1.1 Background of Study
Gas detection system is used for the control of hazardous liquefied petroleum gas and other gases in an environment. People have worked in hazardous atmospheres before the development of Gas detection system. The open flame light sources of pre-historic cave painters were sources of potentially deadly carbon monoxide and consumers of life giving oxygen and in a poorly ventilated area could have eventually proved fatal. Often the potential toxicity of the environment was only poorly recognized, if it was recognized at all. Fatalities and injuries were accepted as a risk of doing the job, or the tasks were given to unwilling workers under armed guard. Some of the first attempts to detect toxic atmospheres came in coal mines. Coal mines are notorious sources of combustible and toxic gases as well as low oxygen levels. Open flame lamps served as some of the first detection systems.
A low oxygen environment would cause the flame to burn low, or become extinguished. An atmosphere rich in combustible gases would cause the flame to burn more brightly. However, too much combustible gas resulted in the very explosion that was trying to be avoided. A later improvement on this method was the flame lamp, which contained the flame inside a glass barrel and allowed the hot gases to escape through a flame arresting wire mesh. Graduating marks were placed on the glass to allow a rough calculation of the presence of combustible gas or the absence of oxygen. While this method greatly improved the intrinsic safety of this detection method, a dropped lamp could still prove fatal in the wrong environment.
Another attempt at an intrinsically safe detection method was also used in coal mining applications into the twentieth century. This was the use of small caged birds to detect toxic environments (the proverbial ‘canary in a coal mine’). The concept was that these birds would exhibit the effects of the toxic environment before they became injurious to humans. As you can imagine, a healthy bird at the beginning of the work period was a vital requirement. While effective in certain applications, these birds were not capable of detecting all hazardous conditions. In the 1920's a number of significant advancements in the field of gas detection came into play. In Japan Dr. Jiro Tsuji developed a method of detecting combustible gases using light-wave interference in 1925. Dr. Tsuji later went on to found Riken Keiki Co., Ltd, currently represented in North America by RKI Instruments. In 1927 Dr. Oliver Johnson of the Standard Oil Company developed a method of detecting combustible gases using a platinum catalyst in a Wheatstone bridge electronic circuit. Dr. Johnson later went on to found Johnson-Williams or J-W, one of the first gas detection companies in the United States. Since the 1920's a number of advancements have been made in these two technologies.
In addition, a number of other technologies like MQ-6 gas sensor have also come into use and today it is used in this project work. The MQ-6 gas sensor is made up of SnO2 which has lower conductivity in clean air. A simple electro-circuit is used here which is used to convert the changing conductivity into corresponding output signal of gas concentration. Both methane and propane can be detected easily by MQ-6 sensor because it has high sensitivity towards Methane, Propane and Butane. It is a low cost sensor suitable for different applications.
1.2 Statement of Problems
Gas detectors are an essential application for home and commercial safety; they are also employed in numerous industrial industries. They are used in welding shops to detect combustibles and toxics and in nuclear plants, to detect combustibles. They are also commonly used to detect hazardous vapors in wastewater treatment plants and are very efficient in confined spaces where there is no continuous employee occupancy. Such spaces include tanks, pits, vessels and storage bins. They may also be placed at a site to detect toxins prior to occupant entry where it commonly used for gas leak detection system, fire/safety detection system and gas leak alarm.
It can be found in a variety of locations such as on oil rigs to monitor manufacture processes and emerging technologies such as photovoltaic. They may also be used in firefighting. Typical installation areas being gas yards (Bullets), gas banks with multi cylinders in manifold, user production departments/utility areas like kitchens. Other areas of application and the common gases it can detect are listed in the table below:
Table 1.2: Common Gasses and Detection Applications
The table is available in the acquired complete research material.
1.3 Aim and Objectives of Study
The aim of this study is to design and construct a gas detection system.
The Objectives of this project include:
- To design a potable and lower cost gas detector system for liquefied petroleum gas.
- To trigger an alarm when gas is detected.
- To improve the feasibility of networks, smart detection for health and safety and for increasing the efficiency of heating, cooling, and ventilation systems in buildings. It could replace the need for single-purpose or much larger equipment to detect, for example, urban air quality problems.
In addition, the project which are made with a flexible plastic, have low power requirements. This means it will be able to be used in conjunction with energy harvesting technologies for continuous operation, and could be integrated into textiles as well as electronics.
1.4 Significance of the Project
The significant of the project is that it improves health, safety, and efficiency as it detects gas leakages at homes, offices, business firms, in a car, storage tank environment or in a service station, etc. It can easily be implemented to industrial level by upgrading its ranges of detection.
The significant of this project cannot be over emphasized because anywhere people live or work with gas, so it plays an important role in monitoring the people health and safety and as well increasing role in managing buildings for high efficiency.There are many gases that can be harmful to organic life, such as humans or animals so the system detects these gases including combustible, flammable and toxic gases, and oxygen depletion while avoiding false alarms.
1.5 Scope of Study
The project senses high sensitivity LPG (iso-butane, propane, LNG and cigarette smoke) from concentration of 200 PPM to 10,000 PPM using 9 volts battery powered supply. It has small sensitivity to alcohol.
1.6 Justification of the Project
This project helps people to upgrade their safety standards, comply statutory even though it has small sensitivity to detect alcohol, it can be used as liquor tester. The project has excellent sensitivity combined with a quick response time. It’s most important and basic function is to prevent accidents and protect life and property from disaster.
It provides along lasting safety means for detecting the leakage of gas into the area of an appliance when the appliance is in a shutdown condition or not in operation. It provide a novel gas detection and monitoring system which is economical to manufacture and which may be readily installed in conventional trailers, boats or the like which are normally dependent upon a stored supply of pressurized gas.
1.7 Limitations of Study
The heart of any gas monitoring instrument is the sensor. Each sensor type has its own characteristics which define its strengths and limitations. The gas sensor used in this project has little sensitivity to smoke when used in the kitchen.
- It works well only on minimum power supply of 5V and its sensitivity depends on humidity and temperature.
- Although gas detectors are generally a reliable technology, with some models capable of lasting up to five years, their proper function is generally dependent on user maintenance, battery inspection and calibration. Calibration is a safety procedure executed to ensure that detectors are measuring the correct level of gas.
- In addition, the life-span of gas detectors also often depends on the amount of gas vapors to which they are exposed. Contaminated sensors may not register dangerous gas levels, which is why frequent calibration is essential.
- One of the limitations experienced during the project construction is financial difficulties and sourcing of materials/components. Also, I received electric shock from the soldering iron while soldering the circuits.
1.8 Project Report Organization
This project report is written in such a way that each chapter is related to the next as shown in the block diagram below. The organization of the project report is well detailed and vast in its coverage. It covers all the activities encountered during the research and construction work.
- The first chapter is the introductory chapter, which covers the background of the project, aims and objectives, scope of the project, constraints and block diagram overview of the states.
- Chapter two presents the literature reviews.
- Chapter three covers the system analysis and design in details including the design methodology.
- Chapter four presents the system implementation which entails the component layout, the wiring schedule, the wiring diagram and also the complete schematic diagram.
- Chapter five covers the testing and integration of the project design. The system testing was first carried out accordingly in a laboratory setting.
- Chapter six is the summary and conclusion which includes the summary of achievements, problems encountered during project design, recommendation and suggestion for further improvement.
