Brochure

F-27855-10102
System Design Considerations
Note: The information in this section describes characteristics of the
VB-8xx3 valve bodies, which are used in the Vx-8xx3 valve assem-
blies.
Control Precision
2-Way Valves: The flow curve shown below is representative of all
sizes. All valve plugs have lower gain when nearly closed to enhance
control at low demand. 2-Way valves are nominally equal percentage
and normally used for water and low pressure steam.
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Flow Characteristics
VB-8xx3 Valve Body
Characteristics
Control Precision
3-Way Valves: 3-Way mixing valves are designed so that the flow from
either of the inlet ports to the outlet is nominally linear, which means
the total flow from the outlet is almost constant over the stroke of the
valve stem. The flow is limited at the initial opening similar to an equal
percentage curve to enhance system stability. Typical flow character-
istics of the VB-8303 series valve bodies are shown below.
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Rated Flow
Stroke
Nominal
Three-Way Valve Characteristics
Stem In
Stem Out
0%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
80% 60%
40%
20%
100%
"A" Port
"B" Port
Rangeability
Rangeability is the ratio of rated flow to the minimum controllable flow
through a valve. The nominal rangeability of the VB-8xx3 Series is
greater than 100:1.
Temperature/Pressure Ratings
Temperature and pressure ratings of 2-Way and 3-Way valves are
shown below. Ratings conform with published values and disclaimer.
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
281°F (138°C)
Minimum Fluid
Temperature
20°F (-7°C)
169 psig
(1166 kPa)
VB-8213-0-5-P
VB-8xx3-0-5-P (Cast Iron Body with Flanged End
Fittings)
Standards: Pressure to ANSI B16.1, Class 125, with 200 psi (1379
kPa) up to 150 °F (65 °C), decreasing to 169 psi (1165 kPa) at 281°F
(138 °C).
Materials: Valve body: Cast iron, ASTM A126 Class B.
Trim: Stainless steel stem, forged brass plug, metal-to-metal or EPDM
seat ring with TFE/EPDM packing parts and silicone packing grease.
Close-off Ratings
Nominal actuator close-off ratings are based on ANSI IV (0.01% leak-
age) for valves with EPDM seat rings such as VB-8213 and VB-8223.
Metal-to-metal trim valves such as VB-8303 are designed for ANSI III
(0.1% leakage).
5. VB-8/9000 Globe Valves
Sizing and Selection
5. VB-8/9000 Globe Valves
Sizing and Selection