What specification of paint workshop requires the installation of combustible gas alarm?

General scheme of installing flammable gas (benzene) leakage alarm in spray booth

One: Why should an industrial explosion-proof gas leakage alarm be installed in the painting room?

Because the paint contains benzene compounds, which will volatilize into the air during the painting operation, benzene compounds are toxic and flammable. According to GB65 14- 1995 "Safety Regulations for Painting Work", the hygienic standard of painting workplace should meet the relevant requirements in GB 1-2002 "Hygienic Standard for Design of Industrial Enterprises". The maximum allowable concentrations of benzene volatiles in the air of workplace are: benzene 17 mg/m3, toluene 60 mg/m3 and xylene 90 mg/m3; So we need a gas alarm to monitor the concentration of benzene volatiles in the painting room at any time.

At the same time, toluene and xylene are highly explosive, and when they reach a certain concentration, they will explode when they meet an open flame. Therefore, it is required to install flammable gas concentration leakage alarm products in such places. Not only for the safety of workers' on-site work, but also for the long-term future development.

Because the painting operation mainly drives the hydraulic pump through a special form of aerodynamic force, the high-pressure paint is sprayed into a very fine fan-shaped mist, and a coating film is formed on the painting surface at high speed. At the same time, paint is toxic and harmful, flammable and explosive, so paint is very dangerous. ?

1, fire and explosion: paint and thinner are flammable and explosive liquids, which are atomized by spray paint pump to form a large number of flammable and explosive gas and liquid mixtures, which are prone to explosion when encountering fire sources. Improper storage of paint, etc. , it may also lead to fire. ?

2. Poisoning suffocation: paint and thinner are toxic, poor ventilation effect, and failure to wear hood and gas mask as required can all lead to poisoning suffocation accidents. ?

Second, if the concentration of benzene gas in the painting room is too high, the following phenomena will occur:

1, the pungent smell is particularly strong, especially choking the nose.

2, affect the normal work of workers.

3. The hand-held alarm instrument worn by the field staff will give off abnormal alarm sound.

4. When the leakage is large (the concentration is relatively high, reaching the set light alarm of 25% or over alarm of 50%), the fixed alarm will give an automatic alarm and automatically turn on the exhaust fan.

5. In severe cases, disasters and accidents such as fire and explosion will occur.

Three. Importance and necessity of installing industrial explosion-proof flammable gas (benzene) alarm system

The production line that paints or uses paints must be equipped with combustible gas alarm and linked with emergency cut-off valve. According to the requirements of GB 50493-2009, it is necessary to set up combustible gas alarm. When there is a gas concentration of olefin gas or flammable and toxic gas in the air, the detector detection signal is immediately transmitted to the alarm control unit through the cable, and the controller displays the gas concentration. When the gas concentration exceeds the set alarm concentration value, the alarm controller sends out an acousto-optic alarm signal and outputs a linkage control signal to control fans and other equipment to eliminate dangerous situations, so as to ensure safe production in the factory and avoid accidents. It is recommended to use CRGD- 1 industrial explosion-proof wall-mounted combustible gas alarm produced by Nideli to detect natural gas leakage in boiler room.

Importance of installing combustible gas alarm in spray booth. The main components of the spray booth are benzene gas, mainly toluene and xylene. It belongs to flammable and explosive gas. When the concentration of toluene and xylene in the operation workshop is too high, explosion and fire will occur in case of open flame, static electricity, lightning or improper operation, and people will be deprived of oxygen, suffocate and even die in a closed space. The installation of combustible gas alarm can effectively avoid explosion and fire, thus avoiding the safety of property and personnel. The function of combustible gas alarm is to detect the leakage concentration of flammable and explosive gas, and once it exceeds the standard, it will immediately give an alarm to remind the staff to take safety measures. From its function, we can easily see the importance of gas alarm. If a gas alarm is installed, if the concentration in the workshop is too high, once the natural gas concentration reaches the alarm value set by us, the alarm will remind you to sound an alarm, and measures should be taken to avoid the explosion accident to the greatest extent. In order to ensure the reliability of the product performance, we suggest that users regularly maintain and calibrate the product during the use of the gas alarm. If in doubt, please consult professional and technical personnel.

Combustible gas explosion is a combustion process that produces high temperature (up to 3000℃) and high pressure in an instant (thousands of seconds), and the explosion wave speed can reach 300m/s, which is extremely destructive.

According to the on-site investigation and the discussion of the personnel of relevant departments, under the premise of ensuring the safety of painting operation and not affecting production, the following scheme is formulated: an alarm is set for the gas concentration that is easy to accumulate in the corner of the painting room, and a gas alarm is installed near the painting production line. It is used to monitor the leakage point of benzene gas and the gas concentration accumulated in the space in time, prevent potential safety accidents as soon as possible, send out alarm signals, or start the chain protection system to control the accident losses to a minimum.

Safety is life, safety is responsibility, and safety is benefit!

4. The basic structure and working principle of explosion-proof combustible gas monitoring and alarm control system?

The gas detection alarm mainly consists of four parts:

1. Combustible gas detector: monitor the concentration of benzene gas in the leakage point and environment in real time. Because the main component of paint is benzene (toluene, xylene), its specific gravity is heavier than air, and when the gas concentration is too high, it will go down (ground), so the combustible gas detector is installed below the gas release source or leakage point (the specific gravity of paint is higher than air, and here they will be about 30-60 cm away from the ground). So as to timely and accurately detect the paint concentration; when the gas leakage concentration reaches the lower limit alarm, an audible and visual alarm is sent out to remind workers to check and maintain in time; when the gas leakage concentration reaches the upper limit alarm, a control signal is sent to an automatic cut-off valve; and when the gas source is cut off, an emergency audible and visual alarm is sent out to remind workers to take measures.

2. Monitoring and alarm control system: real-time monitoring of all leakage points and concentration of gas leakage or accumulation. When the alarm setting value is reached, an audible and visual alarm will be given, and the interface linked with other fire control systems will be reserved. Installed in unattended duty room, real-time monitoring of natural gas leakage and alarm to ensure production safety.

3. Connect the exhaust fan: When the gas concentration detected by the combustible gas detector reaches the high and low alarm limit, the alarm controller will send a signal to the exhaust fan to run automatically.

4. Connection part: refers to the armored cable or cable with metal sleeve that transmits the signal of gas detector to the monitoring alarm control system to prevent electromagnetic interference.

When the gas detector detects combustible gas in the air, it converts the gas concentration into corresponding 4-20ma current signal or RS485 digital signal, and transmits it to the monitoring alarm control system through the connecting cable. The monitoring and alarm controller converts the electrical signal into a digital signal and displays the gas concentration value on the LCD. When the detected value is greater than the alarm set value, the buzzer or warning light will send an alarm signal to remind the staff to pay attention, repair the cause in time to eliminate the fault or start the interlocking emergency system.

Verb (abbreviation of verb) Precautions for painting operation in spray booth (although gas alarm is installed, necessary basic work should be done)

1. Tools and equipment used in painting operation should be in good condition, and the liquid hose connected to the spray gun must be a hose with good conductivity, and the spray gun should be connected to the ground through the hose to eliminate static electricity generated in the process of paint liquid flow in time. ?

2. Check the safety device of the spray gun. Confirm that the safety bolt is effective and the connector is firmly connected.

3. The painter should put non-explosion-proof items outside the cabin, such as lighters, mobile phones, walkie-talkies and all other electronic equipment.

4, before the start of the painting operation, within 20 meters of the no-fire zone, set up red, white and warning tape to set up a warning zone, and make a good mark, and arrange special care. ?

5. Does the lighting, ventilation and all electrical equipment and painting equipment in the painting operation area meet the overall explosion-proof and anti-static requirements?

6. The paint storage area, paint mixing area, empty paint bucket area, empty paint bucket, waste solvent, residual paint, rags and other special containers must be provided with red and white warning belts by the painting supervisor in the painting workshop/work area, and eye-catching warning signs such as "No fireworks in the paint storage area" must be hung. ?

7. The safety supervisor of the safety supervision department is responsible for detecting combustible gas (portable combustible gas detector can be equipped and carried with you) half an hour after the start of painting operation in the closed cabin, and then every 1 hour until the end of the operation. ?

Six, flammable gas (benzene) detector installation position and quantity analysis (see CAD drawings).

According to the requirements of the security department and the actual investigation on the production site, the layout (see CAD attached figure) and installation method of the gas detector are shown in the following figure:

First, consider the size of the inspection area (installation site). The detection radius of the combustible gas (benzene) alarm (probe) provided by our company is 7.5m, and the distance between each probe does not exceed 15m.

Secondly, consider the internal structure of the studio. Because the concentration of paint components is too high, they all gather at a position about 60 cm from the ground, so they are installed and fixed at a position about 60-80 cm from the ground. Or arrange points below the concentration that is easy to leak.

Finally, consider the warehouse in spray booth. Because the painting needs a storage place or the empty barrels used up in the painting room will be stored somewhere, these places are places where the paint concentration is easy to gather, so it is necessary to monitor the concentration.

According to the above three steps, the installation location and approximate position of gas detectors can be preliminarily judged, and the coverage area of each detector is about 30 square meters (the specific installation depends on the site situation and does not affect the work). The structure of each spray booth and the internal situation of the workshop are different, so we should adjust measures to local conditions!

The spray booth covers an area of 100 square meter, so according to GB 15322. 1-2003 "combustible gas detector part 1: point combustible gas detector with measuring range of 0 ~ 100% LEL", the coverage area of each alarm is Then, the support controller outputs the mode connection through the bus 485. The specific number of installations can be calculated with reference to the detection area of the detector.

Seven. Specification of connecting wire between combustible gas detector and controller:

1. If the number of installations is between 1-2, it is recommended to choose 3X 1 square RVVP cable signal shielding wire, as shown in the figure:

2. If the number is greater than 2, it is recommended to select 4X 1 square RVVP cable signal shielding wire, as shown in the figure:

Eight. Matters needing attention in operation management of combustible gas detector

1, wrong understanding of alarm

Many people think that as long as there is combustible gas or toxic gas near the detector, the controller should send out an alarm signal. If there is no combustible gas or toxic gas, the alarm may fail. This understanding is wrong. ?

The detection object of this alarm is combustible gas in the air, such as combustible gas: the monitoring range is 0- 100%LEL, but only when the concentration of combustible gas reaches the alarm set value (for example, the alarm low alarm value is set to 25%LEL), the controller will send an alarm signal, and if there is combustible gas, there is no need to alarm.

2. The explosion-proof facilities of the gas detector itself are damaged, which has not attracted enough attention?

In use, explosion-proof facilities such as explosion-proof seals are damaged, loose and explosion-proof pipes are broken, and no one cares. ?

As we all know, the installation place of the alarm belongs to flammable and explosive places, especially the detector is in direct contact with the combustible gas on site. If the explosion-proof facilities are damaged and not repaired or updated in time, when the concentration of combustible gas reaches the minimum alarm limit, it may directly cause a fire, which will not only prevent disasters, but also become a fire source.

3. The control system has no corresponding gas detector distribution map.

In the process of use, the controller operates the distribution map of combustible gas detectors on the cabinet, and when an alarm occurs, the position of the corresponding combustible gas detector and the position of the release source cannot be confirmed accurately in time.

Because there is more than one gas detector in the whole monitoring area, each gas detector has its own monitoring area and detection range. Each gas detector has a corresponding alarm display on the control system. In order to accurately and timely judge the location of the release source, the control system should have a gas detector distribution map.

4. Change the position of the gas detector at will.

In the process of replacing the production device, the position of the gas detector is changed at will, which leads to the decrease of the sensitivity of the gas detector or the detection dead angle in the device.

The determination of detection points is based on process equipment, equipment and facilities, gas concentration and other related aspects. In the process of reconstruction and expansion, if the position of gas detector is changed without considering the function and detection range of gas detector, there will inevitably be places where the detection position is repeated or undetectable. Moreover, in the process of disassembly, the sensitivity of gas detector may be reduced due to vibration and other reasons. ?

5. The inspection is not in place

In actual use, either the inspection is not thorough or the inspection period is too long, which leads to the disconnection of alarm management. ?

According to the Code for Use of Combustible Gas Detection and Alarm, the combustible gas detection and alarm should be calibrated regularly. The inspection contents are: check the operation of the system; Conduct visual inspection once a week, check the connection parts, movable parts, display and control knobs, check the fault lights, check the explosion-proof seals and fasteners, check whether the probe is blocked, check the waterproof situation, and so on. ?

6. Improper test method

When testing the reliability of gas detection alarm, such as combustible gas detector, the liquefied gas of lighter is directly contacted with the sensor, which leads to the damage of gas sensor and the decrease or failure of detector sensitivity.

7. Incomplete files.

There is no special person to manage the gas alarm, and the files are incomplete. ?

As important safety equipment, gas detectors and alarm control systems should be managed by special personnel, and basic data should be established and improved. Strengthen maintenance and make relevant records.

Nine, combustible gas alarm system composition and technical specifications

1, combustible gas detector

Product overview:

CR combustible gas detector is a new type of gas detection instrument produced by our company. This machine is composed of high-performance gas sensor and microcontroller technology, combined with excellent SMD technology. It has the advantages of good repeatability, good temperature and humidity characteristics, long service life and convenient operation, and is suitable for the detection of gas concentration in industrial environment. The detector adopts three-wire 4 ~ 20mA current signal or four-wire RS485 bus output, which has the characteristics of long transmission distance and good anti-interference performance. The detector is widely used for gas detection in oil refinery, chemical plant, metallurgy, communication, gas, painting room, restaurant, gas station, gas filling station, sewage treatment, electric power industry and other places that may produce gas harmful to human body.

(1), main functions

* The probe has the characteristics of high sensitivity, fast response, long service life and short polarization time.

* 4 ~ 20ma standard analog output \ RS485 bus output

*2 Switch passive alarm contact output

* infrared remote control operation

* with sound and light alarm.

* Flameproof design, suitable for dangerous places in 1 zone and zone 2.

(2), product standards

The design, manufacture and verification of this product shall comply with the following national standards: GB3836. 1-20 10 "Explosion Environment Part 1 Part: General Requirements for Equipment" GB3836.2-20 10 "Explosion Environment Part 2: Flameproof Enclosure Protection Equipment"

(III) Main technical indicators

Sampling method: natural diffusion;

Detection principle: catalytic combustion type;

Detection range: 0-100% lel; ?

Working voltage: DC 24V 6V；; ; ?

Power consumption: ≤ 3W; ?

Working mode: continuous detection; ?

Range deviation: ≤ 3% lel; ?

Operation mode: infrared remote control; ?

Response time (T90): ≤ 30s; ?

Working temperature:-40℃ ~ 70℃; ?

Working humidity: ≤95%RH (non-condensing);

Explosion-proof mode: flameproof type; ?

Explosion-proof grade: ExdⅱC T6 Gb；; ;

Protection grade: IP65；; ?

Environmental pressure: 86 kpa ~106 kpa; ?

Output signal: 4 ~ 20ma three-wire system; ?

Explosion-proof connection thread: M20* 1.5 (inner pipe thread); ?

Cable used: ≥ 1.5 mm2×3 shielded cable (three-wire system);

Maximum distance between detector and host: ≤1000 m; ?

Service life of sensor: three years; ?

Product size:180mm×140mm× 80mm; ?

Weight: about 1Kg.

2. Gas alarm controller

(1), product overview

CR gas alarm controller and our company's CR gas detector can form an intelligent detection control system for industrial gas, which can be used for monitoring and alarming gas concentration in industrial field. ?

When the measured gas or liquid volatilizes in the air, the detector generates an electrical signal proportional to the concentration of the measured gas in the air and transmits it to the controller, which displays the concentration of the measured gas after processing. When the measured gas concentration reaches or exceeds the set value, the controller will send out an audible and visual alarm signal, output relevant control signals, and start the corresponding control device, thus avoiding the occurrence of major accidents. ?

The man-machine interface of this product adopts large-screen LCD and advanced keyboard for interactive operation, with Chinese and English interface, clear display and simple operation; Its unique software anti-interference technology realizes soft detection of machine faults, with high reliability and easy maintenance. ?

(2), the main features:

* Switch between Chinese and English to meet the needs of different users.

* Embedded microprocessor, which has rich software functions, completes transmitter signal sampling, real-time data calculation, system fault detection, power management, key scanning, display drive, alarm display, alarm peripheral drive and other functions. ?

* It can connect analog (4-20mA current output) and digital (RS485 output) detectors at the same time, with huge capacity.

Flexible selection of multiple upload protocols?

* Can manage detectors that detect different gas types, different ranges and different data units.

*6-channel passive relay contact output, linkage programmable (can be extended to 8 channels), normally open and normally closed optional, convenient for control requirements.

* Wall-mounted installation, simple and convenient

(3), technical parameters

Working voltage: AC176v ~ AC 264v (50hz1%).

Power consumption: ≤100 w.

Working environment: temperature-10℃ ~+50℃, humidity ≤ 95% RH?

Atmospheric pressure: 86 ~106 kpa

Protection grade: IP44

Input signal: 4 channels of 4-20mA analog input, 1 channel RS-485 MODBUS-RTU four-bus input (32 detectors can be connected).

Transmission distance:1500m (2.5mm2)

Detection gas type: %LEL, ppm,% by volume.

Alarm output: four sets of programmable relay outputs, normally open and normally closed, freely selectable (capacity: 10A/ 30V DC or 10A/ 250VAC).

Alarm settings: lower limit alarm and upper limit alarm.

Alarm mode: acousto-optic alarm.

Alarm sound: > 90dB

Alarm record: 1500 alarm information.

Display: 192*64LCD display in Chinese and English.

Overall dimensions: length× width× thickness: 340mm× 240mm×110mm?

Weight:? About 3 kilograms

Installation method: wall hanging

Factory configuration: mainframe, key, certificate of approval and instruction manual.

Ten, portable combustible gas detector using technical instructions:

Portable combustible gas detector, that is, hand-held, can be carried on the staff, similar to patrol inspection and charging work. It can be turned on at any time, charged by built-in lithium battery, and stand by for about 24 hours, as shown in the figure:

Portable appearance tricolor, black, blue, yellow, random delivery.

Introduction of main technical parameters:

main feature

1. The measurement accuracy is high.

◆ CRPNDL-A 1 The gas detector adopts a high-speed CPU processor, which can quickly and accurately handle system tasks and ensure the reliability of the detector.

◆ Imported gas sensors are adopted, with high precision, strong reliability, fast response and recovery time, good gas selectivity and strong anti-interference ability.

2. The display is intuitive

◆ Liquid crystal display, which can display gas concentration in real time.

◆ Good shock resistance.

3. Low power consumption

Small size, light weight, low power consumption and easy to carry.

◆ Use high-performance lithium battery for long working hours, and use charging protection and undervoltage protection at the same time to ensure more reliable battery use and longer service life.

◆ Fast preheating and quick response time.

Technical parameters:

◆ Detection principle: inlet sensor for catalytic combustion of flammable and explosive gases.

◆ Detection gas: combustible gas.

◆ Sampling method: natural diffusion

◆ Battery: lithium battery

◆ nominal voltage: 3.6V capacity 1600mAh.

◆ Standby working time: > 8 hours (normal temperature) Flammable and explosive gas

◆ Measurement accuracy: 5% f? S

◆ Response time: ≤30S

◆ Charging voltage: DC5V

◆ Working temperature: -40℃ ~ 60℃

◆ Working humidity: ≤95%RH

◆ Alarm system: acousto-optic alarm and vibration.

Product size: 80*50*30 (mm)

◆ Product weight: 0.3KG

◆ Alarm volume: ≥75dB