Institution news
It is safe to say that serious fractures of pressure equipment are rare due to rigorous processes during design and fabrication. Nevertheless, pressure testing plays a vital role in a variety of industries to minimise risk, prevent equipment failure and to ensure the safe operation of a plant.
Pressure testing comes with the obvious risk of sudden release of energy due to a fracture of the components under test, as well as many other risks involved that are frequently poorly understood and planned for and, in turn, can lead to serious accidents.
Case study 1: Fatality during pressure testing at an offshore drilling rig
During a pressure test with nitrogen in 2009, a pressure relief valve vented and the reaction force from the valve caused the assembly to rotate through 90° and hit the deck of the rig. During the rotation, a member of the crew was struck on the head causing a fatal injury.
An investigation report concluded that the following key aspects had not been properly implemented:
- Exclusion zone
- Segregation of hazard
- Identification of pressure relief points
- Setup of temporary supports
Case study 2: Serious injury due to ruptured hose
In 2015, a test operator suffered multiple facial injuries and subsequent blindness after a hydraulic hose ruptured during pressure testing. The investigation showed that the following was not done properly:
- Implementation of safe systems of work
- Segregation and safeguards
- Maintenance and inspection of equipment used in pressure testing
Case study 3: Life-changing injury due to unsafe pressurisation
A life-changing accident occurred in 2017 because a component on a test rig was pressurised above the safe limit. This caused a hose and a metal fitting to whip round and strike a worker on the leg, leading to amputation. Appropriate pressure relief arrangements and safeguards could have prevented the injury.
What to do to mitigate the risks
Such accidents usually happen because there is either a lack of safe systems of work, or they are not followed when the people responsible for the testing do not fully appreciate the risks involved, typical failure mechanisms, and safeguards that should be utilised to reduce the risks.
Many companies operate by inertia, carrying out testing in the manner that they have always done and with more experienced members of the team training staff directly responsible for the tests predominantly on the job.
Although on-the-job learning has many benefits, there is a risk that several areas of knowledge may be left lacking, for example:
- Different types of testing available
- Types of failure
- Risks associated with pressure testing beyond the sudden release of energy from a failed pipe or vessel
- Correct documentation
- Use of pressure limiting devices
- Importance of correct equipment selection and operation
- Requirements for segregation and exclusion zones
To help mitigate risks and fill these knowledge gaps, the Institution has just launched a new training course focused on pressure testing, which explains the process and best practice, equipment and hazards associated with the test.
For more information, please visit imeche.org/training/pressure-testing