Webster JBE Series, Operation, Maintenance & Installation Manual

Section  B - Components

JBE(X) Manual

Page 10

system (linkage), the damper shaft is connected by 

linkage to the jackshaft. On a parallel positioning system 

(linkageless), the shaft is directly coupled to the actuator 

for the air damper.
The air damper mounts to the fan inlet and controls the 

air flow to the fan. On low NOx burners, the air damper 

is connected to the FGR adapter plate, so that the flue 

gas can enter down-stream of the damper where there is 

a negative pressure. If an optional silencer were used, it 

would be mounted to the inlet of the air damper.

Blades

Figure B-7 Multi-blade damper 
3.  Burner Drawer

Figure B-8 Burner Drawer Assembly

The burner drawer contains the pilot, scanner, diffuser 

and oil gun. These components are all attached to the 

backplate. The burner drawer is removed as a complete 

unit for adjustment and inspection. The burner drawer 

slides through the windbox, head extension and into the 

gas manifold. It is attached to the burner by bolting the 

backplate to the windbox.  
The pilot, scanner, oil gun and diffuser position can be 

adjusted (in and out) by sliding the tube through the 

backplate.  Setscrews are used to lock these tubes into 

position. The oil gun can be removed for inspection or 

extended gas firing without removing the burner drawer.

Diffuser

The diffuser provides the directional control of the 

combustion air for mixing and combustion stability. The 

diffuser uses a combination of outer swirl air and inner 

straight air. An inner ring is fastened to the diffuser in 

some applications.
The JBE diffuser sits inside the head section of the 

burner and is secured by one of two methods:

1) On smaller JBE(X)5 & JBE(X)7 burners with 12” and

Figure B-9 Diffuser

14” heads (“J” head and “K” head respectively), the 

diffuser has two straps which attach the cylindrical 

portion of the diffuser to the burner head extension. 

Adjustment may be made by loosening the bolts in the 

slotted holes located on each side of the head extension 

and then carefully sliding them forward or back. Once 

desired adjustment has been achieved, re-tighten bolts 

to lock it in that position. 

2) On larger JBE(X)7 and JBE(X)9 burners with 16” (“L” 

head) and larger, the diffuser is attached to the center 

tube of the drawer assembly. Adjustment to this type of 

diffuser requires loosening the setscrews that secure the 

center tube position on the back of the drawer assembly. 

Once loosened, carefully slide the tube forward or back 

through the drawer assembly backplate. When desired 

position is achieved, re-tighten setscrews on back of 

drawer assembly to secure the center tube. It may be 

necessary to remove the diffuser (for example if spud 

changes are to be made). First, ensure that all power 

to the burner has been locked out. On smaller burners, 

remove the two side fasteners used for adjustment of 

diffuser, then remove the side access cover on the head 

extension. Once the access cover is removed, it will be 

necessary to partially withdraw the drawer assembly 

in order to move the diffuser back. Once the diffuser is 

moved back sufficiently, it may be withdrawn sideways 

through the access opening. Diffuser removal on larger 

units is much the same, although there are no side bolts 

through the head extension and the diffuser must be 

unfastened from the center tube of the drawer assembly 

before it can be withdrawn from the access opening. 

When removing and re-installing the diffuser in the 

JBE(X) burner, there are a few things to keep in mind. 

First, the diffuser position is critical for proper firing. 

Before removing or adjusting the diffuser, it is wise to 

make reference marks where the diffuser position is set 

(side bolts for smaller units or the large center tube on 

larger units). Secondly, when re-installing a diffuser, it 

is important that the scanner’s sight tube be positioned 

properly. The diffuser will have a larger hole which the 

scanner tube must pass through by at least 1/8”. Note 

the hole position before removing the diffuser so that 

when it is replaced, the hole will be in the correct position 

and the sight tube may be placed through it. Also note 

the position of the proven gas pilot with reference to the 

sight tube. The tube is positioned next to the gas pilot so 

that the swirl direction of the diffuser will cause the flame 

of the pilot to curl in front of the scanner tube.