Brochure

F-27855-10106
Flow Characteristics
3-Way mixing valves are designed so that the flow from either of the
inlet ports to the outlet is approximately linear, which means the total
flow from the outlet is almost constant over the stroke of the valve
stem. Typical flow characteristics of
VB-9313 series valve bodies are shown below.
Rated Flow
StrokeStem In
Stem Out
"A" Port
"B" Port
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
0%
20% 40% 60% 80%
100%
Typical Flow Characteristics
Rangeability
Rangeability is the ratio of rated flow to the minimum controllable flow
through a valve. For mixing valves, control begins as soon as plug
displacement allows flow. Thus, 3-Way valve rangeability normally
exceeds 500:1, which is the reciprocal of 0.2% nominal leakage.
VB-9313 Valve Body
Characteristics
Temperature/Pressure Ratings
VB-9313-0-5-P (Flanged Cast Iron Body)
Standards: ANSI B16.1–1993
Materials: ASTM A126 Class B
Water
Two-position
Two-position control valves are normally selected “line Size" to keep pressure drop at a minimum. If it is desirable to reduce the valve below line
size, then 10% of “available pressure” (that is, the pump pressure differential available between supply and return mains with design flow at the
valve location) is normally used to select the valve.
Proportional to Bypass Flow
Proportional mixing valves used to bypass flow are piped on the outlet side of the load to throttle the water flow through the load and therefore
control heat output of the load. These valves are usually selected to take a pressure drop equal to at least 50% of the “available pressure.” As
“available pressure” is often difficult to calculate, the normal procedure is to select the valve using a pressure drop at least equal to the drop in
the coil or other load being controlled (except where small booster pumps are used) with a minimum recommended pressure drop of 5 psi (34
kPa). When the design temperature drop is less than 60°F (33°C) for conventional heating systems, higher pressure drops across the valve are
needed for good results (see Conventional Heating System Pressure Drops table below).
Conventional Heating System Pressure Drops
Design Temperature
Load Drop °F (°C)
Recommended Pressure Drop*
(% of Available Pressure)
Multiplier on
Load Drop
60 (33) or More 50% 1 x Load Drop
40 (22) 66% 2 x Load Drop
20 (11) 75% 3 x Load Drop
* Recommended minimum pressure drop = 5 psi (34 kPa).
Secondary Circuits with Small Booster Pumps:13 50% of available pressure difference (equal to the drop through load, or 50% of booster pump
head).
50
(345)
250 (121)
200 (93)
150 (65)
100 (38)
50 (10)
300 (149)
150
(1034)
250
(1724)
350
(2458)
100
(689)
Pressure — psig (kPa)
Temperature — °F (°C)
200
(1379)
300
(2068)
400
(2758)
Maximum Media
Temperature
300°F (149°C)
Minimum Fluid
Temperature
40°F (4°C)
165 psig
(1138 kPa)
VB-9313-0-5-P
Temperature and Pressure Ratings for VB-9313 Series Valve Bodies
5. VB-8/9000 Globe Valves
Sizing and Selection
5. VB-8/9000 Globe Valves
Sizing and Selection