JP2000137528A - Method and device for detecting orifice clogging in pressure-type flow rate controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge clogging with simple operation without disassembling piping by comparing reference pressure attenuation data when an orifice is not clogged with pressure attenuation data at the time of an actual operation and judging the propriety of clogging according to whether or not they are dissociated for not less than a prescribed degree. SOLUTION: A setting flow rate is held to a high setting flow rate. The high setting flow rate is switched to a low setting flow rate and it is kept. Upper stream side pressure is measured and pressure attenuation data is obtained. Reference pressure attenuation data measured when an orifice is not clogged and pressure attenuation data obtained by measurement are compared with same conditions. When pressure attenuation data is dissociated from reference pressure attenuation data for not less than a prescribed degree, clogging is reported. The clogging detector is constituted of a central processing unit CPU, a memory device for data storage M, a communication part PT 42 with outside, the outer circuit 4 of a trigger circuit, an alarm circuit 46 at the time of clogging, a power source circuit SC 48 and the outer power source 50 of ±15 V, for example.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure type flow rate control device for various fluids such as gases used for manufacturing semiconductors, chemicals, chemicals, precision machine parts, etc., and more particularly, to orifice holes which cause clogging. The present invention relates to a method for detecting the clogging when the operation is performed and a detection device for the method.

[0002]

2. Description of the Related Art Conventionally, most of fluid supply devices in semiconductor manufacturing facilities and chemical manufacturing facilities which require high-precision flow rate control use mass flow controllers.

However, the mass flow controller includes:
In the case of a thermal type flow sensor, the response speed is relatively slow, the control accuracy in the low flow rate region is poor, the accuracy varies from product to product, there are many operational troubles, stability is low, and the product price is high. There are various inconveniences, such as replacement parts being expensive and running costs being high.

The inventors of the present invention have conducted intensive studies to improve these disadvantages, and as a result, have developed a pressure type flow control device using an orifice disclosed in Japanese Patent Application Laid-Open No. 8-338546.

The features of this pressure type flow control device are as follows. Pressure ratio P ₂ / P of gas before and after orifice
_{When 1} (P ₁ : upstream pressure, P ₂ : downstream pressure) becomes lower than the critical pressure ratio of gas (about 0.5 in the case of air or nitrogen, etc.), the flow velocity of the gas passing through the orifice becomes the speed of sound. Thus, pressure fluctuations on the downstream side of the orifice are not transmitted to the upstream side, and a stable mass flow rate corresponding to the state on the upstream side of the orifice can be obtained.

That is, when the orifice diameter is constant, if the upstream pressure P ₁ is set to be about twice or more the downstream pressure P ₂ ,
Downstream flow Q _C flowing through the orifice upstream side pressure P ₁
, And a linear relationship of Q _C = KP ₁ (K: constant) is established with high accuracy. That is, if the orifice diameter is the same, this constant K is also constant.

The configuration of the pressure type flow control device will be described with reference to FIG. The upstream flow path 4 of the orifice 2 is connected to a control valve CV that is opened and closed by a drive unit 8, and the downstream flow path 6 is connected to a fluid reaction device (not shown) via a gas extraction joint 12. .

The pressure P ₁ on the upstream side of the orifice is the pressure detector 1
4 and the pressure indicator 2 via the amplifier 16
2 is displayed. The output is digitized through the A / D converter 18, and the arithmetic circuit 20 calculates the downstream flow rate Q of the orifice by Q = KP ₁ (K: constant).

On the other hand, the upstream temperature T ₁ detected by the temperature detector 24 is output to the temperature correction circuit 30 via the amplifier circuit 26 and the A / D converter 28, and the flow rate Q is temperature corrected and calculated. flow rate Q _C is output to the comparison circuit 36. Here, the arithmetic circuit 20, the temperature correction circuit 30, and the comparison circuit 3
6 are collectively referred to as an arithmetic control circuit 38.

From the flow rate setting circuit 32, an A / D converter 34
Set flow rate Q _S via is output and sent to the comparison circuit 36. In the comparison circuit 36 and the calculated flow rate Q _C set flow rate Q _S
Difference signal Q _Y of is calculated by Q _Y = Q _C -Q _S, is output to the drive unit 8 through the amplifying circuit 40. The drive unit 8 and controls the opening and closing of the control valve CV in the direction difference signal Q _Y becomes zero, thereby controlling such downstream flow rate is equal to the set flow rate.

[0011]

THE INVENTION Problems to be Solved] This pressure-type flow rate control apparatus is superior in that it can control the downstream flow rate with high accuracy by simply detecting the upstream pressure P _1, the fine in order to use the orifice The weak point is that the holes are clogged. The orifice is a micron-order orifice hole, and the orifice hole may be clogged with dust or the like, making it impossible to control the flow rate.

Although the inside of the pipe whose flow rate is controlled must be highly purified, there is a possibility that dust, dust, and the like during the piping remain. When the orifice is clogged, the flow control cannot be performed, so that the whole plant becomes unstable and a large number of defective products are generated.
Also, depending on the type of gas fluid, there was a risk that a chemical reaction would run away and cause an explosion. To prevent this,
It has also been considered to incorporate a gasket filter in the pipe, but it has a drawback that affects the conductance of the pipe.

FIG. 13 shows the flow characteristics when the orifice is clogged. The post-purge flow rate characteristic is a characteristic when there is no clogging. For example, when the set value is designated as 100% in FIG. 13, if there is no clogging, the N ₂ gas is 563.1 SCCM (O mark). ) Should flow. All subsequent reaction systems are designed with the expected flow rates. However, if there is clogging, only 485 SCCM (mark) flows in this case, and the reaction as designed cannot be expected. Here, SCCM indicates a gas flow rate (cc) per minute under a standard condition.

As described above, when the orifice is clogged, a phenomenon that the flow rate becomes lower than the set value appears. In semiconductor and chemical plants, when the amount of raw material gas is excessive or insufficient, an explosion occurs or a large amount of damage occurs to a product, and how to detect clogging of an orifice has been a major issue.

[0015]

SUMMARY OF THE INVENTION The present invention solves the above disadvantages.
2. The pressure according to claim 1, wherein
The orifice clogging detection method in the flow control device
Control valve and orifice and the upstream pressure between them.
It consists of a pressure detector to detect and a flow rate setting circuit.
Force P₁Is the downstream pressure P_TwoDownstream side by holding at least about 2 times
Flow rate Q_CTo Q _C= KP₁(K: constant)
Calculation flow Q_CAnd set flow rate Q_SDifference signal Q_YBy con
In the flow control device that controls the opening and closing of the troll valve,
Flow Q_STo the high set flow Q_SHAnd a first step of holding the
High set flow rate Q_SHTo the low set flow rate Q_SLSwitch to and hold upstream
Side pressure P₁To obtain pressure decay data P (t)
When there is no clogging in the orifice under the same conditions as in two steps
Measured reference pressure decay data Y (t) and said pressure decay
A third step of comparing data P (t) with pressure decay data
P (t) is less than a predetermined degree from the reference pressure decay data Y (t).
Consists of the fourth step to notify clogging when the upper part is opened
Have been.

The clogging detection method in a pressure type flow rate control apparatus according to claim 4, the pressure detector 14 and a flow rate setting circuit 32 for detecting the control valve CV and the orifice 2 an upstream pressure P ₁ therebetween Thus, the upstream pressure P ₁ is maintained at about twice or more the downstream pressure P ₂ and the downstream flow rate Q _C
Is calculated using Q _C = KP ₁ (K: constant), and the calculated flow rate Q
In the flow control device which controls the opening and closing of the control valve CV by the difference signal Q _Y between the _C and the set flow rate Q _S, the set flow rate Q
The first step of holding _S at the high set flow rate Q _SH , switching the high set flow rate Q _SH to the low set flow rate Q _SL and holding the same, measuring the upstream pressure P ₁ and the upstream temperature P _t and performing this measurement a second step of calculating the pressure attenuation data P (t) by using the values, standards under the same conditions, were calculated using the upstream pressure P _t and the upstream temperature T _t measured when there is no clogging in the orifice The pressure decay data Y (t) and the pressure decay data P
(T) and pressure decay data P
The fourth step is to notify the clogging when (t) is separated from the reference pressure attenuation data Y (t) by a predetermined degree or more.

Further, the pressure type flow control device according to claim 7 is provided.
The orifice clogging detector at the
To detect the orifice and upstream pressure between them
It consists of a detector and a flow rate setting circuit.₁Downstream
Side pressure P_TwoOf the downstream flow rate Q_CTo
Q_C= KP₁(K: constant), and the calculated flow rate Q _C
And set flow rate Q_SDifference signal Q_YControl valve
In the flow control device that controls opening and closing, the orifice is clogged.
High set flow rate Q under tight conditions_SHTo low set flow rate Q_SL
Pressure P measured by switching to₁Reference pressure decay
Memory device storing the data Y (t) and the actual orifice
High set flow rate Q under extreme conditions_SHTo low set flow rate Q_SLSwitch to
And the upstream pressure P₁The pressure decay data P (t) of
Pressure detector, pressure decay data P (t) and reference pressure
Central processing unit for performing comparison operation with force attenuation data Y (t)
And the pressure decay data P (t) is the reference pressure decay data Y
(T) When opening a predetermined degree or more, c
It is composed of an alarm circuit.

The pressure type flow control device according to claim 9,
The orifice clogging detection device is connected to the control valve CV.
Orifice 2 and upstream pressure P between them₁Detect
The pressure sensor 14 and the flow rate setting circuit 32
Force P₁Is the downstream pressure P_TwoDownstream side by holding at least about 2 times
Flow rate Q_CTo Q_C= KP₁(K: constant)
Calculation flow Q_CAnd set flow rate Q_SDifference signal Q_YBy con
The flow control device that controls the opening and closing of the trawl valve
A pressure detector 14 for measuring the upstream pressure P of the fiss;
A temperature detector 24 for detecting the upstream temperature T of the fiss;
High set flow rate Q under conditions where clogging does not occur in fiss 2_SHFrom
Low set flow rate Q_SLPressure P measured by switching to_tas well as
Upstream temperature T_tPressure P calculated using₁Standards of
A memory device M storing pressure decay data Y (t);
The reference pressure attenuation data Y (t) is calculated, and
High set flow rate Q under the actual conditions of fiss 2_SHTo low set flow rate
Q _SLPressure P measured by switching to_tAnd upstream temperature
T_tUsing upstream pressure P ₁Pressure decay data P (t)
, And the pressure decay data P (t) and the reference
Central arithmetic processing for comparing with pressure decay data Y (t)
The apparatus CPU and the pressure decay data P (t) correspond to the reference pressure decay.
Report clogging when opening more than predetermined degree from data Y (t)
It comprises an alarm circuit 46 for informing.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to an orifice clogging detection method and a clogging detection device used in a pressure type flow control device similar to that shown in FIG. 12. The preconditions for operating the pressure type flow control device are the same. It is. In other words, if you set the upstream pressure P ₁ or more to about 2 times the downstream pressure P ₂ is the downstream flow rate Q _C of the orifice depends only on the upstream pressure P _1,
The linear condition of Q _C = KP ₁ is established with high accuracy.
When the orifices are the same, the proportionality constant K is constant,
The constant K may be changed only when converting to an orifice having a different orifice hole.

Therefore, in order to control a specific fluid to a constant flow rate Q _S , it is sufficient to control the opening and closing of the control valve CV so that the upstream pressure P ₁ becomes a value of P ₁ = Q _S / K. Become. That is, the control valve CV may be opened and closed in a one-to-one correspondence while the upstream pressure P ₁ is constantly measured.

[0021]

1 shows an example of a clogging detection device in a flow control device according to the present invention. This device is functionally equivalent to the device of FIG. 12, but differs in that it is microcomputer controlled. Therefore, the same portions as those in FIG. 12 are denoted by the same reference numerals, and the description thereof will be omitted. Different reference numerals and details will be described below.

The CPU is a central processing unit, which corresponds to the operation control circuit 38 in FIG. 12, M is a memory device for storing data, 42 is a communication port PT with the outside, 44 is an external circuit such as a trigger circuit, 46 Is an alarm circuit for clogging, 4
8 is a power supply circuit SC, 50 is an external power supply of ± 15V.
AMP represents an amplifier circuit, and A / D represents an A / D converter.

As the control valve CV, a so-called direct-touch type metal diaphragm valve is used, and a piezoelectric element type driving device is used for the driving section 8 thereof. The drive section 8 of the control valve CV includes a magnetostrictive element type drive device, a solenoid type drive device,
A motor type driving device, a pneumatic type driving device, and a thermal expansion type driving device are used.

Although a semiconductor strain type pressure sensor is used for the pressure detector 14, a metal foil strain type pressure sensor, a capacitance type pressure sensor, a magnetoresistive type pressure sensor, or the like can also be used. is there.

Although a thermocouple type temperature sensor is used for the temperature detector 24, various known temperature sensors such as a resistance temperature sensor can be used.

As the orifice 2, an orifice having a hole formed by cutting a plate-shaped thin metal gasket is used. In addition to this, a hole is formed in the metal film by an extremely fine pipe or etching and electric discharge machining. A known orifice such as a formed orifice may be used.

The flow control device using the orifice is FCS
The flow control device FCS shown in FIG. 1 incorporates the orifice clogging detection device according to the present invention. Next, a normal flow control mode of the flow control device FCS shown in FIG. 1 will be described with reference to a flowchart of FIG.

FIG. 2 is a flow chart of flow control during plant operation, which is executed by the central processing unit CPU according to a program stored in the memory device M. If it is confirmed (Y) in step n1 is a flow rate control mode, the flow rate setting signal from the flow rate setting circuit 32 (set flow rate) Q _S is input (n2). Pressure detector 1
4, the upstream pressure P ₁ is measured (n3), and the downstream flow rate Q is calculated by the central processing unit CPU through the amplifier circuit 16 and the A / D converter 18 through Q = KP ₁ (K: constant). (N4).

At the same time, the upstream temperature T ₁ is
Is detected by (n5), via an amplifier circuit 26 and A / D converter 28 is input to the device CPU, flow temperature correction is performed on the basis of this data, conversion flow rate Q to the calculated flow rate Q _C (N6). Among unit CPU, calculated flow rate Q _C and the set flow rate Q difference _S Q _Y is Q _Y = Q _C
It is calculated by -Q _S (n7).

[0030] As the flow rate difference signal Q _Y becomes zero, controlling the control valve CV in the following steps. First Q
_{If Y} <0 (n8), the control valve CV is controlled in the opening direction by the drive unit 8 (n9), and if Q _Y > 0 (n10), the control valve CV is driven in the closing direction (n1).
1) Then, the process returns to step n3. If Q _Y = 0,
Assuming that the flow control has been completed, the control valve CV is fixed at the current opening (n12). It Since Kashii flame to completely zero flow rate difference Q _Y, Step n8 and n10
Can have some margin.

[0031] keep describes the set flow rate Q _S of the flow rate setting circuit 32. The set flow rate (flow rate setting signal) Q _S is usually given at a voltage value, yet the relationship of the set value P ₁ and P ₁ = Q _S / K of the upstream pressure is established. For example, if the flow rate is 0
-5 (V), pressure range 0-3 (kgf / c
m ² abs). When representing this range percentage to 0-100 (%), the full scale 100 (%) corresponds to the flow rate Q _S 5 (V), the upstream pressure ^{_{P 1 3 (kgf / cm 2}} abs) ing. For example, the flow rate Q _S if the set value is 50 (%) 2.
5 (V), the pressure P ₁ is 1.5 (kgf / cm ² abs)
Is equivalent to The following description is based on the above.

Next, a reference decay mode for measuring reference pressure decay data Y (t) serving as basic data for detecting clogging of the orifice will be described. Is this standard damping mode, when the clogging of the orifice is completely free state, the upstream pressure P ₁ when closed (fully closed state) from the state greatly opened control valve (fully opened state) how decays Is used as reference data for comparison with the case where there is clogging.

FIG. 3 is a flow chart showing a first embodiment of the reference attenuation mode, in which a program stored in the memory device M is started and executed by a signal from the external circuit 44.

[0034] When it is confirmed that the reference decay mode (n20), the high set flow rate Q _SH is CP as a set flow rate Q _S
It is set to U (n21). The high set flow rate Q _SH is generally 100% of full scale. The state upstream pressure P ₁ in is measured, expressed by the maximum pressure P _m as the maximum value in this range (n22). Next, the external circuit 4
The low set flow rate Q _SL is set as the set flow rate Q _S by the trigger signal from No. 4, and at this time, time t = 0 (s).
(N23). As the low set flow rate Q _SL 0% is common. That is, the upstream pressure P ₁ after the maximum value to zero (fully closed control valve) to measure the attenuation of the upstream pressure P _1.

From t = 0, the upstream pressure P ₁ is measured (n2
4), the time and pressure data (t, stores the P ₁ / P _m) in the memory device M (n25). The reason for setting P ₁ / P _m is only to normalize the pressure, and it is not necessary to standardize at all, or another method may be used. Time is advanced by a minute time Δt to (n26), until the measurement time t _m (2
7) The data (t, P ₁ / P _m ) is measured and stored in the memory device M. Here the measurement time t _m may be any time capable of storing data, for example, 5 (s), 20
(S). Next, a number of data (t, P _{1) obtained}
/ P _m ), Y (t) = exp (−kt) is fitted by the least squares method (n28), and the attenuation parameter k
Is calculated (n29). In actual actual measurement, the measurement time tm can be switched and set in eight steps from 1 s to 10 s.
In the case of a 0 μm orifice, the upstream pressure P ₁ at 50 points is measured during this period.

Thus, the reference pressure decay data Y
(T) is given as theoretical formula Y (t) = exp (−kt). For the same orifice hole without clogging, the damping parameter k has a constant value. This reference pressure decay data Y (t) is stored in the memory device M.

The reference pressure decay data Y (t) is shown by a thin solid line in FIG. 4, and the maximum value is normalized to 1. Of course the values of pressure P ₁ may be attenuated data without normalization.
In the above method, the change of Q _SH → Q _SL is changed from 100% → 0%,
That is, although the control valve CV is changed from fully open to fully closed, the present invention is not limited to this. For example, it is possible to set Q _SH = 50% and Q _SL = 20%.
Among them, 100% → 0% is merely selected as the one showing the most remarkable attenuation curve.

The reference pressure decay data Y (t) is measured under the best condition in which the orifice is not clogged, and the state without clogging in a general sense does not mean the best condition. . For example, in some cases, it is determined that there is no clogging even if there is a small amount of clogging. In this embodiment, the full scale value is ± 0.2%, and therefore, when the standardization is 1, ± 0.002 is set. Error range without clogging. This error range can be variously changed according to the situation.

Next, the flow factor FF will be described. The flow control device according to the present invention has an advantage that a plurality of gas types can be controlled by the same orifice. As described above, in the orifice of the same orifice diameter, the downstream flow rate Q _C is Q _C = KP _1: has been found that given by (K constant). In this case, it is known that the constant K changes when the gas type changes.

For example, N_TwoGas, Ar gas, O_TwoTo gas
Correspondingly, the constant K is_N, K_A, K _OLet's express it. Through
Always N_TwoExpressed by flow factor FF based on gas
Things are going on. Therefore, N_TwoGas, Ar gas,
O_TwoGas flow factor FF to FF_N, FF_A, FF
_OFF_N= K_N/ K_N= 1, FF_A= K_A
/ K_N, FF_O= K_O/ K_NGiven by That is,
Low factor FF is the actual gas flow rate and N_TwoConverted flow rate
FF = actual gas flow rate / N_TwoDetermined by converted flow rate
Is a defined factor. Table 1 shows the flow parameters for each gas type.
Kuta values are listed.

[0041]

[Table 1]

The inventors have determined that the reference pressure decay data Y (t)
It has been found that the attenuation parameter k of = exp (-kt) has a close relationship with the flow factor FF. The relational expression is, like the flow rate, the actual gas attenuation parameter = FF × N ₂ gas attenuation parameter. Therefore, N ₂
If only the gas damping parameter k _N is measured, the damping parameter k of an arbitrary gas can be determined by k = FF × k _N.

FIG. 5 is a flowchart of the clogging detection mode for the orifice actually used. Since it is difficult to detect clogging during actual plant operation, when the set flow rate reaches a specified value (ie, an arbitrary value / threshold value exceeding 1 V) after the end of the process, the direction of decrease is triggered. Enter the clogging detection mode as a signal.

In this embodiment, if the set flow rate value becomes 1 V,
Trigger signal Tr ₁ is input to the central processing unit CPU. It is confirmed from this signal that the mode is the clogging detection mode (n30).
(T) is transmitted to the CPU (n31). This data includes Y (t) for the actual gas to be actually measured.
Or the attenuation parameter k for N ₂ and the flow factor FF. In the latter case, Y (t) = exp
The reference pressure decay data Y (t) for the actual gas can be calculated by (−kt × FF). In this embodiment, a table as shown in the table below is stored in the memory device M as the Y (f) at the time of initial setting, and clogging is detected by comparing the table with the table.

[Table 2]

Next, the high set flow rate Q_SHAt this point
Is set to t = 0 (s) and time measurement is performed (n32).
Outflow pressure P₁Is measured and the value is referred to as the maximum pressure P_mTo be
(N33). While repeating the minute time Δt many times (n3
4) High setting time t_O(N35), the low set flow rate
Q_SL, And at this time, t = 0 (s) again (n
36). In this embodiment, as described above, the high set flow rate Q_SH=
100%, low set flow rate Q _SL= 0% and the high setting time t_O
= 1 (s). This high setting time t_OIs the upstream pressure P
₁Can be taken arbitrarily as long as the time is stable.

[0046] In addition, while repeating a number of times a minute time Δt (n37), and time is the low set time t ₁ (n3
8) The upstream pressure P ₁ (t ₁ ) is detected (n39).
Pressure decay data P (t ₁ ) normalized by the maximum pressure P _m =
P ₁ (t ₁ ) / P _m is the reference pressure decay data Y (t ₁ )
If it is within the range of the error m from (n40), no clogging is displayed and the alarm signal AL is turned off (n42).
If it is out of the error range (n40), clogging is displayed and the alarm signal AL is turned on (n41).

The low setting time t ₁ is a comparison time,
The time may be 0.6 (s) or 1.6 (s), and a time that can be easily compared may be selected. Also, the pressure decay data P (t)
Used the one in which the upstream pressure P ₁ (t) was standardized by the maximum pressure P _m, but it need not be separately standardized. If not standardized, it is better to use the standard pressure decay data Y (t) without standardization. In this case, step n40 is _{| P 1 (t 1) -Y} (t 1) | / become P _m <calculation formula n. That is, when normalized, P (t) = P ₁ (t) / P
_m , but when not standardized, P (t) = P ₁ (t)
That's it. In addition, pressure decay data P
There is a constant of (t), the important thing is that P (t) and Y (t)
Is set to the same condition except for clogging of the orifice.

In this embodiment, the error m is 0.2% F.
S. That is, m = 0.002 is set. However, this error range merely provides a range in which no clogging occurs, so that 0.5% F. S. Ie, m = 0.005
May be set, and the arbitrarily has an arbitrary property according to the accuracy.

In this embodiment shown in FIG. 5, the clogging is determined based on the data of one point at t = t ₁ , but the determination may be made at a plurality of points. A comparison determination may be made. Note that in actual implementation, t =
t ₁ to the ~t = continuously above-mentioned clogging determination for 4-5 points tn, the final Metsume determined with a cumulative average of the difference data in the initial reference value and the measured values to each point Is going.

As can be seen from FIG. 4 showing the pressure decay curve,
± 0.2% F. with respect to the thin solid line without clogging.
S. Is given by a dotted line. If it falls within this dotted line range, there is no clogging. The bold solid line is the normalized pressure decay data. Since the measured value after about 1.6 seconds is out of the range of the dotted line, clogging is displayed and an alarm is issued.

FIG. 6 is a time chart of signals in the embodiment of FIG. The high set flow rate Q _SH is input at the rise of the trigger signal _Tri , and after the low set flow rate Q _SL is set after t _O seconds, the pressure decay data P (t) after t ₁ second is actually measured. If outside the error range, the alarm signal AL is turned on.

In the present invention, the reference pressure decay data Y
(T) and the pressure decay data P (t) may or may not be standardized. In addition, the present invention is not limited to the above-described embodiment, but includes various modifications and design changes within the technical scope thereof without departing from the technical idea of the present invention.

FIG. 7 shows reference pressure decay data Y (t) as basic data for detecting clogging of an orifice.
FIG. 6 is a flowchart of a second embodiment of the reference attenuation mode for obtaining the second embodiment, and corresponds to FIG. 3 of the first embodiment.

In the first embodiment shown in FIG. 3, when obtaining the reference pressure decay data Y (t), the effect of the temperature T of the fluid upstream of the orifice on the pressure decay is completely taken into consideration. Absent. This is the same when measuring the pressure decay data P (t) in the clogging detection mode shown in FIG.

On the other hand, in actual clogging detection, the fluid temperature T at the time when the reference pressure decay data Y (t) is obtained.
And the temperature T of the fluid when the clogging is detected is hardly equal, and there is usually a temperature difference between the two.

When clogging is detected by the method shown in the first embodiment, the reference pressure decay data Y
If there is a difference between the fluid temperature upstream of the orifice when (t) is measured and the fluid temperature upstream of the orifice when the pressure decay data P (t) is measured, the accuracy of the clogging detection will deteriorate. Specifically, it has been confirmed by experiments that when the temperature difference is about 10 ° C., an error of about 3% occurs in the detected value of the clogged area.

The second embodiment shown in FIG. 7 and FIG. 8, which will be described later, has been developed in order to prevent a decrease in the accuracy of clogging detection due to a difference in temperature on the upstream side of the orifice. Even if there is a difference between the fluid temperature on the upstream side of the orifice at the time of detecting the data Y (t) and the pressure decay data P (t), the reference pressure decay data Y (t) is used in order to prevent the detection accuracy of the clogging from decreasing. The pressure decay data P (t) is obtained by calculation from the theoretical expression of the flow of the fluid using the detected temperature and pressure values of the fluid.

First, reference pressure decay data Y (t) is obtained.
The method will be described. The reference pressure decay data Y
(T) shows the case where the orifice 2 in FIG. 1 has no clogging.
5 shows a pressure attenuation state on the upstream side of the orifice.
Referring to FIGS. 1 and 7, trigger from external circuit 44
The signal starts the program stored in the memory device M.
Be executed. Confirm that it is in reference attenuation mode
And (n20a), set flow rate Q_SHigh set flow rate Q_SHBut
It is set in the CPU (n21a). This high set flow rate Q
_SHIs generally 100% of full scale. This
Upstream pressure P₁Is measured and the highest
Maximum pressure P as large value_m= P_O(N22a).
According to a trigger signal from the external circuit 44, the set flow rate
Q_SHigh set flow rate Q _SHIs set, (n21
a), this state is maintained for 2 seconds, and after 2 seconds, the set flow rate
Q_SAs low flow rate Q_SLIs set. At this point
Time t = 0 (s) is set (n23a). Low set flow rate Q_SL
Is generally 0%. That is, the upstream pressure P₁To
Upstream from maximum value to zero (control valve fully closed)
Side pressure P₁Is measured.

From t = 0, the upstream pressure P ₁ = P _t and the upstream temperature T ₁ = T _{t are} measured (n43a), and the time, pressure data and temperature data (t, P _t , T _t ) are stored in the memory device M. (N43a). This data is measured by advancing the time by a minute time Δt (n26a) and storing the data in the memory device M while measuring until the measurement time tm (n27a). Here, the measurement time tm may be a time during which data can be accumulated, for example, 5 (s) and 20 (s).
And so on. In actual actual measurement, the measurement time tm can be switched and set in eight steps from 1 _S to 10 _{S. In} the case of an orifice having an inner diameter of 150 μm, the At 50 points upstream pressure P ₁ ,
The upstream temperature T ₁ of is measured.

The upstream pressure P ₁ , the upstream temperature T
_In parallel with the measurement of ₁ , using these read data, the reference pressure decay data Y (t) = Z _{S in the} CPU.
The operation of (t) is performed (n45a). Then, the calculated reference pressure attenuation data Y (t) = Z _S (t) is stored in the memory device M.

In the second embodiment, the reference pressure decay data Y (t) = Z _S (t) is obtained by calculating the drop of the upstream pressure P ₁ based on a so-called “fluid theoretical formula”. is "upstream pressure P value Z which displays the degree of drop in ₁ log
_S (t) "is calculated in the CPU.

In the present embodiment, the following equation is used as the "theoretical equation of fluid".

(Equation 3) Here, P _O = P _m is the upstream pressure at the initial time (standard time), P _t is the upstream pressure after the lapse of time t, S is the cross-sectional area of the orifice 2, and C _t is the gas at the time t. constant of specific heat ratio, R _t is at the gas constant in time t, T _t is in the upstream temperature in time t, V is the internal volume of the FCS device, t _n is the elapsed time (unit time × n from the measurement start Th). The constant C of the gas specific heat ratio is given by the following equation.

(Equation 4) Here, k is a specific heat ratio of the gas.

The value Z _S (t) expressing the degree of the pressure drop of the upstream pressure P _O in logarithm is given by the following equation.

(Equation 5) Here, C _O · R _O · T _O are the constant of the specific heat ratio of the gas at the initial stage (base time), the gas constant, and the upstream temperature.
C _t , R _t , and T _t are the constant of the gas specific heat ratio, the gas constant, and the upstream temperature at the time point (n-th) from the start of measurement.

Each time t ₁ , t _2, ... From the measurement start time t = 0.
Reference pressure decay data Y (t) using the above equation for each t _n
= Z _S (t) is calculated by the CPU, and the result is sequentially stored in the memory device M.

Next, detection of clogging of the orifice actually used will be described. FIG.
4 is a flowchart of an orifice detection mode in the embodiment. Since it is difficult to detect clogging during actual plant operation, when the set flow rate reaches a specified value (ie, an arbitrary value / threshold value exceeding 1 V) after the end of the process, the direction of decrease is triggered. Enter the clogging detection mode as a signal.

In this embodiment, if the set flow rate value becomes 1 V,
The trigger signal is input to the central processing unit CPU. It is confirmed from this signal that the mode is the clogging detection mode, and (n
30a), the reference pressure decay data Y from the memory device M
(T) is transmitted to the CPU (n31a). This data includes Y for the actual gas to be actually measured.
(T) = Z _S (t), or may be obtained by multiplying the reference pressure attenuation data Z _S (t) for N ₂ by a constant A for a flow factor FF determined in advance according to the gas type.

Next, the high set flow rate Q _SH is input, and the time is set as t = 0 (s), and the time is measured (n32a).
The upstream pressure P ₁ is measured, and its value as the maximum pressure P _m (n33). While repeating the minute time Δt many times (n3
4a) When the high set time t _O is reached (n35a), the flow rate is switched to the low set flow rate Q _SL , and this time is set to t = 0 (s) again (n36a). In the present embodiment, as described above, the high set flow rate Q _SH = 100%, the low set flow rate Q _SL = 0%, and the high set time t _O = 2 (s). The high setting time t _O can be arbitrarily set as long as the upstream pressure P ₁ is stabilized.

Further, while repeating the minute time Δt many times,
(N37a), the time is the low set time t ₁Becomes (n38
a), upstream pressure Pt₁And upstream temperature Tt₁Detect
(N39a). Detected upstream pressure Pt₁, Upstream
Temperature Tt₁Is stored in the memory device M as needed, and
In the central processing unit CPU, the primary pressure Pt₁of
Logarithmic value of pressure drop (ie, pressure decay data)
TA P (t₁) = Z (t ₁)) Is calculated (n48).

Calculated pressure decay data P (t ₁ ) = Z
(T ₁ ) is compared with the reference pressure attenuation data Y (t ₁ ) previously input to the memory device M (n49), and | Y
If (t ₁ ) −P (t ₁ ) | is out of the permissible error range m (n49), clogging is displayed and the alarm AL is turned on. (N41a). Also, | Y (t ₁ ) −P
If (t ₁ ) | is within the allowable error range, time addition is performed (n = 50), and measurement, calculation and comparison at the second unit time t = t ₂ are repeated, and t = When t _n is reached (n = 51), the display without clogging and the alarm AL are finally turned off (n42a).

In the clogging detection mode of the second embodiment shown in FIG. 8, the pressure decay data P (t ₁ ) is determined at step n48.
= Z (t ₁ ), and clogging is determined in step n49 based on the calculated value. If there is no clogging, time is added in step 51, and the next upstream pressure P _t and the temperature _Tt are detected.
However, instead of such a method, in parallel to this with the detection of the upstream pressure P _t and temperature T _t for each unit time continuously in step n46, the step n48
In this case, the pressure decay data P (t ₁ ) for each unit time may be calculated, and clogging may be determined for each unit time using the calculated value.

FIGS. 9, 10 and 11 show the second embodiment of the present invention.
FIG. 9 shows test results in the case where clogging of an orifice was detected according to an example.
Pressure drop characteristics (FIG. 9), calculation results of Z (t) (FIG. 10) and reference time when unit time t (0.012 sec), reference temperature 25 ° C., temperature fluctuation + 10 ° and −10 °, 11 shows the difference between the calculated value (25 ° C.) Z _S (t) and the calculated value Z (t) at the time of clogging inspection (FIG. 11).

In the case of the second embodiment, as apparent from FIGS. 9 and 10, the upstream side gas temperature T (t) at the time of clogging inspection is ± 10 ° C. lower than the reference temperature (25 ° C.). Even if the temperature differs, the calculated values of the pressure drop characteristics (FIG. 8) and Z (t) are almost the same as those at the reference temperature (25 ° C.), and the error due to the change in the upstream gas temperature is almost completely eliminated. To be corrected. As a result, even if the upstream gas temperature is considerably changed from the gas temperature at the time when the reference attenuation data is obtained, highly accurate and stable clogging detection can be performed.

[0073]

According to the present invention, as described in detail above, the reference pressure decay data Y (t) when the orifice is not clogged.
And the pressure decay data P (t) during actual operation,
It is to judge whether or not clogging is performed based on whether or not (t) is separated from Y (t) by a predetermined degree or more. Therefore, clogging can be determined by an extremely simple operation without disassembling the piping, so that an emergency such as an explosion can be avoided and the stability of the plant can be guaranteed. That is, the present invention provides an inexpensive and highly reliable method for detecting orifice clogging and a device therefor, which contributes to the widespread use of pressure type flow controllers using orifices.

In particular, according to the second embodiment of the present invention, the upstream gas temperature T (t) at the time of clogging detection corresponds to the upstream gas temperature at the time when the reference pressure decay data Y (t) is obtained. , It is possible to perform highly accurate clogging detection excluding an error due to a temperature change.

[Brief description of the drawings]

FIG. 1 is a block diagram of an example of a clogging detection device in a flow control device according to the present invention.

FIG. 2 is a flowchart of flow control during plant operation.

FIG. 3 is a flowchart for obtaining reference pressure decay data Y (t) used in the clogging detection method according to the first embodiment of the present invention.

FIG. 4 shows a graph of reference pressure decay data Y (t) without clogging and pressure decay data P (t) with clogging.

FIG. 5 is a flowchart for executing a clogging detection method according to the first embodiment of the present invention.

FIG. 6 shows time charts of various signals.

FIG. 7 is a flowchart for obtaining reference pressure attenuation data Y (t) used in a clogging detection method according to a second embodiment of the present invention.

FIG. 8 is a flowchart for executing a clogging detection method according to a second embodiment of the present invention.

FIG. 9 is a graph showing a pressure drop characteristic when the temperature is changed in the second embodiment of the present invention.

FIG. 10 is a graph showing calculated values of pressure decay data Z (t) when the temperature is changed in the second embodiment of the present invention.

FIG. 11 shows a reference pressure decay data (25 ° C.) Z _S (t) when the temperature changes in the second embodiment of the present invention.
And the difference between the calculated value of the pressure decay data and the calculated value of the pressure decay data.

FIG. 12 is a block diagram of a conventional pressure type flow control device.

FIG. 13 is a set value flow characteristic diagram when the orifice is clogged.

[Explanation of symbols]

2 is an orifice, 4 is an upstream channel, 6 is a downstream channel, 8
Is a drive unit, 12 is a gas extraction joint, 14 is a pressure detector,
16 is an amplification circuit, 18 is an A / D converter, 20 is an arithmetic circuit, 22 is a pressure display, 24 is a temperature detector, 26 is an amplification circuit, 28 is an A / D converter, 30 is a temperature correction circuit, 32
Is a flow rate setting circuit, 34 is an A / D converter, 36 is a comparison circuit, 38 is an arithmetic control circuit, 40 is an amplification circuit, 42 is a communication port, 44 is an external circuit, 46 is an alarm circuit, 48 is a power supply circuit, 50 Is an external power supply, AMP is an amplifier circuit, A / D
Is an AD converter, AL is an alarm circuit, CPU is a central processing unit, CV is a control valve, ES is an external power supply, M
Is a memory device, and SC is a power supply circuit.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] August 12, 1999 (1999.8.1)
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

The clogging detection method in a pressure type flow rate control apparatus according to claim 4, the pressure detector 14 and a flow rate setting circuit 32 for detecting the control valve CV and the orifice 2 an upstream pressure P ₁ therebetween Thus, the upstream pressure P ₁ is maintained at about twice or more the downstream pressure P ₂ and the downstream flow rate Q _C
Is calculated using Q _C = KP ₁ (K: constant), and the calculated flow rate Q
In the flow control device which controls the opening and closing of the control valve CV by the difference signal Q _Y between the _C and the set flow rate Q _S, the set flow rate Q
The first step of maintaining _S at the high set flow rate Q _SH , and switching and maintaining the high set flow rate Q _SH at the low set flow rate Q _SL , measuring the upstream pressure P ₁ and the upstream temperature T _t and performing this measurement a second step of calculating the pressure attenuation data P (t) by using the values, standards under the same conditions, were calculated using the upstream pressure P _t and the upstream temperature T _t measured when there is no clogging in the orifice The pressure decay data Y (t) and the pressure decay data P
(T) and pressure decay data P
The fourth step is to notify the clogging when (t) is separated from the reference pressure attenuation data Y (t) by a predetermined degree or more.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0059

[Correction method] Change

[Correction contents]

[0059] measured from t = 0 the upstream pressure P ₁ = P _t and the upstream temperature _{T 1 = T t (n43a)} , time and pressure data and temperature data _{(t, P t, T t} ) of the memory device It is stored in M ( n44a ). This data is measured by advancing the time by a minute time Δt (n26a) and measuring the data until the measurement time tm (n27a).
It is stored in. Here, the measurement time tm may be a time during which data can be accumulated, for example, 5 (s), 20
(S). In actual measurement,
The measurement time tm can be switched and set in eight steps from 1 _S to 10 _S , and the inner diameter is 150 μm.
In this case, the upstream pressure P ₁ and the upstream temperature T ₁ at 50 points are measured during this period.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0067

[Correction method] Change

[Correction contents]

Next, the high set flow rate Q_SHAt this point
Is set to t = 0 (s) and time measurement is performed (n32a),
Upstream pressure P₁Is measured and the value is referred to as the maximum pressure P_mTo be
(n33a). While repeating the minute time Δt many times (n
34a), high set time t_O(N35a), low
Constant flow Q_SL, And at this time, t = 0 (s) is set again.
(N36a). In this embodiment, as described above, the high setting flow
Quantity Q_SH= 100%, low set flow rate Q_SL= 0%, high setting
Time t_O= 2 (s). This high setting time t _OIs upstream
Side pressure P₁Can be taken arbitrarily as long as the time is stable
Wear.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

Further, while repeating the minute time Δt many times,
(N37a), the time is the low set time t ₁Becomes (n38
a), upstream pressure Pt₁And upstream temperature Tt₁Detect
(N39a). Detected upstream pressure Pt₁, Upstream
Temperature Tt₁Is stored in the memory device M as needed.(N
47)Next, in the central processing unit CPU, the primary side pressure
Force Pt₁Logarithm of the pressure drop (ie, pressure
Force attenuation data P (t₁) = Z (t₁)) Is calculated
(N48).

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0069

[Correction method] Change

[Correction contents]

Calculated pressure decay data P (t ₁ ) = Z
(T ₁ ) is compared with the reference pressure attenuation data Y (t ₁ ) previously input to the memory device M (n49), and | Y
(T ₁ ) −P (t ₁ ) | is out of the allowable error range m
If so, the clogging is displayed and the alarm AL is turned on. (N41a). | Y (t ₁ ) −P (t ₁ ) |
Is within the allowable error range, time is added (n = 50), and measurement is performed at the second unit time t = t ₂ ,
The calculation and comparison are repeated, and when t = t _n is reached (n = 5
1) Finally, the display without clogging and the turning off of the alarm AL are performed (n42a).

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0070

[Correction method] Change

[Correction contents]

In the clogging detection mode of the second embodiment shown in FIG. 8, the pressure decay data P (t ₁ ) is determined at step n48.
= Z (t ₁ ), and clogging is determined in step n49 based on the calculated value. If there is no clogging, time is added in step 51 and the next upstream pressure P _t and the temperature _Tt are detected.
However, instead of such a method, in parallel to this with performed continuously detected for each unit time of the upstream pressure P _t and temperature T _t in step N39a, step n4
8, the pressure decay data P (t ₁ ) for each unit time
May be calculated, and clogging may be determined for each unit time using the calculated value.

[Procedure amendment 7]

[Document name to be amended] Drawing

[Correction target item name] Fig. 7

[Correction method] Change

[Correction contents]

FIG. 7

[Procedure amendment 8]

[Document name to be amended] Drawing

[Correction target item name] Fig. 8

[Correction method] Change

[Correction contents]

FIG. 8

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tadahiro Omi 2-1-17-1, Yonegabukuro, Aoba-ku, Sendai, Miyagi Prefecture (72) Inventor Seiichi Iida 1-5, Sumiyoshi Yamate, Higashinada-ku, Kobe, Hyogo Prefecture No. 3 (72) Inventor Tetsu Kagazume 2381-1, Kita-Shimojo, Fujii-machi, Nirasaki, Yamanashi Prefecture Inside Tokyo Electron Yamanashi Co., Ltd. (72) Inventor Jun Hirose 1-238-1, Kita-Shimojo, Fujii-machi, Nirasaki, Yamanashi Prefecture (72) Inventor Tomio Uno 2381-2, Kita Shimojo, Fujii-machi, Nirasaki-shi, Yamanashi Prefecture Within Tokyo Electron Yamanashi Co., Ltd. (72) Inventor Koji Nishino 2-3-2, Noribori, Nishi-ku, Osaka-shi, Osaka Co., Ltd. Fujikinnai (72) Inventor Shinichi Ikeda 2-3-2, Nobori, Nishi-ku, Osaka-shi, Osaka Fujikin Incorporated (72) Inventor Michi Yamaji 2-3-2, Noribori, Nishi-ku, Osaka-shi, Osaka Fujikin Co., Ltd. (72) Inventor Ryosuke 2-3-1, Noribori, Nishi-ku, Osaka-shi, Osaka Fujikin Co., Ltd. (72) Inventor Eiji Deda Osaka, Osaka 2-3-2, Noribori, Nishi-ku, Yokohama-shi Fujikin Co., Ltd. (72) The inventor Takashi Hirose 2-3-2, Noribori, Nishi-ku, Osaka, Osaka Prefecture, Japan (72) Kazuhiro Yoshikawa, No.2 in Nishi-ku, Osaka, Osaka Fujikin Co., Ltd. (72) Inventor Mutsunori Oga 2-3-2, Nobori, Nishi-ku, Osaka-shi, Osaka

Claims (10)

[Claims] 1. A consists control valve (CV) and orifice (2) and the pressure detector for detecting the upstream pressure P ₁ between them (14) and the flow rate setting circuit (32), the upstream pressure P ₁ flow rate Q _C and Q _C = KP ₁ on the downstream side and holds more than about twice the downstream pressure P _2: calculated in (K constant), the difference signal Q of this calculated flow rate Q _C and the set flow rate Q _S in the flow control device for opening and closing control control valve (CV) by _Y, switching a first step of holding the set flow rate Q _S at a high set flow rate Q _SH, the high set flow rate Q _SH to the low set flow rate Q _SL retention The upstream pressure P ₁ is measured and the pressure decay data P
A second step of obtaining (t) and a third step of comparing the reference pressure decay data Y (t) measured when the orifice is not clogged under the same conditions with the pressure decay data P (t),
The pressure decay data P (t) is the reference pressure decay data Y (t)
4th notifying of clogging when opening more than predetermined degree
A method for detecting clogging of an orifice in a pressure type flow control device comprising a process. 2. The high set flow rate Q _SH is a 100% flow rate (full scale flow rate), and the low set flow rate Q _SL is a 0% flow rate (control valve is completely closed). 2. The orifice clogging detection in the pressure type flow control device according to claim 1, wherein the clogging is notified when the pressure decay data P (t) after the time is more than the reference value of the reference pressure decay data Y (t). Method. 3. The reference pressure decay data Y (t) and the pressure decay data P (t) are represented in the form of Y (t) = exp (−kt) (where k is a damping parameter). An orifice clogging detection method according to claim 1 or 2. 4. A consists control valve (CV) and orifice (2) and the pressure detector for detecting the upstream pressure P ₁ between them (14) and the flow rate setting circuit (32), the upstream pressure P ₁ flow rate Q _C and Q _C = KP ₁ on the downstream side and holds more than about twice the downstream pressure P _2: calculated in (K constant), the difference signal Q of this calculated flow rate Q _C and the set flow rate Q _S in the flow control device for opening and closing control control valve (CV) by _Y, switching a first step of holding the set flow rate Q _S at a high set flow rate Q _SH, the high set flow rate Q _SH to the low set flow rate Q _SL retention A second step of measuring the upstream pressure P ₁ and the upstream temperature Tt and calculating the pressure decay data P (t) using the measured values; and measuring under the same conditions when the orifice is not clogged. Pressure decay calculated using the determined upstream pressure Pt and upstream temperature Tt A third step of comparing the data Y (t) with the pressure decay data P (t); and a step of comparing the pressure decay data P (t) with the reference pressure decay data Y (t) by a predetermined degree or more. Orifice clogging detection method in pressure type flow control device comprising fourth step of reporting clogging 5. The high set flow rate Q _SH is a 100% flow rate (full scale flow rate), and the low set flow rate Q _SL is a 0% flow rate (control valve is completely closed). 5. The clogging detection of an orifice in the pressure type flow control device according to claim 4, wherein the clogging is notified when the pressure decay data P (t) after time is more than the reference pressure decay data Y (t) by a reference value or more. Method. 6. The reference pressure decay data Y (t) and the pressure decay data P (t) are expressed as follows: _{(However, P O · C O · R} O · T O is the reference time of the upstream pressure gas specific heat ratio of the constant-gas constant and gas temperature of the gas, P _t
C _t · R _t · T _t are the upstream pressure of the gas at the time of arrival, the constant of the gas specific heat ratio, the gas constant, and the gas temperature. The orifice clogging detection method according to claim 4 or 5, wherein the calculation is performed as: 7. A consists control valve (CV) and orifice (2) and the pressure detector for detecting the upstream pressure P ₁ between them (14) and the flow rate setting circuit (32), the upstream pressure P ₁ flow rate Q _C and Q _C = KP ₁ on the downstream side and holds more than about twice the downstream pressure P _2: calculated in (K constant), the difference signal Q of this calculated flow rate Q _C and the set flow rate Q _{S In} the flow control device that controls the opening and closing of the control valve by _Y , the high set flow rate Q under the condition that the orifice (2) is not clogged
And the memory device M which stores the low set flow rate Q _SL to be measured by switching the upstream pressure P ₁ of the reference pressure attenuation data Y (t) from _SH, high set flow rate Q in the actual conditions of the orifice (2)
The pressure detector for measuring the low set flow rate Q _SL to the switching by the upstream pressure P ₁ of the pressure attenuation data P (t) from _SH (14)
, Pressure decay data P (t) and reference pressure decay data Y
A central processing unit CPU for performing a comparison operation with (t), and an alarm circuit (46) for reporting clogging when the pressure attenuation data P (t) is separated from the reference pressure attenuation data Y (t) by a predetermined degree or more. Orifice clogging detection device in pressure type flow control device. 8. The reference pressure decay data Y (t) and the pressure decay data P (t) are expressed as Y (t) (or P (t)) = ex.
The orifice clogging detecting device according to claim 7, wherein the device is expressed in the form of p (-kt) (where k is an attenuation parameter). 9. consists control valve (CV) and orifice (2) and the pressure detector for detecting the upstream pressure P ₁ between them (14) and the flow rate setting circuit (32), the upstream pressure P ₁ flow rate Q _C and Q _C = KP ₁ on the downstream side and holds more than about twice the downstream pressure P _2: calculated in (K constant), the difference signal Q of this calculated flow rate Q _C and the set flow rate Q _S A pressure detector (14) for measuring an upstream pressure P of an orifice in a flow control device that controls opening and closing of a control valve by _Y.
And a temperature detector (2) for detecting the orifice upstream temperature T.
And 4), upstream of calculation with the high set flow rate Q _SH under conditions no clogging low set flow rate Q was measured by switching the _SL upstream pressure P _t and the upstream temperature T _t in the orifice (2) and the memory device M which stores the pressure P ₁ of the reference pressure attenuation data Y (t), as well as calculating the reference pressure attenuation data Y (t), from the high set flow rate Q _SH in the actual conditions of the orifice (2) low set flow rate Q _SL in switched by using the upstream pressure P _t and the upstream temperature T _t measured to calculate the pressure attenuation data P of the upstream pressure P ₁ (t), and further the pressure attenuation data P (t) A central processing unit CPU for performing a comparison operation with the reference pressure decay data Y (t);
An orifice clogging detection device in a pressure type flow control device comprising an alarm circuit (46) for notifying clogging when (t) is separated from reference pressure decay data Y (t) by a predetermined degree or more. 10. The reference pressure decay data Y (t) and the pressure decay data P (t) are expressed as follows: _{(However, P O · C O · R} O · T O is the reference time of the upstream pressure gas specific heat ratio of the constant-gas constant and gas temperature of the gas, P _{t
· C t · R t · T} t orifice Clogging detection apparatus according to claim 9 which is adapted to calculate as a a) constant, gas constant and gas temperature on the upstream side pressure and gas specific heat ratio of the gas upon reaching .