Low Pressure Boilers Ch 7
Non-adhering sludge is best removed when the boiler is ___.
under light load
Priming and carryover can be caused by opening the main steam valve too quickly.
True
Priming and carryover can lead to water hammer and possible pipe rupture.
True
Rusting of the boiler metal is caused by oxygen in the boiler water.
True
Scale acts as an insulator and slows down the transfer of heat to the water.
True
Scale formation can result in an increase in fuel required to generate steam.
True
Sodium sulfide is an oxygen scavenger that is commonly used to treat boiler water.
True
The bypass feeder is located on the main steam header to provide efficient feeding.
True
Automatic valves are used to control the amount of chemicals added by the bypass feeder.
False
Corrosion is the accumulation of sludge on boiler heating surfaces.
False
Oxygen in the boiler water is used to remove non-adhering sludge.
False
Scale and sediment cause pitting of the boiler metal surfaces.
False
Sludge is removed from the boiler using the surface blowdown valve.
False
Sludge rises when the boiler is on light load and is removed using the try cocks on the water column at the NOWL.
False
Slug feeding is used to generate foam to prevent carryover.
False
The chemicals used to treat the boiler water depend on the pressure inside the boiler.
False
Water that contains a small quantity of minerals is hard water.
False
Well water requires chemical treatment but city water does not.
False
___ is a condition caused when steam bubbles are trapped below the boiler water surface.
Foaming
A boil-out procedure is performed when a new boiler is installed.
True
Boiler water treatment is required for makeup water introduced to the boiler.
True
Boiler water treatment required for most low pressure boilers is minimal if the boiler recovers all or most of the condensate returns.
True
Chemicals added to the boiler water change scale-forming salts into non-adhering sludge.
True
Dissolved solids are impurities such as calcium, silica, and iron dissolved in solution.
True
Fuel oil contamination of the boiler water can be prevented by dumping all fuel oil heater returns to waste.
True
Fuel oil contamination of the boiler water most commonly occurs in plants using No. 6 fuel oil.
True
Oxygen in the boiler water can be removed by adding sodium sulfite.
True
___ is the exposure to highly alkaline elements, causing boiler metal corrosion at stress zones.
Caustic embrittlement
___ in the boiler water causes corrosion and pitting of the boiler metal.
Oxygen
___ can lead to water hammer.
Priming, Carryover, & High surface tension
___ is used as an oxygen scavenger to remove oxygen from the boiler water.
Sodium sulfite
Overheating of heating surfaces results in ___.
bags, blisters, & burned-out tubes
Non-adhering sludge is removed from the boiler by using the ___.
bottom blowdown valve
In low pressure boiler operation, chemicals for reducing oxygen and preventing scale can be added using a ___.
bypass feeder
Small particles of water carried into steam lines are called ___.
carryover
Fuel oil is removed from the steam and water side of a boiler by using ___.
caustic soda
High surface tension on the boiler water is shown by ___.
fluctuation in the gauge glass
Increased surface tension of boiler water can be caused by ___.
fuel oil inside the boiler
Water that contains large quantities of minerals is called ___.
hard water
Water is ___ to reduce the amount of oxygen.
heated
Hard water contains ___.
scale-forming salts
Scale is caused by ___.
scale-forming salts, hard water, & mineral deposits
