Chemical processing facilities frequently operate under hazardous area classifications due to the presence of flammable gases, vapors or liquids. A Class 1, Division 2 (C1D2) designation applies where these substances are not normally present in flammable concentrations but may occur under abnormal conditions such as equipment leaks or process upsets. These environments impose strict safety requirements on monitoring systems, especially when electrical or electronic devices are placed within the classified zone.
The challenge for maintenance and reliability teams is clear:
- Physical access to critical assets is often restricted for safety and process continuity reasons.
- Conventional vibration sensors may require explosion-proof housings, conduit sealing and additional approvals, increasing both cost and installation complexity.
- Intermittent monitoring—or worse, no monitoring—can allow mechanical faults to progress undetected, leading to costly downtime or catastrophic failures.
Therefore, the industry has sought ways to capture the same, or better, diagnostic insight without introducing potential ignition sources or requiring equipment shutdowns.
Limitations of Traditional Monitoring in C1D2 Zones
While contact accelerometers and proximity probes are widely used in nonhazardous areas, deploying them in C1D2 locations typically involves additional engineering controls. These may include:
- Intrinsically safe barriers to limit energy to safe levels
- Explosion-proof enclosures that can withstand and contain internal ignition events
- Rigid conduit systems to protect cabling and maintain hazardous area integrity
These measures, while effective, can add significant cost and often require process interruptions for installation. In certain cases, particularly where assets are elevated, enclosed or otherwise difficult to reach, continuous monitoring may become impractical.
Noncontact Optical Vibration Measurement Principles
Noncontact optical methods address these challenges by enabling vibration measurements without placing any powered devices within the C1D2 zone. Instead, a sensor positioned outside the hazardous area captures motion optically—often through existing sightlines or protective windows.
The basic principle involves recording the displacement of a surface over time using high-resolution video or laser-based measurement techniques. This displacement data is then processed to derive vibration metrics such as amplitude, frequency content and phase relationships. Unlike traditional point sensors, optical systems can measure across multiple locations simultaneously, providing a more holistic view of machine dynamics.
In a chemical processing context, these systems are particularly useful for:
- Identifying resonance conditions in large structural or piping systems
- Detecting early-stage bearing or shaft faults in pumps, compressors and mixers
- Assessing misalignment or looseness that may lead to process inefficiencies or safety risks
Deployment in Hazardous Environments
The practical application of optical vibration measurement in C1D2 zones requires careful planning:
- Sensor placement must provide a clear line of sight while remaining outside the hazardous boundary.
- Lighting conditions may need adjustment to ensure data quality, though many optical systems can operate in low-light conditions common in industrial facilities.
- Mounting stability is critical, as even small movements of the sensor platform can introduce measurement errors.
Once positioned, the system can capture motion data continuously or on-demand, depending on operational requirements. This allows reliability teams to perform both periodic inspections and long-term trend monitoring without ever entering the hazardous area.
Case Example: Continuous Monitoring in Oil & Gas & Chemical Processing
In a recent deployment, a chemical processing facility with C1D2-classified pump galleries implemented a remote optical vibration monitoring system as part of its reliability program. The installation allowed for continuous observation of critical pump shafts and coupling areas from a safe control room location. Within weeks, the system detected subtle increases in vibration amplitude at a bearing housing, correlating to a developing lubrication issue. Because the fault was identified early, maintenance could be scheduled during a planned outage, avoiding an unscheduled shutdown that would have cost several days of lost production.
Similarly, oil and gas facilities have applied the same approach through integrated condition monitoring platforms, enabling cross-site visibility and long-term data trending for multiple hazardous locations.
For maintenance and reliability professionals in the chemical processing industry, the ability to monitor equipment health without entering hazardous zones represents a significant step forward in both safety and operational efficiency. Noncontact optical vibration measurement enables early fault detection, supports predictive maintenance strategies and reduces the risk associated with manual inspections in C1D2 areas.
While the technology does not replace all forms of vibration analysis, it fills a critical gap where traditional sensors are impractical or unsafe to install. These systems are likely to become a standard component of hazardous area reliability programs across chemical, oil and gas and other process industries.
