Glossary Terms Book 1 Flashcards
Baffle
A wall, barrier or panel used to change the direction of flow of a liquid or gas. On the water side of a boiler, baffles may be used to direct the flow of water inside drums or headers. On the fireside of the boiler, baffles may be used to redirect the flow of hot combustion gases through banks of tubes. Fireside baffles are usually made of high temperature refractory material.
Drum
The boiler shell together with the heads form a drum to contain the fluid being heated. The term drum is normally applied to watertube boilers whereas the term shell is commonly used when referring to firetube boilers.
Economizer
Also used in large high pressure steam boilers to preheat the boiler feed water before it enters the boiler
Forced Draft Fan
This is the fan that blows air for combustion into the furnace through the windbox
Header
A larger pipe that supplies to or collects from a series of smaller pipes or tubes. It is also called a manifold
Heating Surface
This includes all parts of the boiler plates and tubes that have water or steam on one side and are swept by fire or hot combustion gases on the other side. The amount of heating surface a boiler contains is used to determine the kW or horse power rating of the boiler.
Mud Drum
This is the lower drum on watertube boilers where mud or sludge will collect and be removed from the unit. Also called a lower header
Stack
This is the hollow duct through which combustion gases are elevated for discharge to the atmosphere. It may also be called a smokestack or chimney.
Superheater
Used in large high pressure steam boilers to increase the temperature of the steam above the original boiling point temperature. It produces very dry steam
Uptake
The duct used to convey the spent combustion gases from the boiler proper to the stack. Also known as the flue vent or breeching.
Water Line
The actual level of water in a boiler. It is the point at which water and steam separate.
Watertubes
These tubes have water circulating inside the tube with heat being applied to the outside.
Combustion Chamber
The area of a boiler where air and fuel combine to cause burning. The combustion process should start and finish here. This is also called the “furnace” or “firebox”.
Combustion or Flue Gases
These are the hot gaseous products from the burning of the fuel
Gas Passage
These are the areas in a boiler through which the flue gases travel in order to transfer the heat to the boiler metal, then the water. One pass is the travel of the gases “once” along the length of the boiler. If the gases are reversed and pass through another section of the boiler, this is a second pass.
Water Legs
These are narrow water-filled sections found in some types of boilers. They usually are located around the furnace area to transfer more heat to the water in the boiler. Some types require extra support depending on the internal boiler pressure.
Dry-back Boiler
A firetube boiler that has brickwork or insulated metal at the rear reversing chamber to redirect the flue gases
Externally Fired Boiler
A boiler that has the combustion chamber located outside of the shell or drum and surrounded by brickwork. The first types of firetube boilers were constructed like this.
Firetubes
These are the smaller diameter cylindrical tubes through which the flue gas travels inside and are surrounded by water on the outside
Handhole
A handhole is a small hand-sized inspection, cleaning and maintenance port leading from the outside of the boiler into the pressure area of the boiler. A handhole cover assembly and gasket seals the port during operation
Heads
These are the steel plates that close off the ends of the boiler drum. Also referred to as end plates. They can be flat, curved, or dished. Curved heads are used on watertube drums whereas flat heads are used on firetube shells.
Internally Fired Boiler
A boiler that has the combustion chamber located within the shell of the boiler. Modern firetube boilers are constructed this way
Maximum Allowable Working Pressure (MAWP)
This is the pressure that the boiler has been designed to withstand while in operation. It is stamped on the boiler and must not be operated above this pressure. A factor of safety is also applied so the boiler can safely withstand pressures above this level.
Packaged Boiler
A boiler supplied by the manufacturer completely assembled and equipped including controls and mounted on its own base
Refractory
The protective insulation material that is applied to parts of the boiler to withstand high temperatures
Shell
This is the larger cylindrical section of a firetube boiler that contains the firetubes. An internally fired boiler would would also have the furnace inside the shell
Stays
Metal sections of various designs that are installed at various locations in firetube boilers to provide extra strength and support to flat surfaces. Areas to be stayed include tubesheets and water legs.
Steam Space
The space above the water line in a steam boiler where the boiling water and steam can separate from each other.
Tubesheet
Flat metal plates which close off the ends of the shell and to which the firetubes are attached. They require extra support or staying to prevent bulging from internal pressure.
Water Space
The portion of the boiler that is normally filled with water
Wet-Back Boiler
This is a firetube boiler that has a water-filled section surrounding the flue gas reversing chamber
Electrode
A conductor through which electric current is passed. It may be in the form of a wire, plate, or rod
Furnace Explosion
Occurs in a furnace when an accumulation of combustible gases ignites and explodes. A small furnace explosion would be termed a furnace puff
Steam Trap
A device installed on steam lines to remove condensate without allowing the loss of any steam. Some types may also be capable of removing air
Check Valve
A valve that has a hinged valve disc free to swing back and forth when pushed. If fluid passes in the flow direction, the disc is pushed open aned flow in not hindered. If the flow tries to reverse, the disc is pressed against the valve seat and flow is not allowed to reverse. In other words, this is a one-way valve. A lift check is another type of check valve
Conductivity
The term used to describe the ability of a fluid to conduct an electric current. This principle is used in the electric probe type of low water fuel cut-offs. Some types of dissolved solids must be in the water in order to conduct the current
Steam Stop Valve
This is the main valve on the steam line leaving the boiler. It must be able to positively stop the flow of steam from a boiler.
Altitude Gauge
A pressure gauge that indicates two pressures. Manually, it indicates the system pressure due to the vertical height of water which must be calculated, and also the actual water pressure produced by the circulating pump. The water pressure indicated on the gauge should always be higher than the calculated pressure due to the height of the water. In other words, the pump must produce more pressure than what will exist in the water lines due to the static pressure exerted by the water in the system
Hydronic Heating
Another name to describe a hot water heating system
Limit Controls
Controls that have their set point adjusted higher than the boiler operating controls setpoint. If, for any reason, the normal operating controls fail to limit the rise in temperature or pressure in a boiler, the limit controls will shut off the fuel supply to the boiler. Also known as “interlocks”.
Low-Water Fuel Cut-Off
A low-water fuel cut-off is a safety device or interlock that cuts off the fuel supply to the burner if the boiler water level drops below a safe level. This level should be showing in the gauge glass. Another term that is used is the Low Water Fuel Cut-off (LWFCO).
Gasket
A seal that fills the space between two piping faces to prevent leakage
Mercury Switch
Consists of a small glass bulb. Electrical contacts forming part of an external wiring circuit are mounted inside the bulb at either one end or both. The bulb also contains a small amount of mercury, which is used to open or close the electrical contacts inside the bulb. When the bulb is tilted to one side or the other, the mercury, being an electrical conductor, will open or close the circuit. Due to mercury being a carcinogen, its use is being discouraged.
Micro-Switch
A very sensitive electrical switch that operates by small movements of a lever. In the case of a LWFCO, it could be the movement of a bellows or a float movement connected to a lever. This switch is replacing mercury switches
Solenoid Valve
This is an electrically operated valve used on pilot and main fuel lines. It consists of an electrical coil into which a metal plunger can be drawn when current is applied to the coil. The plunger has a valve disk attached at the bottom that will open or close off the flow of fuel through the valve. When current is applied the plunger rises allowing fuel to flow through the valve and when the current is shut off, the plunger falls onto its seat by gravity closing off the flow of fuel
Aquastat
A control device used to regulate the water temperature in a hot water boiler and heating system. It would be function like an on-off control
Operating Controls
Controls that operate the combustion equipment on a boiler. Changes in steam or hot water demand from the boiler require a corresponding change in the firing rate of the boiler.
Flame Scanner
A device used to observe the flame in a boiler. If the flame is exstinguished for any reason, the flame scanner sends a signal to close the fuel supply valve to prevent a possible explosion
Thermocouple
A device used as a flame detector. It consists of two dissimilar wires welded together at one end to form a measuring or hot junction. When exposed to heat from the flame, a small voltage is generated, causing current to flow through the circuit. This keeps a solenoid valve open or allows it to close if there is a flame failure
Hydrostatic Test
A very common procedure performed on boilers. The unit is completely filled with water, making sure any air is removed. Then water (hydraulic) pressure is applied at 1 1/2 times the maximum allowable working pressure of the boiler.
Pressure Explosion
A term usually applied to the pressurized parts of the boiler. A ruptured tube or a crack that allows steam or water to escape to the point of the boiler requiring shutdown is considered a boiler failure.
Refractory
This is the protective layer of material that is applied to various parts of the boiler to withstand high temperatures and abrasion. It usually has an appearance similar to cement or bricks.
Thermal Shock
When strong internal stresses are produced in metal, such as when it is subjected to a sudden change in temperature.
Water Hammer
A series of shocks caused by a sudden change in velocity of water or other liquid flowing inside a pipeline. It should be avoided as it may become severe enough to rupture the pipe or pipe fittings.
Combustion Gases
These are the hot gaseous products from the fire. They are also called flue gases
Rattler
A rotating device used for vibrating scale off of the waterside (outside) of a firetube boiler, or the inside of a watertube boiler
Soot Blower
A device used to blow accumulated soot or ash off tubes and heating surfaces in a boiler. Air or dry steam issues from nozzles to dislodge the soot or fly ash as the soot blower traverses or is rotated to clear the deposit from a section of the boiler. Mainly used on high pressure oil or coal-fired boilers
Tags
When valves or equipment are out of service, tags are applied to warn operators not to open or put the equipment into operation. Tags are very important when maintenance is being performed in a plant
Relative Density (specific gravity)
The ratio of the mass of a certain volume of oil to the mass of an equal volume of water. Above 1=heavier than water; less than 1=lighter than water
Viscosity
Measure of the internal resistance to flow of the oil. Thick is high viscosity, while thin is low viscosity. Usually expressed in Saybolt seconds universal (SSU) which is the number of seconds it takes a stipulated quantity to pass through a restriction at some stipulated temperature
Flash Point
The lowest temperature at which the fuel oil gives off enough vapour to ignite when exposed to an open flame but not continue to burn
Fire Point
A temperature above the flash point which results in the fuel continuing to burn once ignited. As a guideline, Flash Point +25C (+50F) = Fire Point
Balanced Draft
This is a draft system on larger boilers that has both a forced draft fan and an induced draft fan
Excess Air
This is the amount of air in excess of the theoretical air required for complete combustion
Induced Draft Fan
This is the fan used to draw combustion gases out of the boiler, and blow them up the stack
Stack
This is the vertical hollow duct through which the combustion gases are elevated for discharge to the atmosphere. It may also be called a smoke stack or chimney
Theoretical Air
This is the amount of air that is theoretically required for complete combustion
Windbox
This is the box surrounding the burner damper on a boiler. The fan blows combustion air into the box and the damper regulates and directs the air into the burners
Flange
A projecting disc-shaped collar on an object for attaching it to another object
