Boiling out in steam boiler must be performed correctly according to procedure. Before a new boiler is put in service, the internal surface of steam boiler section must be cleaned to remove oil, grease and protective coating.
Before perform boiling out in steam boiler, all pressure parts should be properly inspected for interferences along with the required hydrostatic test created, the piping of blowdown and chemical which are connected to steam drum must be checked to ensure that they're clear and free.
As a way to lessen the quantity of foreign matter which might be presented into the boiler via the pre-boiler process, the pre-boiler process must be water-flushed. It's adequate for drying out of any kind of refractory comprised in the setting.
Mechanically eliminate grease and oil whenever possible from drums and headers prior to boiling out. Examine just about all drum internal pertaining to tightness of bolted components. The following equipment must be available for excellent functioning:
- Forced draught fan
- Induced draught fan
- Condensate storage tanks
- Sampling equipment
- Control equipment
- Water fill-up pump
- Boiler feed water pump
- Firing equipment
It's necessary that the operators on responsibility for the duration of the boiling out operation are well known with standard firing and performing procedures and safe practices.
Preparation to boiling out in steam boiler:
- Thermometers must be connected on the steam drum and water drum to evaluate metal temperatures.
- The non-permanent drum pressure gauge of about 15 kg/cm² full range must be mounted.
- The gasket must not be utilized for the duration of boiling out for the steam drum and water drum manholes. The non-permanent gasket must be fitted.
- All of steam boiler instrument leads which aren't utilized must be isolated for the duration of boiling out.
- Procedures must be designed to dissolve chemical for boiling out.
The procedures of boiling out in steam boiler:
- It's assumed that all tubes are already examined for obstructions and the needed hydrostatic tests are already created. Ensure that all debris are eliminated from the drum. After having the common safety measures to make certain that the boiler and location are cleared of personnel, close the boiler (with the exception the drum vent) and also close all access and inspection doors.
- Get rid of a manhole on the steam drum and fill up the boiler till water shows up in the drum.
- Dissolve the needed amount of chemicals for early demand. As an early demand for boiling out, 0.3 kilograms of H2SO3, 4 kilograms of Na3PO4.12H2O, and 2 kilograms of NaOH are suggested for every 1000 kilograms of water presented by the boiler and water walls whenever filled up to the suggested working level. These chemicals must not to be put in with a solid straight into the drum. In dealing with the chemicals and the solution, good treatment must be used to prevent injury to skin, eyes and clothing.
- Add the chemical solution by means of the steam drum manhole and close the manhole. Right after the chemical solution have been put in, increase a drum water level to the suggested working level.
- Close all superheater vents and also drains with the exception the outlet header drain on the last step. This must be kept open for the duration of the whole boiling out time period. Keep the drum vents wide open.
- Purge and clear the furnace to make sure removing of combustible gases. Once the furnace is purged, the light oil torches or burners are lighted in a style to deliver the heat as uniformly as doable. Firing equipment, settings, vent, drain, etc. must be run while in normal start-up.
- Fire the boiler to take the pressure approximately 10 kg/cm²G in about 8 hours. Maintain this pressure for 4 hours to make sure circulation. Close up the drum vents while the drum pressure gets to 2 kg/cm²G. At the same time check out expansion of the unit wherever doable.
- Observation of the temperature of the water drum must be created for an indicator of excellent circulation so as that all components of the unit can be carefully boiled out.
- Soon after 4 hours shut down all burners, permit the boiler pressure to reduce. Right after the pressure has decreased apparently (about 4.5 kg/cm²G) the water level must be increased in order that the gauge glass is almost full.
- Blow down the boiler employing bottom blowdown valves. Don't permit the level to move out of sight in the gauge glass. Recover the water level to normal right after the blowdown.
- Do it again this cycle (from item 7 to item 10) 3 times in overall, increasing pressure progressively, setting up the water level concurrently, keeping the higher pressure for 4 hours, the cutting the fires and blowing down.
- Solution samples must be provided regularly while in the boiling out time period. When the boiler water alkalinity and phosphate concentration have decreased to ½ of the initial values, extra boil out chemicals must be included to recover the initial concentrations.
- The boil out must be carried on till the solution sample show that oils and siliceous materials are taken off. If samples of the alkaline solution present no rise of oil (and below 5 ppm) or siliceous materials, the burners must be shut off and unit must be cooled progressively. If the drum pressure falls to 2 kg/cm²G, the drum vents and superheater header drains must be opened wide. If the steam drum metal temperature drops under 90o C, drain the boiler.