Bently Nevada 330425-02-00 Accelerometer Acceleration Transducer

The Bently Nevada 330425-02-00 is a high‑range piezoelectric accelerometer engineered for critical machinery monitoring in metric‑standard, non‑hazardous industrial environments where casing acceleration levels frequently exceed the capabilities of standard 50 g sensors. This variant features the M8 x 1 integral mounting stud (suffix -02) and carries no hazardous area approvals (suffix -00), making it the ideal choice for installations that adhere to International Organization for Standardization (ISO) metric fastening conventions and operate in safe (non‑classified) areas. It is particularly well‑suited for European, Asian, and global facilities where M8 threads are the norm and where high‑amplitude vibration measurement is required without the regulatory overhead of explosion‑proof certifications.

The 330425 series is designed to meet American Petroleum Institute (API) Standard 670 for accelerometers, providing a 75 g peak amplitude range with a sensitivity of 25 mV/g. The 330425-02-00 uniquely combines this extended range with a metric mounting thread, offering a seamless solution for machinery with M8 mounting holes and vibration levels that exceed 50 g. Its lower sensitivity (compared to the 330400’s 100 mV/g) allows accurate measurement of strong vibration signals without saturation, while the rugged IP68‑rated, hermetically sealed housing ensures reliable operation in harsh environments.

This configuration is the direct metric‑thread equivalent of the 330425-01-00, sharing the same performance and approvals but offering the M8 stud for compatibility with metric hardware. The M8 thread provides slightly larger diameter (8 mm vs. ¼‑28 UNF’s ~6.35 mm) and finer pitch (1 mm vs. 28 TPI), offering greater thread engagement and resistance to loosening under vibration—a critical advantage in high‑vibration environments. The -00 suffix indicates no hazardous area approvals, making it a cost‑effective choice for safe areas.

This introduction focuses exclusively on the 330425-02-00 configuration, highlighting its unique value as the standard M8‑threaded, non‑certified, high‑range accelerometer in the Bently Nevada portfolio. It compares this variant with other options (e.g., the ¼‑28 non‑certified high‑range 330425-01-00, the M8 non‑certified lower‑range 330400-02-00, and the M8 certified high‑range 330425-02-05) to guide proper selection for metric, safe‑area, high‑amplitude applications.

Functional Description and Metric Thread Advantage

The 330425-02-00 accelerometer operates on the piezoelectric principle, converting mechanical acceleration into an electrical charge that is conditioned into a low‑impedance voltage signal. Its sensitivity of 25 mV/g (2.5 mV/m/s²) is intentionally lower than the 330400’s 100 mV/g to extend the usable measurement range to 75 g peak without saturating the amplifier. This range extension is essential for machinery with inherently high vibration levels, such as high‑speed gearboxes, reciprocating compressors, and turbines with strong blade pass frequencies, where a 50 g sensor would clip the signal.

The M8 x 1 integral mounting stud is the preferred metric thread for vibration sensors in many parts of the world, particularly in Europe, Asia, and regions following ISO standards. The M8 thread offers a larger diameter and finer pitch compared to ¼‑28 UNF, providing better mechanical stability and resistance to loosening under high‑vibration conditions. This is especially beneficial for the 330425, which is designed for high‑amplitude environments where secure mounting is critical for measurement integrity. The M8 stud also eliminates the need for thread adapters, which can introduce additional mechanical compliance and reduce high‑frequency response.

The 330425-02-00 is mechanically identical to the 330400-02-00: 23 mm diameter, 59 mm height (including stud), 99 g weight, and 3‑pin MIL‑C‑5015 connector. It uses the same mounting torque (4.1 N·m) and the same cable options (130539, 169253, 167103). This mechanical interchangeability allows users to upgrade from a 330400 to a 330425 without changing mounting hardware or cabling, provided the vibration levels justify the change.

The -00 suffix indicates no hazardous area approvals, so the sensor is certified only for general industrial use (FCC, EMC, RoHS, China RoHS, and ABS for marine). It is NOT rated for ATEX, IECEx, or CSA hazardous locations. This makes it the economical choice for safe areas where explosion protection is not required.

Detailed Comparison with Other Configurations – Metric and High‑Range Focus

To assist in proper selection for metric, high‑amplitude, safe‑area applications, the following table compares the 330425-02-00 with its main alternatives: the ¼‑28 non‑certified high‑range version (330425-01-00), the M8 non‑certified lower‑range version (330400-02-00), and the M8 certified high‑range version (330425-02-05, custom). This comparison highlights the unique value of the -02-00.

Selection Guide – Key Differences

The 330425-02-00 is the standard M8‑threaded, non‑certified, high‑range option. Choose this variant when:

• Peak vibration amplitudes routinely exceed 50 g.

• The machinery is in a non‑hazardous (safe) area.

• The mounting thread is M8 x 1.

• You do not require explosion‑proof or intrinsic safety certifications.

If you need ¼‑28 UNF thread, choose 330425-01-00. If your vibration levels are consistently below 50 g and you need higher sensitivity, the 330400-02-00 is more suitable. If you require hazardous area approvals with M8 thread, you would need a custom order (330425-02-05).

Hardware Characteristics – Specific to 330425-02-00

Physical Dimensions and Mounting

• Thread: M8 x 1 integral stud (male). This metric thread is compatible with ISO 261 coarse pitch standards, commonly used in European and Asian machinery.

• Height: 59 mm (2.3 in) including stud.

• Diameter: 23 mm (0.93 in).

• Weight: 99 g (3.5 oz) typical (no cable).

• Mounting Surface Finish: Recommended 32 µin rms or better (~0.8 µm Ra).

• Mounting Torque: 4.1 N·m (3.0 ft·lb). Use a torque wrench to avoid over‑tightening. The M8 stud provides a larger thread engagement area than ¼‑28, enhancing stability.

Connector and Cabling

• Connector: 3‑pin MIL‑C‑5015 receptacle (316L stainless steel). This is the standard connector for all 330400/330425 series accelerometers.

• Compatible Cables:

  • 130539: 18 AWG, 3‑conductor shielded, with fluorosilicone elastomer boot (recommended for rugged environments).

  • 169253: 22 AWG, 3‑conductor shielded.

  • 167103: 22 AWG, armored cable.

• Maximum Cable Length: 305 metres (1000 ft) without signal degradation.

• Mating Connector: 00531080 for custom cable assemblies.

Environmental and Electrical Specifications

• Power: -24 V dc ±0.5 V, 2 mA nominal bias current.

• Output Bias Voltage: -8.5 V dc ±0.5 V.

• Grounding: Case isolated – essential for avoiding ground loops.

• Operating/Storage Temperature: -55°C to +121°C (-67°F to +250°F).

• Shock Survivability: 5000 g peak.

• Humidity: 100% condensing (hermetically sealed case).

• IP Rating: IP68 (sensor only) – dust tight and watertight.

• Magnetic Field Susceptibility: < 225 mg/gauss at 50 gauss, 50‑60 Hz.

Base Strain Sensitivity Notes

Base strain sensitivity can affect low‑frequency measurements if the mounting surface flexes. For the 330425-02-00:

• If the serial number begins with “G” (newer sensors): Base strain sensitivity is only 0.005 g/mstrain – no extra mounting base required.

• If the serial number does NOT begin with “G” (older, pre‑April 2004): Base strain sensitivity is 0.100 g/mstrain without the mounting base, but reduces to 0.0005 g/mstrain when using the supplied Mounting Base (API adapter) – part number 37439-02 (M8 to M8). Bently Nevada recommends using the base for these older units to ensure optimal low‑frequency performance.

Application Guidelines – When to Use 330425-02-00

The 330425-02-00 is recommended for machinery where peak vibration levels commonly exceed 50 g and where metric mounting is standard. Typical applications include:

• High‑Speed Gearboxes with Metric Mounting – Gear mesh forces can produce high‑amplitude, high‑frequency vibrations; the 75 g range provides ample headroom, and the M8 thread matches European gearbox designs.

• Reciprocating Compressors (Metric Designs) – Impact forces from piston motion generate high g‑levels; the M8 stud ensures secure mounting.

• Turbine Blade Pass Frequencies – In certain turbine stages, blade pass vibrations can be high; the M8 thread is common in many turbine applications.

• Heavy‑Duty Industrial Fans and Blowers with Metric Hardware – Large imbalance or aerodynamic forces can produce high casing accelerations.

• Marine and Offshore Machinery – The sensor carries ABS approval, making it suitable for safe‑area marine applications where metric threads are often used.

When to choose 330400-02-00 instead:

• Expected peak vibration levels are consistently below 50 g.

• Higher sensitivity (100 mV/g) is needed to detect low‑amplitude bearing defects or early‑stage faults.

• You prioritize signal‑to‑noise ratio over range extension.

When to choose 330425-01-00 instead:

• Your mounting thread is ¼‑28 UNF (common in North America).

When to choose 330425-02-05 (custom):

• You need hazardous area approvals with M8 thread.

Installation Best Practices for 330425-02-00

1. Surface Preparation – Clean the mounting surface to remove paint, rust, or debris. Achieve a surface finish of 32 µin rms or better (e.g., by lapping). For metric surfaces, ensure the tapped hole is M8 x 1 and is perpendicular to the measurement axis.

2. Stud Installation – Apply a thin layer of anti‑seize compound (if required) and hand‑tighten the integral M8 stud into the prepared hole. Then torque to 4.1 N·m (3.0 ft·lb). Do not use the connector housing to apply torque; use a wrench on the hex flats of the stud.

3. Cable Connection – Align the 3‑pin connector and tighten the coupling nut securely. For long cable runs, use the recommended 18 AWG cable (130539) to minimise voltage drop and signal loss. Route cables away from high‑voltage lines and avoid sharp bends.

4. Grounding – Because the case is isolated, the sensor does not require a separate ground. However, the cable shield should be connected to the monitoring system’s common reference at the power supply end to minimize electrical noise.

5. Base Strain Consideration – If the sensor’s serial number does not begin with “G”, install the supplied Mounting Base (37439-02 for M8 to M8) between the stud and the machine surface. This reduces base strain sensitivity dramatically.

6. Environmental Protection – For outdoor installations, use splash boots (available separately) and ensure all cable connections are sealed. The sensor itself is IP68, but the cable termination may require additional protection.

Comparison with Other Metric High‑Range Options – Why Choose 330425-02-00?

• vs. 330425-01-00 – Both are non‑certified and have identical performance. The -01 uses ¼‑28 UNF; the -02 uses M8. Choose based on your machinery’s mounting standard. If your plant uses metric fasteners, the -02 is the natural choice.

• vs. 330400-02-00 – The 330425-02-00 offers 75 g range (vs. 50 g) but lower sensitivity (25 mV/g vs. 100 mV/g). Choose the 330425 when vibration levels exceed 50 g; choose the 330400 for better low‑amplitude detection.

• vs. 330425-02-05 – The -05 adds hazardous area approvals (ATEX, IECEx, CSA). If your installation is in a safe area, the -00 is more economical and does not require certified barriers. The -05 is a custom order, so the -00 is the standard metric high‑range option.

Ordering Information

When ordering the 330425-02-00, use the full part number exactly as shown:

• 330425 – Base model (accelerometer, 75 g, 25 mV/g)

• -02 – Mounting thread: M8 x 1 integral stud

• -00 – Agency approval: None

Compatible Cables and Accessories

Note: The 330425-02-00 does not include a cable; order separately. Ensure cable length does not exceed 305 m.

Certifications and Compliance

Because the -00 option has no hazardous area approvals, it is certified for general industrial use only. It complies with:

• FCC Part 15 – Radio frequency interference limits.

• EMC Directive 2014/30/EU – Electromagnetic compatibility.

• RoHS Directive 2011/65/EU – Restriction of hazardous substances.

• China RoHS – EFUP of 15 years (SJ/T 11364-2024).

• ABS – (Marine Vessels, Offshore Units) – the sensor itself is approved for maritime use even without explosion protection.

It is NOT rated for ATEX, IECEx, or CSA hazardous locations. If your installation requires intrinsic safety, you must order a variant with the -05 option (e.g., 330425-02-05, custom).

Warranty and Support

The Bently Nevada 330425-02-00 is covered under the standard manufacturer’s warranty (refer to Bently Nevada Terms and Conditions). For technical support, application assistance, or custom configurations (e.g., metric thread with approvals), contact your local Bently Nevada sales representative or access the Bently Nevada Media Library at bntechsupport.com.