Monitoring application of toxic and harmful gases in sewage treatment           (Shanghai Yi Chang Industrial Co., Ltd. All rights reserved, please indicate the source of ripping / reprinting)  In the operation of sewage treatment facilities, the monitoring of toxic and harmful gases is one of the indispensable links in the whole set of sewage treatment equipment. For sewage treatment plants, sewage pipe networks, garbage ponds, etc., where hazardous gases such as hydrogen sulfide, methane, ammonia, etc. can be generated, gas detectors must be used for detection, and sensor technology should be used to detect the concentration of toxic and harmful gases after treatment and treatment. The measured data is saved and recorded through wired or wireless transmission technology, real-time monitoring of H2S, CH4, CO, CO2, Cl2, NH3 and other toxic and harmful gas concentrations in dangerous places, providing timely and effective security warning information. And the implementation of linkage control through the detection instrument has reached the effect of reducing the concentration of dangerous gases. The toxic and harmful gas monitoring equipment commonly used in sewage treatment plants mainly includes: online hydrogen sulfide detector, explosion-proof rust alarm lamp, data recording equipment, gas concentration alarm linkage equipment, signal safety barrier and so on. Shanghai Yichang Industrial Co., Ltd. has been operating toxic and harmful gas detection instruments and peripheral equipment for more than 10 years. It has its own unique and effective measures and solutions for the operation of the whole system. The installed gas detectors such as ITRANS2 and YC18SEN operate well in various sewage treatment sites. The high corrosion-resistant casing and stable product performance save a lot of cost and increase the safety guarantee for the equipment user. In the continuous learning and progress, the product performance is gradually improved, the cost of the whole set of equipment is controlled, and the convenience and safety of the use of the equipment are continuously increased. The main products of the toxic and harmful gas monitoring system include: 1·ITRANS2, YC18SEN and other models of hydrogen sulfide, ammonia, flammable gas detector. The instrument must include signal output, alarm relays, linkage relays, and safe and reliable continuous operation. 2. The controller or data logger that receives the data, the data logging instrument must ensure a sufficient number of channels, and generally need 2 to 3 more spares. The recording instrument has a bus alarm relay, which can remind the workstation personnel to observe the concentration level of toxic and harmful gases in the field. 3. On-site alarm device for explosion-proof and rust-proof installation. It can be a screw-mounted explosion-proof warning light or a thread-mounted explosion-proof buzzer. Choose according to the environmental conditions on site. 4. Fixing mounting brackets or U-bolts according to the site conditions make installation and debugging more convenient and quick.  Selection of technical parameters of main equipment for detection of toxic and harmful gases in sewage treatment: 1, Select the measuring instrument's range, resolution, alarm point, accuracy: hydrogen sulfide detector select 0~500ppm detection range, resolution 1ppm, alarm point can be set to about 10ppm range (NIOSHREL: 10ppm (15mg/m 3 ) 10min most Peak limit); recognition accuracy is less than 10%. The ammonia detector has a detection range of 0~200ppm and a resolution of 1ppm. The alarm point can be set to about 20ppm (the concentration of ammonia gas at 9.8mg/m 3 has no obvious stimulating effect on the human body), and the recognition accuracy is less than 10%. Flammability (CH4) gas detection range 0~100% LEL, resolution 1% LEL, alarm point setting 20% ​​LEL, accuracy within 5%, T90 response time within 30 seconds. [Other gases can be determined according to ITRANS2 and YC18SEN models] 2, The signal output connection mode of the equipment: hydrogen sulfide, ammonia gas, sulfur dioxide and other toxic gases can be selected as two-wire or three-wire signal output, and the flammable gas must be a three-wire signal output. The signal output is a separate, isolated safety signal for easy wiring. 3, The relay output of the equipment (known: relay switch): hydrogen sulfide, ammonia, sulfur dioxide and other toxic gas detectors must have a set of relays (ITRANS2 and YC18SEN models have two sets of relay output, try to meet the requirements of the site The flammable gas detector has high and low limit relays. 4, Other performance parameters included: Ex d IIC T6 for explosion protection; IP65 for protection class; corrosion resistant metal material with anti-rust coating; mounting and fixing - with screw holes and threaded interface for easy installation and fixing; electrical interface Meet the national standard requirements to facilitate the connection of the line.     Unit conversions encountered when viewing occupational health standards or national standards: Conversion formula for ppm readings in standard conditions and milligrams per cubic meter (mg/m 3 ) Ppm=mg/m 3 ×B÷M Where: B is the molar volume of the gas (mol), constant 22.4 (in standard conditions 0 ° C, standard atmospheric pressure, 1 mole of any ideal gas accounted for about 22.4 liters, this volume is called the gas molar volume, the unit is L/mol (L/mol) M is the molecular weight of the gas (eg hydrogen sulfide 34, ammonia gas 17, carbon monoxide 28)  Three-wire system and two-wire equipment connection (power + signal + external equipment) simple schematic type:  Installation precautions for gas detection instruments in wastewater treatment applications: 1. A gas detector (diffusion type sampling) generally monitors a gas environment within a radius of 5 to 7 meters centered on the instrument mounting point. In some special environmental conditions, the specific installation quantity and installation position should be determined according to specific wind speed, pressure, temperature, humidity, terrain and other factors. 2. Gas detection should be selected as close as possible to the outlet, valve, pipe interface or the vicinity of 1~3 meters which is easy to leak and produce toxic and harmful gases, but do not affect the operation of other equipment; Extremely harsh environments such as high humidity, do not exceed the environmental range of the gas detector; avoid external factors such as splashing (soaking) water and oil and causing physical damage to the instrument. 3. Gas detectors can be installed in a variety of ways, such as roof hoisting, wall mounting, bracket mounting or pipe mounting. Be sure to be firm and reliable during installation, and consider the maintenance and calibration of the gas detector. 4. When the gas detector is installed, the sensor inlet hole position should be fixed downwards (the special fixed wind direction can determine the installation direction of the detector according to the wind direction), the fixing nut should be completely tightened, and the gas sensor and instrument circuit protection housing should be completely sealed to achieve Explosion-proof standard requirements. 5. The gas detector must be wired in the event of a power failure. The battery can be energized only after careful wiring. The flammable gas detector should be commissioned only if it is determined that there is no gas leakage at the site. 6. The gas detector should be calibrated at least once a year to ensure detection accuracy. The detector is prohibited from performing calibration tests on the standard that exceeds the detection range. The flammable gas detector is strictly prohibited from using the gas of the lighter for field experiments, so as to prevent the sensor from dying or the sensor failure due to excessive concentration of flammable gas. Â
Related accessories: Monitoring and application of toxic and harmful gases in wastewater treatment (WL).pdf