Valve solenoid

A schematic setup to evaluate the closeness of a solenoid valve. 

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Titrations may be automated using a pump to deliver the titrant at a constant flow rate, and a solenoid valve to control the flow (Figure 9.5). The volume of titrant delivered is determined by multiplying the flow rate by the elapsed time. Automated titrations offer the additional advantage of using a microcomputer for data storage and analysis. 

Fig. 10. Use of solenoid valve for shutdown. Upon signal to shutdown, the solenoid closes a controller air signal port and opens a vent port.

Loop two or more elements where a signal passes between them for measurement and/or control, eg, sensor -i- transmitter -i- control + valve device two or more elements combined for a discrete state condition, eg, block valve -i- solenoid valve -i- actuator -I- limit switches... 

Air—electric samplers can be installed directly in the pipe wall. One type of Hquid sampler is operated by a solenoid valve that activates an air cylinder. A shaft is moved in and out of the pipe by this cylinder and samples are expeUed into a container below the sampler. Sample volumes of from 2—30 mL are possible. 

Solenoid Valves The electric solenoid valve has tw o output states. Wlien sufficient electric current is supplied to the coil, an internal armature moves against a spring to an extreme position. This motion causes an attached pneumatic or hvdraiilic valve to operate. Wlien current is removed, the spring returns the armature and the attached solenoid valve to the deenergized position. An intermediate pilot stage is sometimes used when additional force is required to operate the main solenoid valve. Generallv, solenoid valves are used to pressurize or vent the actuator casing for on/off control-valve application and safetv shutdown applications. 

Limit Switches and Stem-Position Transmitters Travel-limit switches, position switches, and valve-position transmitters are devices that, when mounted on the valve, actuator, damper, louver, or other throtthng element, detect the component s relative position. The switches are used to operate alarms, signal hghts, relays, solenoid valves, or discrete inputs into the control system. The valve-position transmitter generates a 4-20-mA output that is proportional to the position of the valve. 

The slide is located in the compressor casting below the rotors, allowing internal gas recirculation without compression. Slide valve is operated by a piston located in a hydraulic cylinder and actuated by high-pressure oil from both sides. When the compressor is started, the slide valve is fuUy open and the compressor is unloaded. To increase capacity, a solenoid valve on the hydraulic hne opens, moving the piston in the direction of increasing capacity. In order to increase partload efficiency, the slide valve is designed to consist of two parts, one traditional shde valve for capacity regulation and other for built-in volume adjustment. 

FIG. 17-60 Reverse-pulse fahric filter (a) filter cylinders (h) wire retainers (c) collars (d) tube sheet (e) venturi nozzle (f) nozzle or orifice (g) solenoid valve (h) timer (/) air manifold (k) collector housing (/) inlet (m) hopper (n) airlock (o) iipperplenum, (Mikropul Division, US. Filter Coip.)... 

Small interrupters and MCCBs particularly may be electrically operated through a solenoid valve. 

Control of the compressor is achieved by engaging the required number of cylinders. In. say. a 16-cylinder compressor if we engage only four cylinders, the compressor will run at 25 7r capacity, and if w c engage eight cylinders, the compressor will run at. 5()C< capacity. Electrically operated solenoid valves are provided for capacity control. Energy can be conserved by using static controls, as discussed in Section 6.15. 

To control the room temperature llow of chilled w atei is controlled in AHU, Figure I 3.49(e). A thermostat senses the room condition and iictivates a motorised solenoid valve in AFIU coil which in turn adjusts the flow of... 

The unit shown on the next page in figure 4.4.1 is a somewhat simplified version of a tested, actual unit. The six gaseous feed components enter through check valves at a pressure regulated to about 4 atm higher pressure then experimental pressure, e.g., 22 atm. Six mass flow controllers set the flows and all but the nitrogen lines are secured with power to open solenoid valves (SV). 

Gas compressor anti-surge (GM-OFF) control circuit, comprising transmitters, computers and pneumatic control valve Reverse flow protection (on axnal compressors only) as supplementary protection device against surging, working independently of the control circuit Expander emergency stop valve with pneumatic actuator and solenoid valve... 

Expander bypass (stack) valve with pneumatic actuator and solenoid valve... 

Solenoid valve actuator Electric motor, AC A Atmospheric outlet FC Control element closes on failure of auxiliary energy supply FO Control element opens on failure of auxiliary energy supply O Silencer... 

All valves are equipped with hydraulic actuators, electronic positioning controllers for precise positioning, and solenoid valves for rapid (trip) opening of bypass valves and emergency closure tripping of trip and inlet control valves. 

The actuating time for a quick-closing/quick-opening operation effected by the solenoid valves is 0.6 sec, and the actuating time under normal control is 5 sec for the inlet valves and 0.6 sec for the bypass valves. These actuating times apply to the full valve stroke outside the end position damping range. 

Combustor-shell pressure transducer line drain solenoid valve energized. 

The physieal realization of a system to eontrol room temperature is shown in Figure 1.6. Flere the output signal from a temperature sensing deviee sueh as a thermoeouple or a resistanee thermometer is eompared with the desired temperature. Any differenee or error eauses the eontroller to send a eontrol signal to the gas solenoid valve whieh produees a linear movement of the valve stem, thus adjusting the flow of gas to the burner of the gas fire. The desired temperature is usually obtained from manual adjustment of a potentiometer. 

A solenoid valve is shown in Figure 2.18. The eoil has an eleetrieal resistanee of 4ff, an induetanee of 0.6 H and produees an eleetromagnetie foree F it) of times the eurrent i t). The valve has a mass of 0.125 kg and the linear bearings produee a resistive foree of C times the veloeity u t). The values of and C are 0.4 N/A and 0.25 Ns/m respeetively. Develop the differential equations relating the voltage v t) and eurrent i t) for the eleetrieal eireuit, and also for the eurrent i t) and veloeity u t) for the meehanieal elements. Henee deduee the overall differential equation relating the input voltage v t) to the output veloeity u t). 

Gas solenoid valve This is assumed to have first-order dynamics of the form... 

Remote Depressuring - A pilot operated valve is sufficiently positive in action to be used as a depressuring device. By using a hand valve, a control valve or a solenoid valve to exhaust the piston chamber, one can open the pilot-operated valve and close it at pressures below its set point from any remote location, without affecting its operation as a pressure relief valve. 

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