Flowserve Valtek Beta Positioners for Control Valves - Manual

24-1 Flowserve Corporation, Valtek Control Products, Tel. USA 801 489 8611 Valtek No. 49035
Valtek Beta Positioners
General Information
This bulletin contains instructions for installing, cali-
brating, troubleshooting, and performing maintenance
as required for the Valtek
® Beta Positioner mounted on
control valves.
Instructions for maintaining and calibrating the NT 3000
I/P module are contained in Installation, Operation,
Maintenance Instructions 47, NT 3000 Series Electro-
pneumatic Transducer Module. For calibration and
maintaining the remote I/P see Installation, Operation,
and Maintenance Instructions 30, Electro-pneumatic
Transducer.
Product users and maintenance personnel should read
thoroughly and follow exactly the instructions contained
in this bulletin prior to operation of the positioner. If there
is any question concerning this bulletin, call your Valtek
representative.
To avoid possible injury to personnel or dam-
age to equipment, WARNING and CAUTION
notes must be strictly adhered to. Modifying
this product, substituting non-factory or infe-
rior parts, or using maintenance procedures
other than outlined could drastically affect per-
formance, be hazardous to personnel and
equipment, and may void existing warranties.
NOTE: Numbers in parenthesis correspond to the part
item numbers in Figure 17.
Beta Positioner Overview
The Valtek Beta Positioner is available with either a
pneumatic (P/P) module for air control signals or an
electro-pneumatic (I/P) module for milliampere electri-
cal control signals. It is double-acting, capable of sup-
plying air to either side of the actuator piston while
exhausting the other side to the atmosphere. The unit is
adjustable to two and three-way split range without
special feedback springs. The Valtek Beta positioner
can be interchanged with the 80R and XL positioners
without changing the brackets or takeoff arms.
The Beta Positioner with I/P module is intrinsically safe
for FM/CSA class 1, division I, groups A, B, C, and D;
class II, groups E, F, and G, and CENELEC EEx ia IIc,
when installed with the appropriate energy limiting
safety barriers (See Figure 1). It is also explosion proof
for FM/CSA class II, groups E, F, and G, and CENELEC
EEX d IIb + H
2
. Since the positioner is insensitive to
supply pressure changes and can handle supply pres-
sures from 30 to 150 psi a supply regulator is usually not
required; however, an air filter is highly recommended.
NOTE: The air supply should conform to ISA Standard
S7.3 (a dew point at least 18
°
F below ambient tempera-
ture, particle size below 5 microns, oil content not to
exceed 1 part per million).
Positioner Operation
The Beta Positioner is a force-balanced instrument.
Figure 2 shows a Beta Positioner, with either a pneu-
matic or electro-pneumatic (I/P) module, installed on a
double-acting actuator for air-to-open action. Position-
ing is based on a balance of two forces; one proportional
to the instrument signal and the other proportional to the
stem position.
With the I/P model, the current signal is first converted
to a 3-15 psi air signal. For the pneumatic model, the
3-15 psi signal is passed directly into the positioner. The
pressure signal acts upon the diaphragms in the instru-
ment signal capsule creating a downward force. The
motion of the actuator stem is transmitted to the top end
of the feedback spring through the follower arm and
cams. As a result, tension in the feedback spring will
vary as the stem position changes.
for Control Valves