The regulator of the kinds of the fault have a plan
The regulator in the role of the process control is known, in many control process requests the regulator in failure in a certain position to protect the process does not appear accident, which requires the regulator in the design of fault-security realize three broken (to snuff out, without electricity, fault signal) protection measures. For electric regulator, it is simpler, broken signal, can according to the control module and stay in the setting of the full open and seated, keep any of position, and without electricity, natural stay in fault position, or with a repositioning of the electric actuator can also be a run to the valve fully open or seated.
For pneumatic-valve for, the case is more complex, so we mainly discuss the pneumatic-valve three broken the position method. Generally speaking, we are choosing pneumatic film regulator, must determine first choose open or shut gas gas, this is to choose the protection regulator to snuff out position, if process requirement to snuff out the valve open when, can choose to often open (gas closed) type regulator, conversely choose closed (gas open) type regulator. This is only a vague plan, if the process requirement, power off, fault signal expired three broken protection, the regulator will need to configure some accessories to form a protection system to achieve the control requirements, these accessories mainly have the position valve, electromagnetic valve, tank, etc. The following is a single function pneumatic film regulator and double role of pneumatic-valve two the position scheme.
A, pneumatic film regulator scheme (regulator with electricity-air valve locator)
The scheme is mainly by the pneumatic-valve, electricity-air valve locator, lose electric (signal) comparator, single electric electromagnetic reversing valves, pneumatic valve, the position of the valve position signal back to implement etc. Its principle of work is as follows:
1, broken air source: when the control system fault source (loss of air), pneumatic valve automatically shut off the position will locator output signal pressure pneumatic control valves in the membrane of the interior, the output signal pressure and control valve spring produce reverse force of phase equilibrium, pneumatic control valve of the valve position keep in fault position. The guaranteed a valve should be set at slightly less than the minimum value air launched.
2, broken power supply: the power when the control system fault (lose electric), lose electric (signal) comparator control electric control electromagnetic reversing valves of single output voltage disappear, single electric electromagnetic reversing valves lose electric, single electronic directional control valve of the electromagnetic in rotary in the role of reposition spring down move, electromagnetic valve reversing, the position of the valve will pneumatic film chamber pressure emptying, pneumatic the position valve is closed, the locator's output will signal pressure pneumatic control valves in the membrane of the interior, the output signal pressure and control valve spring produce reverse force of phase equilibrium, pneumatic control valve of the valve position keep in fault position.
3, fault signal: when the control system fault signal (lost signal), lose electric (signal) is used to test, broken electric single directional control valve of the electromagnetic voltage signal and single electric electromagnetic reversing valves lose electric, single electronic directional control valve of the electromagnetic in rotary in the role of reposition spring down move, electromagnetic valve reversing, the position of the valve will pneumatic film chamber pressure emptying, pneumatic the position valve is closed, the locator's output will signal pressure pneumatic control valves in the membrane of the interior, the output signal pressure and control valve spring produce reverse force of phase equilibrium, pneumatic control valve of the valve position keep in fault position.
Position feedback signal by a signal is given back to the valve.
The advantages of this scheme: "three broken" protect start-up, rapid response system, action quick. The overall cost is cheaper.
The shortcomings of the scheme, electromagnetic valve long-term charged, the influence is used life. With more accessories, installation, debugging is more complex, the valve position feedback to another of the valve position with the return signal, in with the handwheel, is more complex.
Second, double role pneumatic-valve scheme (regulator with electricity-air valve locator)
The scheme is mainly by the control valves, gas control reversing valves, the locator, self-locking valve, check valve, pressure reducing valve, storage tank etc. Its principle of work is as follows:
When the control system fault source (loss of air), self-locking valve (its function and the way a valve instead) automatically open, will air control of the directional control valve control air undo, gas control of the directional control valve in the rotary piston in spring under the function of reset, and two gas directional control valve control one of the exhaust, another inlet, check valve closed, air storage tank by stored in the air to the valve gas supply, so as to realize the seated or fully open valve. Seated or fully open conversion can be adjusted by gas control of the directional control valve connection means.
If the realization of the valve to the position, the position with pneumatic valve and change the pipeline connection, with locking valves direct control the position valve, cancel gas control reversing valves, check valve, storage tank can.
If want to realize the broken air, to ensure that the valve is several times action, can use the following solutions.
His own cause of the storage tank, check valve, atresia valve, cut-off valve etc. Its principle of work is as follows:
When gas source fault (loss of air), check valve closed, locking the loss of air, in the rotary piston valve closure in spring under the function of reset, and pneumatic reversing, disconnect system air pipelines, storage tank through pipelines, storage tank to valve by gas supply, to ensure that the valve is several times action, to achieve continuous control purpose. Due to the limited capacity of the storage tank, and the storage tank air pressure with the valve actuation falling, do not use for a long time storage tank for valve gas supply. This plan with the capacity of the storage tank should be better than general protection with the capacity of the storage tank. The scheme is broken in air, the valve movements of The Times and the storage tank of volume.
For the position of pneumatic film regulator scheme, and a reference: in the locator and actuators series between the position valve and two the 3-way magnet valve each one, in the position when he breathed his last with the valve to the position in fault signal, the use of electromagnetic valve to the position, however, electromagnetic valve must and locator to chain (in control procedures set), namely locator have signal, solenoid valves will be electric, the locator once lost signal, electromagnetic valve must immediately without electricity. |
