Maintenance and troubleshooting of ENOTEC SILOTEC 8000 silo analyzer

Maintenance and troubleshooting of ENOTEC SILOTEC 8000 silo analyzer

System positioning: O2/COE analysis for bin smoldering monitoring

SILOTEC 8000 is an O2/COE analysis system designed specifically for storage containers such as silos, coal bunkers, and biomass silos. It continuously extracts gas from the top space of the silo, while measuring oxygen content and CO equivalent, for early identification of smoldering fires. When smoldering occurs in the silo, the generation of hydrocarbons and CO consumes oxygen, resulting in an increase in COe concentration and a decrease in O2 concentration. SILOTEC 8000 can quickly capture this change and provide critical signals for safety interlocking, inerting protection, or alarm.

The system consists of electronic unit SME-53, measuring cell SIL-KES-0001, gas sampling probe SIL-GSF-8000, pneumatic unit, and GRP protective box. The electronic unit can be installed in a safe zone, and the measuring cell and sampling probe can be installed on the top of the silo, suitable for ATEX Zone 22 area. The sampling probe can extend into Zone 20. The maximum working pressure of the system is 0.5 bar, the maximum process gas temperature is 100 ° C, and the ambient temperature is -20 ° C to+55 ° C.

Measurement Principles and Safety Boundaries

SILOTEC 8000 adopts in-situ extraction measurement. The sampling probe is equipped with a sintered metal filter with a filtration accuracy of 3 μ m, which can safely isolate the explosive environment of dust in the silo from the heating sensor. The extraction system generates a continuous sample gas flow rate through an air injector, with a fast reaction speed. If equipped with a blowback module, compressed air can be used regularly to blow back the filter and reduce blockage.

Simultaneously install O2 sensors and COe sensors in the measurement pool. The O2 sensor is based on the zirconia principle, with instrument air (20.95% O2) as the reference side and sample gas as the measurement side. The difference in oxygen partial pressure on both sides generates an mV signal, which is converted to oxygen concentration using the Nernst equation. The COe sensor adopts the MXP principle and can detect CO, H2, and CxHy hydrocarbons. The catalytic electrode oxidizes incompletely oxidized gas molecules, generating a voltage signal related to the concentration of COe.

The safety boundary must be strictly adhered to: the system must not be used near flammable gases, otherwise there is a risk of explosion. The COe sensor requires a minimum of 0.3% O2 to measure correctly, and accuracy decreases below this value. The surface temperature of the measuring pool and the inlet and outlet of the sample gas may exceed 100 ° C. Insulated gloves must be worn during maintenance, and the power supply to the electronic unit must be cut off first. The measuring tank shall not be disassembled until it has cooled to below 35 ° C. It is absolutely forbidden to directly connect the probe to the 230V main power supply, otherwise it will immediately damage the heating element.

Installation and wiring points

The installation of electronic units should avoid vibrations greater than 2g and maintain a minimum distance from adjacent objects: 200mm at the top and bottom, and 50mm on the side. The ambient temperature must be between -20 ° C and+55 ° C, with a protection level of IP66. The installation position should be convenient for observing the display screen and operating the keyboard, and it is recommended to install it at a visual height.

The shielding layer of the probe signal cable FEP-0007/8 can only be connected to the PE terminal at the electronic unit end, and the probe end must not be grounded. The maximum length of the cable is 50m, the minimum bending radius of FEP-0007 is 252mm, and FEP-0008 is 329mm. The installation temperature is -5 ° C to+50 ° C, and the operating temperature is -40 ° C to+90 ° C. The signal cable should intersect perpendicularly with the power cable to avoid parallel wiring. The ferrite magnetic ring must be installed according to the specified wiring harness, otherwise the CE certification will be invalidated.

Pneumatic cable FEP-0002 is used for reference air and test gas, with a minimum bending radius of 138mm. When connecting, use a support sleeve, clamping ring, and nut, tighten by hand first, and then use a wrench to tighten 1.25 turns. The sampling probe flange needs to be air tight welded, and the filter locking torque is 250Nm. The electronic unit PE must be connected to the bin PE potential by the customer.

When wiring, please note that the O2 measuring cell, thermocouple, heater, probe solenoid valve, and COe sensor correspond to different terminals and colors. Thermocouple compensation cables must use ENOTEC original cables, otherwise the measurement will be inaccurate. COe sensor wire number 11-14, O2 sensor signal wire is white/brown and orange, heater is black/blue/green yellow.

Initial power on and software configuration

Before powering on, check whether the system number is consistent, whether the nameplate voltage matches, whether the wiring is correct, whether the gas circuit is airtight, whether the flange leaks, and whether the on-site conditions are consistent with the data sheet.