Pressure Vessel Risk Management: Know the Different Hazard Levels and Chemical Leak Causes to Avoid

November 8, 2021

Pressure vessels must be assigned one of five possible hazard levels. Just as the AS 43434:2014 standards state, these rating act as essential warnings. They tell everyone who approaches the fluid-charged enclosures that a potential hazard is contained, and it also classifies that hazard. Hazard Level A is the most dangerous, which means Hazard Level E is the least dangerous pressure containment condition.

Pressure Vessel Warnings: Hazard Level Classifications

Again, Hazard Level A is the most dangerous, Hazard Level B the second most dangerous, and so on, until we reach Hazard Level F. Using the criteria covered in the aforementioned AS standards chapter, those letters are pre-assigned. But what factors influence and affect the levels. That's something every engineer and technician should know, even if they don't have access to a copy of the guidelines and categories.

• Hazard level A - Large pressure vessels
• Hazard level B - Shop manufactured vessels
• Hazard level C and D - Low and extra-low pressures
• Hazard level E - The hazard is negligible

Again, the ruling standards are found in the AS 4343:2014 guidelines. Committee audited, those standards must be adhered to by the fabrication service and the installation engineers, plus the site managers. Stamps and labels are assigned with the levels, plus a certification. To deviate from this procedure is to risk a hefty fine. Worse still, though, poorly followed hazard level procedures risk catastrophic incidents.

Common Causes Of Chemical Leaks In Pressure Vessels

Overpressure Failure

Pressure vessels are designed to contain rated fluid stresses. If the tank geometry and weld seams are held to the rated design limits, leaks are unlikely. On the other hand, if the unit is exposed to higher fluid stresses, the possibility of a chemical leak looms large. Weld seams and sheet metal tolerances become dangerously stressed when overpressure incidents are tolerated. That's a bad enough practice in a hot water device, but it's so much worse if the under-pressure medium is a corrosive chemical.

Chemical Corrosiveness

The next pressure vessel has been fabricated by the latest engineering codes, yet a leak has still developed. Let's head back to the laboratory and model the incident. The wall thickness is adequate and the seams are perfectly applied, so why is a steady trickle of caustic liquid pooling on the ground? Well, perhaps the alloy seams aren't fully reinforced. Perhaps the alloy walls are not stress-fracture free. Aggressive compounds just need the tiniest chink in a vessel's armour plating to begin their corrosive efforts.

Material Incompatibilities

The wrong gasket material has been sourced. Now the leak is entirely bypassing the pressure vessel. Even though the storage unit has been built to handle all conceivable chemical incidents, the fittings and extraneous parts around the tank are letting the whole showdown. It's like using a steel door on a walk-in safe when the adjacent walls are made of soft plaster. The hardened door isn't going to fail, but the same can't be said for those soft walls. If the pressure vessel is robustly fabricated and designed to handle all chemical loads, then its fittings must adhere to that same code-ratified convention.

Contact Details

Fusion - Weld Engineering Pty Ltd
ABN 98 068 987619

1865 Frankston Flinders Road,
Hastings, VIC 3915

Ph: (03) 5909 8218

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