BLOWING DOWN A BOILER
Foam sometimes forms on the surface of the boiler water and is usually indicated by drops of water appearing with the steam.
This condition is caused by the presence of oil, dissolved salts, or similar type organic matter in the water. One method of elimin ating this problem is by draining off part of the water in the boiler, and adding an equal amount of fresh, clean water. Another me thod consists of blowing the foam from the water with a specially connected pipe or hose. The boiler should have a blow down tap ping for this purpose. The first method is the easiest. The second one (i.e. blowing down the boiler) requires considerable experience.
BOILER OPERATION AND MAINTENANCE
Always follow the manufacturer’s recommendations for boiler operation and maintenance. If you do not have these instructions an owner’s manual), you should contact the local dealer for advice or write to the manufacturer.
The sections that follow contain recommendations for oper ating and maintaining boilers. Because many of these recommen dations specifically pertain to either steam or hot-water space heating boilers, they were divided and listed accordingly.
The final three sections (BOILER WATER, CLEANING BOILERS, and INSULATING BOILERS) contain general recommenda tions for all boilers.
STEAM BOILERS
Operating and maintaining a steam boiler differs in certain respects from the procedures followed for hot-water space heating boilers. Many of these differences are evident in the recommenda tions that follow.
1. Keep a steam boiler filled to the water level recommen ded by the manufacturer when not in use.
2. Check the water level in the boiler before starting it. The heating surface can be damaged if the water level is too low.
3. Keep the water level at the center of the water gauge glass during operation. If the water level is too low, use the man ual feed valves to add more water. These valves are found in most systems.
4. Always add water to the boiler gradually. If at all possible, avoid adding water to a hot boiler. Never add water to an operating cast-iron boiler. Cold water fed rapidly into such boilers may come in contact with the hot surface of the cast-iron heat exchanger, causing it to crack. Shut off the boiler and wait until it has cooled down before adding water. After the boiler has had sufficient time to cool, slowly add water through the cold water feed line.
5. Check the low-water cutoff at regular intervals. Sediment or rust accumulating under the float of .the low-water cut off can cause it to malfunction. As a result, a drop in the boiler water level would not register properly.
6. Check all boiler accessories to make certain they are func tioning properly. Movable parts shC’uld be inspected and oiled regularly.
7. Never allow a low-pressure steam boiler to exceed the upper safe pressure limits recommended by the manufac turer (usually ,three to four lbs. pressure).
HOT-WATER SPACE HEATING BOILERS
Recommendations for operating and maintaining hot-water space heating boilers are as follows:
1. Keep the boiler and the pipes in the heating system filled with water when not in use. Keeping the pipes filled with water reduces the possibility of rust and corrosion.
2. Check the water level in the boiler before starting it. The heating surface can be damaged if the water level is too low.
3. Always add water to a boiler gradually. Never add water to a hot boiler. Shut the boiler down and allow it to cool first.
4. Check all boiler accessories to make certain they are functioning properly. Movable parts should be inspected and oiled regularly. Such maintenance should also include the pump in a forced hot-water heating system.
5. When operating a hot water space heating boiler, make certain all flow valves are open.
6. Never allow a boiler to exceed the upper safe temperature limit recommended by the manufacturer (usually about 200°F).
BOILER WATER
Boiler water should be clean and kept clean for efficient oper ation. This is true for all boilers. Never add dirty or rusty water to a boiler. Even hard water may eventually interfere with the efficient operation of a boiler, and should therefore be chemically treated before being added.
The Steel Boiler Institute has adopted a chemical condition ing compound for .treating water used in low-pressure steam and hot-water space heating boilers. Many manufacturers provide this chemical compound with their boilers. Always treat the water immediately after the boiler and the heating system have been cleaned.
CLEANING BOILERS
A boiler should be inspected at least once every year for the accumulation of soot and other deposits that could impair its operation. This inspection should take place before the start of the heating season.
The accumulation of soot will result in improper combustion. The soot can be removed with a chemical cleaner or a flue brush. Many boiler manufacturers provide access to the heating surfaces through a removable top jacket panel and cover plates (Fig. 88). The flue brush is used to push the soot down between the sections or fins to collect in the combustion chamber below. It can .then be removed from the combustion chamber without any great difficulty.
Oil burners, gas burners, and coal stokers should also be in spected for dust accumulations and cleaned. Always follow the manufacturer’s recommendations for cleaning the boiler and automatic firing equipment. If you do not have an owner’s manual , contact a field representative or write to the manufacturer.
TROUBLESHOOTING BOILERS
Boilers are subject to numerous problems, many of which are due to improper type and design, or poor servicing. The fol lowing are some of the problems usually encountered:
1. Boiler does not deliver enough heat. This is a very com mon complaint, but the boiler may not be causing the problem. The problem may be caused by the automatic fuel burning equipment (see Chapters 16 and 3 of Vol ume 2) , the radiators or convectors (see Chapter 2, Vol ume 3), or the automatic controls (see Chapters 5-6, Volume 2). Each of these chapters contain troubleshoot ing sections. Even a pipeline with improper pitch will cause the heat from the boiler to be blocked or trapped. If the boiler is found to be the cause of insufficient heat, the problem can be traced to any one (or more) of the following causes:
a. Boiler is too small for the heating system.
b. Improper arrangement of boiler sections in cast- iron boilers.
c. Poor draft.
d. Poor fuel.
e. Heating surfaces are covered with soot.
2. Boiler delivers no heat. The automatic controls should be checked first. Sometimes a low-water cut-off on steam boilers will shut off the burner or stoker before enough steam has formed. Another possible cause is that .too much water is being fed into a steam boiler. As a result,not enough space is provided for the steam to form at the top of the boiler. Too little water in a hot-water space heating boiler can be caused by the limit control moving down to a lower setting.
3. Too much time required to get up steam in a steam boiler.
This common problem can be traced to the following possible causes:
a. Too little or badly arranged heating surface.
b. Heating surfaces covered with soot.
c. Heating passages too short.
d. Poor fuel or fuel firing.
e. Poor draft.
f. Boiler too small.
g. Boiler defective.
4. Boiler is slow to respond to the operation of the dampers.
Slow response to damper operation can be caused by any of the following:
a. Air leakage into the chimney or stack.
b. Poor fuel or fuel firing.
c. Boiler too small.
d. Clinkers on grate or ash pit full of ashes (coal-fired boilers).
5. Water line is unsteady. The problem of an unsteady water line may simply be due to connecting the water column to an e tremely active section of the boiler. Therefore, it is extremely unlikely that the actual water level in the boiler can be read from the water column. Other possible causes of this problem are:
a. Dirt or grease in the water.
b. Varying pressure difference on the system.
c. Excessive boiler output.
Water disappears from the gauge glass. The complete loss of water from the gauge glass could be due to prim ing (i.e. water globules being carried over into the steam). Other causes include:
a. Foaming.
b. Pressure drop too great in return line.
c. Improper water gauge connection.
d. Valve closed in the return line.
3. Water is carried over into the steam main. This problem is usually caused by one of the following:
a. Priming or foaming.
b. Water line is too high.
c. Outlet connections from boiler too small.
d. Steam liberating surface too small.
e. Boiler output excessive.
4. Flues require cleaning too frequently. A frequent build up of soot and dirt in flues can be caused by any of the following:
a. Combustion rate too slow.
b. Poor draft.
c. Smokey combustion.
d. Excess air in firebox.
5. Low carbon dioxide. This condition can generally be traced to one of the following causes:
a. Air leakage between cast-iron sections.
b. Improper conversion job.
c. Problem with burners.
6. Smoke from boiler fire door. The following conditions may be the cause of this problem:
a. Dirty or clogged flues.
b. Incorrect setting of dampers.
c. Poor or defective draft in the chimney.
d. Incorrect reduction in the breeching size.