PRESERVATION OF FIRE TUBE BOILERS DURING IDLE CONDITION

                                                    At many times we have seen the utility engineers request the Boiler manufacturer/service engineer for guidelines on how to preserve the fire tube boiler during Idle Condition, so we thought of sharing a brief on the guidelines.

WET PRESERVATION:

If the boiler is kept idle for a short period of 14 days, it could be laid up “WET” as follows :

• Fill the boiler completely with water, up to overflow level. By admixing an alkalizing agent, bring the pH value of the boiler water to 9.5 and add a corresponding quantity of oxygen binding agent.
• For better admixing, the boiler water should be heated briefly up to 85 deg. C, to drive about the oxygen in it. Take care that no pressure builds up in the process.
• Periodical heating of boiler water up to 70 deg. C Approx. in every 4 days is recommended by lighting the burner.
• An adequate level of oxygen-scavenging chemicals to the tune of 150 ppm could be administered.
• Idle period beyond 14 days should follow dry preservation procedure.
• Before the re-commissioning of the boiler, the boiler water must be drained off.

DRY PRESERVATION:

If the boiler is to be kept idle for a long period it should be laid up ‘DRY” as follows :

• Drain the boiler thoroughly, clean it internally and dry it out. This could be achieved by draining the water at about 60 deg. C. and with the vessel’s temperature the moisture is expected to get evaporated.
• The water service tank, pumps, and all piping should also be dried out.
• In a very high humidity area, it is recommended to place trays of lime inside the boiler shell to absorb any moisture. Then close the door, manholes, dampers, etc; properly so that no ingress of moisture or air can take place.