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The 3 Pass Dry Back Boiler
Available in Steam or Hot Water Versions
Ranging from 15 to 800 Bhp and pressures up to 300 psig

  • Three-pass design.
  • 81% minimum efficiency.
  • Davited rear doors.
  • Low maintenance.
  • 5 sq. ft. heating
  • surface/HP.
  • Durable design.
  • Heavily constructed.
STANDARD FEATURES :
  • Boiler is of three pass dry back, scotch type, built and stamped in accordance with the requirements of the ASME Code, and listed by the National Board of Boilers and Pressure Vessel Inspectors.
  • Large combustion chamber with low heat release for complete combustion.
  • Rear smoke box includes slip-on stack connector and features hinged and davited rear door (40 Hp & larger) with 16” dia. access door with 2” observation port (80 Hp & larger).
  • Front doors are hinged, bolted and insulated (80 Hp & larger) to provide ready access to all firetubes.
  • Large 12” x 16” manholes are standard on larger units (70 Hp & up). Cleanout hand holes 3” x 4” are furnished in the bottom of the boiler shell.
  • Insulated with 2” high-density fiberglass, the shell is covered with 22 gauge grip jacketing and spray baked on powder coat finish.
  • 2 1/2” dia. steel firetubes (2” dia. through 30 Hp) are rolled and beaded on power boilers, expanded and flared on low pressure boilers.
  • Twin lifting lugs are securely welded to the top of the shell. Heavy steel support legs on skids provide support for the boiler & burner.
Standard Steam Trim
Standard Water Trim
  • Operating & limit pressure control
  • Modulating pressure control on modulating burners
  • Water column with gauge glass, trycocks. Combination low water cut-off and pump controller
  • Probe Aux, L.W.C.O.
  • Steam pressure gauge with syphon and test cock.
  • Stack Thermometer
  • Water column drain valve
  • Safety relief valve(s) per ASME code
  • Operating & limit temperature control
  • Modulating control on boilers with modulating burners
  • Probe type low water cut-off control
  • Combination pressure, altitude, temperature gauge
  • Stack thermometer
  • Hot water return baffle for thermal shock resistance
  • Safety relief valve(s) per ASME code
Boiler Specifications
(all dimensions are in inches)
BOILER HORSEPOWER   15 20 25 30 40 50 60 70 80 100
HEATING SURFACE FIRESIDE SQ. FT. 75 100 125 150 200 250 300 350 400 500
STEAM OUTPUT FROM & @212°F LB/HR 517 690 862 1035 1380 1725 2070 2415 2760 3450
GROSS OUTPUT MBH 502 670 837 104 1339 1675 2008 2343 2687 3348
FIRING RATE, GAS 1,000 BTU/CFH CFH 630 840 1050 1260 1680 2100 2520 2940 3360 4200
FIRING RATE, LP GAS 91,500 BTU GPH 6.9 9.2 11.5 13.8 18.4 23 27.5 32.1 36.7 45.9
FIRING RATE, #2 OIL 140,00O BTU GPH 4.5 6 7.5 9 12 15 18 20.7 24 30
FIRING RATE, #5 & #6 OIL 150,000 BTU GPH 4.2 5.6 7 8.4 11.2 14 16.8 19.3 22.4 28
A *NOTE: 1 STEAM OUTLET SIZE 150 PSI IN 1 1/4 1 1/4 1 1/4 1 1/2 1 1/2 2 2 2 1/2 2 1/2 3 A
A *NOTE: 2 STEAM OUTLET SIZE 15 PSI IN 2 1/2 3 3 4 4 4 6 6 6 6 A
B *NOTE: 2 WATER SUPPLY SIZE 30 PSI IN 2 1/2 3 3 3 4 4 4 6 6 6 B
C *NOTE: 2 WATER RETURN SIZE 30 PSI IN 2 2 1/2 3 3 3 3 4 4 4 6 C
D FEEDWATER CONNECTION IN 1 1 1 1 1 1 1 1 1/4 1 1/4 1 1/4 D
E BLOWDOWN CONNECTION (VESSEL) BOTTOM IN 1 1 1 1 1 1/4 1 1/4 1 1/4 1 1/4 (2) 1 1/2 (2) 1 1/2 E
F STACK OUTLET SIZE OD. IN 8 8 10 10 12 12 12 16 16 16 F
G FURNACE OD. IN 16 16 18 18 20 20 20 24 24 24 G
H SHELL ID. IN 36 36 42 42 48 48 48 54 54 54 H
I WIDTH WITHOUT TRIM IN 44 44 50 50 56 1/2 56 1/2 56 1/2 62 62 62 I
J WIDTH WITH TRIM IN 49 49 55 55 61 61 61 68 68 68 J
K LENGTH, FRONT TO REAR IN 69 84 78 89 99 119 135 117 129 153 K
L LENGTH OVERALL IN 103 118 113 124 134 154 170 155 167 191 L
M SKID LENGTH IN 72 90 84 96 102 120 138 117 132 150 M
N SKID WIDTH IN 30 30 36 36 40 40 40 44 44 44 N
O STEAM SUPPLY LOCATION IN 29 26 30 35 40 48 48 53 53 67 O
P WATER SUPPLY LOCATION IN 18 24 23 27 30 1/2 30 1/2 36 36 33 39 P
Q WATER RETURN LOCATION IN 45 56 51 59 68 84 1/2 84 78 87 105 Q
R BLOWDOWN LOCATION 15 PSI & UP IN 18 17 18 18 23 23 1/4 23 1/4 25 25 - 66 25 - 89 R
S 1 1/4" SURFACE BLOW-OFF CONNECTION IN 41 50 36 53 61 39 40 45 41 51 S
T STACK OUTLET LOCATION IN 58 73 66 77 86 106 122 102 114 138 T
U SUPPLY HEIGHT IN 51 51 57 57 63 63 63 71 71 75 U
V STACK HEIGHT IN 54 1/2 54 1/2 60 1/2 60 1/2 68 5/8 68 5/8 68 5/8 77 77 76 3/4 V
W SHELL TO FLOOR HEIGHT IN 12 12 12 12 12 12 12 14 14 14 W
X BURNER PROJECTION IN 32 32 32 32 32 32 32 32 32 36 X
Y DOOR SWING IN 0 0 23 23 28 28 28 31 31 31 Y
AA TUBE REMOVAL REAR IN 32 47 39 50 58 78 94 66 78 102 AA
BB TUBE REMOVAL FRONT IN 41 56 48 59 63 83 99 73 85 109 BB
WATER CAPACITY @ NWL GAL. 123 165 193 233 330 425 502 436 510 628
WATER CAPACITY FLOODED GAL. 146 195 225 271 383 493 582 528 606 761
APPROX. SHIPPING WEIGHT (HIGH PRESS.) 150 PSI LBS. 2975 3225 3850 4125 6100 7375 8250 9400 10300 12450
APPROX. SHIPPING WEIGHT (LOW PRESS.) 15 & 30 PSI LBS. 2850 3075 3650 3925 5750 6950 7550 8100 9300 11100
BOILER HORSEPOWER   15 20 25 30 40 50 60 70 80 100
BOILER HORSEPOWER   125 150 200 250 300 350 400 500 600 700 800
HEATING SURFACE FIRESIDE SQ. FT. 625 750 1000 1250 1500 1750 2000 2500 3000 3500 4000
STEAM OUTPUT FROM & @212°F LB/HR 4312 5175 6900 8625 10350 12075 13800 17250 20700 24150 27600
GROSS OUTPUT MBH 4184 5021 6695 8369 10042 11716 13390 16738 20085 23432 26780
FIRING RATE, GAS 1,000 BTU/CFH CFH 5250 6300 8400 10500 12600 14700 16800 21000 25200 29400 33600
FIRING RATE, LP GAS 91,500 BTU GPH 57.3 68.8 91.8 114.7 137.7 160.6 183.6 229.5 275.4 321 367
FIRING RATE, #2 OIL 140,00O BTU GPH 37.5 45 60 75 90 105 120 150 180 210 240
FIRING RATE, #5 & #6 OIL 150,000 BTU GPH 35 42 56 70 84 98 112 140 168 196 224
A *NOTE: 1 STEAM OUTLET SIZE 150 PSI IN 4 4 4 6 6 6 6 6 8 8 8 A
A *NOTE: 2 STEAM OUTLET SIZE 15 PSI IN 8 8 8 10 10 10 12 12 12 12 12 A
B *NOTE: 2 WATER SUPPLY SIZE 30 PSI IN 6 8 8 8 10 10 10 12 12 12 12 B
C *NOTE: 2 WATER RETURN SIZE 30 PSI IN 8 6 6 6 8 10 10 10 10 12 12 C
D FEEDWATER CONNECTION IN 1 1/2 1 1/2 2 2 2 2 2 2 2 2 2 D
E BLOWDOWN CONNECTION (VESSEL) BOTTOM IN (2) 1 1/2 (2) 1 1/2 (2) 2 (2) 2 (2) 2 (2) 2 (2) 2 (2) 2 (2) 2 (2) 2 (2) 2 E
F STACK OUTLET SIZE OD. IN 16 16 20 20 20 24 24 24 26 26 30 F
G FURNACE OD. IN 26 26 34 34 34 42 42 42 48 48 48 G
H SHELL ID. IN 60 60 75.5 75.5 75.5 90 90 90 102 102 102 H
I WIDTH WITHOUT TRIM IN 68.5 68.5 84.5 84.5 84.5 99 99 99 111 111 111 I
J WIDTH WITH TRIM IN 73 73 89 89 89 105 105 105 118 118 118 J
K LENGTH, FRONT TO REAR IN 175 195 164 195 216 177 189 224 216 246 278 K
L LENGTH OVERALL IN 214 234 210 241