MX25340 pages

Datasheet
MX2534 Case Expansion Transducer System
Overview
The MX2534 Case Expansion Transducer System consists
of a loop-powered DC Linear Variable Differential
Transducer (LVDT) mounted in an appropriate enclosure.
The unit produces a 4-20mA signal that is directly
proportional to the position of the LVDT plunger rod. It
can be externally powered, or when used with a SETPOINT
Machinery Protection System UMM module, the UMM
itself provides all necessary power.
The NEMA 4 enclosure provides physical protection of the
LVDT and its cable connection. The LVDT itself is a
hermetically sealed unit rated to IP68. It is designed for
use in the moderately high steam environments and
ambient temperatures found adjacent to an HP turbine
case.
The MX2534 is designed specifically to measure thermal
expansion of steam turbine cases relative to their
foundation. The case expansion measurement is typically
required as part of a suite of supervisory measurements
on steam turbines in power generation service. Refer to
page 2 of this datasheet for additional details on the case
expansion measurement.
Connection to the MX2534 is made by means of the
MX2531 cable assembly*, available in lengths up to 100
feet (30 m). One end has an integral 6-pin MIL connector
that mates directly to the LVDT; the other end is provided
with flying leads, allowing transition to longer field wiring
runs in a junction box.
The MX2534 is available with or without a spring return
mechanism. When used without a spring return, the
LVDT plunger rod is rigidly attached to a

Document 1171717
Rev. C (Oct 2013)

bracket on the turbine’s sliding foot, such that the plunger
is pushed or pulled by the bracket as the turbine expands
or contracts.
When used with a spring return, the plunger rod is
supplied with a rounded tip and merely rests against the
sliding foot’s bracket. As the turbine expands, the plunger
is compressed. As the turbine contracts, the internal
spring mechanism pushes the plunger outward such that
it is in constant contact with the bracket. The selection of
either version allows flexibility in retrofit situations, but
the spring return version is more tolerant of side-to-side
and up-and-down movement that would otherwise strain
the LVDT with a rigid bracket attachment scheme.
Because the spring mechanism is hermetically sealed
inside the LVDT body, it is less prone to corrosion and
wear than older designs with external spring mechanisms.
However, the spring return must be specified at time of
ordering. It is not an external assembly that can be
retrofit to non-spring LVDTs.
* NOTE: In instances where a continuous run will be used between the
LVDT and its associated monitoring system, the MX2531 cable assembly
is not required. One (1) mating connector (p/n 99501-026) is supplied
loose with each MX2534 and does not need to be ordered separately.
This allows the installer to attach their own field wiring directly to the
mating connector pins.