28
ACCESSORIES
Orifices
(see Fig. 12)
The orifice restricts the field of view (target area), reduces and maintains air flow, maintains air block and
increases discrimination between flame and background radiation. The orifice is secured within the ball of
a swivel mount with an orifice retainer. The orifice can also be placed within a one inch union (not pro-
vided), or within the 35-318-X mounting flange.
The scanner should ideally sight a target area of 4 to 25 square inches (25-150 cm
2
) of the flame front. The
flame front is a plane within the combustion space separating the region of unburned fuel from the burning
fuel.
Note: There is an inverse relationship between discrimination and sensitivity.
Heat Insulating Nipple
The heat insulating nipple P/N 35-127-3 (BSP) or 35-127-1 (NPT) prevents heat transfer from the hot
sight pipe to the scanner head.
Sealing Coupling with Quartz Window
The sealing coupling (P/N 60-1199-x) is used whenever a coupling or seal is required for scanner piping.
The size is one inch US standard taper pipe thread (1" NPT). The sealing coupling has a quartz window to
block off the scanner from the furnace pressure and heat. When the sealing coupling is used, the 1" tee/
wye is used for the purge air inlet. Be sure the quartz window is properly seated to seal off the scanner. Do
not overtighten coupling collar because damage to the window may result. For best results, hand tighten
coupling collar.
FIGURE 11.
ALTERNATE PURGE
AIR SUPPLY
60-1199-1,2
SEALING COUPLING
with Quartz Window
FIELD
OF
VIEW
1” SWIVEL MOUNT
FIELD OF VIEW
BALL
SWIVEL MOUNT
ORIFICE
ORIFICE
RETAINER
