Pneumatics in the mining industry: how do modern solutions affect safety and efficiency?
Pneumatic equipment is a type of equipment that is increasingly used in various industries, including mining. Their use brings a number of benefits that make them an alternative to traditional power tools. In this article we will present an overview of modern pneumatics solutions and discuss their practical application in the mining industry. You will also learn what pneumatic devices are used in mines and what benefits they bring. You will also find out what criteria for selecting pneumatic equipment are important in the mining industry and what to pay attention to when using them.
Pneumatics is a branch of mechanical engineering that deals with the design and use of machinery and equipment driven and controlled by compressed air or gases with similar properties. In mining, pneumatics is used, among other things, to operate tools such as impact wrenches, chisels and hammers. Pneumatics also plays an important role in the manufacture of ventilation and cooling systems used in many industries including mining.
The interest in pneumatics in the mining industry can be attributed to its advantages such as: simplicity of construction and operation of pneumatic systems, high reliability and safety of operation in harsh environmental conditions, ease of speed and drive force control, and the possibility of remote control.
However, pneumatics also has some limitations and disadvantages, such as low energy efficiency (compared to hydraulics), noisy operation of pneumatic equipment, the need to clean and dry compressed air and the risk of condensation in the system.
Therefore, specialists in industrial pneumatics need to constantly improve their qualifications and skills to stay abreast of new technologies and solutions. Knowledge of the basics of physics, fluid mechanics, electronics and automation is also essential.
Advantages and disadvantages of pneumatics compared to other types of propulsion
- Simplicity of design and operation of pneumatic equipment
The simplicity of design and operation of pneumatic equipment is one of the main advantages of pneumatics over other types of propulsion. Pneumatic assemblies consist of a small number of parts (valves, actuators, fittings), which are easy to design and implement in automatic control systems. Pneumatic units do not require complex electrical or hydraulic systems, making them easy to install and maintain. Pneumatic applications are also resistant to mechanical and thermal damage and can operate in various environmental conditions (e.g., moisture, dust, temperature). The simplicity of design and operation of pneumatic equipment translates into lower purchase and operating costs, as well as greater operational reliability.
Pneumatic actuators require no maintenance during operation. The internal mating parts of an actuator are lubricated with grease before assembly and do not require re-lubrication. It is recommended to replace the seals of an actuator every 5 years during periodic repairs resulting from repair cycles. During servicing it is advisable to wash and re-lubricate mating parts with ŁT 43 grease.
- High reliability and safe operation in harsh environments
The high reliability and operational safety of pneumatic equipment is an another advantage of pneumatics over other propulsion types. Pneumatic devices are resistant to overloading and overheating, and do not generate sparks, which prevents the risk of fire or explosion.
The pneumatic equipment also complies with machine safety standards and provides protection for the operator against electric shocks or mechanical injuries. CPP “PREMA” S.A. has obtained a Certificate of Conformity with the European Union ATEX Directive issued by the KOMAG Institute of Mining Technology. Pneumatic equipment is easy to stop or disconnect in case of failure or danger. The high reliability and operational safety of pneumatic equipment translates into lower maintenance and repair costs and higher production efficiency.
Actuators, air preparation blocks and mechanical valves manufactured by CPP “PREMA” S.A. are Group I, Category M2 equipment, while the ATE series of eclectically controlled valves are Group I, Category M1.
- Ease of speed and drive force adjustment, and remote control capability
The speed and precision of control of pneumatic equipment is another advantage that pneumatics possess over other drive types. Pneumatic actuators are capable of fast and repetitive movements with high force and torque. Pneumatic units are also easy to program and synchronize with controls such as valves, sensors, limit switches or cyclograms. Pneumatic units are also equipped with safety valves to prevent pressure overload in the system. The speed and precision of pneumatic equipment control translates into greater productivity and quality of work.
- Low energy efficiency (compared to hydraulics)
The low energy and environmental cleanliness of pneumatic equipment is another advantage of pneumatics over other types of propulsion. Pneumatic devices consume little electricity because the main source of energy is compressed air. Compressed air is also a renewable and non-polluting energy source that does not emit harmful substances into the atmosphere. Pneumatic equipment is also lightweight and resistant to high temperatures, reducing the risk of overheating or ignition. The low energy and environmental cleanliness of pneumatic equipment translates into lower operating costs and environmental protection.
- Operating noise of pneumatic equipment
The operating noise of pneumatic applications is one of the disadvantages of pneumatics compared to other types of propulsion. Noise is mainly generated when compressed air is discharged into the environment. This noise can be unpleasant for people and harmful to health. Therefore, appropriate silencers should be used and compressed air pressure should be limited. Noise can also be reduced by using flexible hoses and vibration dampers.
Some pneumatic devices that can generate even lightly harmful noise are:
- Compressor: 80-90 dB,
- Electromagnetic valve: 60-70 dB,
- Linear actuator: 50-60 dB,
- Piston rotary engine: 70-80 dB.
- The need to clean and dry the compressed air and the risk of condensation in a system
The need to clean and dry compressed air and the risk of condensation in the system is another disadvantage of pneumatics compared to other types of propulsion. Compressed air contains solid contaminants, oil, bacteria and moisture, which can damage pneumatic equipment and reduce its performance. Therefore, it is necessary to use appropriate filters and dryers for compressed air.
Compressed air preparation blocks manufactured by CPP “PREMA” S.A. are used to remove solid and partially liquid contaminants from the working medium, to set and maintain a constant pressure of the working medium and to saturate the compressed air with oil to protect it from corrosion and ensure proper operation of actuators and control elements. They are an essential component of pneumatic systems to ensure correct operation and long life of pneumatic components.
Some examples of compressed air purifying and drying devices include, but are not limited to:
- Filter-dehydrator: removes oil and water droplets by centrifugal method,
- Fine filter: removes fine particles and oil by deep filtration method,
- Activated carbon filter: removes oil residues by adsorption,
- Radiator: lowers the air temperature by heat exchange method,
- Adsorption dehumidifier: lowers the dew point temperature by the moisture adsorption method by the desiccant.
Types and construction of pneumatic equipment used in the mining industry
- Pneumatic equipment’s operation principle (compressors, valves, actuators, sensors, etc.).
The operation principle of pneumatic equipment is to convert the energy of compressed air into mechanical energy. Compressed air is supplied to the application by means of compressors or suprechargers. Depending on the type and design of the pneumatic device, compressed air can be used for various purposes, such as:
- Motion control of linear or rotary actuators,
- Control of air flow and pressure with the use of valves,
- Position or pressure detection with sensors,
- Driving pneumatic tools or machines.
Here are some examples of pneumatic equipment used in mining:
- Compressor: used to compress atmospheric air,
- Valve: opens or closes air flow,
- Actuator: converts compressed air energy into linear or rotary motion,
- Sensor: used to measure physical quantities such as pressure, temperature or piston position.
- Division of pneumatic devices by the method of energy transfer (pressure and vacuum devices)
Pneumatic devices can be divided by the way energy is transferred into pressure and vacuum devices:
- Pressure equipment: uses compressed air at pressures higher than atmospheric to drive or control mechanisms. Examples of pressure equipment include steam or water boilers, tanks in firefighting units, industrial pipelines or tank systems.
- Vacuum devices: use compressed air at less than atmospheric pressure to create a vacuum in an enclosed space.
- Division of pneumatic devices by type of drive (linear and rotary devices)
Pneumatic devices can be divided by type of drive into linear and rotary devices:
- Linear devices: are those devices that, convert the energy of compressed air into linear motion. Examples of linear devices include: reciprocating actuators, which are used to move machine components or equipment.
Compressed air supplied alternately to the chambers of the actuator from both sides of the piston through the connection ports moves the piston-piston rod assembly sequentially in both directions. To prevent the piston from hitting the lids, pneumatic cushioning is used. At the end of the movement, the piston, entering the lid chamber, cuts off the free flow of air from the actuator, thus decelerating its speed. From this point on, the outflow of air from the closed piston chamber can only take place through the throttling hole in the lid, making the piston’s movement slow and smooth until contact with the lid. The amount of cushioning (i.e., the final velocity of the piston) can be adjusted by screwing in or out the choke according to the markings on the covers.
- Rotary devices: convert the energy of compressed air into rotary motion. Examples of rotating devices include air motors, which are used to drive tools or machines, and rotary-pulse or angle encoders, which are used to measure and control the position of rotating parts.
- Division of pneumatic devices by function (executive, control and auxiliary devices)
Pneumatic devices can be divided by function into executive, control and auxiliary devices.
- Executive devices: those devices develop an input signal to a control object based on a control signal. Examples of executive systems are: pneumatic actuators (used to move machine components or equipment), relays and contactors (used to control current loads with high voltages or currents).
- Control devices: those devices generate a control signal based on a setpoint signal and a feedback signal. Examples of control elements are: pneumatic controllers (used to regulate process parameters), automatic or manual controllers (used to maintain the setpoint of the regulated parameter).
- Auxiliary units: devices that facilitate the operation or increase the reliability of actuators and controls. Examples of auxiliary units include: pneumatic valves (used to pass or stop air flow), air filters and dehumidifiers (used to clean and remove moisture from air), pressure gauges and pressure sensors (used to measure and display air pressure).
Safety and operation principles of pneumatic equipment
- Legal and technical standards for the use of pneumatic equipment in mining
Legal and technical standards for the use of pneumatic equipment in mining are set by various documents, such as:
- Standards of the Polish Committee for Standardization (Polski Komitet Normalizacyjny – PKN), which are developed by specialists from various backgrounds interested in a particular subject area. Examples of PKN standards for pneumatic equipment in mining are: PN-EN ISO 4414:2011 Pneumatic equipment of machinery – General principles and safety requirements; PN-EN 1570-1:2012+A1:2015.
Ordinances of the Council of Ministers or the Minister responsible for economic affairs, which specify the types of technical equipment subject to technical supervision and the conditions for their operation. Examples of regulations on pneumatic equipment in mining are:
- Ordinance of the Council of Ministers of December 7, 2012 on the types of technical equipment, subject to technical supervision; Ordinance of the Minister of Economy of December 21, 2005 on the conditions of operation of machinery and other technical equipment with an increased risk of failure.
- Principles of selection, installation and maintenance of pneumatic equipment
The principles of selection, installation and maintenance of pneumatic equipment are as follows:
- Principles of selection: the technical and functional parameters of pneumatic equipment should be considered, such as working pressure, capacity, force, speed, stroke, piston diameter, type of control, IP rating, etc. Pneumatic equipment should also be matched to the working conditions and quality requirements of compressed air.
- Installation rules: the diagrams of pneumatic and electropneumatic systems, and the instructions of the manufacturer of pneumatic equipment must be followed thoroughly. It is also necessary to ensure that the system components are properly connected and sealed, and properly protected from mechanical damage or corrosion.
- Maintenance rules: regularly check the condition and cleanliness of pneumatic components, and repair any defects or leaks. It is also necessary to use appropriate lubricants and filtering agents for compressed air treatment, and replace worn or damaged parts. For equipment with mining shaft approvals, it is heavily disencouraged to use parts other than the manufacturer’s factory parts.
- Code of conduct in case of failure or damage to pneumatic equipment
The steps for dealing with failure or damage to pneumatic equipment are as follows:
- Immediately turn off the supply of compressed air to the damaged instrument and disconnect it from the source of electrical or other power.
- Inform your supervisor or maintenance person of the situation and do not attempt repairs on your own.
- Secure the failure site from unauthorized access and mark it with appropriate warning signs.
- Observe safety precautions when repairing a malfunction or damage, such as using appropriate protective equipment, keeping a safe distance from hot or moving parts, avoiding contact with hydraulic oil or other hazardous substances.
- Maintenance work that requires disassembling the device into parts must not be performed in a hazardous area.
- After the repair, check if the device works properly and make sure that it does not pose a threat to the health and life of its users. In order to eliminate the accumulation of static electricity after installation of the device, it should be grounded. When cleaning the surface of the device, use only damp cloths to wipe it clean.
Summary
The use of pneumatics in mining has many advantages over other types of drives. These include: higher productivity, quality and flexibility of production processes, lower energy and material consumption, better diagnostics and automation of pneumatic systems, as well as lower environmental and climate impact. The use of modern pneumatic solutions positively affects the safety and efficiency of pneumatic mining applications.
It is worth remembering that if you have any doubts, the staff of CPP “PREMA” S.A. can help you select ATEX actuators with the right force and parameters you need.
Thanks to Ms. Wioleta Nowak, M.Sc. for substantive assistance in the preparation of the guide.