9. Boiler Pressure Vessel Safety Flashcards
What is a pressure vessel?
A relatively high-pressure component, with a greater cross-section than the associated pipe/tubing capable of storing, distributing, or handling a gas/vapour/liquid under pressure.
In a pressure vessel, what is considered low/intermediate/high pressure?
Low pressure = gas <150psi or liquid <1500psi
Intermediate pressure = gas between 150 and 3000psi or liquid between 1500 and 5000psi
High pressure = gas >3000psi or liquid >5000psi
What are the four main types of boiler found in the workplace?
- Fire-tube boilers
- Water-tube boilers
- Tubeless boilers
- Electric boilers
What are fired and un-fired pressure vessels?
Fired pressure vessels are essentially boilers, and include combustion.
Un-fired pressure vessels, are pressure vessels that are not connected to any flames. These can be positive or negative pressure vessels.
What are the three basic elements/components of a basic boiler?
The vessel or shell itself
A series of tubes that pass through the vessel
A heat source (burner or electrical element)
What is a fire-tube boiler?
The vessel contains water.
A fuel burner produces hot gasses that are passed through tubes in the vessel.
Typically smaller, operating at pressures up to 150psi.
What is a watertube boiler?
Water filled tubes run through the vessel.
The burner fills the vessel with hot gases.
Watertube boilers can be very big, and operate at pressures greater than 3,500psi
What are electric boilers?
Electric boilers use electrical elements to heat water.
They can be extremely small and highly-efficient.
Electric boilers are common in HVAC systems.
What are the two types of unfired pressure vessel?
Thick-walled.
Thin-walled.
Neither is typically portable.
*Portable pressure vessels (compressed gas cylinders) are the arguable third type, because they are portable.
What is a thin-walled pressure vessel?
An unfired pressure vessel, which may be positive or negative pressure.
The vessel diameter is 10 times (or greater) than the wall thickness.
What is a thick-walled pressure vessel?
An unfired pressure vessel, which may be positive or negative pressure.
The vessel diameter less than 10 times than the wall thickness.
Compare/contrast pressure vessels and boilers.
Pressure vessels hold liquids, gases or both under pressure.
Boilers hold a liquid, that is heated. Boilers often have to withstand high pressure, in which case the boiler would be considered a pressure vessel.
List 4 examples and purposes of pressure vessels in the workplace.
- Storage of compressed air for pneumatic tool operation.
- Storage of pressurized liquids for dispensing into a production process.
- Storage of compressed gasses for use in medicine.
- Vacuum trucks used for cleaning drains and pipes.
List 4 examples and purposes of boilers in the workplace.
- Industrial kitchens
- Building heating systems
- Pulp/paper manufacturing
- Autoclaves for medical sterilization
What is a tubeless boiler?
A vessel containing water is heated from an external flame.
What direct OHS hazards are associated with failure of a pressure vessel?
- Sudden release of pressure
- Sudden release of materials under pressure
- Flying pieces of the vessel and associated components
What indirect OHS hazards are associated with failure of a pressure vessel?
- Release if materials that are harmful to the environment
- Worker exposure to combustion exhaust gasses
- Confined space hazards associated with workers entering pressure vessels
What are the four basic known causes of pressure vessel accidents?
- Failures from corrosion
- Material failures from stress
- Incorrect burner firing and shutdown
- Failure of safety devices
Who regulated pressure vessel safety?
In BC: Technical Safety BC.
Usually a quasi-government agency that is not the OHS regulator.
What is ASME?
American Society of Mechanical Engineers
Name two key mandatory design standards for pressure vessels.
ASME boiler and pressure vessel code 2019
CSA B51
List a control to prevent each of the four basic known causes of pressure vessel accidents?
Corrosion:
correct material, anticorrosion chemicals
Stress Failure:
correct design, manufacture, installation, operation and repair
Incorrect Burner Firing or Shutdown:
operator training, correct design
Failure of Safety Devices:
correct design and operation, inspection and maintenance
What is the three-pronged approach to reduce the risk of hazards associated with pressure vessels?
Safety by design & design standards
Mandatory standards (installation, inspection, maintenance and repair)
Mandatory education and training for operators
What key safety information is covered in the ASME boiler and pressure vessel code 2019, and CSA B51?
Requirements for explanatory nameplate
Safety device requirements
structural strength requirements
qualifications of those who manufacture, install or repair
Required registration of pressure vessels with regulators
Inspection requirements
What regulation primarily covers pressure vessels in BC?
The Power Engineers, Boiler, Pressure Vessel and Refrigeration Safety Regulation.
(PBPR Regulation)
Who enforces the PBPR regulation?
The Power Engineers, Boiler, Pressure Vessel and Refrigeration Safety Regulation is enforced by Technical Safety BC.
What is a chief engineer, context pressure vessels?
A power engineer, designate by the owner, to be responsible for operation and maintenance of a plant.
Responsible for ensuring regulated work is performed by qualified persons.
What is a shift engineer, context pressure vessels?
A power engineer, under a chief engineer, who is in charge of a plant when the chief engineer is not present.
What are the safety duties of power engineers operating boilers?
To inspect every boiler, pressure vessel, and associated parts as soon as practicable after starting shift.
How are plants classified (context pressure vessels)?
Plants are classified by the type and capacity of the boilers.
List four legal operations of boiler owners.
Owners must hold and post a valid operating permit.
Owners must designate a chief engineer, and shift engineers for then the chief is away from the plant.
Owners are responsible for the safety of all employees.
Owners must apply for a new permit if there are changes that may re-classify a plant.
What are the three main categories of safety devices in pressure vessels?
Gauges, alarms, etc.
(alert operators to problems)
Automatic intervention devices
(Monitors that automatically intervene in an emergency)
Pressure relief devices
(mechanical pressure relief devices)
What are the three basic types of pressure relief devices (context pressure vessels)
Reclosing
(open when pressure high, closes once pressure reduced)
Non-reclosing
(opens when pressure high, but must be replaced or manually closed )
Vacuum
(opens when interior is under-pressure and re-closes once pressure increases.
List three types of reclosing pressure relief valves.
Safety Valves
Gas & vapour valve that opens at a set pressure, and closes at a lower pressure. Part of normal operation and safety release.
Relief Valves
Liquids valve that open and close at a set pressure. Regularly open/close during operations. Not true safety device.
Safety Relief Valves
Liquid, gas, and vapour valves that pen and close rapidly for safety relief.
List three types of non-reclosing pressure relief devices.
Rupture discs
Pin devices (Pins hold a plug in place and break or buckle under excess pressure)
Fusible plugs
(melt under heat to allow venting)
What are pressure vacuum relief devices (context pressure vessels)
When the pressure inside the vessel is excessively low relative to the external pressure, the device opens to equalize pressures within acceptable levels.
Briefly summarize the role of the ASME Boiler Code and CSA B51 in pressure vessel safety programs.
The ASME Code and CSA B51 most importantly provide mandatory requirements for:
- pressure vessel design
- manufacture, installation, inspection, maintenance, and repair of pressure vessels and their associated component
