Chapter 104 Flashcards
The feed water control switch is commonly operated by?
low-water fuel cut-off float
Feed water supply to most steam boilers is usually controlled by?
Float switch
List two types of Mercury pole switches:
Single/double pole
What happens at the highest operating level of the water in the boiler?
Feed water supply switch opens. Stopping the power supply to the control valve or supply pump. (Stops water supply to boiler)
When the water level is insufficient or pump fails to start?
Fuel cut-off switch opens and cuts off the power to the fuel valve and sounds an alarm (double pole Mercury switch)
What does ASME, Section IV cover?
Low water fuel cutoff.
In a steam heating plant where does the steam give up most of its heat?
Radiators, convectors
If control of the feed water supply is the primary function of the cut-off device what is required by code?
A second cut-off
Second source heating boiler water is controlled by the low water fuel cut of device in two ways:
Electric feeder valve, float operated mechanical feeder valve
Hartford loop return line is connected where on a steam heating boiler?
It’s connected to the loop at the lowest safe water level
What kind of pump requires a steaming heating boiler to be equipped with a Hartford loop?
Non positive displacement (centrifugal pump)
If multiple heating boilers require water which valve will open the pump switch to shut it off?
The valve that closes last
An undersized condensate receiver may cause what?
Loss of condensate to the sewer
What’s the general rule for the size of a condensate receiver tank?
Be able to hold enough condensate equivalent to 20-30 minutes of normal water evaporation in the boiler
When should a larger condensate receiver tank be used?
Systems extended over larger area
What is a disadvantage of the float mechanism feeder?
Unsteady valve operation due to violent fluctuations of returning condensate
What will cause grooving in the condensate receiver?
Carbon dioxide
How can an operator get rid of carbon dioxide from ruining the condensate return lines?
Filming amines that will coat the metal
A float operated mechanical feeder valve should:
Not open until the level is well below the feed pump cut-in level
Equalizing lines on a condensate receiver float chamber:
Will dampen water level fluctuations
Bleeding water out of the control line on the condensate receiver will result in what?
Pressure drop in the control line
A feed water makeup supply should?
Be able to satisfy firing rate
Neutralizing amines:
Raise the pH of condensate
A condensate receiver low water cut-off will?
Stop the pump in order to prevent damage
A float operated mechanical feeder valve should?
Not open until the level is well below the feed pump cut-in level
A thermal element, used on hot water boilers is capable of sending temperature and?
Converting it to a pressure signal
