Pressure Vessel Inspection
A pressure vessel contains product under pressure or vacuum. As they are under pressure or vacuum, pressure vessels are potentially dangerous should they fail. Technical standards specify how pressure vessels are constructed to ensure they are safe in use. Pressure Vessel Inspection is a detailed review of the vessel to ensure it complies with the technical standards.
Pressure Vessels can be dangerous if faulty
The immense expansion of released energy from a pressure vessel can lead to devastating damage to plant and lives can be lost. Even a simple compressed air cylinder can explode, and they do.
In 2008 two guys lost their lives when a pressure vessel operating with compressed air exploded here in Australia.
In refineries and mineral processing plants, in hospitals, dry cleaners wineries, your local tire dealer, autoclaves at Kentucky Fried Chicken, pressure vessels are everywhere in our daily lives.
A pressure vessel can be essentially a simple canister to store contents under pressure. They can also be a very complex processing structure. The vessel may weigh hundreds of tons and be connected to a varity of pipe systems, other pressure vessels and boilers.
A pressure cooker is a pressure vessel
The common pressure cooker used in many homes is also a pressure vessel. We have seen the nasty burns inflicted when a simple gasket fails on a pressure cooker. A large industrial pressure vessel would have many times more the destructive potential in an industrial accident.
To make matters worse in many industries the contents under pressure in a pressure vessel are highly volatile, hazardous, may be lethal, and often highly flammable.
Pressure Vessel Inspection
Qualified and competent engineers and inspectors are required to assess the safe operation of each pressure vessel. This begins at the pressure vessel design, and the manufacturing. A Pressure Vessel Inspection at the manufacturing phase is quite different to the In-Service Inspection.
A pressure vessel design must be registered with Work Safe prior to manufacture. Refer: Application for registration of a Pressure Vessel
A manufacturer can be fined $60K for beginning to manufacture a pressure vessel without an approved design. At manufacture, quality systems and Inspections are required. These ensure the materials used and manufacture techniques and skills are managed to produce a compliant item of plant. This must be in accordance with the design that will safely provide the intended production service.
Imported Pressure Vessels.
If the pressure vessel is manufactured off-shore and imported, the importer becomes responsible and liable under the WHS Act as the manufacturer.
Irrespective of the manufactured location, evidential documentation records and inspections are required to prove materials and manufacturing of that pressure vessel is compliant with the registered design.
An Inspection and Test Plan (ITP) is used in conjunction with the Manufacturers Data Records (MDR) to accurately record the manufacturing processes. This is a lawfully binding record of manufacture for this pressure vessel and is to be transferred to owners with the vessel. Any repairs or alterations to the pressure vessel are required to be recorded in this record
Manufacturing Pressure Vessels to comply with standards
The skills knowledge, expertise and qualifications of an Inspector at the manufacturing phase is quite different to the In-Service Inspector. At manufacture, it is essential that an experienced pressure vessel designer produces a suitable design.
The welding engineer makes the determination of the correct fabrication and welding of that pressure vessel design. A design verifier is required to verify that design. In production, the welding engineer is required to control manufacture for material ordering to shipment of the completed vessel.
The Qualified welding Inspector verifies the entire process. Only here in Australia are certified level personnel able to conduct welding design functions in welding. Every other country in the world weld design is a function of a qualified welding engineer.
It is a bit of a hangover of the old Australian ‘she’ll be right mate’ that it continues in Australia. There are non-accredited not-for-profit organisations conducting inspections in Australia. Again only in Australia can they get away with this. In any other country an accredited Inspection Body is engaged to conduct independent 3rd Party Inspection.
For design and inspection the volume and pressure, the processes and type of product under pressure are all considered to determine hazard level of the pressure vessel.
Pressure vessel location is also important
The location of the vessel is assessed. Is it used as a transportable vessel on our roads and rail tracks, or is it housed in a refinery with lethal or flammable contents adjacent to other highly hazardous pressure vessels. What’s the knock on affect, the consequence of failure?
Pressure vessels are often used in companion with other plant to store or process products in production and manufacturing processes.
Standards and codes determine what must be considered in a process of design, registration, and Inspection in accordance with Work Safe in Australia, and similar directives in other countries.
The In-Service Inspection begins at the commissioning of pressure vessels for operation. In-Service Inspection includes the inspection of pressure vessels, boilers, and certain classes of pressure pipe systems that may interconnect items of pressure plant.
The Work Safe regulations define via various standards and codes the responsibilities of pressure vessel plant owners in the commissioning, the operation, the maintenance and the In-Service Inspection of pressure vessels.
Standard require that In-Service Inspectors must be suitably qualified and competent, and engaged by an Inspection Body. That Inspection Body must operate under a quality system ISO 17020, and should be NATA accredited in Australia.
In-Service Inspection is a very complex process, dependent on many variables by definition of the varied types of pressure plant in operation. The diverse range of products and processes operating under pressure in pressure vessels, the corrosion mechanisms and process variables, operating temperatures that affect the safe operation of the pressure vessels, all contribute to a complexity that requires highly skilled, competent and experienced engineers to manage plant integrity, and ensure the necessary and statutory In-Service Inspections are conducted and reported correctly by an accredited Inspection Body.
Anyone can hang a shingle out and say ’I’ll take a look at that for you’. There are many people inspecting pressure equipment that are not operating in accordance with the standards. This brings about a risk to the plant owner who will be liable in the event of an incident. The person conducting the inspection will be found liable, and if not operating in accordance with the standards may be found negligent. The regulations call for very significant fines and jail terms for negligent actions in relation to the safe operation of pressure vessels.
Owners of pressure plant, or PCBU acting as an agent for the owner of pressure vessels have a duty of care to be aware of their obligations under the Work Health Safety Act in all states and territories of Australia and New Zealand. This includes that they ensure that employees are suitably trained to manage the safe operation of pressure plant. Persons who conduct an inspection without compliance to the standards are operating unethically, misleading their clients into a false sense of security.
Unethical conduct by engineers and Inspectors can be a cause to have credentials withdrawn.
Agent for the owner
A PCBU conducting service on pressure vessels and pressure systems is acting as an agent for the owner. As such the agent for the owner can be liable if that pressure vessel is found to be non-compliant.
As an example we see service repair guys telling owners that safety valves do not need replacement. In fact the standards are very clear on the repair or replacement requirements for safety valves, and pressure reducing devices.
In the event of a failure the owner will be found liable if the safety devices are not compliant, and the agent of the owner may be called to account by the owner.
If the In-Service Inspection Body records on report a corrective action for an item of pressure plant, the owner needs to action that correction rather than seek opinion of nonqualified service technicians.
Repairs to pressure vessels
The pressure vessel has been designed for safe operation. Changes to that design must be registered with Work Safe. Any repair work is to be conducted by qualified and competent personnel.
Minor repairs may be conducted where the pressure vessel design is not altered. A like for like repair where all design elements including the materials remain as per the registered design.
A welding engineer is responsible for all weld repair elements to the vessel.
Any repair considered that may alter design elements of the vessel may require design, design verification, and reregistration of the design.
Any repair at all is to be conducted in accordance with all relevant codes and standards with all welding records, ITP and MDR records maintained for the vessel life.
Persons conducting repairs to pressure vessels, boilers and pressure pipe systems take on the role of manufacturer as prescribed under the respective codes and standards, and are liable for that repair work conducted for the life of the vessel.
Repairs to pressure vessels have contributed to pressure vessel failures and fatalities. The Dry Powder Vessel that exploded and killed two guys in Broome 2008 had been weld repaired.
Imported Pressure Vessels
Given the massive down turn in manufacturing in Australia over the past 40 years, most pressure vessels are now imported.
We often see imported vessels that simply do not comply being imported, installed and operational without any regard to the Australian standards. Tool shops are importing air receivers and selling them without regard for compliance.
People are buying pressure vessels unaware of regulatory requirements.
There is no excuse for negligence in the event of an incident with the air receiver or the tools hanging off that air receiver, or processing plant.
The importer may be liable under the WHS Act as the manufacturer. The owner is certainly liable.
Boilers used to generate steam can range in size from that coffee machine at you favourite café, to large power station boilers that generate super-heated steam to drive the turbines that generate electricity.
Back in the day steam trains, ships and traction engines were common place, with the only means of propulsion being the steam engine power.
Under extreme pressure due to the rapid expansion of the stream, boilers can be very dangerous. When a boiler explodes the results are catastrophic.
Just look at how excited the kettle gets as it comes to boiling and releases steam when you make your next cuppa.
As a result of the disastrous effects of exploding boilers on steam powered engines the Boiler codes were developed in the early 1900’s to ensure boilers were manufactured, operated and inspected for safe operation.
Since the introduction of boiler codes the frequency of explosions has reduced. Incidences have not entirely stopped however as can be seen in news events and on google, largely due to a failure to adhere to safe work guidelines in boiler codes and standards.
The Inspection of boilers begin at manufacture, and continue for the complete life cycle of the boiler.
In detail the design of the boiler and its components, many of which are pressure vessels, the materials used and the manufacturing processes are defined in various codes and standards.
It is essential that competent independent Inspection is conducted throughout the life cycle to ensure the boiler is constructed and operated safely.
Statutory requirements are in place in every state and territory both nationally and internationally for the safe operation of boilers and the associated pressure vessels, and pressure pipe systems.
Therefore the plant owner, agents for the owners, the PCBU’s, engineers, operators, the Inspection Bodies all have a duty of care and responsibilities to maintain compliance.
Very significant legal consequences are prescribed for a failure to comply, including very hefty fines and jail terms.
To comply with regulatory requirements Boilers are inspected every year.
The process of inspection is very extensive. External inspections are conducted while the boiler is live and operating looking for any unusual parameter, leaks, vibrations, corrosion, and so on.
Then the boiler needs to be decommissioned, key elements and components stripped and repaired for a dry inspection. When re-built the boiler operation and all safety devices are tested for operation, including flame out shut downs, alarms for low water, water treatments, and absolutely essential pressure reducing devices, or safety valves are tested at maximum operating pressures. Only when the boiler is deemed to be safe to operate is a certificate issued.
The costs of Inspection is directly relevant to the size and ‘horse power’ of the boiler and associated equipment.
A small package boiler may be a few hundred dollars to inspect, plus the service and any repairs costs.
A power station boiler plant will be tens of thousands of dollars for the complete shut-down work scope
At the end of the day a very small price to comply with regulatory requirements and operate the boiler safety.