Q. What are the maintenance to be carried out in boiler?
Ans : Boiler maintenance: The boiler maintenance should always be executed with skill and in accordance with valid rules and regulations from the authorities. Below some recommendations are given for periodical inspections and maintenance.
Daily operation : Daily normal operation of the boiler, some work and check procedures have to be considered every day.
Step A: Check the boiler steam pressure and the water level.
Step B: Check that the feed water control system is operational see separate instructions.
Step C: Check the boiler water condition and inquire necessary countermeasures with regard to the feed and boiler water treatment. If necessary, blow-down the boiler.
Step D: Check the function of the oil burner at different capacities through the inspection holes on the boiler.
Step E: Check the flue gas temperature after and or the draft loss across the boiler. If either the temperature or the draft loss is too high the smoke tube section, for the oil fired as well as the exhaust gas part, must be cleaned.
Q. What are the weekly checks?
Ans : Weekly routine checks
Step A: Drain each water level glass for about 10-15 seconds.In case of contaminated boiler water sufficient water treatment the draining of the water level glasses must be done more often.
Step B: Check the safety water level device.
Step C: Depending on the boiler water tests, blow-down the boiler. Open the blowdown valves quickly for a few seconds, and then close and open for about 5-10 seconds. Repeat this operation when required according to the boiler water tests.
Step D: Perform scum blow out by means of the scum valve when required. The scum blow out must be carried out until the drained water is clean.
Q. What are the monthly routines?
Ans : Monthly routine checks
Step A: Test all stand-by pumps.
Step B: Check all boiler mountings for damage or leaks and repair & replace if necessary.
Incorrect feed water treatment is commonly causing hard deposits or corrosion. Insufficient blow-down will cause sludge deposits in the tubes and accumulation of sludge in the bottom of the boiler. If hard deposits are not removed.it may lead to overheating in the boiler plate material, which is exposed to the flame in the furnace wall area. This may cause material damages. Incorrect feed water- treatment does not always lead to hard deposits. For example, a too low or too high pH-value may give an electrolytic reaction causing corrosion in the boiler. When the boiler interior is inspected, examine all parts carefully and be attentive to deposits, corrosion, and cracks. It is advisable to pay special attention to this inspection.
Q. What are the procedure and remarks for Boiler inspection?
Ans : Procedure and remarks for Boiler inspection
Step A: Shut off the boiler and allow it to cool (below 100 deg C).
Note: The boiler should NOT be depressurised by lifting the safety valves and then filled with cold feed water as the stress induced by too rapid cooling may cause damage.
Step B: Empty the boiler and close all valves. If the boiler is connected to a second boiler, check that the valves between them are closed.
Step C: Unscrew and remove the manhole hatch(es) on the boiler and enter the boiler when it is sufficiently cold. Check the welding in the boiler. A careful examination should be carried out with respect to any possible corrosion or crack formation. Special care should be taken to the water line area in the pressure vessel where oxygen pitting may occur. lf deposits are forming in the boiler tubes, the boiler should be chemically cleaned.it is advisable to consult a company of cleaning specialists rho will examine the boiler deposits and treat the boiler accordingly.
Note: After chemical treatment the boiler should be blown-down at Least twice a day for approximately one week. This will ensure that excessive sludge deposits due to chemical treatment do not collect in the bottom of the pressure vessel.
Contamination If the boiler is contaminated with foreign substances like oil, chemicals corrosion products etc, it is very important to act immediately to avoid damage to the boiler.
Step C: Check the function of the high steam pressure switch by lowering the set point or by raising the steam pressure, e.g by closing the main steam valve slowly. The burner must stop automatically.
Inspection of the boiler
A. Inspection of furnace: The furnace should be inspected at least twice a 3 year. During this inspection, the following issues should be taken into consideration: Check for cracks at the refractory and that the furnace walls are free from excessive soot deposits. Examine carefully the area opposite the burner. Too much soot deposits indicate that the burner should be adjusted. Check that the smoke and stay tubes are intact and that soot deposits are within normal limits.
B. Inspection of exhaust gas section: The exhaust gas section should be inspected at least twice a year. During this inspection, the following issues should be taken into consideration: Check the welding in the exhaust section. A careful examination should be carried out with respect to any possible corrosion or crack formation. Check that the inlet box and outlet box are intact and that soot deposits are within normal limits. Check that the smoke tubes and stay tubes are intact and that soot deposit are within normal limits.
C.Inspection of boiler water side
The boiler water side (interior) must be carefully inspected at least twice a year. This inspection is of great importance and no doubt the most important of all the maintenance measures. Since it has a direct influence on the boiler longevity and on the security. At these inspections, hard deposits, corrosion, and circulation disturbances can be found at an early stage, and preventive measures must be taken to avoid unexpected material damage and boiler break down. The presence of hard deposits at the furnace wall and the smoke tubes reduces their heat transfer properties and decreases, the capacity of the boiler. Further, it can be established whether the feed water treatment is satisfactory and whether the blow down is carried out sufficiently.
Layers of thin oil film are exposed to the heating surfaces cause a bad heat transfer in the boiler, leading to overheating followed by burned out pressure parts, In order to remove such contamination a boiling out or acid cleaning are performed immediately.
Note: Corrosion products from the pipe system or insufficient boiler water treatment may result in corrosion in the boiler itself. It is therefore important to observe that such circumstances do not occur in the system.