flowserve.com
Gestra® Check Valves •
Threaded End Guided Disc Check Valve
MB 26a
Available Sizes: ½" to 2"
(DN 15 to 50)
Application
The MB 26a is used for preventing back flow in liquid and
gas lines. Often used in hot water systems and as vacuum
breakers on tanks and heat exchangers.
Stainless Steel Body with Stainless Steel internals in sizes
from ½" to 2" with NPT threaded connections.
Features and Benefits
• Spring assisted closure for rapid shut off and positive
shutoff.
• Low pressure drop.
• Teflon seats provide bubble-tight shut off.
• Can be installed in any position.
• Rugged industrial design.
Materials
• Body – Stainless Steel (ASTM A351 CF8M)
0RESSURE 4EMPERATURE 2ATINGS
• Cap – Stainless Steel (ASTM A351 CF8M)
"ODY 3TYLE
• Spring – AISI 304
.OMINAL 3IZE
• Disc – AISI 316
-" !
-AXIMUM 3ERVICE
0RESSURE
• Seat – (PTFE)
;INCH=
;MM=
;PSIG= ;BARG=
2ELATED
4EMPERATURE
• Washer – AISI 304
; &= ; #=
• Nut – AISI 304
& #
-INIMUM 4EMPERATURE
• Joint Gasket – PTFE
%ND#ONNECTIONS
$IMENSIONSAND 7EIGHTS
.OMINAL3IZES
$IMENSIONS
;MM=
,;INCH=
;MM=
(;INCH=
;MM=
7;INCH=
!PPROX 7EIGHT
.04
;INCH=
;MM=
;LBS=
;KG=
600
psi
Maximum Δp
(40 bar)
psi
Maximum Δp
(40 bar)
MB 26a
Available Sizes: ½" to 2"
(DN 15 to 50)
[Imp.
gal/min.] [m3/h]
700
2000
[l/s]
200
Partial Opening
(Unstable Range)
Full Opening
(Stable Range)
DN
100
1000
60
600
400
300
100
40
30
20
200
10
100
6
60
40
30
40 &
50
4
3
10
25 &
32
2
20
1
15 &
20
10
0.6
6
4
3
1
0.4
0.3
It is important to avoid oversizing the check valve, which
can lead to chatter and premature failure. Chatter is the
rapid opening and closing of the valve, caused when
sufficient opening pressure cannot be sustained upstream
of the valve.
The curves on the right show the flow rate of the check
valve in GPM of water at 68°F (20°C) as a function of the
pressure drop through the valve.
It is imperative that the intersection point of the flow rate
and the pressure drop is on the straight portion of the
curve.
0.1
1
0.06
0.6
0.4
0.3
Capacity Charts
Check valve sizing is a function of the flow through the
valve and the associated pressure drop. Check valves must
be sized according to the application conditions and not
simply matched to the existing pipe size.
0.2
2
Volume flow
600
Gestra® Check Valves •
Threaded End Guided Disc Check Valve
0.1
0.04
0.03
0.02
0.2
0.01
0.01
0.1
0.02 0.03 0.04 0.06
0.1
0.2
0.3 0.4 0.5
3
4 5 6 7
[bar]
[psi]
0.1
0.2
0.3 0.4
0.6 0.8 1
2
Pressure drop %p
/PENING0RESSURES
.OMINAL3IZES
;INCH=
;MM=
;PSI=
;MBAR=
If the intersection falls on the curved portion, chattering
will likely occur and a different valve must be chosen.
Body Pressure/Temperature Rating
The chart shows the maximum shell (body) pressure
and temperature rating. Operating differential pressure
is limited to the maximum service pressure shown in the
chart.
Spring Materials
Special applications may require different spring material
and/or tensions. If special springs are required, please
consult your local Flowserve Gestra representative.
How to Order
Specify valve type and size.
The MB 26A series is only available with NPT ends.
For Example: MB 26A 2"