A boiler is a closed vessel in which fluid is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central heating, boiler-based power generation, cooking, and sanitation.
A safety valve is a valve that acts as a fail-safe. An example of safety valve is a pressure relief valve (PRV), which automatically releases a substance from a boiler, pressure vessel, or other system, when the pressure or temperature exceeds preset limits. Pilot-operated relief valves are a specialized type of pressure safety valve. A leak tight, lower cost, single emergency use option would be a rupture disk.
Deflagration is subsonic combustion in which a pre-mixed flame propagates through an explosive or a mixture of fuel and oxidizer. Deflagrations in high and low explosives or fuel–oxidizer mixtures may transition to a detonation depending upon confinement and other factors. Most fires found in daily life are diffusion flames. Deflagrations with flame speeds in the range of 1 m/s differ from detonations which propagate supersonically with detonation velocities in the range of km/s.
A boiling liquid expanding vapor explosion is an explosion caused by the rupture of a vessel containing a pressurized liquid that is or has reached a temperature sufficiently higher than its boiling point. Because the boiling point of a liquid rises with pressure, the contents of the pressurized vessel can remain a liquid as long as the vessel is intact. If the vessel's integrity is compromised, the loss of pressure drops the boiling point, which can cause the liquid to convert to gas expanding rapidly. BLEVEs are manifestations of explosive boiling.
A relief valve or pressure relief valve (PRV) is a type of safety valve used to control or limit the pressure in a system; excessive pressure might otherwise build up and create a process upset, instrument or equipment failure, explosion, or fire.
A containment building is a reinforced steel, concrete or lead structure enclosing a nuclear reactor. It is designed, in any emergency, to contain the escape of radioactive steam or gas to a maximum pressure in the range of 275 to 550 kPa. The containment is the fourth and final barrier to radioactive release, the first being the fuel ceramic itself, the second being the metal fuel cladding tubes, the third being the reactor vessel and coolant system.
An air handler, or air handling unit, is a device used to regulate and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system. An air handler is usually a large metal box containing a blower, furnace or A/C elements, filter racks or chambers, sound attenuators, and dampers. Air handlers usually connect to a ductwork ventilation system that distributes the conditioned air through the building and returns it to the AHU, sometimes exhausting air to the atmosphere and bringing in fresh air. Sometimes AHUs discharge (supply) and admit (return) air directly to and from the space served without ductwork
A forced-air central heating system is one which uses air as its heat transfer medium. These systems rely on ductwork, vents, and plenums as means of air distribution, separate from the actual heating and air conditioning systems. The return plenum carries the air from several large return grills (vents) to a central air handler for re-heating. The supply plenum directs air from the central unit to the rooms which the system is designed to heat. Regardless of type, all air handlers consist of an air filter, blower, heat exchanger/element/coil, and various controls. Like any other kind of central heating system, thermostats are used to control forced air heating systems.
Ducts are conduits or passages used in heating, ventilation, and air conditioning (HVAC) to deliver and remove air. The needed airflows include, for example, supply air, return air, and exhaust air. Ducts commonly also deliver ventilation air as part of the supply air. As such, air ducts are one method of ensuring acceptable indoor air quality as well as thermal comfort.
A blowdown stack is an elevated vent or vertical stack that is used to vent the pressure of components of a chemical, refinery or other plant if there is a process problem or emergency. A blowdown stack can be used to complement a flare stack or as an alternative. The purpose is to prevent 'loss of containment' of volatile liquids and gases. Blowdown from several systems may be combined in a blowdown header prior to the stack. A knock-out pot may be provided at the base of the stack to remove any liquids. Blowdown stacks may either be ignited or un-ignited. The height of the blowdown stack must be tall enough to ensure the safe dispersal of vapour.
Explosion protection is used to protect all sorts of buildings and civil engineering infrastructure against internal and external explosions or deflagrations. It was widely believed until recently that a building subject to an explosive attack had a chance to remain standing only if it possessed some extraordinary resistive capacity. This belief rested on the assumption that the specific impulse or the time integral of pressure, which is a dominant characteristic of the blast load, is fully beyond control.
A dust explosion is the rapid combustion of fine particles suspended in the air within an enclosed location. Dust explosions can occur where any dispersed powdered combustible material is present in high-enough concentrations in the atmosphere or other oxidizing gaseous medium, such as pure oxygen. In cases when fuel plays the role of a combustible material, the explosion is known as a fuel-air explosion.
A rupture disc, also known as a pressure safety disc, burst disc, bursting disc, or burst diaphragm, is a non-reclosing pressure relief safety device that, in most uses, protects a pressure vessel, equipment or system from overpressurization or potentially damaging vacuum conditions.
The term separator in oilfield terminology designates a pressure vessel used for separating well fluids produced from oil and gas wells into gaseous and liquid components. A separator for petroleum production is a large vessel designed to separate production fluids into their constituent components of oil, gas and water. A separating vessel may be referred to in the following ways: Oil and gas separator, Separator, Stage separator, Trap, Knockout vessel, Flash chamber, Expansion separator or expansion vessel, Scrubber, Filter. These separating vessels are normally used on a producing lease or platform near the wellhead, manifold, or tank battery to separate fluids produced from oil and gas wells into oil and gas or liquid and gas. An oil and gas separator generally includes the following essential components and features:
- A vessel that includes (a) primary separation device and/or section, (b) secondary "gravity" settling (separating) section, (c) mist extractor to remove small liquid particles from the gas, (d) gas outlet, (e) liquid settling (separating) section to remove gas or vapor from oil, (f) oil outlet, and (g) water outlet.
- Adequate volumetric liquid capacity to handle liquid surges (slugs) from the wells and/or flowlines.
- Adequate vessel diameter and height or length to allow most of the liquid to separate from the gas so that the mist extractor will not be flooded.
- A means of controlling an oil level in the separator, which usually includes a liquid-level controller and a diaphragm motor valve on the oil outlet.
- A back pressure valve on the gas outlet to maintain a steady pressure in the vessel.
- Pressure relief devices.
A shutdown valve is an actuated valve designed to stop the flow of a hazardous fluid upon the detection of a dangerous event. This provides protection against possible harm to people, equipment or the environment. Shutdown valves form part of a safety instrumented system. The process of providing automated safety protection upon the detection of a hazardous event is called functional safety.
A high-integrity pressure protection system (HIPPS) is a type of safety instrumented system (SIS) designed to prevent over-pressurization of a plant, such as a chemical plant or oil refinery. The HIPPS will shut off the source of the high pressure before the design pressure of the system is exceeded, thus preventing loss of containment through rupture (explosion) of a line or vessel. Therefore, a HIPPS is considered as a barrier between a high-pressure and a low-pressure section of an installation.
Hydrogen safety covers the safe production, handling and use of hydrogen, particularly hydrogen gas fuel and liquid hydrogen. Hydrogen possesses the NFPA 704's highest rating of four on the flammability scale because it is flammable when mixed even in small amounts with ordinary air. Ignition can occur at a volumetric ratio of hydrogen to air as low as 4% due to the oxygen in the air and the simplicity and chemical properties of the reaction. However, hydrogen has no rating for innate hazard for reactivity or toxicity. The storage and use of hydrogen poses unique challenges due to its ease of leaking as a gaseous fuel, low-energy ignition, wide range of combustible fuel-air mixtures, buoyancy, and its ability to embrittle metals that must be accounted for to ensure safe operation.
A blast damper is used to protect occupants and equipment of a structure against overpressures resultant of an explosion. The blast dampers normally protect air inlets and exhaust penetrations in an otherwise hardened structure. Blast dampers are related or identical to blast valves, the latter name is generally used to describe blast mitigation devices as they relate to nuclear explosions.
Surge control is the use of different techniques and equipment in a hydraulic system to prevent any excessive gain in pressure that would cause the hydraulic process pressure to exceed the maximum working pressure of the mechanical equipment used in the system.
Instrumentation is used to monitor and control the process plant in the oil, gas and petrochemical industries. Instrumentation ensures that the plant operates within defined parameters to produce materials of consistent quality and within the required specifications. It also ensures that the plant is operated safely and acts to correct out of tolerance operation and to automatically shut down the plant to prevent hazardous conditions from occurring. Instrumentation comprises sensor elements, signal transmitters, controllers, indicators and alarms, actuated valves, logic circuits and operator interfaces.
