of the pressure vessels. The leak tests are conducted to ensure the permissible leak specified in the document.

  • Mechanical Integrity Tests: Mechanical Integrity can be defined as the management of critical process equipment to ensure it is operated and maintained properly. These are mainly conducted for instability of vacuum pressure vessels or buckling.

Maintenance of pressure vessels

Pressure vessel maintenance improved its standards over the course of time in order to reduce the risk of pressure vessel failure. Maintenance of a pressure vessel includes repair and replacement of worn out parts of a vessel.

  • Preventive maintenance is recommended for every manufactures. This is performed ritualistically to avoid the breakdown of vessels.

  • In Breakdown maintenance it is performed when the pressure vessel experience an unforeseen defect.

  • Periodic maintenance is mostly recommended by the manufacturer and performed as per the recommendations.

Universal Engineering’s professional design engineering services wing offers design and detail engineering services for the clients in Oman, Saudi Arabia, Kuwait, Qatar, Bahrain and UAE. We are experts in Pressure vessel design, Stress analysis of piping, structural design, ASME Joint review, Design of Storage tanks, code calculations, FEA/FEM, and spotless service on design management.


The content of this article is taken from web open source. The blogs are intended only to give technical knowledge to young engineers. Any engineering calculators, technical equations and write ups are only for reference and educational purpose.

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