10. When burning oil, prevent incomplete combustion in the furnace: Unburned oil is deposited on the cooler surfaces in the back of the unit, such as the economizer and air heater, and this creates a potentially dangerous condition.
11. When the steam drum reaches about 25 psig, close the vent valves on the boiler drum. Check the steam pressure gauge now to be sure that it is registering.
12. Ease up on the stem of the main steam stop valve to prevent any serious expansion stresses. If there is no steam on either side of the main steam stop valve, gently lift and reseat it to make sure that it is not stuck. Open the drain valve on the boiler side of the main stop valve.
13. Observe the water level carefully to ensure that no water is carried over into the superheater. Maintain a normal water level in the drum by blowing down or feeding water as may be required.
14. Operate the vent and drain valves in the superheater headers and economizer by following the manufacturer's instructions. In general, drain valves in the superheater inlet header are closed first, followed by the drains in the superheater outlet header. In any case, the superheater outlet header drain and vent valves must not be completely closed until enough steam flow through the boiler outlet valve is assured.
15. Check for leaking gasket joints. If a leaking gasket is discovered, shut down the boiler and tighten the joints.
16. If the gasket still leaks, drop the pressure again, replace the gasket, and repeat the lighting off sequence.
Before cutting in the boiler, proceed as follows:
1. Open all drain valves between the boiler and the header, especially the drains between the boiler and the two stop valves.
2. Warm up the steam line between the boiler and the header by backfeed through the drip line or by means of the bypass valve.
3. When the steam line is thoroughly heated and at header pressure, open the bypass valve.
4. When the boiler pressure almost reaches line pressure, open the bypass line around the main steam stop valve to equalize pressures and temperatures in the piping; then slowly open the main steam stop valve. As the boiler reaches line pressure and is actually steaming, slowly raise the nonreturn valve stem to the full open position.
5. After the boiler is on line, close all superheater drains.
6. Inspect the entire boiler, and close any drain valves that are not discharging condensate.
7. Close the economizer-recirculating valve when an adequate continuous feedwater flow is established.
8. Close the drain valve at the nonreturn valve.
9. Close the bypass valve around the nonreturn valve.
10. A boiler with a pendant (nondrainable) superheater has a slightly different operation. Superheaters of this type trap condensate in the loops that must be boiled off before the firing rate can be increased and the steam flow started.
11. Maintain a constant firing rate. The strength of thick steam drums may be impaired by excessive temperature differentials between the top and the bottom of the drum, if the proper firing rate is not maintained. Tubes may start leaking at rolled seats and the superheater tubes may overheat.
12. On boilers generating saturated steam, follow the above instructions for removing air and condensate.
Success in operating boilers depends largely upon the operator's performance. No fixed set of rules can be established to fit all conditions. Consequently, the operator must see and interpret all prevailing operating conditions and, if necessary, take action to control, modify, or correct them. To be able to do this, the operator must be thoroughly familiar with the characteristics and standard operating procedures for the boiler for which the operator is responsible. This section acquaints you with some of the basic operating procedures that generally apply to most, if not all,Continue Reading