Vacuum Breakers - page 2
SERIES VB8 VACUUM BREAKERS
Catalog Number
VB8-38-BR-P-S-E
Pipe Thread
Size
20.3
1. 4 9
0.73
Outlet Pipe
Size
Total Length
“L”
Engaged
Length “E”
O.D. of Tube
“D”
Hex Body Size
Diameter of
Orifice
Diameter of
Ball
10.0
0.73
0.36
In. H
2
0
In. Hg
PSI
VB8-151
1-1/2”
4.9
0.36
0.18
7. 9
0.58
0.29
21.0
1. 5 4
0.76
10. 5
0.7 7
0.38
In. H
2
0
In. Hg
PSI
VB8-126
1-1/4”
7. 1
0.52
0.26
6.9
0.51
0.25
19.5
1. 4 3
0.70
10.0
0.73
0.36
In. H
2
0
In. Hg
PSI
VB8-101
1”
5.9
0.43
0.21
6.6
0.48
0.24
25.0
1.8 4
0.90
15.3
1.13
0.55
In. H
2
0
In. Hg
PSI
VB8-76
3/4”
15.0
1.10
0.54
5.1
0.37
0.18
18. 0
1.3 2
0.65
9.3
0.68
0.34
In. H
2
0
In. Hg
PSI
VB8-51
1/2”
10.6
0.78
0.38
4.4
0.32
0.16
10. 5
0.7 7
0.38
7. 0
0.51
0.25
In. H
2
0
In. Hg
PSI
VB8-38
3/8”
4.3
0.32
0.16
3.5
0.26
0.13
Horizontal
Top
Outlet
Bottom
Outlet
No
Spring
VB8-51-BR-P-S-E
VB8-76-BR-P-S-E
VB8-101-BR-P-S-E
VB8-126-BR-P-S-E
VB8-151-BR-P-S-E
VB8–38 –BR –P–S–E
VB8
Vacuum Breakers
E = EPR
(Specify alternate by name)
S = Stainless Steel
P = Plain
T = Threaded
BR = Brass
SS = Stainless Steel
38 = 3/8”
51 = 1/2”
76 = 3/4”
101 = 1 ”
126= 1-1/4”
151= 1-1/2”
Dimensions are in inches and for reference only.
Certified drawings are available on request.
Vertical
3/8
1/ 2
3/4
1
1-1/ 4
1-1/ 2
1/ 4
3/8
1/ 2
3/4
1
1-1/ 4
1-1/ 2
1-3/4
2-1/8
2-3/8
2-15/16
3-1/16
1-1/ 8
1-3/8
1-5/8
1-7/ 8
2-5/16
2-1/2
9/16
11 /1 6
13 /16
1-1/16
1-5/16
1-9/16
3/4
1
1-1/ 4
1-1/ 2
1-3/4
2
1/ 4
9/32
13/32
19/32
3/4
7/ 8
3/8
1/ 2
5/8
7/ 8
1-1/16
1-3/16
Vacuum Required to Open
Series
Size
Body
Outlet
Ball
Seal
Explanation of Catalog Numbers
Note: Stainless Steel Ball was used to arrive at all figures. Values
given are averages of test results and may vary slightly.
VACUUM BREAKERS
OPERATING
PARAMETERS
Temperature
Up to 365°F
Pressure
Up to 300 psig
Note: Maximum
limits vary in rela-
tion to changes in
pressure, and tem-
perature. Consult
Johnson for safe
limitations under
your specific appli-
cation conditions.
Assembly dimen-
sions are +/- 1/8”.
Johnson Vacuum Breakers provide a simple, dependable way to relieve
unwanted vacuum which may develop in a closed vessel or pipeline. They can
be used to prevent contamination from back siphonage in fluid handling sys-
tems, and to protect equipment against collapse or implosion. They combine
tight closing with instant response, provide large air venting capacity, and are
designed for easy installation and long service life.
2
5
4
1
3
1
Body
Retainer Tube
Ball
O-Ring
Spring
2
3
4
5
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