air handling system

Available in various combinations, filters and regulators are a must for any machine. Consideration should also be given to the use of other devices that perform functions such as energy isolation, blocking, marking and lubrication.
All pneumatic movements require clean, dry air with sufficient flow and pressure. The process of filtering, conditioning and lubricating compressed air is called air conditioning, sometimes simply air conditioning. In manufacturing plants, air preparation is provided from central compressors, and additional air preparation is useful at every point of use of the machine.
Figure 1: This air handling unit includes many NITRA pneumatic components, including filters, regulators with digital pressure switches, distribution blocks, lubricators, soft start/reset valves, and manual shutoff devices connected to a modular valve block.
The Air Conditioning System (commonly referred to as FRL after the filter, regulator and lubricator included in the kit), essentially the breathing mask on the machine, is its personal protective equipment. Thus, it is a mandatory system consisting of many components. This article discusses the components used in a machine’s air handling system and shows how each is used, as shown in Figure 1.
Working pressure air preparation systems are usually assembled in line and have various port and housing sizes. Most air handling systems are 1/8″ diameter. up to 1 in. NPT female, with some exceptions. These systems are often modular in design, so when choosing an air handling system, it is important to select similarly sized equipment for ease of assembly and access to accessories.
Typically, each pneumatic block has a pressure range of 20 to 130 psi to match the normal air supply pressure in manufacturing plants (between these values). While shut-off valves may have a pressure range of 0 to 150 psi, other air conditioning devices such as filters, regulators, and soft start/dump valves require a minimum operating pressure to activate the internal pilot and drain valves. The minimum operating pressure can be between 15 and 35 psi, depending on the equipment.
Manual closing of safety valves. Crushing, crushing, cuts, amputations and other injuries due to accidental or automatic movement of the machine due to the failure of the worker to safely turn off and isolate sources of energy, and block / mark the machines before performing repair or maintenance work. Usually this happens. Pneumatics are one such source of energy, and because of the potential for injury, OSHA and ANSI have important regulations regarding locking out/labeling hazardous energy sources and preventing accidental starting.
Figure 2. Turning the red handle of the NITRA manual shut-off valve counterclockwise safely removes air from the conveyor area, eliminating the risk of pinching during maintenance.
Air handling systems not only protect machines from debris and moisture, they also protect operators from hazards by providing a means to safely divert pneumatic power from machines. Manually closing a relief valve or pneumatically isolated block valve eliminates the pneumatic energy causing movement and provides a means of locking the valve in the closed position as part of the blocking/tagging procedure. It shuts off inlet air pressure and relieves outlet air pressure to the entire machine or area, Figure 2. Its enlarged outlet depressurizes quickly and can be loud, so a suitable muffler (silencer) should be used, especially if the ear area does not require protection.
These shut-off or block valves are usually the first component connected to the process air on the machine, or the first valve after the FRL component. These valves are activated with a rotary knob manually or by push and pull; both configurations can be padlocked. To facilitate visual identification, the handle should be colored red to indicate a safety device, such as an emergency stop button.
It is worth noting that even if the shut-off valve relieves air pressure, entrapped air (energy) may still remain after the AHU. The use of a three-position center-closing valve is just one of several examples, and it is the responsibility of the designer to provide and document a manual or automatic sequence for removing such air to safely service the machine.
Pneumatic Air Filters Filters are an important part of an air treatment system to remove particulate matter and moisture. These filters are available in centrifugal or coalescing designs. Centrifugal types remove particles and some moisture, while coalescent types remove more water and oil vapor. Dryers not discussed here may require significant dehumidification and are installed downstream of the unit’s air compressor.
Standard industrial air filters typically consist of a replaceable 40 micron filter element housed in polycarbonate bowls of various sizes to accommodate different flow rates, and typically include metal bowl guards. For more stringent filtration requirements, 5 micron filter elements are available. For special applications, finer microfilters can be used to remove particles of 1 micron or less, but this requires a coarser inlet filter. Depending on usage, periodic filter replacement can help, but an outlet pressure switch can be used to detect clogged filter – or better yet, a differential pressure switch that measures the pressure at the filter, the output of which is controlled by the PLC.
Regardless of the filter design, the filter removes solids, water and oil vapors – all of which are trapped in the filter – or accumulate as a solution at the bottom of the bowl, which can be drained using manual, semi-automatic or automatic drainage. . For manual draining, you must manually open the drain plug to drain the accumulated liquid. The semi-automatic drain turns on every time the compressed air supply is turned off, and the automatic drain turns on when the air supply is turned off or when the liquid in the bowl activates the float.
The type of drain used depends on the power source, application, and environment. Very dry or infrequently used equipment will work fine with a manual drain, but proper maintenance requires checking the fluid level. Semi-automatic drains are suitable for machines that often shut down when air pressure is removed. However, if the air is always on or water accumulates quickly, an automatic drain is the best choice.
Regulators. Regulators used to supply compressed air to a machine at a constant pressure are typically a “set it and forget it” system with a typical adjustable pressure range of 20–130 psi. Some processes operate at the lower end of the pressure range, so low pressure regulators provide an adjustable range from zero to about 60 psi. The regulator also supplies instrument air at normal pressure, typically in the 3–15 psi range.
Since air supply at a constant pressure is critical to the operation of the machine, a regulator with a locking pressure adjustment knob is required. There should also be a built-in pressure gauge that will help you quickly determine the actual air pressure. Another useful device is an adjustable pressure switch installed after the pressure regulator and controlled by the machine controller.
Pressure regulators have inputs and outputs that must be connected correctly. Air must flow from the inlet to the outlet, and reinstalling the regulator will cause it to malfunction.
Rice. 3. As the name suggests, the NITRA Combined Filter/Regulator combines the functions of a filter and a regulator in one compact unit.
In most cases, the regulator should also have a pressure relief function. In depressurize mode, if the pressure setpoint on the regulator decreases, the regulator output will decrease the outlet air pressure.
The filter/regulator combination includes all the functions of a stand-alone filter and regulator in one compact unit, as shown in Figure 3. Precision filter/regulator combinations also provide finer pressure control.
Lubricators Lubricators add lubrication to the air supply system in the form of oil mist, rather than removing contaminants like a filter. This lubricant increases speed and reduces wear on pneumatic equipment such as hand held pneumatic tools, including grinders, impact wrenches and torque wrenches. It also reduces leakage from working parts by sealing the stem, although most modern pneumatic equipment such as valves, cylinders, rotary actuators and grippers do not require seal lubrication.
The lubricators are available with various port sizes and the lubrication speed can be adjusted. A sight gauge is included for ease of maintenance and in most cases oil can be added while the unit is pressurized. It is necessary to correctly adjust the mist volume and maintain the oil level. A suitable oil must be added (usually a light viscosity oil such as SAE 5, 10 or 20 with rust and oxidation inhibitors added). In addition, the equipment to be lubricated must be located close enough to the lubricator that the oil mist remains suspended in the air. Excess oil can lead to oil mist, oil puddles and slippery floors in the facility.
Soft start/reset valves Soft start/reset valves are essential equipment for operator safety and typically include 24 VDC or 120 VAC solenoid valves controlled by emergency stop, safety devices or light curtain safety circuits. It releases pneumatic energy that induces movement, shutting off inlet pressure, and relieves outlet pressure in the event of a power outage during a safety incident. When the circuit is energized again, the solenoid valve gradually increases the outlet air pressure. This prevents the tool from moving too fast and failing to start.
This valve is installed after the FRL and normally directs air to the solenoid valve that causes the movement. The relief valve releases pressure quickly, so a high capacity muffler should be used to attenuate the sound. An adjustable flow regulator is designed to control the rate at which air pressure returns to a set pressure.
Air handling accessories All of the above pneumatic air handling units are supplied with mounting brackets for stand-alone use, or mounting accessories can be purchased separately. Air treatment systems are often modular in design, allowing individual shut-off valves, filters, regulators, lubricators and soft start/descent valves to be easily assembled on site with other components.
When connecting these modular devices to create combo units, mounting brackets and adapters are often required. These adapters include U-brackets, L-brackets, and T-brackets, each with one or more mounting tabs. Air distribution blocks can also be installed between the pneumatic components.
Figure 4. The entire air handling system is about half the size, weight, and cost of a system assembled from separately purchased components.
Conclusion Total air preparation systems (TAP) are an alternative to individually matching all air preparation components. These versatile systems include filters, regulators, shut-off/bleed valves, soft starters, electrical shutdown devices, pressure switches and indicators. TAP is about half the size, weight and cost of an air treatment system assembled from separately purchased components, fig. 4.
A better understanding of pneumatic air preparation components and their use helps protect both machines and operators. Thus, pressure relief valves and soft start/descent valves must be manually closed to control, isolate and remove compressed air from a machine or system. Filters, regulators and lubricators are used to prepare for use as air passes through the system.