SECTION 19: D
IRECT
FIRED
PROCESS
AIR
HEATERS
59
the process air heater in compliance
w
ith:
United States: Refer to NFPA 86 - latest re
v
ision,
O
v
ens and F
u
rnaces /ANSI Z83.25 - latest re
v
ision,
Direct Gas-Fired Process Air Heaters.
Canada: Refer to CSA 3.19 - latest re
v
ision, Direct
Gas-Fired Process Air Heaters.
19.1 Direct Fired Process Air Heater Models
• 100% O
u
tside Air - Ventilating and Bake Cycle
Mode
• 100% O
u
tside Air - Ventilating
w
ith Red
u
ced
Airflo
w
for Bake Cycle Mode
• 100% O
u
tside Air - Ventilating
w
ith Recirc
u
lation
for Baking Cycle Model (80% Recirc
u
lated Air
after the b
u
rner and 20% O
u
tside Air)
• 100% O
u
tside Air - Ventilating
w
ith Recirc
u
lation
for Baking Cycle Model (90% Recirc
u
lated Air
across the b
u
rner and 10% O
u
tside Air)
Other terms may be
u
sed to describe the bake cycle
mode s
u
ch as; C
u
re or C
u
re Time Cycle, Dry or
Drying Cycle, and Flash Kick Cycle. Ventilation air
and the term o
u
tside air are also
u
sed
interchangeably.
All process heaters come eq
u
ipped
w
ith t
w
o High
Limit discharge controllers, one for the
v
entilation
cycle - maxim
u
m 160 °F (71 °C) (a
u
tomatic reset)
and one for the bake cycle mode - maxim
u
m 300 °F
(149 °C) (man
u
al reset). The discharge temperat
u
re
controller limits the temperat
u
re to a maxim
u
m
250 °F (121 °C).
19.2 Installer's Responsibilities
1. All access opening(s) to the heated space,
ser
v
ed by the Process Heater that can be
u
sed
by personnel to enter the space, m
u
st ha
v
e
door interlock s
w
itch or s
w
itches to sh
u
t do
w
n
the Process Heater if in the bake cycle.
2.
On recirc
u
lation Process Heaters, the ret
u
rn air
d
u
ct from the ser
v
ed space m
u
st ha
v
e filters
installed to pre
v
ent partic
u
late matter from
entering the heater. If not s
u
pplied by the Pro-
cess Heater, then the installer m
u
st s
u
pply
them. These filters m
u
st be appro
v
ed by the
a
u
thority ha
v
ing j
u
risdiction of the installation.
3.
The ret
u
rn air d
u
ct system m
u
st be installed
w
ith doors, panels or other means for access to
facilitate inspection, maintenance, cleaning
and access to fire protection de
v
ices.
4.
Instr
u
ctions m
u
st be pro
v
ided to req
u
ire peri-
odic inspection and cleaning of the recirc
u
la-
tion air d
u
ct. The installer m
u
st s
u
pply this
information.
5.
The gas piping installer m
u
st locate a man
u
al
emergency gas sh
u
toff
v
al
v
e in an appropriate
location that allo
w
s access to sh
u
t off the flo
w
of gas to the Process Heater in case of an
emergency.
6.
If a post p
u
rge (cool-do
w
n) cycle is not s
u
p-
plied
w
ith the Process Heater, then the installer
m
u
st s
u
pply a timing circ
u
it that allo
w
s 100%
v
entilation air of the space to cool the prod
u
cts
do
w
n and p
u
rge any airborne contaminants.
7.
It is also s
u
ggested that the follo
w
ing B
u
rn
Hazard Warning be installed at all access
opening(s) to the heated space, ser
v
ed by the
Process Heater that can be
u
sed by personnel
to enter the space.
Summary of Contents for XT112
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