Specifications

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MX Protection, Control and Monitoring Features FCD LMENTB2300-01 – 07/08

1.4 Emergency Shutdown (ESD)

Up to three independent ESD signals may be applied, prioritized and conﬁgured for different actions

for the ESD event associated with each. Either of these ESD signals may be applied to the actuator

to override any existing command signal and send the valve to its preselected shutdown position,

providing the actuator is in Remote mode (default conﬁguration for ESD is “Ignore, take no action”).

Any new command signal will be ignored until the ESD signal is removed. During setup, the actuator

may be conﬁgured to close, open, stop, take no action, or “move to a previously conﬁgured position”

on receipt of the ESD signal. The ESD action may also be conﬁgured to override any inhibit signal,

the local selector switch, the local stop switch, an overtorque condition, lost phase, or jammed valve

protection. Motor thermal protection may be bypassed for critical ESD applications in non-hazardous

or special service locations. Disabling the motor thermostat voids all third-party certiﬁcations,

including Factory Mutual, CSA, ANZex, and ATEX.

1.5 Remote External Interlocks/Inhibits

Three user-deﬁned inputs are provided for the connection of remote contacts that will prevent motor-

ized operation of the actuator. These are effective in both Remote and Local modes and may only be

overridden by a maintained ESD signal, if so conﬁgured (refer to Figure 12.5 for wiring connections).

For ESD connections, the user may select either a single common or isolated commons.

1.6 Absolute Position Encoder

An absolute position encoder (patent pending), incorporated into MX actuators, includes 18 phototransis-

tors which are switched on and off by a gear/wheel mechanism. Valve position is sensed by an 18-bit,

optical, absolute position encoder with redundant position sensing circuits designed for Built-In Self-Test

(BIST).

Each of the position sensing circuits is redundant, facilitating BIST. The BIST feature discerns which

failures will signal a warning only and require a warning plus safe shutdown of the actuator. Open and

closed positions are stored in permanent, nonvolatile memory. The encoder measures valve position at

all times, including both motor and handwheel operation, with or without power present, and without

the use of a battery. The absolute encoder is capable of resolving ±7° of output shaft position and over

10,000 output drive rotations.

This design permits continuous monitoring of valve position during motor and handwheel operation.

The encoder is 100% repeatable and requires no backup power source for operation. The output is used

to control the open and closed valve position and measure and report valve position, as well as provide

local and remote position feedback.

The positioning accuracy is better than 99% for valves requiring 50 or more turns.

Maximum actuator turns = 10,000•

Resolution = ± 7 degrees•

Figure 1.2 – Absolute Position Encoder

18-bit optical, redundant position encoder

provides continuous valve position

monitoring without battery backup

with Built-In Self-Test (BIST) capabilities.