Bently Nevada 330425-01-05 Accelerometer Acceleration Transducer

The Bently Nevada 330425-01-05 is a high‑range piezoelectric accelerometer engineered for critical machinery monitoring in hazardous (classified) locations where casing acceleration levels frequently exceed the capabilities of standard 50 g sensors. This variant features the widely used ¼‑28 UNF integral mounting stud (suffix -01) and carries multiple international hazardous area approvals (suffix -05), including ATEX, IECEx, CSA, and ABS. It is the definitive solution for high‑amplitude vibration measurement in explosive atmospheres, such as oil refineries, chemical plants, offshore platforms, and gas turbine installations where both safety certification and extended range are mandatory.

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 330425-01-05 uniquely combines this high‑amplitude capability with comprehensive intrinsic safety certifications, making it suitable for use in Zone 0, Zone 1, Zone 2, and Division 1/2 hazardous areas. 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 industrial environments.

This configuration is the direct high‑range equivalent of the 330400-01-05, sharing the same thread, approvals, and mechanical footprint, but offering a 50% increase in measurement range. The ¼‑28 UNF thread is a de‑facto standard in North America and many international installations, providing compatibility with a wide range of mounting hardware. The -05 approval package includes ATEX (Ex ia IIC T3, Ex ec IIC Gc, Ex tc IIC Dc), IECEx, CSA (Class I Div 1/2, Zone 2, Zone 22), and ABS marine approvals, enabling deployment in virtually any hazardous area worldwide.

This introduction focuses exclusively on the 330425-01-05 configuration, highlighting its unique value as the only standard ¼‑28 UNF, fully certified, high‑range accelerometer in the Bently Nevada portfolio. It compares this variant with the non‑certified high‑range version (330425-01-00), the certified lower‑range version (330400-01-05), and the metric‑thread certified version (330425-02-05, custom) to guide proper selection for demanding safety‑critical applications.

Functional Description and Certification Significance

The 330425-01-05 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 to extend the usable measurement range to 75 g peak without saturating the amplifier. This range extension is critical 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, resulting in inaccurate amplitude readings and potentially missed fault indications.

The -05 certification package adds intrinsic safety (Ex ia) and increased safety (Ex ec) ratings, allowing installation in the most demanding explosive environments. The sensor carries the ATEX marking Ex ia IIC T3 Ga for Zone 0/1, Ex ec IIC Gc for Zone 2, and Ex tc IIC Dc for Zone 22 (dust). It is also certified under IECEx with equivalent ratings and by CSA for Class I, Division 1, Groups A, B, C, D; Class II, Groups E, F, G; Class III; and Class I, Division 2 as well as Zone 2 and Zone 22 for North American installations. The ABS approval covers marine vessels, offshore units, and mobile offshore structures.

The entity parameters for the 330425-01-05 are identical to those of the 330400-01-05: Ui = 28 V, Ii = 150 mA, Pi = 0.84 W, Ci = 10.8 nF, Li = 0 μH. These values define the maximum electrical parameters that can be applied to the sensor without compromising intrinsic safety. When connected through an approved intrinsic safety barrier, the sensor can be safely used in Zone 0 environments (continuous presence of explosive gas). The sensor’s wide operating temperature range (-55°C to +121°C) and IP68 rating ensure reliable performance in extreme conditions, from Arctic cold to desert heat.

The combination of 75 g range and hazardous area certifications makes the 330425-01-05 a globally versatile transducer for high‑vibration, high‑risk installations. It eliminates the need for thread adapters (which can introduce mechanical resonances) while meeting the strictest safety standards. For applications requiring both high range and safety compliance, this is the standard factory‑offered solution.

Detailed Comparison with Other Configurations

To assist in proper selection, the following table compares the 330425-01-05 with its main alternatives: the non‑certified high‑range version (330425-01-00), the certified lower‑range version (330400-01-05), and the metric‑thread certified version (330425-02-05, custom). This comparison highlights the unique positioning of the -01-05.

Selection Guide – Key Differences

The 330425-01-05 is the standard ¼‑28 UNF, fully certified, high‑range option. Choose this variant when:

• Peak vibration amplitudes routinely exceed 50 g.

• The machinery is in a hazardous (classified) area requiring ATEX, IECEx, or CSA certifications.

• The mounting thread is ¼‑28 UNF.

If you need metric thread (M8) with same approvals, you would require a custom order (330425-02-05). If your vibration levels are consistently below 50 g and you need higher sensitivity, the 330400-01-05 is more suitable. For safe areas, the 330425-01-00 is the non‑certified equivalent.

Hardware Characteristics – Specific to 330425-01-05

Physical Dimensions and Mounting

• Thread: ¼‑28 UNF integral stud (male). This thread is compatible with many mounting bases and adapters.

• 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.

• Mounting Torque: 4.1 N·m (3.0 ft·lb). Use a torque wrench to avoid over‑tightening.

Connector and Cabling for Hazardous Areas

• Connector: 3‑pin MIL‑C‑5015 receptacle (316L stainless steel). This connector is approved for use in hazardous areas when properly mated.

• Compatible Cables (must respect intrinsic safety cable parameters):

  • 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. The total Ci (sensor + cable) and Li (sensor + cable) must not exceed the barrier’s allowable values.

• 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) 37439-01 (¼‑28 to ¼‑28). Bently Nevada recommends using the base for older units even in hazardous areas; the base itself is non‑incendive and can be installed in classified locations if properly grounded.

Intrinsic Safety and Hazardous Area Approvals – Detailed for 330425-01-05

The 330425-01-05 carries the following markings and certifications (as per the datasheet):

• ATEX:

  • Ex ia IIC T3 Ga (Zone 0/1)

  • Ex ec IIC Gc (Zone 2)

  • Ex tc IIC Dc (Zone 22)

• IECEx: Ex ia IIC T3 Ga, Ex ec IIC Gc, Ex tc IIC Dc

• CSA:

  • Class I, Division 1, Groups A, B, C, D

  • Class II, Groups E, F, G

  • Class III

  • Class I, Division 2, Groups A, B, C, D

  • Class I Zone 2, AEx ec IIC Gc

  • Zone 22, AEx tc IIC Dc

• ABS: Approved for Marine Vessels, Offshore Units, and Mobile Offshore Units.

Entity Parameters (identical for all -05 variants):

Conditions of Safe Use (ATEX/IECEx Zone 0/1):

• The sensor must be connected to an associated intrinsically safe apparatus that meets the entity parameters.

• Cable type A or B (per EN 60079‑25) must be used, respecting cable capacitance and inductance limits.

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

Conditions for Zone 2 (North America):

• The supply electrical parameters must not exceed the entity parameters.

• The mating connector must provide at least IP54 ingress protection (IEC 60079‑0 and IEC 60079‑7/15).

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

Requirements for North America (CSA):

• The sensor may only be powered by a power supply unit with a limited energy electric circuit per CAN/CSA C22.2 No. 61010‑1‑12 and ANSI/UL 61010‑1, or Class 2 as defined in the Canadian Electrical Code (C22.1, Section 16‑200) and/or National Electrical Code (NFPA 70), Article 725.121.

Installation Best Practices for 330425-01-05 in Hazardous Areas

1. Intrinsic Safety Barrier – Always connect the sensor through a 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.

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, use lower‑capacitance cables (e.g., 130539 with 18 AWG) to maximize allowable length. The maximum physical length of 305 m (1000 ft) is a guideline; the limiting factor is the electrical parameters.

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.

4. Connector Sealing – In hazardous areas, ensure the 3‑pin MIL connector is properly mated and sealed (IP54 or better) as required by ATEX/IECEx. Use appropriate cable glands and sealing compounds if needed.

5. Mounting Surface Preparation – Clean and lap the mounting surface to 32 µin rms or better. Apply anti‑seize compound if necessary, and torque the 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 (37439-01) 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.

Comparison with Other Certified Options – Why Choose 330425-01-05?

• vs. 330425-01-00 – The -00 lacks any hazardous area approvals. If your plant has classified areas, the -05 is mandatory. The -05 also adds ABS approval, which is beneficial for marine applications.

• vs. 330400-01-05 – Both have identical approvals and 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 – Both are certified high‑range variants. The -02 uses M8 x 1 thread; the -01 uses ¼‑28 UNF. Choose 330425-01-05 if your machinery has ¼‑28 mounting holes; choose the metric version if you have M8 holes (custom order).

Ordering Information

When ordering the 330425-01-05, use the full part number exactly as shown:

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

• -01 – Mounting thread: ¼‑28 UNF integral stud

• -05 – Agency approval: Multiple (CSA, ATEX, IECEx, ABS)

Compatible Cables and Accessories for Hazardous Areas

Important: When ordering cables for hazardous areas, ensure the cable parameters (capacitance, inductance) do not exceed the allowable limits when combined with the sensor’s Ci and Li and the barrier’s specifications. Consult the barrier manufacturer’s documentation for cable length calculations.

Certifications and Compliance – Special Note

The 330425-01-05 is certified for intrinsic safety (Ex ia) and increased safety (Ex ec) and dust protection (Ex tc). It is suitable for use in Gas Groups IIC (hydrogen, acetylene) and IIB (ethylene) and IIA (propane). The temperature class T3 indicates a maximum surface temperature of 200°C under fault conditions, well above the sensor’s operating range.

The sensor is also RoHS compliant and meets China RoHS requirements with an EFUP of 15 years. For the most current approval certificates, refer to the Approvals Quick Reference Guide (108M1756) or visit bntechsupport.com.

Warranty and Support

Bently Nevada (Baker Hughes) provides a standard product warranty covering defects in materials and workmanship. For technical support, application engineering, or assistance with intrinsic safety calculations, contact your local Bently Nevada representative or access the Bently Nevada Media Library at bntechsupport.com.