Method for detecting malfunction of valve on the downstream side of throttle mechanism of pressure type flow control apparatus

With a pressure type flow control apparatus, a valve on the downstream side of a throttle mechanism is released and a flow rate setting value Qe inputted to the pressure type flow control apparatus is changed to detect the magnitude ΔV of change of a flow rate output signal Qo from the pressure type flow control apparatus while the flow rate setting value Qe is changed, so that normal functioning of the releasing operations of the valve on the downstream side of the throttle mechanism is confirmed when the magnitude ΔV of change of the flow rate output signal Qo is above the predetermined value. If the releasing operations are malfunctioning, the magnitude ΔV of changes is found to be below the predetermined value.

This is a National Phase Application in the United States of Application No. PCT/JP2007/000630 filed Jun. 13, 2007, which claims priority on Japanese Patent Application No. 2006-183061, filed Jul. 3, 2006. The entire disclosures of the above patent applications are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a method for detecting the malfunction of a valve installed on the downstream side of a throttle mechanism in a pressure type flow control apparatus by monitoring a flow output signal, and it is mainly directed at the use for fluid supply facilities with a pressure type flow control apparatus to be used with semiconductor manufacturing, food processing, chemical products-related facilities, and the like.

BACKGROUND OF THE INVENTION

In recent years, pressure type flow control apparatus have been increasingly used in gas supply facilities in semiconductor manufacturing, chemical products-related facilities, and the like, replacing thermal type flow control apparatus. The simple structure of a pressure type flow control apparatus makes it possible to reduce production costs and downsize the facilities. Furthermore, a pressure type flow control apparatus rivals, or exceeds, a thermal type flow control apparatus both in accuracy and responsiveness.

In these gas supply facilities, it is a common practice to regularly inspect devices and valves to see the operational conditions. Inspection activities on gas supply facilities thus is indispensable for the stable supply of a gas from gas supply facilities.

In response to such a demand as described above, applicants of the present invention have developed a method for detecting the malfunction of a valve while gas is supplied using a pressure type flow control apparatus as shown inFIG. 9, and disclosed the method in Japanese Patent Application No. 2005-253996. In particular, techniques in the aforementioned Japanese Patent Application No. 2005-253996 have made it possible to check operational conditions of valves V1, V2, V3, and to check for the existence of sheet leaks (hereinafter called a “check”), within a gas supply facility. As shown inFIG. 9, the valves V1, V2, V3are checked without removal from pipe passages, thus achieving excellent practical effects. In accordance withFIG. 9, Go designates a purge gas, Gp designates a process gas, FCS (flow control system) designates a pressure type flow control apparatus,1a,1b,1cdesignate pipe passages, and E designates a process chamber.

In accordance with the gas supply facility shown inFIG. 9, in order to determine whether valves V1, V2, V3are operating normally or not (i.e., being open or closed), checks are conducted by following the steps shown inFIG. 10.

First, the malfunction check starts with Step So. Then, at Step S1, valve V1is closed, valve V2is switched from “open” to “closed”, and valve V3is closed. After these operations, a pipe passage1bon the downstream side of the FCS is filled with N2. Next, at Step S2, the displayed pressure P1of the FCS is checked to see if the increase/decrease ΔP1of the pressure P1is zero or not. In the case that ΔP1is not zero and P1goes up, it is determined that there is an abnormal condition with either valve V1or valve V2, or both valves V1and V2(i.e., either sheet leaks or operational irregularity is present). And, in the case that P1goes down, it is determined that V3is abnormal (i.e., sheet leaks or operational irregularity are present) (Step S3).

Next, at Step S4, a process gas (i.e., a use gas) Gp is flowed into the FCS by making valve V1open and valve V2close, and the displayed pressure P1of the FCS is checked at Step S5. In the case when a rise of P1is observed, it is determined that V1is functioning normally (Step S7); on the other hand, in the case that there is no rise of P1, it is determined that valve V1is malfunctioning (Step S6), thus the operational conditions of V1are confirmed. Then, after V1is closed and V2is opened at Step S8, the displayed pressure P1of the FCS is checked (Step S9). In the case when there is no rise of P1, it is determined that valve V2is malfunctioning (Step S10), thus the operational conditions of valve V2are confirmed. On the other hand, when a rise of P1is observed, it is determined that valve V2is functioning normally (Step S11).

Then, at Step S12, it is determined whether or not the malfunction of valves found at the Step S2is applicable to the operational malfunction of a valve V3. Specifically, if the result of Step S2is “NO” (that is, one of valves V1, V2, V3is malfunctioning), and valves V1and V2are functioning normally, it is determined that a valve V3is malfunctioning (Step S13). If the result of Step S2is “YES”, then, it is determined that all the valves V1, V2, V3are functioning normally (Step S14).

After it is determined that the aforementioned valves V1, V2, V3are all operating normally, sheet leaks are then checked at Step S15. To determine whether the operational conditions of the valves are normal or not, there exist prerequisites that(a) there should be no outside leaks (i.e., leaks from joints, bonnets, and the like) with valves V1, V2, V3, FCS, pipe passages1a,1b,1c, and the like, except sheet leaks,(b) driving parts of all valves are under normal operation,(c) the FCS is functioning normally, and(d) V1and V2are not simultaneously released.

However, as shown inFIG. 11, the system is constituted so that, with a pressure type flow control apparatus FCS, a flow rate of a gas passing through a throttle mechanism is computed on the basis of the gas pressure P1and gas temperature T1on the upstream side of a throttle mechanism8such as an orifice, a sonic nozzle, or the like, (Japanese Unexamined Patent Application Publication No. 8-338546 and others). Therefore, for example, even when valve V3on the downstream side of the throttle mechanism is closed, and the flow rate of a gas passing through throttle mechanism8is found to be zero, a gas flow rate Qf is computed by flow rate computation apparatus20of flow rate computation circuit13if gas pressure P1is applied to pipe passage3, thus what is computed is outputted as a flow rate output signal Qo. Specifically, even when there occurs no gas flow due to the malfunction of releasing valve V3, a flow rate output signal Go is outputted to the outside. InFIG. 11,2designates a control valve,12designates a flow rate output circuit,14designates a flow rate setting circuit,16designates a computation control circuit,21designates a comparison circuit, and Qy designates a control signal (Qy=Qe−Qf).

When opening/closing operations of the valve V3on the downstream side of the FCS are conducted while the gas supply facility is at work, there is no way to find out directly if a malfunction of the releasing operations of the valve V3exists or not.

The reason for this is, as described above, that even when a flow rate of gas passing through throttle mechanism8is found to be zero (valve V3is in the state of closure), a flow rate output signal Qo is outputted to the outside if there exists pressure P1on the upstream side of throttle mechanism8. In other words, it is assumed that valve V3is kept open all the time from the viewpoint of a flow rate output signal Qo even when valve V3actually remains closed due to malfunction of valve V3.

Patent Document 1: Japanese Unexamined Patent Application Publication No. 8-338546

Patent Document 2: Japanese Unexamined Patent Application Publication No. 2000-66732

Disclosure of the Invention

SUMMARY OF THE INVENTION

Object of the Invention

It is an object of the present invention to provide a method for detecting the malfunction of a valve downstream of a throttle mechanism of a pressure type flow control apparatus with which the aforementioned problem of detecting the malfunction of the valve on the downstream side of the throttle mechanism of the pressure type flow control apparatus occurs; that is, the problem that accurate determination of the malfunction at the time of releasing operations of the valve on the downstream side of the throttle mechanism cannot be performed by using the pressure P1on the upstream side of the throttle mechanism of the pressure type flow control apparatus (or a flow rate output signal Qo) due to the structure of a pressure type flow control apparatus so that a flow rate output signal Qo is outputted externally due to the pressure P1on the upstream side of the throttle mechanism when there exists no flow of a gas passing through the throttle mechanism. This problem can be overcome, thus achieving a prompt, accurate determination of malfunction of the opening operation of the valve on the downstream side of the throttle mechanism on the basis of changes of the flow rate output signal Qo from the pressure type flow control apparatus when the valve on the downstream side of the throttle mechanism is undergoing opening/closing operations without the pressure type flow control apparatus having to be converted to a malfunction detection mode by the gas supply facility.

Means to Achieve the Object

One embodiment of the present invention is used in a gas supply facility wherein the pressure type flow control apparatus is so made that the fluid pressure P1is adjusted to make the flow rate control signal Qy to be zero by computing the flow rate Qf of fluid passing through the throttle mechanism by using the fluid pressure P1on the upstream side of the throttle mechanism, and a control valve2on the upstream side of the throttle mechanism is operated to open or close by making a difference between the flow rate computation value Qf of the fluid and a flow rate setting value Qe to be a flow rate control signal Qy. Thus, the flow rate computation value Qf of the fluid is outputted as a flow rate output signal Qo. A valve on the downstream side of a throttle mechanism of the pressure type flow control apparatus is released and a flow rate setting value Qe to be inputted to a pressure type flow control apparatus is changed in order to detect the magnitude of changes ΔV of the aforementioned flow rate output signal Qo while the flow rate setting signal Qe changes. This determines whether the releasing operations of the valve on the downstream side of the throttle mechanism are functioning normally in the case that the magnitude ΔV of changes of the flow rate output signal Qo is found to be above the predetermined value. On the other hand, the releasing operations are malfunctioning in the case wherein the magnitude ΔV of changes is found to be below the predetermined value.

Another embodiment of the present invention is so made that, when changing a flow rate setting value Qe to be inputted to a pressure type flow control apparatus, a flow rate setting value Qe′ larger than a steady-state flow rate setting value Qe″ or a flow rate setting value Qe′ smaller than a steady-state flow rate setting value Qe″ is inputted as a flow rate setting value Qe.

A different embodiment of the present invention used in a gas supply facility wherein a pressure type flow control apparatus is so made that fluid pressure P1is adjusted to make a flow rate control signal Qy to be zero by means that a flow rate Qf of fluid passing through a throttle mechanism is computed by using the fluid pressure P1on the upstream side of the throttle mechanism and a control valve2on the upstream side of the throttle mechanism is opened/closed by making the difference between the flow rate computation value Qf and flow rate setting value Qe to be a flow rate control signal Qy, thus the aforementioned flow rate computation value Qf of fluid is outputted as a flow rate output signal Qo, a valve on the downstream side of a throttle mechanism of the pressure type flow control apparatus is closed and a flow rate setting value Qe to be inputted to the pressure type flow control apparatus is set to zero, to detect the magnitude ΔV of changes of the aforementioned flow rate output signal Qo while it is changing after the flow rate setting value Qe having been set to zero. This distinguishes the situation where the releasing operations of the valve on the downstream side of the throttle mechanism are functioning normally, in which case the magnitude ΔV of changes of the flow rate output signal Qo is found to be above the predetermined value, from the situation where the releasing operations are malfunctioning, in which case the magnitude ΔV of changes is found to be below the predetermined value.

Another embodiment of the present invention is so made that the flow rate setting value Qe to be inputted to the pressure type flow control apparatus concurrently with the closure of the valve on the downstream side of the throttle mechanism or with the delay of a given time Δt is set to zero.

A different embodiment of the present invention is used in a gas supply facility for which a pressure type flow control apparatus is so made that fluid pressure P1is adjusted to make a flow rate control signal Qy to be zero by computing the flow rate Qf of fluid passing through a throttle mechanism by using the fluid pressure P1on the upstream side of the throttle mechanism, and a control valve2on the upstream side of the throttle mechanism is operated to open or close by making a difference between the flow rate computation value Qf of the fluid and a flow rate setting value Qe to be the flow rate control signal Qy. Thus, the flow rate computation value Qf of the fluid is outputted as a flow rate output signal Qo, a valve on the downstream side of the throttle mechanism of the pressure type flow control apparatus is released and a flow rate setting signal Qe is inputted to the pressure type flow control apparatus, in order to detect the magnitude ΔV of changes of the flow rate output signal Qo after the valve on the downstream side of the throttle mechanism has been released. The releasing operations of the valve on the downstream side of the throttle mechanism are determined to be functioning normally in the case that the magnitude ΔV of changes of the flow rate output signal Qo is found to be above the predetermined value; on the other hand, the releasing operations are determined to be malfunctioning in the case that the magnitude ΔV of changes is found to be below the predetermined value.

Another embodiment of the present invention is so made that the magnitude of the drop rate of the flow rate output signal Qo is detected by means that the flow rate setting signal Qe is inputted to the pressure type flow control apparatus with a delay of the predetermined time Δt after the command to release the valve on the downstream side of the throttle mechanism has been transmitted.

Embodiments of the present invention may be made such that an orifice or a sonic nozzle is used for the throttle mechanism.

Effects of the Invention

The present invention is so constituted that changes are made by means that a flow rate setting value Qe of a pressure type flow control apparatus is switched to “ON” or “OFF” either concurrently with opening or closing operations of a valve on the downstream side of a throttle mechanism of a pressure type flow control apparatus, or with a delay of a given time Δt after opening/closing operations of the valve on the downstream side having been made, thus determining whether the valve on the downstream side of the throttle mechanism is functioning normally or not by observing the changes of a flow rate output signal Qo between opening or closing operations of the valve on the downstream side of the throttle mechanism and also between “ON” or “OFF” of the flow rate setting value Qe. As a result, it can be determined whether opening operations of the valve on the downstream side of the throttle mechanism of the pressure type flow control mechanism are functioning normally or not, easily and simply, while a gas supply facility is at work. This is accomplished without installing or adding an extra testing device and without the pressure type flow control apparatus having to be switched to a malfunction detecting mode for the gas supply facility, but simply by monitoring a flow rate output signal Qo of the pressure type flow control apparatus. Thus, the problem that “the existence of a flow rate output signal Qo of a pressure type flow control apparatus does not lead directly to the opening operations of a valve on the downstream side of a throttle mechanism” is easily overcome.

REFERENCE CHARACTERS AND NUMERALS

Qe A flow rate setting value (a flow rate setting signal)

Qe″ A steady-state flow rate setting value

Qe′ A flow rate setting value

Qc A flow rate computation value

Qf A switching flow rate computation value

Qo A flow rate output signal

Qy A flow rate control signal

P1Gas pressure on the upstream side of a throttle mechanism

K A flow rate conversion rate

IV2A current for operating a valve V2

ΔV Deviation of a flow rate output signal at the time when a valve V2on the downstream side of a throttle mechanism is not released

Qo′ A flow rate output at the time when a valve V2on the downstream side of a throttle mechanism is not released

Qo A flow rate output at the time when a valve V2on the downstream side of a throttle mechanism is normally functioning

EV An electro-magnetic valve

U A pressure supply line for operating a valve

Pe A vacuum pump

VR A flow rate valve

Pb Baratron vacuum pump

PG A process gas

N2A gas for operating a valve

C A chamber

PLC A programmable controller

PL A data logger

S A gas supply source (N2)

Qe″ A steady-state flow rate

Qe′ A set flow rate different from a steady-state flow rate

1A gas supply

2A control valve

3A pipe passage on the upstream side of a throttle mechanism

4A valve actuating part

5A pipe passage on the downstream side of a throttle mechanism

6A pressure detector

7A temperature detector

9A gas outlet

12A flow rate output circuit

13A flow rate computation circuit

14A flow rate setting circuit

15A flow rate conversion circuit

16A computation control circuit

19A temperature compensation circuit

21A comparison circuit

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

Best Mode for Carrying Out the Invention

Preferred embodiments in accordance with the present invention are explained hereinafter in reference to drawings.FIG. 1shows the components of a pressure type flow control apparatus used with the present invention.FIG. 2is an illustration of a method for detecting malfunction of a valve on the downstream side of a throttle mechanism in accordance with Embodiment 1 of the present invention.

Referring now toFIG. 1, the major part of a pressure type flow rate control apparatus FCS comprises a gas supply1, a control valve2, a valve actuating part4, a pressure detector6, a throttle mechanism8, a gas outlet9, a flow rate output circuit12, a flow rate computation circuit13, a flow rate setting circuit14, a computation control circuit16and others. In accordance withFIG. 1,3designates a pipe passage on the upstream side of a throttle mechanism,5designates a pipe passage on the downstream side of a throttle mechanism,7designates a temperature detector,15designates a flow rate conversion circuit,10,11, and22designate amplifiers,17and18designate A/D converters,19designates a temperature compensation circuit,20designates a flow rate computation device,21designates a comparison circuit, Qc designates a computation flow rate signal, Qf designates a switching computation flow rate signal, Qe designates a flow rate setting signal, Qo designates a flow rate output signal, Qy designates a flow rate control signal, P1designates gas pressure on the upstream side of a throttle mechanism, and k designates a flow rate conversion rate. With preferred embodiments shown inFIG. 1,FIG. 2and others, an orifice has been used for throttle mechanism8. However, it goes without saying that the orifice can be replaced by a sonic nozzle or a diaphragm valve.

The aforementioned pressure type flow control apparatus FCS shown inFIG. 1is mainly used in the case wherein the ratio P2/P1of the gas pressure P1on the upstream side of the throttle mechanism and the gas pressure P2on the downstream side of the throttle mechanism is equal to or lower than the critical value of a fluid (that is, where the gas flow is in the critical state). A flow rate Qc of gas passing through the throttle mechanism8is given by Equation Qc=KP1(where K is a proportionality constant). A pressure type flow control apparatus is used to control the flow rate of a gas, which can exhibit both critical and non-critical states of flow. With some other types, the flow rate Qc of gas passing through throttle mechanism8is given by Equation Qc=KP2m(P1−P2)n(where K is a proportionality constant, m and n constants, and P2the gas pressure on the downstream side of a throttle mechanism). However, the fundamental constitutions of these other flow control systems are the same as that of the pressure type flow control apparatus FCS shown inFIG. 1. Therefore, explanations are omitted herewith.

In the pressure type flow control apparatus FCS, the setting value of the control flow rate is given by a voltage value as the flow rate setting signal Qe. For example, when the pressure control range 0˜3 (kgf/cm2abs) of the pressure P1on the upstream side is expressed by the voltage range 0˜5V, it means that Qe=5V (a full scale value) is the flow rate Qc under the pressure P1of 3 (kgf/cm2abs). More specifically, when the conversion rate k of a flow rate conversion circuit15is set at 1 and the flow rate setting signal Qe=5V is inputted, a switching computation flow rate signal Qf (Qf=kQc) becomes 5V, thus the control valve2is operated for opening/closing until the pressure P1on the upstream side gets to 3 (kgf/cm2abs). This means that gas of a flow rate Qc=KP1, corresponding to P1=3 (kgf/cm2abs), flows through throttle mechanism8.

FIG. 2is an explanatory drawing of a test unit used for executing a method for detecting the malfunction of a valve on the downstream side of a throttle mechanism in accordance with Embodiment 1 of the present invention. Namely, as shown inFIG. 2, the test unit is so constituted that a gas supply valve V1and a valve V2on the downstream side of the throttle mechanism are connected to the upstream side and downstream side of a pressure type flow control apparatus FCS respectively, thereon a programmable controller PLC and a data logger DL are set, and following the prescribed program from the programmable controller PLC, a flow rate setting signal Qe is supplied to valves V1, V2and a flow rate setting circuit14of a pressure type flow control apparatus FCS, and a valve releasing signal IV2to a valve V2, a flow rate setting signal Qe to the FCS and a flow rate output signal Qo from the FCS are recorded on the data logger respectively. WithFIG. 2, S designates a gas source and C designates a chamber.

Specifically, such a test system as shown inFIG. 2has been formed in order to detect the malfunction of valve V2on the downstream side of the throttle mechanism of the pressure type flow control apparatus FCS (operations from closure to opening not being able to be performed), and as shown inFIG. 3, first a flow rate value Qe which differs from a steady-state flow rate value Qe″ is sent as a flow rate setting signal Qe to the FCS, and then the flow rate setting signal Qe equal to the steady-state flow rate value Qe″ is inputted.FIG. 3(a) shows the case wherein the flow rate setting value Qe′, which differs from the steady-state flow rate value Qe″, is made to be larger than a steady-state flow rate value Qe″, andFIG. 3(b) shows the case wherein the flow rate setting value Qe′, which differs from a steady-state flow rate value Qe″, is set smaller than the steady-state flow rate value Qe″.

As shown inFIG. 3, when the flow rate setting signal Qe is inputted to the FCS and a releasing operation current IV2(an exciting current) is supplied concurrently to the valve V2on the downstream side of the throttle mechanism, the flow rate output Qo from the pressure type flow control apparatus FCS shows changes as illustrated in the lowermost parts ofFIGS. 3(a) and (b). Specifically, a deviation ΔV in a flow rate output occurs between a flow rate output Qo′ in the case that the valve V2on the downstream side of the throttle mechanism is not released and a flow rate output Qo″ in the case that the valve V2is released normally, thus making it possible to determine whether the valve V2on the downstream side of the throttle mechanism has been normally released or not, by monitoring the flow rate output signal Qo from the pressure type flow control apparatus FCS.

Specifically, at the preparatory stage for finishing a process treatment operation or starting a process treatment operation for which a chamber C is used, the flow rate setting signal Qe and the valve releasing current IV2are supplied to a pressure type flow control apparatus FCS and to a valve V2on the downstream side of a throttle mechanism, respectively, through the mediation of the programmable controller PLC, and then the state of changes of the flow rate output signal Qo from the FCS is observed, thus determining whether valve V2on the downstream side of the throttle mechanism has been released normally, if the deviation ΔV is found to be above the set value, or whether valve V2has not been released normally, if the deviation ΔV is found to be below the prescribed value.

Embodiment 2 is made so that an operational malfunction of a valve V2on the downstream side of a throttle mechanism is detected at the time of the completion of a process treatment.FIG. 4is an explanatory drawing of a test system used with Embodiment 2. InFIG. 4, EV designates an operational electro-magnetic valve, V1designates a valve on the FCS upstream side, Pe designates a vacuum pump, Pb designates a Baratron vacuum pump, VR designates a flow rate valve, N2designates an operational gas, and PG designates a process gas.

The detection of the operational malfunction of the valve V2on the downstream side of the throttle mechanism has been performed in a manner such that changes of a FCS flow rate output signal Qo are monitored after a flow rate setting signal Qe to the FCS is set to zero (the FCS shutdown) at the time when a treatment process is terminated, for two distinct cases. In one case, as shown inFIG. 5(a), the shutdown of a flow rate setting signal Qe of the pressure type flow control apparatus FCS and the closure of the valve V2on the downstream side of the throttle mechanism are conducted concurrently (hereinafter called a normal step), and in the other case, as shown inFIG. 5(b), some delay of time Δt is made between the closure of the valve V2on the downstream side of the throttle mechanism and the shutdown of a flow rate setting signal of the FCS (hereinafter called a multi-step).

As shown inFIGS. 5(a) and (b), it is assumed that there exists a malfunction in releasing of the valve V2on the downstream side of the throttle mechanism in the case that the flow rate output signal Qo shows no drop after the closure of the valve V2on the downstream side of a throttle mechanism and the closure of the FCS (the closure of the control valve2of the FCS) and the same state of flow rate output signal Qo′ is maintained. The reason for this assumption is that the fact that there is seen a flow rate output Qo′ without the flow rate output Qo not becoming zero means there remains a gas pressure between throttle mechanism8and the valve V2on the downstream side of the throttle mechanism, and there is seen no decrease in the remaining pressure (that is, a valve V2not releasing the pressure).

With regard to actually determining the malfunction of a valve, it is required that first the internal capacity of a pressure supply line U for operating a valve between an electro-magnetic valve EV and the valve V2on the downstream side of the throttle mechanism, and also the delay time between the input of a current signal for closing the valve V2on the downstream side of the throttle mechanism and an actual closing operation of valve V and others are taken into consideration, and then a threshold value of the drop rate of a flow rate output signal Qo of the FCS is established; thus it is determined that there exists a malfunction with the releasing operation of a valve V2on the downstream side of the throttle mechanism in the case that the drop rate of the flow rate output signal Qo is below the prescribed drop rate.

FIG. 6shows the relationship of the difference ΔtV between the closing operation signal input for the valve V2on the downstream side of the throttle mechanism and an actual operating time and also the flow rate output Qo of the FCS (the pressure P1on the upstream side of a throttle mechanism) and the pressure P2on the downstream side of a throttle mechanism. As apparent fromFIGS. 6(a) and (b), if the aforementioned ΔtV is small (FIG. 6(b)), the amount of change of a flow rate output Qo of the FCS (the pressure P1n the upstream side of a throttle mechanism) becomes small, thus making it difficult to determine whether a valve V2is malfunctioning by monitoring the drop rate of the flow rate output signal Qo.

It goes without saying that the magnitude of ΔtV depends upon the properties of valve V2, electro-magnetic valve EV, the internal capacity of a pressure supply line U for operating a valve, and the like, and further that changes of the pressure P2on the downstream side of the throttle mechanism varies largely according to the conditions, such as the flow rate range in use of a pressure type flow control apparatus, the pressure on the camber side, and the like.

With Embodiment 3, the malfunction of a valve V2on the downstream side of a throttle mechanism (releasing not functioning) is detected by monitoring a FCS flow rate output signal at the time of a startup of a pressure type flow control apparatus FCS. This is mainly used to detect any operational malfunction of valve V2on the downstream side of the throttle mechanism during the preparatory stage of starting up a process system.

A test device used with Embodiment 3 is same as that shown inFIG. 4. Specifically, with Embodiment 3, the malfunction of a releasing operation of a valve V2on the downstream side of the throttle mechanism is determined by monitoring the drop quantity of a FCS flow rate output signal Qo which occurs within a time Δt (a delay time Δt=0.2 sec) from a valve V1on the primary side of the pressure type flow control apparatus FCS, and valve V2on the downstream side of the throttle mechanism is released until a flow rate setting signal Qe being inputted to the FCS and by making the drop quantity as a basis.

FIG. 7shows the relationship of the FCS flow rate output signal Qo, a delay time Δt=0.2 sec, a delay time ΔtV in releasing valve V2on the downstream side of the throttle mechanism, and the like, with Embodiment 3. At the preparatory stage of starting up the process, when valve V1on the upstream side of the FCS and valve V2on the downstream side of the throttle mechanism are made open, and the FCS is operated with a delay time Δt=0.2 sec (a flow rate setting signal Qe in), the FCS flow rate output signal Qo drops during the delay time Δt in the case that valve V2on the downstream side of a throttle mechanism is functioning normally for a releasing operation, and conversely there would be no changes in the FCS flow rate output signal Qo during a delay time Δt when valve V2on the downstream side of the throttle mechanism is not releasing normally.

As with Embodiment 2, a degree (a drop rate) of change of the FCS flow rate output signal varies largely depending on the delay time in releasing valve V2on the downstream side of the throttle mechanism. Accordingly, it is found that the drop rate during the delay time Δt of the FCS flow rate output signal Qo is largely affected by the length of pressure supply line U for operating valve V2on the downstream side of the throttle mechanism, the type of an electro-magnetic valve EV, the flow rate setting range for the pressure type flow control apparatus FCS, and the like.

FIG. 8shows the results of monitoring the state of the drop of the flow rate output signal Qo when a flow rate setting signal Qe of a pressure type flow control apparatus FCS and the number of valves V2on the downstream side of a throttle mechanism are changed. A standard type with a rated flow rate of 1 SLM is employed for the pressure type flow control apparatus FCS. A valve having a Cv value of 0.1 and a valve having a Cv value of 0.2 are used for valves V1and V2respectively. Furthermore, pressure supply line U for operating valves V1and V2has an internal diameter of 2.5 mmφ and the length of 1 m. A flow rate control valve VR and a vacuum pump Pe are so adjusted that pressure P2downstream of the throttle mechanism is 120 Torr when N2=2 SLM is supplied.

As apparent fromFIG. 8, the average pressure drop rate of the FCS flow rate output signal Qo was 89.9% (with one valve V2) to 79.4% (with four (4) valves V2) when the setting flow rate signal Qe of the FCS was Qe=100%; the results were 85.4% (V2=1) to 79.7% (V2=4) when Qe=50%; the results were 86.3% (V2=1) to 70.6% (V2=4) when Qe=5%. It is thus possible to detect the malfunction of a valve (releasing not functioning) in any case. A pressure drop rate is obtained by computing the value as (B−A)/A×100%, where B is a flow rate output signal Qo of the FCS after completing the process, and A is a value of a flow rate output signal Qo′ after 0.2 sec at the time of a multi-step (see FIG.8(a)).

Feasibility of Industrial Use

The present invention can be applied to any gas supply facility as long as a pressure type flow control apparatus FCS is being used. Releasing operations of a valve on the downstream side of a throttle mechanism of a pressure type flow control apparatus FCS can be accurately detected with the conditions of changes of a flow rate output signal Qo when a flow rate setting input Qe of a pressure type flow control apparatus FCS is changed.