The performance of dust explosion monitoring systems is influenced by various factors, which can be summarized into the following four categories:
1. Technical characteristics of the instrument and equipment themselves
Testing basic principles: Different basic principles have significant impacts on precision. For example, the light scattering method has a fast response but is affected by the refractive index of smoke and dust, while the β-ray method has good stability but requires regular calibration of the source.
Key component characteristics: The reliability of laser/LED light sources, the sensitivity of photodetectors, and the accuracy of total flow in pump casings directly affect signal detection performance. After 5000 hours, the compressive strength of inferior light sources is likely to decrease by 30%, causing deviations.
Optimization algorithm compensation level: Determine whether there are optimization algorithms such as temperature and humidity compensation, granularity adjustment, and cross-interference removal to ensure the stability of data processing methods. Automated measurement combined with calibration can reduce errors caused by factors such as cigarette smoke from 40% to an acceptable level.
II. Uncontrollable factors in the natural environment
Temperature and humidity:
When the environmental humidity exceeds 60%, the moisture absorption and expansion of particulate matter can increase the light scattering pressure resistance by 3 to 5 times, leading to false positives;
For every 10℃ increase in temperature, the PM10 reading increases by 8% to 12%.
Cyclone dynamics model: Wind speed > 0.5 m/s impairs cutting efficiency, and infiltration causes damage to 15% to 20% of particles > 10 μm.
Chemical pollutants: VOCs can adhere and alter the refractive index (+7% to +15% error), and corrosive substances (such as H₂S > 5ppm) can cause sensor gap corrosion drift > 20%FS.
III. Differences in smoke and dust characteristics
Particle size distribution: Instrumentation is generally calibrated based on PM2.5/PM10. If the specific smoke dust is dominated by large particles (>10μm), the light scattering method is likely to underestimate the concentration value; for ultra-fine particles (<0.1μm), the value may be falsely high.
Physical properties:
Greyish-black smoke dust (such as dust) has weak light absorption and transmission, and is easily overlooked;
Milky white smoke dust (such as wheat flour) has strong transmittance, and there is a high possibility of an error margin of ±15%;
Viscous soot (such as epoxy resin) can adhere to sensors, causing a drift of ±2% per week.
IV. Operation and maintenance standards
Calibration status: It is recommended to calibrate the industrial scene every 6 months. Long-term failure to calibrate can increase the error of the dust explosion monitoring system from ±5% to ±15% or more.
Reasonable sampling layout: It is necessary to bypass oscillation areas such as air supply outlets and exhaust fans, and follow the “cross-over method” to arrange more grid points (with spacing ≤2m). The relative height of the breathing zone should be set at 1.5~1.8m.
Maintenance frequency: Dust accumulation on the lens for 3 months without cleaning can cause a slight decrease in reading values by ±10% to ±20%; a total flow error of ±5% in the sampling pump can lead to errors in concentration data.