DIMENSIONS - WEIGHTS
MA
TERIALS
Series 174A
•
Bronze body construction
•
Nonmetallic disc-to-metal seating
Series 740
•
Iron body construction
•
Nonmetallic disc-to-metal seating
PRESSURE - TEMPERA
TURE
Series 174A
Pressure range: 30 psi to 150 psi (2 to 10 bars) with
corresponding high BTU/hr ratings from 650,000
to 14,370,000 BTU/hr.
Maximum Temperature: 250
°
F (121
°
C).
No. 374A
Pressure range: rated up to 550,000 BTU/hr at a 30
psi (2 bars) setting only.
Series 740
Pressure range: 30 PSI to 75 psi (2 to 5 bars) with cor-
responding high ratings from 925,000 to 10,700,000
BTU/hr.
Maximum Temperature: 250
°
F (121
°
C).
ST
ANDARDS
Tested and rated by A.S.M.E. National Board of Boiler
and Pressure Vessel Inspectors.
Meets Military Spec. MIL-V-18634B, Type I, Class 3A,
Style A (Bronze Body), Style B (Iron Body).
CAP
ACITY
ES-174A-740 0026
© Watts Regulator Co., 1998
Printed in U.S.A.
USA:
815 Chestnut St., No. Andover
, MA 01845-6098; www
.wattsreg.com
Canada:
5435 North Ser
vice Rd., Burlington, ONT
. L7L 5H7; www
.wattscda.com
HV
NB
ASME
Size (Dn)
Height
Length
Weight
No.
in.
mm
Model
in.
mm
in .
m
m
lbs.
kg.
374A
3
⁄
4
x
3
⁄
4
20 x 20
–
3
5
⁄
8
92
2
1
⁄
2
64
1.13
.5
174A
3
⁄
4
x
3
⁄
4
20 x 20
M3
5
1
⁄
8
130
2
1
⁄
2
64
1.50
.7
174A
1 x 1
25 x 25
M1
5
3
⁄
4
146
3
76
3.13
1.4
174A
1
1
⁄
4
x 1
1
⁄
4
32 x 32
M1
8
3
⁄
8
213
4
3
⁄
4
121
6.25
2.8
174A
1
1
⁄
2
x 1
1
⁄
2
40 x 40
M
9
229
4
7
⁄
8
124
7.25
3.3
174A
2 x 2
50 x 50
M
1
1
5
⁄
8
295
6
1
⁄
4
159
13.75
6.2
Series 740
740
3
⁄
4
x 1
20 x 25
M1
5
5
⁄
8
143
3
7
6
1.88
.9
740
1 x 1
1
⁄
4
25 x 32
M
7
1
⁄
4
184
3
1
⁄
2
89
3.13
1.4
740
1
1
⁄
4
x 1
1
⁄
2
32 x 40
M
8
3
⁄
4
222
4
5
⁄
8
117
6.13
2.8
740
1
1
⁄
2
x 2
40
x
50
M
9
1
⁄
4
235
5
1
⁄
4
133
7.50
3.4
740
2 x 2
1
⁄
2
50 x 65
M
1
1
5
⁄
8
295
6
3
⁄
4
171
16.50
7.5
Series 174A
BTU/hr Steam Pressure Discharge Capacities
As tested and rated by the National Board of Boiler and Pressure Vessel Inspectors
Set
3
⁄
4
" x
3
⁄
4
"
1" x 1"
1
1
⁄
4
" x 1
1
⁄
4
"1
1
⁄
2
" x 1
1
⁄
2
"
2" x 2"
Pressure
20 x 20mm
25 x 25mm
32 x 32mm
40 x 40mm
50 x 50mm
psi
bars
Model M3
Model M1
Model M1
Model M
Model M
30
2.07
650,000
1,005,000
1,682,000
2,020,000
3,815,000
33
2.27
695,000
1,075,000
1,788,000
2,150,000
4,080,000
35
2.41
725,000
1,125,000
1,877,000
2,250,000
4,250,000
36
2.48
740,000
1,145,000
1,916,000
2,310,000
4,344,000
40
2.76
800,000
1,240,000
2,071,000
2,490,000
4,690,000
45
3.10
875,000
1,355,000
2,265,000
2,720,000
5,130,000
50
3.45
950,000
1,470,000
2,459,000
2,950,000
5,575,000
55
3.79
1,025,000
1,590,000
2,653,000
3,190,000
6,010,000
60
4.13
1,100,000
1,702,000
2,847,000
3,425,000
6,450,000
65
4.58
1,170,000
1,820,000
3,041,000
3,660,000
6,890,000
70
4.82
1,245,000
1,935,000
3,235,000
3,890,000
7,330,000
75
5.17
1,320,000
2,055,000
3,429,000
4,125,000
7,770,000
80
5.51
1,400,000
2,166,000
3,605,000
4,360,000
8,215,000
85
5.86
1,470,000
2,285,000
3,817,000
4,590,000
8,650,000
90
6.60
1,545,000
2,400,000
4,011,000
4,825,000
9,090,000
95
6.55
1,620,000
2,520,000
4,205,000
5,060,000
9,530,000
100
6.89
1,695,000
2,635,000
4,399,000
5,290,000
9,970,000
105
7.23
1,770,000
2,750,000
4,593,000
5,525,000
10,410,000
110
7.58
1,845,000
2,865,000
4,787,000
5,760,000
10,850,000
115
7.92
1,920,000
2,980,000
4,981,000
5,990,000
11,290,000
120
8.27
1,995,000
3,100,000
5,175,000
6,225,000
11,730,000
125
8.61
2,070,000
3,215,000
5,370,000
6,460,000
12,170,000
130
8.96
2,145,000
3,330,000
5,564,000
6,690,000
12,610,000
135
9.30
2,220,000
3,445,000
5,758,000
6,925,000
13,050,000
140
9.65
2,295,000
3,565,000
5,952,000
7,160,000
13,490,000
145
9.99
2,370,000
3,680,000
6,146,000
7,390,000
13,930,000
150
10.34
2,445,000
3,795,000
6,340,000
7,630,000
14,370,000
Series 174A
Set
3
⁄
4
" x 1"
1" x 1
1
⁄
4
"1
1
⁄
4
" x 1
1
⁄
2
"1
1
⁄
2
" x 2"
2" x 2
1
⁄
2
"
Pressure
20 x 25mm
25 x 32mm
32 x 40mm
40 x 50mm
50 x 65mm
psi
bars
Model M3
Model M1
Model M1
Model M
Model M
30
2.07
925,000
1,300,000
2,105,000
2,900,000
5,250,000
33
2.27
989,000
1,390,000
2,250,000
3,100,000
5,613,000
35
2.41
1,032,000
1,450,000
2,345,000
3,235,000
5,855,000
36
2.48
1,053,000
1,480,000
2,395,000
3,300,000
5,975,000
40
2.76
1,139,000
1,600,000
2,590,000
3,569,000
6,461,000
45
3.10
1,245,000
1,750,000
2,830,000
3,903,000
7,067,000
50
3.45
1,352,000
1,899,000
3,075,000
4,237,000
7,672,000
55
3.79
1,459,000
2,049,000
3,315,000
4,572,000
8,277,000
60
4.13
1,566,000
2,200,000
3,560,000
4,907,000
8,883,000
65
4.58
1,672,000
2,349,000
3,800,000
5,241,000
9,488,000
70
4.82
1,779,000
2,499,000
4,045,000
5,575,000
10,093,000
75
5.17
1,886,000
2,649,000
4,285,000
5,909,000
10,700,000
Series 740
Series 174A-740
ASME W
ater Pressure
Relief V
alves
for Pr
essur
e Pr
otection of
Hot W
ater Heating Boilers
Sizes:
3
⁄
4
" thr
ough 2" (20 - 50mm)
Series 174A
Bronze body safety relief valves for pressure protection only
of all types of hot water heating boiler equipment. Pressure
range 30 to 150 psi (2 - 10 bars) with corresponding high rat-
ings from 650,000 to 14,370,000 BTU/hr. Female inlet and
outlet connections. Sizes
3
⁄
4
" to 2" (20 to 50mm).
Series 374A
Iron body with forged bronze inlet, 550,000 BTU/hr rating.
Size
3
⁄
4
" (20mm) only.
Series 740
Iron body with expanded outlets for hot water space heating
boilers. Pressure range 30 to 75 psi (2 to 5 bars) with corre-
sponding high ratings from 925,000 to 10,700,000 BTU/hr.
FEA
TURES
•
Seat located above drain; water can’t be trapped and
sediment can’t foul seat.
•
Non-mechanical seat-to-disc alignment will not
stick or freeze.
•
Water seal of high temperature resisting material isolates
spring working parts from water during relief.
SPECIFICA
TIONS
Boiler Relief Valves
An ASME Section IV certified pressure relief valve shall be
installed on each boiler as noted. The valve shall have a
BTU rating in excess of the BTU rating of the boilers heat-
ing output. Each hot water space heating boiler shall be
equipped with a pressure relief valve set to relieve below
the maximum boiler working pressure. The valve shall fea-
ture a raised seat and non-mechanical disc alignment.
Working parts and spring shall be isolated from any dis-
charge by a high temperature resistant material. Valve shall
be a Watts 174A or 740 Series.
ES-174A-740
OPERA
TION
As thermal expansion conditions develop, pressure builds up
to the setting of the relief valve. This will cause discharging of
small quantity of
water
.
Should operating controls fail, permitting runaway firing, the
boiler water may reach steam temperatures. The valve will
then open to discharge
steam
at the rate or faster than the
boiler can generate it, thus restoring system pressure to a
safer level.
Important
: The discharge line must be the same size as the
valve outlet, and must pitch downward from the valve to a
safe place for disposal.
Valve lever must be tripped at least once a year to insure that
waterways are clear. This device is designed for emergency
safety relief and shall not be used as an operating control.
Series 174A
Series 740
For Hot W
ater Boiler Applications
Job Name
Contractor
Job Location
Approval
Engineer
Contractor’s P.O. No.
Approval
Representative
W
atts pr
oduct specifications in U.S. customary units and metric
ar
e appr
oximate and ar
e pr
ovided for r
efer
ence only
. W
atts r
e-
serves the right to change or modify pr
oduct design, construction,
specifications, or materials without prior notice and without incur
-
ring any obligation to make such changes and modifications on
W
atts pr
oducts previously or subsequently sold.
Summary of Contents for PVG WW
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