As a pressure vessel owner, you should be aware that along with the regular in-house surveillance of the vessel, every two years, an inspection must be carried out to ensure to safety and optimal functionality of your equipment. This inspection is supposed to be done by a professional, qualified to assess the function of your specific pressure vessel.

With this in mind, have you ever fully understood what these professionals are looking for during the inspection? Well, here is a sneak peak at what takes place during a pressure vessel inspection.

External examination

This is usually a visual examination of the pressure vessel's exterior. What they are looking for here is any cracks, dents or bulges along the sides of the vessels, as well as corrosion of the metal. Cracks, for instance, can cause high stress concentrations which will cause the wall thickness of the vessel to decrease, thereby compromising its functionality and safety. These can be fixed by welding or patching up the crack.

Speaking of wall thickness, this is also part of the external examination of the pressure vessel. It is done using ultrasonic testing equipment to check if the wall and the vessel's head are thinning. Thinning is of concern, since it will affect the efficiency of the pressure vessel as well as its safety, since cracks can easily be formed on thin walls.

Another thing they examine is the external covering of the pressure vessel. These can be peeled off sometimes in order to examine the quality of the metal underneath as well as that of the covering. This is important for vessels such as boilers where the outer coating functions as insulation since any compromise on the coating will affect the functionality of the boiler.

Structural attachments to the pressure vessel must also be looked into to ensure that they allow for expansion and contraction adequately. Therefore, there should be enough room in the pre-drilled bolt holes to allow for these changes. Support structures that hold the pressure vessel in place are also examined for cracks or distortions during this examination.

Internal examination

This is done before the vessel has been cleaned out in order to check for scale deposits. These deposits adversely affect the efficiency of the pressure vessel by impeding heat transfer, thereby increasing the operating costs.

The areas near drains and openings are also examined for corrosion or cracking, which may not be evident from the external examination. Quick opening closures are also examined for wear and functionality, along with any other connections to external areas such as manholes.

Should your pressure vessel have internal components, these are usually examined as well. However, if the wall thickness taken during the external examination shows no change, then most times the internal examination is overlooked.