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18 Cards in this Set
- Front
- Back
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The cut-off switch opens and cutes off power to the fuel valve when the boiler level in the glass shows at least _________ of water. |
20mm |
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A small steam heating boiler with a combination low water cutoff and feedwater control must, by code, have a second, dedicated: |
low-water cutoff |
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In some, unattended heating boilers the low-water cutoff also helps maintain water level by opening a/an _______________ before low water level is reached. |
electric feeder valve |
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In a well balanced steam system with condensate return: a) steam produced equals condensate returned b) condensate returned always exceeds steam produced c) steam produced must be greater than condensate returned d) the condensate receiver requires fresh water makeup e) the condensate receiver requires regular blowdown |
a) steam produced equals condensate returned |
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In a heating plant with multiple boilers: a) a single low water cutoff serves all boilers simultaneously b) the water level is controlled independently in each boiler c) all boilers must be in service at the same time d) the boiler with the highest water leve controls the feedwater pump e) low water cutoffs are not necessary, due to redundant boilers |
b) the water level is controlled independently in each boiler
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Why are Hartford Loops also used in feedwater systems using centrifugal pumps to supply feedwater to the boiler? |
Hartford loop is also used on boilers equipped with a non-positive displacement feed-pumps (centrifugal pumps), since failure of the check valve in the feed line could allow the steam pressure to force the boiler water back into the condensate tank via the pump, creating a low water condition. |
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How can a Hartford Loop can still result in low water level and shut down the heating system. How can this be prevented? |
Although the system is reliable, there is the possibility of developing a low water condition in the boiler due to a failure of the pump or its power supply resulting in a shut down of the low water cut off. This can be prevented by installation of asecondary means of water supply controlled by a float operated, or electrically controlled feeder valve. |
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State why an externally mounted float connected by piping is preferred to an internal float for controlling the water level in a condensate tank. |
An externally mounted float controller feeder valve is attached to the receiver by equalizing lines, which dampen the level fluctuations in the chamber, resulting in a smooth flow of make up water. |
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Because of the variations in flow rate, nearly all large steam heating plants utilize: a) an economizer b) a dearator c) a condensate receiver d) multiple boilers e) steam pressure regulating valves |
c) a condensate receiver |
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A Boiler must be equipped with a second low-water cut-off when: a) the first device is also used to control the feed water flow b) the auxiliary water supply is not able to maintain a safe water level in the boiler c) the normal source of supply is either insufficient or fails altogether d) the second source of supply is controlled by an electric feeder valve e) the second source of supply is controlled by a mechanical feeder valve |
a) the first device is also used to control the feed water flow |
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The three-wire (double-pole) switch is used: a) as a control switch to open the feedwater control valve b) as a cut-off switch for the fuel valve and as an alarm switch c) as a switch to control the operation of the feedwater pump d) as a cut-off switch to close the feedwater control valve e) as a switch to trip the feedwater pump |
b) as a cut-off switch for the fuel valve and as an alarm switch |
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In nearly all LP steam heating systems the feedwater: a) is usually condensate b) requires daily close scrutiny of chemical values c) is a high make-up percentage d) must be dearated e) requires preheating in an economizer |
a) is usually condensate |
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In multiple boiler heating plants the feedwater pump supplying more than one boiler at the same time will be shut down by: a) the first opened motorized feedwater valve b) the last opened motorized feedwater valve c) the first closed motorized feedwater valve d) the last closed motorized feedwater valve e) the low water cut off |
d) the last closed motorized feedwater valve |
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An electric feeder valve will: a) eliminate the need for a low water fuel cut off b) prevent a low water trip c) open before the low water cut off line is reached d) require manual action to open e) open after the unit trips on low water |
c) open before the low water cut off line is reached |
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Dissolved oxygen in condensate: a) will cause pitting in a boiler b) can cause pitting on the return lines c) causes grooving of the condensate lines d) cannot be removed with chemicals e) necessitates the installation of a dearator |
a) will cause pitting in a boiler |
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A Hartford Loop is used on boilers to prevent: a) water level from getting too high b) steam pressure from getting too high c) scale formation on the heating surface d) overheating e) feedwater from entering the boiler by gravity |
d) overheating |
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The cut out level of the feedwater control switch is: a) the level at which the cut off switch opens b) the level at which the supply switch closes c) the level at which the supply switch starts the feedwater pump d) the highest operating level of the water in the boiler e) the lowest operating level of the water in the boiler |
d) the highest operating level of the water in the boiler |
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When a boiler equipped with a combination feedwater control and low water cut off device shuts down due to a low water condition a) the feedwater flow will also stop b) level must be restored to above the cut off line before the unit can be restarted c) it can be restarted by simply resetting the cut off switch d) manual reset switch must be used e) prepurge will not be necessary |
b) level must be restored to above the cut off line before the unit can be restarted |
