- Describe a balanced (double seated) feedwater valve and why it is used? SPO 6-7-8 BOW 2-3-4
A valve with two disks and two seats. One disk opens, with the pressure & one against. With the forces balanced, it opens easily.
- What is a pressure-reducing valve (PRV)? Where is it used? SPO 6-7-8 LPB 2-3 BOW 3-4
The PRV automatically reduces high pressure and maintains a lower delivery pressure.
They are used for heating systems, cookers, city water makeup, control air, gas or oil to a boiler.
- What is a check valve? SPO 6-7-8 LPB 2-3 BOW 2-3-4
A valve that only allows flow in one direction.
- Name the valves found on a boiler. SPO 6-7-8 LPB 3 BOW 2-3-4
Safety valve, water level control valve, drain valve, fill valve, non-return valve, plug valves, check valves, gate valves, globe valves and a maxon valve.
- What is a hydrostatic test? How is it performed and how often should it be done on your boiler? SPO 6-7-8 LPB 2-3 BOW 2-34
It is pressure testing the boiler for leaks.
Close, lock and tag all valves and blank or remove all safeties. Fill the boiler completely with room temperature water to 1-1/2 times the working pressure and call for the inspector.
This should be done on new boilers, after turbine cleaning the boiler tubes and any time repairs are made on the pressure vessel.
- What would you do if you found oil in your boiler? SPO 6-7-8 LPB 2-3
Make sure you know the source and correct if possible. New boiler and those which have accumulated a deposit of oil and grease must be cleaned by boiling out with an alkaline detergent solution. This is a combination of tri-sodium phosphate and di-sodium phosphate. Superheaters must be given a steam blow to loosen debris from the inside surfaces and feed-water systems need flushed. Follow boiler designer recommendations and consult your chemical treatment company.
- What are the essential steps in putting a cold boiler on line with other operating boilers?
- Blow down gauge glass and water column.
- Check the operation of feedwater valves and pump.
- Open the vent on the boiler drum.
- Start the burner on low manual fire,
- Test the flame scanner.
- Test the low water cut-off.
- When boiler pressure starts to build, close the vent.
- Open the equalizing line around the header valve to warm the header
- Open header valve drain and non-return valve drain.
- When the header is hot, open the header valve and close the drain.
- When boiler pressure is 80% of header pressure, unscrew the hand-wheel on the non-return valve and close the drain.
- When boiler pressure equals header pressure, put controls in automatic.
- How do you put a second boiler on line with an operating boiler using non-return valves?
- If the boiler to come on line is HOT, open the equalizing line around the header valve to warm the header.
- Open header valve drain and non-return valve drain.
- When the header is HOT, open header valve and close the drain.
- Increase the fire.
- When boiler pressure is 80% of header pressure, unscrew the hand-wheel on the non-return valve and close the drain.
- When boiler pressure equals header pressure, put controls in automatic.
- What are bags, what causes them and can they be repaired? What are blisters, what causes them and can they be repaired? SPO 6-7-8 BOW 2-3-4
A bag is a bulge in a boiler tube, caused by an overheated area under the scale. Small bags can be heated and driven back into place.
Blisters are the separation of layers in the boiler steel caused by a combination of imperfections in the boiler plate and overheating. Blisters must be cut away and replaced.
- What is scale and what causes it? SPO 6-7-8 LPB 2-3 BOW 2-3-4
Scale is mineral solids in boiler water being deposited on the heating surfaces. It is caused by high TDS (totally dissolved solids) and improper treatment of boiler water.
- What is corrosion? SPO 6-7-8 LPB 2-3
The eating away of metal as a result of low alkaline water, the presence of free oxygen or both, in the water.
- What is caustic embrittlement? SPO 6-7-8 LPB 2-3 BOW 2-3-4
The weakening of boiler steel as the result of inner crystalline cracks caused by long exposure to a combination of stress and high alkaline water
- Name three ways of treating boiler water external of the boiler. Name three chemical tests done on boiler water. SPO 6-7-8 LPB 2-3 BOW 2-3-4
Zeolite water softener, distiller or chemicals.
Nitrate, phosphates, sulfite, conductivity, hardness, pH and chloride.
- Name two chemicals used to control scale in a boiler. SPO 6-7-8 BOW 2-3-4
Polymers, Phosphates amines and chelates.
- What is priming and how is it reduced? What is foaming and how is it reduced? SPO 6-7-8 LPB 2-3 BOW 2-3-4
Priming is boiler water being carried out of the boiler with the steam. It can be reduced by lowering the fire rate, reducing the foaming or lower the water level in the boiler.
- What is water hammer? SPO 6-7-8 LPB 2-3 BOW 2-3-4
It is the condensate carried along with the steam flow through the pipe striking an elbow or tee, possibly rupturing the pipe.
- If your boiler is foaming, how can you tell where the water level is? SPO 6-7-8
Turn off the fire or close the steam valve.
- What is flame impingement and how can it be prevented? SPO 6-7-8 BOW 3-4
It is an unequal distribution of flame contacting the tubes or furnace walls and can be prevented by correct operation and maintenance of the equipment.
- How do you mechanically clean the waterside of boiler tubes and what precaution should be taken? What test should be done after the cleaning? How are boiler tubes cleaned other than with mechanical means. SPO 6-7-8 BOW 2-3-4
When cleaning fire tubes, a knocker raps the inside of a tube, cracking the scale off the outside. When cleaning water tubes, a cutter head rotates inside, cutting and crushing the scale. Always keep the cutter head moving!
A hydrostatic test should be done after the cleaning.
Sometimes acid cleaning by a qualified person is necessary after mechanical cleaning.
- What are pits, what causes them and how can you determine their depth? SPO 6-7-8
Pits are small hollow spots that could develop into holes. They are caused by oxidation.
- Make a plaster cast of the pit and the surroundind plste. After the cast has set, it will show the depth of the pit.
- Ultra sound.
- Eddy current
