Rectification of Burner Block Components in Tangential Corner Fired Boiler

(Anindya Kumar Moulik, Engineer, Boiler Commissioning)

A few problems that came up during setting of burner critical dimensions will be discussed in this article.

Before continuing the actual discussion, a briefing about the several components of a typical burner

block bucket (or chamber) may be helpful. Following components are present in an oil burner bucket:

1. Oil gun Assembly

2. Flame Scanner Assembly

3. Igniter Spark Rod Assembly

4. Coal Burners.

Problems were encountered during the critical dimension setting offlame scanner and igniter spark rod

assembly.

A flame scanner assembly consists of a flame scanner guide pipe, which houses the flame scanner. The

flame scanner guide pipe can be broadly divided into two portions. One portion is rigid (rear) while the

other one is flexible (front). This flame scanner guide pipe is put through a specific flanged hole on the

burner block. The flame scanner goes through this guide pipe and observes or scans the flame. The

scanner guide pipe has an axially mounted circular plate which is welded onto the rigid portion of the

guide. This axially mounted circular plate acts as a restriction to the axial movement of the guide pipe

towards the furnace. In other words, the position of this circular plate decides the length of guide pipe

which is to remain inside the burner block. The portion of guide pipe inside the burner block is flexible,

but no matter how flexible a pipe is, it still has its stretching limitations. Hence if the position of that

restriction plate is erroneous, the flexible portion will either not reach to the desirable point or will go

beyond the tolerance limits of its desirable position. In both the cases, the flame scanner will not be in

the position to scan the flame correctly. Again, it has to be understood that the flexibility of the pipe

cannot be compromised because that portion of the guide pipe will swivel up and down in accordance

with tilting of burner buckets as and when required. In DSTPS,Andal a problem came up during setting of

critical dimension where it was found that the flexible portion could not be stretched out to the

desirable position in most of the oil burner buckets. Investigation showed that the position of the

restriction plate (which is fixed at the manufacturing unit) was incorrect. At site, this restriction plate

was freed from its position by grinding and then it was axially shifted (in a direction away from the

furnace).This in turn helped to increase the stretching limit of the flexible pipe. As a result, the front end

of the flame scanner guide pipe could be positioned within limits of tolerance in the burner bucket.

Finally, the flame scanner was inserted.

Tip of Scanner Guide pipe

Fixed slot for scanner

guide pipe on the burner

bucket

The tip of the guide pipe

should be within -28mm

to -48mm from the tip

surface of the fixed slot

The above photograph shows the grinding of the restriction plate. Post

grinding, this plate was shifted downward (as per the photo) to increase the

reach of the scanner guide pipe tip.