Bentley 3300/20 - 01-01-01-00-00-00 Dual-channel Axial Displacement Monitor Detailed Product Description

I. Product Overview

The Bentley 3300/20 is a dual-channel axial displacement (thrust position) monitoring module within the 3300 series of rotating machinery protection systems. The 3300/20-01-01-01-00-00 introduced here is the standard configuration version, fully adhering to the API 670 industrial standard. This device adopts a modular rack structure and is mainly used for steam turbines, gas turbines, centrifugal compressors, large pump sets, industrial pumps, and other key rotating equipment in the power, petrochemical, metallurgical, and other industries. It continuously monitors the axial movement of the rotor and the clearance between the thrust bearing, achieving condition monitoring, fault early warning, and safety interlock protection. It is the core device for the safety protection of the rotor system of the unit and can be seamlessly integrated with the entire set of sensing, power supply, and rack equipment of the 3300 series.

II. Model Code Interpretation

3300/20 is the main product model, defining the equipment type as a dual-channel axial displacement / thrust position monitor. The subsequent segmented codes represent the hardware and functional configurations of the equipment. The first code 01 indicates the input type, compatible with the Bentley 3300 series standard eddy current sensor system, and compatible with probes, preamplifiers, and signal cables of the same series. The second code 01 represents the standard measurement range, with the factory default range being ±1.0mm, a common specification for industrial sites. The third code 01 represents the analog output form, using isolated 0-10VDC voltage output. The fourth code 00 represents the alarm and logic configuration, using the factory default basic alarm logic, without additional customized channel voting or special interlock functions. The fifth code 00 represents the additional functions and certification configuration, being the original factory standard version, without special function expansion or customized certification requirements.

III. Core Functions

The device is equipped with two completely independent measurement channels, capable of simultaneously receiving two sets of eddy current sensor signals, independently completing axial displacement data acquisition and calculation. The dual-channel monitoring architecture enhances the overall operational reliability. The device can continuously monitor the axial position changes of the rotor and promptly detect potential faults such as thrust bearing wear, axial load abnormalities, deteriorated lubrication conditions, and unbalanced rotor forces, preventing major equipment accidents such as rotor friction, shaft system damage, and unplanned shutdowns. The module integrates graded alarm protection functions, equipped with one warning relay, two dangerous trip relays, and the warning value, dangerous value, and trip value can be customized through local operation buttons, meeting the protection strategy requirements of different units. The device has a complete sensor circuit diagnosis function, capable of real-time inspection of the sensor circuit status composed of probes, extension cables, and preamplifiers. When abnormal conditions such as open circuit, short circuit, or signal over-range occur, it automatically triggers a sensor fault alarm, alerting maintenance personnel to promptly investigate and avoid false monitoring and false interlocks caused by abnormal signals. The front of the device is equipped with an LED digital display and operation buttons, supporting on-site viewing of real-time displacement values, sensor circuit voltage, alarm status, and equipment operation status. Parameters such as range, alarm threshold, output parameters, and relay working mode can be configured on-site, and the settings will be automatically saved. The parameters will not be lost after power loss. The standard 0-10VDC isolated voltage output is directly connected to mainstream industrial control systems such as DCS, PLC, and SCADA, enabling remote data collection, trend recording, and centralized monitoring.

IV. Working Principle

This device operates based on the mature non-contact eddy current measurement principle. The accompanying eddy current probe is supplied with high-frequency alternating current. When the probe approaches the surface of the metal thrust disk, the metal layer will induce eddy currents. When the gap distance between the probe and the thrust disk changes, the intensity of the eddy currents and the equivalent impedance of the probe will also change. The weak change signal corresponding to the gap is transmitted via a high-frequency coaxial cable to the preamplifier. The preamplifier completes signal amplification, shaping, and temperature compensation, and then outputs a linear DC voltage signal that is sent to the 3300/20 monitoring module. The internal circuit of the module performs arithmetic conversion on the input signal and converts the voltage signal into an accurate axial displacement physical quantity. On one hand, the measured values are compared with the preset warning, danger, and trip thresholds to achieve the set conditions, and the corresponding relay is driven to actuate, outputting a switch quantity interlock signal. On the other hand, the displacement values are linearly converted into a 0-10VDC standard voltage signal for external transmission. The two measurement channels operate independently and run according to the default factory logic for monitoring and judgment, ensuring stable and effective measurement results.

V. Main Technical Parameters

The measurement channels are two independent eddy current signal inputs, compatible with the 3300 series sensing components. The sensor system is powered by -24VDC. The standard measurement range is ±1.0mm, and it supports on-site small-scale range adjustment. Under normal temperature conditions, the full-scale error of the entire machine is no more than 1%, and the single-point measurement accuracy can reach ±0.03mm. The resolution meets the requirements of high-precision industrial monitoring. The equipment frequency response range is from DC to 1kHz, suitable for the monitoring scenarios of static axial displacement and low-speed rotating equipment. The input impedance is 10kΩ, which can perfectly match the output characteristics of the accompanying preamplifier. The switch quantity output includes one warning relay, two danger trip relays, with the rated load of the contact points being 250VAC/3A, and the contact mode can be set as normally open or normally closed. The analog output is isolated 0-10VDC DC voltage, the output signal is linearly corresponding to the measurement range, and it is compatible with conventional industrial control acquisition equipment. The equipment's working power supply is -24VDC, and the voltage allowable fluctuation range is ±10% of the rated value. The normal operating power consumption of the entire machine is approximately 5.5W. The working environment temperature range is 0℃ to 60℃, and the storage temperature range is -40℃ to 85℃. The relative humidity of the working environment does not exceed 95%, and it requires no condensation or corrosive gases. The equipment has a standard 19-inch rack structure, with a single slot installation, and the total weight of the equipment is approximately 1.4kg. The product has CE, UL, CSA, etc., international general certifications, and the overall design and performance indicators comply with API 670 rotating machinery protection-related specifications.

VI. Installation and System Configuration

The equipment is installed in a standard rack, which can be directly installed in the 3300 series dedicated system rack, occupying only a single slot, and is convenient for installation and disassembly, suitable for the standard cabinet layout of the industrial control room. When installing the accompanying sensors, the two eddy current probes are axially aligned with the rotor thrust disk, using a symmetrical layout method. The initial installation gap of the probes is set at the midpoint of the sensor's linear range to ensure that the equipment works within the effective measurement range throughout its operation. After powering on the equipment, on-site configuration can be carried out. Enter the configuration menu through the panel buttons, and complete the settings of measurement range, warning alarm value, danger alarm value, trip action value, voltage output correspondence, relay contact type, fault alarm mode, etc. All parameters are automatically saved, and all on-site debugging can be completed without an external upper software. The wiring of the equipment is divided into power wiring, sensing signal wiring, relay interlock wiring, and analog output wiring. When wiring, strictly distinguish the type and polarity of the lines according to the body markings to ensure accurate and reliable wiring.

VII. Typical Application Scenarios It is widely applied in steam turbine generator sets and gas turbine generator sets, mainly monitoring the axial movement of the rotor, and providing safety protection for thrust bearings, shaft seals, and the flow components of the generator set. In the petrochemical field, it is used for various centrifugal compressors and process turbine units, preventing damage caused by excessive axial thrust to the rotor and stator, as well as blade damage. It is compatible with large industrial pumps, induced draft fans, booster fans and other auxiliary equipment, real-time monitoring the axial position of the shaft system, avoiding bearing burnout and instability of the shaft system operation. It can also be used for various expanders and power turbines. It provides axial displacement protection during the entire stages of unit start-stop, load regulation, and steady operation.

VIII. Product Features and Advantages

It adopts a dual-channel independent monitoring design, combined with a complete sensor circuit diagnosis function, effectively identifying sensor circuit faults, reducing false alarms and misoperations in abnormal working conditions, and improving the stability of the entire protection system. Relying on eddy current non-contact measurement technology, the probe has no mechanical wear, and is combined with a high-precision signal processing circuit, providing stable measurement data with a small long-term drift, meeting the high-precision monitoring requirements of industrial applications. It also provides 0-10VDC voltage output and multi-channel relay switch output, with strong interface versatility, enabling quick connection to various mainstream industrial control systems, and low system integration difficulty. The entire machine is designed with industrial-grade hardware, with a wide temperature and humidity adaptation range, and can operate continuously in complex industrial sites such as power plants, chemical plants, and metallurgy. It is equipped with a complete local operation interface, allowing maintenance personnel to complete status viewing, fault determination, parameter modification, and daily maintenance and repair work conveniently and efficiently. The modular design facilitates spare parts replacement, and when a module fails, it can be quickly replaced, effectively shortening the unit downtime.

IX. Supporting Components

This monitoring module needs to be coordinated with components of the same series. The core supporting components include the 3300 series eddy current probes, which can be selected according to the installation space and measurement requirements of the site. It is equipped with the 330180 series preamplifiers, which provide power to the probes and complete the pre-processing of the original signals. It is also equipped with the 330130 series high-frequency coaxial extension cables, used to extend the signal transmission distance of the sensors, suitable for the layout spacing between on-site equipment and control room cabinets. The entire machine also requires the 3300 series standard installation frames and -24VDC dedicated power modules to provide fixed support and stable working power for the monitor.