Bently Nevada LVDT Casing Expansion Displacement Transducer Specification

135613-02 is an original factory linear variable differential transformer (LVDT) contact-type displacement transducer developed by Bently Nevada under Baker Hughes, specially engineered for casing thermal expansion measurement of large rotating machinery and designed to cooperate with 3500/45 differential expansion and axial position monitor module within the 3500 series turbomachinery TSI protection system. Unlike non-contacting eddy-current proximity probes used for shaft vibration monitoring, this LVDT sensor relies on mechanical contact structure to capture slow thermal expansion displacement generated by casing temperature variation during unit startup, load changing and normal steady-state operation of steam turbines, gas turbines and centrifugal compressors. The part number suffix 02 stands for upgraded revised version with optimized cable construction and enhanced high-temperature environmental adaptability compared with baseline 135613-01 model. The whole product is manufactured and inspected in compliance with API 670 rotating machinery protection specification, CE EMC directives and relevant international hazardous area certification standards, and is widely deployed in thermal power generation, petrochemical refining, offshore oil & gas and heavy metallurgy industries to realize continuous online monitoring of casing expansion displacement and avoid equipment clamping damage caused by uneven thermal expansion of unit housing. Each finished transducer completes full-range linearity calibration, high-low temperature cycling test and cable pull resistance inspection before factory outbound delivery to eliminate hidden manufacturing defects.

The core design of 135613-02 focuses on stable low-speed displacement detection under high-temperature cabinet and equipment surface working environment via mature LVDT differential induction measurement principle. Firstly, internal built-in precision coil winding and movable ferromagnetic core convert linear mechanical displacement of the spring-loaded contact plunger into proportional alternating differential voltage signal; matched 3500/45 monitor supplies standard excitation power and executes internal signal demodulation and linear conversion to output standard engineering value for casing expansion data display. Secondly, preloaded internal compression spring structure keeps the front measuring plunger consistently attached tightly to measured equipment casing surface, automatically compensating tiny gap variation caused by mounting bracket slight deformation and equipment micro-vibration during long-term running to guarantee continuous reliable contact measurement without measurement loss. Thirdly, upgraded integrated cable of version 02 features reinforced high-temperature resistant outer sheath and improved internal shielding layout, effectively restraining high-frequency electromagnetic interference induced by surrounding high-power motors and frequency converter equipment, reducing signal drift under complex industrial electromagnetic field compared with earlier version. Fourthly, compatible full software configuration of matched 3500 rack configuration software allows users to set measuring range, alert and danger threshold values flexibly without hardware modification on sensor body; once actual casing expansion value exceeds preset limit, the cooperating monitor module outputs alarm signal and interlock control command via rear relay modules to prevent abnormal unit operation risks. In addition, standardized external thread mounting structure enables convenient field installation on customized mounting brackets according to on-site unit layout, supporting fine adjustment of sensor installation stroke during commissioning phase.

135613-02 consists of three main parts including stainless steel outer housing, internal LVDT coil assembly with movable core, spring preloading mechanism and integrated outgoing signal cable. The outer protective shell is processed with high-strength anti-rust stainless steel via precision turning and polishing treatment to resist oxidation and weak corrosive medium erosion from oil mist and chemical volatile vapor near equipment body. The front-end measuring plunger adopts wear-resistant alloy material to lower abrasion loss after long-time repeated contact friction with high-temperature metal casing surface, extending overall service life under continuous field operation. Internal pre-compressed spring component is made of high-temperature spring steel to maintain stable elastic preload within rated working temperature range without permanent deformation and elastic fatigue failure. The upgraded shielded cable of 02 version is seamlessly crimped with shell tail via sealed compression joint structure to prevent moisture, oil and dust permeating into internal coil cavity and avoid internal circuit short-circuit failure caused by harsh field environment. Standard external mounting thread is reserved on middle housing section for fixing onto customer-designed installation support frame. Finished individual transducer is packed with anti-static plastic bag and shockproof foam liner to prevent extrusion deformation and cable damage during long-distance transportation and warehouse storage.

The transducer obtains fixed-frequency AC excitation power supplied externally from matched 3500/45 monitor module, no independent on-board power supply is required for normal operation. Standard effective full-scale mechanical measuring stroke reaches 25.4 millimeters, and the overall linearity error of full measuring range is controlled within ±0.25% full scale after factory precision calibration to meet high-precision casing expansion measurement requirement. Internal built-in differential winding structure ensures low signal output noise and excellent repeatability for tiny displacement variation capture. The integrated shielded signal cable of version 02 maintains stable insulation performance within rated temperature scope; insulation resistance between internal signal wire and outer shielding layer exceeds 200MΩ under 500VDC dielectric withstand test. Built-in transient surge suppression structure at cable root can resist partial instantaneous overvoltage interference from field wiring induced by grid switching fluctuation and lightning coupling to protect internal coil components from breakdown damage. Processed displacement signal is transmitted via double-shielded cable to the input terminal of 3500/45 monitor for subsequent signal conditioning and analog 4–20mA output conversion to upper DCS and PLC control system.

Rated continuous long-term working ambient temperature range for transducer body installed close to equipment casing is -20°C ~ +135°C, which is optimized for high-temperature equipment surface environment in comparison with base model; permissible short-duration transient peak temperature can bear up to +150°C for short-time abnormal equipment overheating condition. Safe spare storage temperature range for unused spare transducers is -40°C ~ +85°C inside dry, dustproof enclosed warehouse free of corrosive liquid splash and toxic chemical vapor erosion. Applicable working relative humidity scope is 5%RH~95%RH under strict non-condensing environmental condition, well adapting high-humidity coastal petrochemical plant and offshore oil platform equipment installation scenarios with salt fog and oil vapor atmosphere. The finished transducer completes standardized industrial vibration reliability certification test and can endure continuous mechanical vibration of 10Hz~1500Hz frequency range during equipment running and installation without internal core loose displacement and cable joint loosening failure. When installed inside Class I Division 2 and ATEX Zone 2 explosive hazardous area equipment area, matched intrinsic safety wiring accessories shall be configured at cable terminal side complying with local regional explosion-proof electrical regulatory requirements.

135613-02 is exclusively matched with Bently Nevada original 3500/45 differential expansion and axial position monitor module, fully compatible with standard 3500/05 instrument rack and whole series of 3500 system auxiliary equipment including 3500/32 relay output module and 3500/92 communication gateway card. All measuring parameter configuration including range setting and alarm threshold definition is completed via official 3500 rack configuration software, and measured casing expansion data can be converted into standard 4–20mA analog signal to connect mainstream DCS and PLC analog input cards for centralized remote monitoring. Main applicable industrial fields include thermal power generation, onshore and offshore oil & gas exploitation, petrochemical refining, coal chemical processing and heavy metallurgy industry, mainly applied for casing thermal expansion online measurement of large steam turbine, gas turbine and centrifugal compressor units. Real-time collected expansion data provides important reference basis for unit startup curve formulation, load adjustment and equipment abnormal thermal expansion fault early warning to prevent unit casing clamping and rotor rubbing mechanical accidents.

Each individual 135613-02 undergoes multiple mandatory pre-delivery factory inspection items including full-stroke linearity test, high-low temperature alternating cycling aging test, cable insulation resistance inspection and spring preload mechanical fatigue verification to screen out inherent manufacturing defects before formal factory outbound shipment. Original manufacturer limited warranty period lasts twelve consecutive months starting from formal product delivery date to end user; free repair or replacement service is available for products confirmed with inherent factory production defects when installed and operated within rated environmental parameters and standardized mounting requirements during valid warranty term. Any transducer damage resulting from unauthorized internal component disassembly modification, artificial mechanical impact extrusion, excessive bending of outgoing cable, corrosive liquid immersion and long-term continuous over-temperature operation exceeding specified working limit scope is excluded from official warranty coverage, and all corresponding maintenance and component replacement expenses shall be fully borne by end user.