21000-28-05-20-035-04-02 Bently Nevada Compliant Assembly

Product Overview

The Bently Nevada 21000-28-05-20-035-04-02 is a robust, explosion-proof Proximity Probe Housing Assembly designed to shield critical dynamic vibration sensors. Constructed with a heavy-duty aluminum body and an integrated 304 stainless steel sleeve, this assembly is fully compliant with the American Petroleum Institute's API 670 Standard for externally mounted probe housings. It contains a reverse-mount 3300 XL 8mm proximity probe, allowing maintenance teams to easily access, gap, or replace sensors from outside the machine casing without requiring an expensive machinery shutdown.

Core Features

• API 670 Compliant Architecture: Specifically configured to meet stringent petrochemical and power generation criteria for external sensor mounting and safety boundaries.
• Explosion-Proof Aluminum Body: High-strength, lightweight aluminum casting equipped with a screw-in dome cover and robust O-ring path sealing.
• North American Hazardous Certifications: Certified by the Canadian Standards Association (CSA) for Class I Div 1 & 2 (Groups C, D) and Class II (Groups E, F, G) hazardous locations.
• Weatherproof Environmental Armor: Earns a certified CSA Type 4 rating, providing excellent protection against driving rain, industrial dust, and localized corrosive elements.

Technical Specifications

Engineering & Installation Guide

• Mechanical Interface & Weight Limits: Weighing a typical 1.10 kg (2.40 lbs), the 21000 assembly utilizes a lightweight yet robust aluminum housing body. Because it integrates a 2.0-inch standoff adapter, the mandatory 3/4-14 NPT mounting thread option must be systematically inspected for straight alignment. Screw into the machine casing wall tap and compress the thread seal securely to keep a gas-tight fluid barrier.
• Loop Extension Matching Limits: Take note of the physical cable limits. Since this variation features a short 0.5-meter internal probe cable option, the internal sensor connectors will not be visible outside the sleeve body. The maximum combined length allowance of the standoff and penetration tube is capped at 13.5 inches (34.3 mm) to ensure the 0.5m lead can comfortably bridge out without strain.
• Conduit Sealing and Plugging: The Option 04 configuration comes with a single 3/4-14 NPT metal plug. For explosion-proof installations, ensure the open conduit port is completely sealed using an approved cable gland or conduit sealing compound to prevent explosive gases from tracking down the instrumentation loop lines.
• Intrinsically Safe Grounding: For intrinsically safe loops inside hazardous processing zones, verify the installation matches Bently Nevada reference drawing 140979. Ensure proper earth bonding is maintained between the aluminum body shell and the structural machinery frame to negate stray static charges.

Technical FAQs

Q1: What does compliance with the API 670 standard mean for this proximity probe housing assembly?
A1: API 670 is the American Petroleum Institute’s defining standard for machinery protection systems. Compliance guarantees that the housing meets strict global dimensions, structural strength limits, environmental sealing barriers, and external mounting requirements necessary to safely house vibration sensors on critical oil and gas refinery equipment.

Q2: Why does the 21000 housing require a 2-inch standoff adapter combined with a 3.5-inch penetration depth?
A2: The 2.0-inch standoff adapter elevates the main aluminum terminal junction box away from the hot exterior skin of the machine casing. The 3.5-inch penetration depth sleeve then extends down through the insulation and machine wall, positioning the internal 3300 XL 8mm probe tip at the exact proximity gap required to sense shaft movement.

Q3: What is the benefit of the reverse-mount probe configuration contained within this 21000 assembly?
A3: In a standard forward-mount setup, replacing a probe requires unbolting heavy machine covers. The reverse-mount configuration lets you unthread the dome cover and withdraw the probe out through the back of the 304 stainless steel sleeve from outside the machine, cutting asset downtime down to a minimum during routine instrument swaps.