The recommended procedures for securing boilers are as follows:
1. Reduce the load on the boiler slowly, cutting out the fuel supply by proper operation of the fuel-burning equipment.
2. Maintain normal water level.
4. Before securing the final fuel burner, open the drain valves at the steam and nonreturn valve and the drain valve on the superheater outlet header. Be sure the bypass valve around the nonreturn valve is closed.
5. Secure the final fuel burner when the load has been reduced sufficiently.
6. Continue operating the draft fans until the boiler and the furnace have been completely purged.
7. Shut down the draft fans.
8. Close the dampers, including the air heater and superheater bypass dampers, when provided.
9. Follow the manufacturer's instructions for the rate of cooling the boiler. A thermal strain may occur if the change is too fast.
10. When the boiler pressure has started to drop, close the steam stop and nonreturn valve.
11. When the boiler no longer requires any feed and the nonreturn valve is closed, open the valve in the recirculating connection of the economizer, if provided.
12. Let the boiler pressure drop by relieving steam through the superheater drain valve and the drain valve at the nonreturn valve. If the boiler is losing pressure at a rate faster than specified by the manufacturer, throttle the drain valves as necessary to get the proper rate. Do not close the valves completely.
13. When the drum pressure drops to 25 psig, open the drum vent valves.
14. If a regenerative type of air heater is used, the rotor may be stopped when the boiler exit gas temperature is reduced to 200F.
15. The boiler can be emptied when the temperature of the boiler is below 200F. Before sending someone into any part of the boiler, close and properly tag all controls, valves, and drains or blowdown valves connected with similar parts of other units under pressure at the time. This move prevents any steam or hot water from entering the unit. The tags are to be removed only by the authorized person who tagged out the boiler and must remain in place until the work is completed. Ventilate the boiler thoroughly and station a person outside. Inside, use only low voltage portable lamps provided with suitable insulation and guards. Even 110 volts can kill under the conduction conditions inside a boiler. All portable electrical equipment should be grounded; and electric extension cords should be well insulated, designed to withstand rough usage, and maintained in good condition.
Typical emergency situations encountered with the operation of boilers are (1) low water, (2) high water, (3) serious tube failure making it impossible to maintain water level, (4) flarebacks caused by an explosion in the combustion chamber, (5) minor tube failure indicated by trouble in maintaining water level under normal steam demand, and (6) broken gauge glass on the water column. Table F, appendix II, lists the safe procedures to follow when these boiler emergencies occur.
The main purpose of boiler operating logs is to record continuous data on boiler plant performance. Logs become a source of information for analyzing the operation of the boiler for maintenance and repair. The daily operating log sheets provide the basic information around which maintenance programs are developed. The log is arranged for use over a 24-hour period divided into three 8-hour shifts. Log sheets vary among different activities, but you should have no difficulty in making log entries once you understand what information is required. The types of information to be entered in the appropriate column of the log are as follows:
Steam pressure. Based on steam gauge readings and indicates the performance of the boiler.
Steam flow. Actual output of the plant, in pounds per hour, to obtain steam flow. The data from these entries are used to determine the number of boilers to operate for greatest efficiency.Continue Reading