Bently Nevada 330425-02-CN Accelerometer Acceleration Transducer

The Bently Nevada 330425-02-CN is a high‑range piezoelectric accelerometer specifically engineered for critical machinery monitoring in metric‑standard hazardous locations within the Chinese industrial market where casing acceleration levels frequently exceed the capabilities of standard 50 g sensors and where both explosion‑proof safety and ISO metric mounting are mandatory. This variant features the M8 x 1 integral mounting stud (suffix -02) and carries a dedicated China‑specific certification package (suffix -CN), which includes approvals from recognized Chinese testing bodies such as NEPSI or CQST in accordance with GB/T 3836 series standards. It is the definitive choice for installations in Chinese oil refineries, chemical plants, power generation facilities, and offshore platforms that require both metric thread compatibility and compliance with local explosion‑proof regulations, while also needing the extended amplitude range of 75 g.

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-CN uniquely combines this extended range with an M8 thread and Chinese certification, enabling accurate measurement of strong vibration signals without saturation while ensuring full compliance with GB/T 3836 standards. Its lower sensitivity (compared to the 330400’s 100 mV/g) allows the sensor to handle high‑energy transients and steady‑state vibrations without clipping, making it ideal for high‑speed gearboxes, reciprocating compressors, and turbines with strong blade pass frequencies in Chinese hazardous areas.

This configuration is the direct metric‑thread equivalent of the 330425-01-CN, offering the same high‑range performance and Chinese approvals but with the M8 stud for compatibility with metric hardware. The M8 thread provides a 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‑amplitude environments. The -CN approval package includes certification to GB/T 3836.1, GB/T 3836.4, and GB/T 3836.15 for Ex ia IIC T4 Ga (intrinsic safety, Zone 0/1) and Ex ec IIC Gc (increased safety, Zone 2), along with compliance with China RoHS and China EMC requirements. This makes it a fully compliant solution for the local market.

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

Functional Description and Metric Thread Advantage with Chinese Certification

The 330425-02-CN 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, where a 50 g sensor would clip the signal, resulting in inaccurate amplitude readings and potentially missed fault indications. The 75 g range provides a 50% margin over the 330400, accommodating transient spikes, start‑up resonance crossings, and steady‑state high‑amplitude vibrations common in high‑speed rotating equipment.

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 China, where ISO metric fasteners are the standard. The M8 thread offers a slightly 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 -CN certification package adds Chinese explosion‑proof approvals that are mandatory for use in hazardous areas within China, ensuring compliance with local laws, insurance requirements, and safety regulations. The sensor carries certifications in accordance with Chinese national standards GB/T 3836.1 (General Requirements), GB/T 3836.4 (Intrinsic Safety), and GB/T 3836.15 (Installation Requirements) . It is approved for Ex ia IIC T4 Ga (intrinsic safety, Zone 0/1) and Ex ec IIC Gc (increased safety, Zone 2) under the Chinese certification system, typically issued by recognized testing bodies such as NEPSI (National Supervision and Inspection Center for Explosion Protection and Safety of Instrumentation) or CQST (China Quality Supervision and Testing Center for Explosion Protected Electrical Products) . The T4 temperature class (≤135°C) is suitable for most industrial gases.

The entity parameters for the 330425-02-CN are identical to other -CN/-05 variants: Ui = 28 V, Ii = 150 mA, Pi = 0.84 W, Ci = 10.8 nF, Li = 0 μH. These parameters ensure compatibility with Chinese‑approved intrinsic safety barriers and isolators. The sensor’s wide operating temperature range (-55°C to +121°C) and IP68 rating ensure reliable performance in China’s diverse climatic conditions, from the cold of Heilongjiang to the heat of Hainan.

The combination of 75 g range, M8 thread, and Chinese hazardous area approvals makes the 330425-02-CN a globally versatile yet locally compliant transducer for high‑vibration, high‑risk installations with metric hardware in China. It is the standard factory‑offered solution for such demanding applications.

Detailed Comparison with Other Configurations – Chinese Market and High‑Range Focus

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

Selection Guide – Key Differences for China with Metric Threads

The 330425-02-CN is the only standard M8‑threaded, high‑range accelerometer with full Chinese hazardous area certification in the 330425 series. Choose this variant when:

• Peak vibration amplitudes routinely exceed 50 g.

• The machinery is in a hazardous (classified) area requiring Chinese GB/T 3836 certification.

• The mounting thread is M8 x 1.

If you need ¼‑28 UNF thread with same approvals, choose 330425-01-CN. If your vibration levels are consistently below 50 g and you need higher sensitivity, the 330400-02-CN is more suitable. For safe areas, the 330425-02-00 is the non‑certified equivalent. For international hazardous areas where Chinese certification is not required, the 330425-02-05 may be suitable, but it may not be accepted in China without additional certification.

Hardware Characteristics – Specific to 330425-02-CN

Physical Dimensions and Mounting

• Thread: M8 x 1 integral stud (male). This metric thread is widely used in Chinese and international machinery, providing excellent holding power and compatibility with standard M8 mounting holes.

• 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.

Connector and Cabling for Chinese Hazardous Areas

• Connector: 3‑pin MIL‑C‑5015 receptacle (316L stainless steel). This connector is compatible with all 330400/330425 series cables.

• Compatible Cables (must comply with Chinese cable parameter requirements):

  • 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) – but must be derated based on cable capacitance and inductance to stay within the barrier’s limits, as per GB/T 3836.15.

• 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 in hazardous installations.

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

• Shock Survivability: 5000 g peak.

• Humidity: 100% condensing (hermetically sealed).

• IP Rating: IP68 (sensor only).

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

Base Strain Sensitivity

• For serial numbers beginning with “G” (newer production): 0.005 g/mstrain – no mounting base required.

• For serial numbers NOT beginning with “G” (older units): 0.100 g/mstrain without base, but reduces to 0.0005 g/mstrain when using the Mounting Base (API adapter) 37439-02 (M8 to M8). This accessory is particularly useful for installations in China where older sensors may still be in service.

Chinese Hazardous Area Compliance – Detailed for 330425-02-CN

The 330425-02-CN is certified in accordance with Chinese national standards for explosive atmospheres. Typical approval includes:

• Ex ia IIC T4 Ga – Intrinsically safe for Zone 0 (continuous presence of explosive gas) and Zone 1, suitable for Gas Group IIC (hydrogen, acetylene) and T4 temperature class (≤135°C surface temperature).

• Ex ec IIC Gc – Increased safety for Zone 2.

• IP68 – Dust‑tight and watertight, per GB/T 4208.

• The sensor is also compliant with China RoHS (SJ/T 11364) with an EFUP (Environmental Friendly Use Period) of 15 years.

Entity Parameters (subject to final certification; typical values):

Conditions of Safe Use (per GB/T 3836):

• The sensor must be connected to an associated intrinsically safe apparatus that meets the entity parameters and is certified to Chinese standards.

• Cable parameters (capacitance, inductance) must be within the limits specified by the barrier manufacturer and the Chinese certification.

• Operating ambient temperature: -55°C ≤ Tamb ≤ +121°C.

• The mating connector must provide at least IP54 ingress protection as required by GB/T 3836.15.

• Transient protection shall be provided, set at a level not exceeding 140% of the peak rated voltage at the supply terminals.

Installation Best Practices for 330425-02-CN in Metric Chinese Hazardous Areas

1. Intrinsic Safety Barrier – Always connect the sensor through a Chinese‑certified intrinsic safety barrier that limits voltage, current, and power to within the entity parameters. Ensure the barrier’s output parameters (Uo, Io, Po) do not exceed Ui, Ii, and Pi. Use barriers that comply with GB/T 3836.4.

2. Cable Selection and Length Calculation – The sensor’s Ci (10.8 nF) and Li (0 μH) must be added to the cable’s capacitance and inductance. The total must not exceed the barrier’s allowable cable parameters. For long runs (>100 m), use lower‑capacitance cables (e.g., 130539 with 18 AWG) to maximize allowable length.

3. Grounding – The case is isolated, so grounding is not required for the sensor body. However, the cable shield should be grounded at the power supply end (typically at the barrier) to minimize noise. Do not ground the shield at both ends to avoid ground loops. Follow Chinese grounding practices (GB/T 50065).

4. Connector Sealing – In hazardous areas, ensure the 3‑pin MIL connector is properly mated and sealed (IP54 or better) as required by GB/T 3836.15. Use appropriate cable glands and sealing compounds that are certified for use in China.

5. Mounting Surface Preparation – Clean and lap the mounting surface to 32 µin rms or better. The M8 hole must be perpendicular to the measurement axis. Apply anti‑seize compound if necessary, and torque the M8 stud to 4.1 N·m (3.0 ft·lb). Do not use the connector body to apply torque.

6. Base Strain Sensitivity – If the sensor’s serial number does not begin with “G”, install the Mounting Base (37439-02) to reduce strain sensitivity. Ensure the base is properly torqued and grounded per site procedures.

7. Environmental Protection – Although the sensor is IP68, the cable termination and connectors require additional protection (splash boots, conduit, etc.) for outdoor or wet locations in China’s diverse climate.

Comparison with Other China‑Focused Options – When to Choose 330425-02-CN?

• vs. 330425-02-00 – The -00 lacks any hazardous area approvals. For any Chinese installation in a classified area (Zone 0, 1, or 2), the -CN is mandatory. Using the -00 in a hazardous area would violate Chinese safety regulations.

• vs. 330425-01-CN – Both have identical Chinese certifications and performance. The -01 uses ¼‑28 UNF thread, while the -02 uses M8. Choose 330425-02-CN if your machinery has metric mounting holes (common in European‑designed plants, many new Chinese facilities, and international joint ventures). Using the correct thread eliminates the need for adapters, which can degrade high‑frequency response.

• vs. 330400-02-CN – Both are certified and have M8 thread. The 330400 offers 50 g range and 100 mV/g sensitivity. Choose 330425 when vibration levels exceed 50 g; choose 330400 for higher sensitivity (better low‑amplitude detection) when levels are below 50 g.

• vs. 330425-02-05 – The -05 carries ATEX/IECEx/CSA certifications, which may not be directly accepted by Chinese authorities without additional testing and approval. The -CN variant has been pre‑approved to Chinese standards (GB/T 3836), saving time and cost on project certification. For purely domestic Chinese installations, the -CN is the safer and faster choice.

Ordering Information

When ordering the 330425-02-CN, 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

• -CN – Certification: Chinese hazardous area approvals (GB/T 3836)

Compatible Cables and Accessories for Chinese Hazardous Areas

Important: When ordering cables for hazardous areas in China, ensure they are suitable for use with the certified barrier and comply with the cable parameter requirements of GB/T 3836.15.

Certifications and Compliance – Special Note for China

The 330425-02-CN is certified to GB/T 3836.1 (General Requirements), GB/T 3836.4 (Intrinsic Safety), and GB/T 3836.15 (Installation Requirements) . It is also compliant with China RoHS (SJ/T 11364) and China EMC (GB/T 18268.1). For the most current approval certificates (including the specific issuing body and marking), refer to the Bently Nevada China office or the Approvals Quick Reference Guide (108M1756). Always verify that the certification is valid for your specific hazardous area classification and temperature class.

Warranty and Support

The Bently Nevada 330425-02-CN is covered under the standard manufacturer’s warranty. For technical support, application assistance, or help with Chinese certification documentation, contact your local Bently Nevada representative in China or access the Bently Nevada Media Library at bntechsupport.com. Bently Nevada has a strong local presence in China to support customers with site surveys, installation guidance, and regulatory compliance.