Pneumatic control system

Pneumatic Control Systems. The first widely adopted automatic control systems used compressed air as the operating medium. A transition to electronic... 

Signal transmission limitations of pneumatic control systems made it necessary to limit the distance between the control house and the transmitter or control valve. As a result, early control houses were located within or at the periphery of the process unit. 

For the above estimate, total equipment costs for the SFC system was estimated at 35,540. This included the vertical fin coalescing unit, oleophilic ceramic granules, pumps, a pneumatic control system, and such ancillary equipment as a 2000-gal bulk tank with fittings, a skimmer, necessary switches, valves, piping, and wires (D11018P, p. 28). 

The actuation of pneumatic pump is realized due to the time-phased deflection of the elastic membranes controlled by the pressure of compressed air in the pneumatic control channels. A pneumatic control system auxiliary to the microfluidic chips is needed to support the implement of the pneumatic actuation [2]. The outside pneumatic control system usually includes a supply source of compressed air, a solenoid valve array, a sensor, and a controller unit/... 

The pneumatic actuated micropump in a multilayer microfluidic device also has some disadvantages. The elastomeric nature of pump material PDMS may cause the features in the microfluidic devices to shrink or sag. Nonspecific adsorption with biological samples may also occur in the PDMS pneumatic pump. In addition, the necessary valve array and pneumatic control system stand-alone to support the pump occupy large spaces. 

In principle, the controller functions like a human process operator who watches the dial of an instrument indicating the actual value of a process variable, e.g., a rate of flow. When the pointer moves away from the desired value, the operator corrects this by adjusting a valve (the correcting element) so as to restore the flow rate to its desired value. In modern industry the control functions are automated, using electronic equipment. Pneumatic control systems, which were used to some extent in the cement industry in the past, are now virtually obsolete. 

With pneumatic control systems one advantage of split-ranging is that both valves can be connected to the same pneumatic signal line, thus saving the cost of the second line. With... 

Pneumatic control systems use compressed air to modulate the controlled device. In this system, the air is applied to the controller at a constant pressure, and the controller regulates the output pressure to the controlled device according to the desired rate of change. Typical air pressure for an HVAC control system is 20 psi (136 kPa). 

Clarridge, R. E. An Improved Pneumatic Control System, Trans. ASME, April,... 

Buckley, P. S., and W. L. Luyben, Designing Long-Line Pneumatic Control Systems, INTECH, Apr. 1969, 61-66. 

Control of quality and state of engine parts, components of electric, pneumatic, hydraulic systems, load-bearing elements Investigations of parts and units failure causes... 

The pneumatic classification system should be designed to handle ha2ardous dust (28). A ha2ardous dust is one which, when finely divided and suspended in air in the proper concentration, bums, produces violent explosions, or is sufficiently toxic to be injurious to personnel health (see Air pollution control methods Powders, handling). At the least, almost any dust can be irritating to personnel because of inhalation or skin or eye contact. Fully oxidi2ed and hydrated materials are generally considered safe. 

The main shortcomings of the pneumatic controller is its lack of flexibility when compared to modern electronic controller designs. Increased range of adjustability, choice of alternate control algorithms, the communication link to the control system, and other features and services provided by the electronic controller make it a superior choice in most of todays applications. 

Speed-Control Systems The most common sensing element is mechanical some systems are hydraulic or electronic. For valve positioner they all have a hydrauhc servo as first choice, with an occasional choice of pneumatic for lighter loads. 

Depending on the control system and components selected, the process variable from the sensors and signals to the actuator control unit is connected either directly or through transducers. Normally, the input and output are adjusted from pneumatic sensors and control units. The signals produced then are transformed into standard electronic values before connecting to the controller s input and output modules,... 

Pneumatic control A control system that operates on compressed air as the operating medium for the control of valves and dampers, etc. 

During the 1960s, air conditioning system control began to shift from simple electrical or pneumatic control to electronic and rudimentaiy computer control. This new technology was applied to commercial, institutional and commercial buildings where the high cost and complicated nature justified its use. 

Control systems, speed control, pressure control, process control If remote control, will it be pneumatic or electric And, what speed or pressure variation can be tolerated, and how fast must the system respond ... 

The control system will consist of a loop, with detector (sensor), controller and controlled device. The communication between these parts of the loop will be electric, pneumatic or mechanical (see Figure 31.1) [62]. 

Figure 2.28. Simple feedback temperature control system. M-motor with stirrer, PV-pneumatic valve, Tx - temperature measurement, - temperature controller.

Where it is necessary to follow a fixed sequence of operations—for example, during a plant start-up and shut-down, or in batch operations — interlocks are included to prevent operators departing from the required sequence. They may be incorporated in the control system design, as pneumatic or electric relays, or may be mechanical interlocks. Various proprietary special lock and key systems are available. 

The death knell for pneumatic control equipment has been predicted for at least the past 15 years. So far this has not happened, but it is still predicted. The major reason why pneumatic equipment is so popular is that the pneumatic control valve is cheap and requires little maintenance. The pneumatic system also has the advantage of posing no problems in the presence of flammable substances. (Extreme care must be exercised if electrical signals are used in such environments.) One major problem with pneumatic systems is the delay encountered in sending a pneumatic signal over 300 ft (90 m). However, this can usually be avoided by mounting the controller next to the unit instead of in the control room. This does not affect the monitoring of the process, which can still be done in a remote location. 

An inflatable bellows used in a pneumatic suspension system for motor transport irrespective of load the centre of gravity of the vehicle can be maintained at a constant height above ground level with appropriate control systems. 

Advances in quality control requirements for rubber compounds have demanded that special care is exercised in the weighing of the various fillers and critical small volume powders necessary for the formulation. Ingredient weighing systems are available which can be tailored to the specific requirements of individual factories. Additional components can include conveyors, bagging units and pneumatic conveyance systems. 

Thermoelectric flame failure detection Analog burner control systems Safety temperature cut-out Mechanical pressure switch Mechanic/pneumatic gas-air-ration control Thermoelectric flame supervision Thermal combustion products, discharge safety devices Electronic safety pilot Electronic burner control systems Electronic cut-out with NTC Electronic pressure sensor/transmitter Electronic gas-air-ration control with ionisation signal or 02 sensor Ionisation flame supervision Electronic combustions product discharge safety device... 

As mentioned earlier, pneumatic and hydraulic systems have been extensively used in hazardous environments to provide the power necessary to move and drive machinery to complete needed tasks. Their use has demanded development of complex logic systems which involve the addition of valves and piping. These logic control systems are often hard to design, debug, construct, and maintain. 

Basic Process Control System (BPCS) - Pneumatic, electronic, hydraulic or programmable instruments and mechanisms that monitor and/or operate a facility or system to achieve a desired function, i.e., flow control, temperature measurement, etc., which are supervised by human observation. 

Systems with electronic pneumatic control use pressure transducers at the inlet and outlet, the column dimensions and physical properties of the carrier gas to determine the gas hold-up time and the flow rate. 

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