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The principal areas serviced are the main firebox (walls, burners, and pendants), generating banks, economizers, back passes, and convection passes. 1st Call is also capable of using explosives in other areas where ash may build-up such as; silos, service vents and ash hoppers.
1st Call performs precision blasting with smaller charges. By using smaller charges this lowers the possibility of damage from over-pressure. The amount of slag removed per shot will depend on the makeup of the ash. Blasters start out with small charges and increase the size of the charge as required to remove the slag safely.
Detonating Cord (Det Cord) and dynamite are the primary charges used in combination with non electric blasting caps (detonators) as the initiator. This is due to the large amount of stray electricity that could interfere with proper function of electric blasting caps, even causing premature detonation.
The basic methods used to remove slag from boiler areas are described below.
FIREBOX
This method will restrict all personnel from work in or around the boiler for the duration of the operation.
POLE SHOOTING
Telescoping poles are used to reach ash build-up in the fire box. Attached to the pole is the explosive charge with a detonator. The charge is then inserted into the boiler and placed against the built up ash and detonated.
INSIDE THE BOILER
These next two methods allow all personnel to work in and around the boiler while charges are being setup.
VERTICAL TUBES
Explosive charges are zip-tied in place in the gas pass. Each charge is affixed with a detonator. Once all charges are connected they are detonated from outside the boiler.
HORIZONTAL TUBES
Explosive charges are stitched or inserted in the gas passes and initiated from the outside the boiler. With this method, the ash build-up from the gas lanes and the webbing from between the tubes vertically is removed. Depending on the amount of ash build-up, a level may need to be setup, shot, and air lanced more than once. When using explosives to clean the convection pass the area stays dry and only the levels that are plugged are cleaned, which saves time and money.
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