JPS5840629A - Valve operating method - Google Patents

Abstract

PURPOSE:To decrease the number of detectors in use and to perform stable valve control by using detection signals from <=2 valves among series-connected valves, and then operating all valves so that their cavitation coefficients are equal. CONSTITUTION:Pressure detectors Mu and Md are provided at an upstream part and a downstream part of a piping system to detect the pressure of the upstream part and that of the downstream part. One of valves 1-(n) included in the piping system is operated externally, and while detection signals from respective detectors, characteristics of respective valves, and an equal caviation conditional equality are used, the extents of opening of the valves 1-(n) having a cavitation coefficient substantially equal to that of the externally operated valve are calculated through a microphone to vary the extents of opening of the valves except the externally operated valve on the basis of the information.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a valve operating method, and particularly to a valve operating method in a piping system in which two or more valves are connected in series.

When the secondary pressure of the valve is low and the amount of pressure reduction is large, a method of reducing the pressure by connecting two or more valves 1 to 3 in a series as shown in FIG. 1 is used. If these two or more valves 1 to 3 are operated at the same opening degree, the valves on the downstream side are likely to cause cavitation. In order to perform proper valve operation, the valves should be opened and closed so that the cavitation coefficients of all valves are equal. For this purpose, as shown in Figure 1, the upstream, downstream,
- and a pressure detector between each valve 1-30.

The output signal is inputted to the control device DK, and each valve 1 to 302
Determine the target valve differential pressure from the next pressure, and set the valve actuator to -A.
, and control the opening of the six valves IS3 to achieve that differential pressure, but this method requires a large number of pressure detectors and requires independent control of the differential pressure of the six valves. Therefore, control may become unstable.

Therefore, 1. An object of the present invention is to provide a valve operation method that can reduce the number of pressure detectors used and perform stable valve control.

According to the present invention, in a piping system including two or more valves connected in series, pressure detectors are provided in the upstream and downstream parts of the i-piping system to detect the pressure in the upstream s' and downstream parts. , and one of the valves included in the piping system is operated by an operation command or an operation signal from an external operator,
The warpage opening is detected by valve opening detectors, and the detection signals from these detectors, the characteristics of each valve, and the cavitation conditional expression are used to make the cavitation coefficient equal to that of an externally operated valve. Calculate the valve opening degrees of 5 and 6 valves using a microcomputer.

The information is used to control the opening of valves other than those operated from the outside.

Hereinafter, an embodiment of the valve operating method of the present invention will be described with reference to FIG. 2 and FIG. 3.

In FIG. 2, 14--n are six valves provided in series in the piping system, and valve K among them is designed to open and close in response to an external operation signal SI. In addition, M1 to M are the valve actuators that operate the 6 valves, aMIl is the upstream side pressure detector of the piping system EW & digits, Md is the downstream pressure detector provided at the downstream side of the piping system, and M# is the valve actuator of the valve. This is a valve opening detector that detects the opening.

Further, C is a microcomputer, and the microcomputer C is a pressure signal human input valve opening signal input device C3.
, an arithmetic storage device C1, and a valve opening degree signal output device C4.

As shown in Figure 2, valves 1 and -q are installed in order from the downstream side of the piping system.
2...In a piping system in which valves n are connected in series,
The absolute pressure in the upstream part of the piping system is Hn, the absolute pressure in the downstream part is Ho, the opening degree of the valve located first from the downstream side is θi,
Set the loss factor to 21. Let Vi be the cavitation coefficient.

When detecting pressure as a gauge pressure, the average atmospheric pressure set in the arithmetic storage device C of the i-microcomputer C is added to the gauge pressure to approximately obtain the absolute pressure. In addition, since the valve characteristic unique to each scale valve, that is, the relationship between the valve opening degree and the valve loss coefficient, is determined, the valve characteristic related to the valve IK is expressed as λ1 = fl (ji), and this relationship can be expressed as follows: The R-Ha/Ho
shall be.

Next, an external operation signal 8. The procedure for determining the cavitation coefficient of a valve other than the valve operated by the valve will be explained. First, the opening degree θk of the valve is detected by the valve opening degree detection device island and inputted to the valve opening degree signal input device 11ct of the microcomputer C. For the valve characteristic λ stored in device C, = rk(#k) (t)
Calculated from

λl=λk (Hn/Ho) n=λka”
It is calculated by the arithmetic storage unit @C3 of the microcomputer C using the formula (2). Further, the corresponding valve opening degree θi is calculated from θi=r+(λ+) (3), and this value is output using the valve opening degree signal output device C6 of the microcomputer C. When the valve opening degree is manipulated by the valve actuator Ai so as to match this valve opening degree #IK, the cavitation coefficient of the valve t becomes equal to the cavitation coefficient of the valve, and its value is Vl z t/ (n(Rl ) (
4).

This relationship holds true for any first valve, so
The opening degrees of all valves are determined using equations (1), (2), and (3), and using this information, it is possible to operate all valves to equalize the cavitation coefficients.

The above formula can be confirmed from the formula below.

First, if the velocity head is C, the following equation holds true.

Substituting equation (2), Tono (Ha − Ha ) (Hn − He) Rn valve 1f)' (yapitation coefficient V).

Substituting Equations (2) and (6), He(R-1) He(i-i) t Capitesi coefficient Vld of Mayubenho (a≦fish≦Feng) pole
Using the loss coefficient calculated by 112, the ★javitation coefficient of all valves is (tg-
1)-”, which is the same value for all valves.

Now suppose we connect 4 valves, , , , and 4 in series (
Assuming that the connection is made, the pressure of lower SW is Ha, the pressure between 1 and 1 is connected to the valve, the pressure between 1 and 1 is connected to the valve, and the pressure between 1 and 1 is connected to the valve, and the pressure between the dam is set to 1, and the pressure between Let the pressure on the upstream side be Hs, and the upstream pressure H4 be *d1*62a dB and d, respectively.

The differential pressure before and after T is the velocity head, or 'V'727
7 meters, let λ be the loss coefficient and k be the cavitation coefficient, and = R(t-s)/n, where we now choose for the valve, and the above equation (2) and 1
5), the following Table 1 is obtained. However, Ho=20 meters,
Since the mountain is 60 meters, I chose the valve.

(i -1)/a (1-s)/a = λ,
(H7Ho) = λ, R.

In addition, if you select "Valve", you will obtain Table 2 below.

here (s-t)/4(1-1)/4 H = λ, (H4/no) = λ, R.

As can be seen from Table 1 and the notation above, the cavitation coefficient v1 can be made substantially the same.

According to the invention, the valve 1. Valve 2: Use valve n to make the pressure Ho in the downstream part of the piping system match the predetermined pressure target value . When performing so-called constant pressure control, a
Since H (1 is maintained approximately equal to He', the detected pressure H of the downstream pressure detector Md is
By setting the target pressure value H.' as a constant in the microcomputer C instead of inputting K, the same operation as described above can be performed.

Figure 3 shows an example of a piping system Km in which E1 valves are connected in series and constant pressure control is performed on the downstream side.
In the figure, a constant pressure control system [G, j'! Detection pressure H・
The valve opening/closing signal Sl is outputted so as to reduce the deviation between the target pressure value 8. and the pressure target value 8. Valve 1 operates accordingly. The valve l operated by this constant pressure control device GK#C once 0. The opening degrees of valves 2 and 3 are determined by the microcomputer CK so as to satisfy the cavitation conditions. That is, the i-microcomputer C obtains the opening degree -1 of the valve l via the valve opening degree detector M-, calculates the loss coefficient λ of the valve l based on (1) 2, and then sets the target pressure setting @CS. Set pressure target value Ho'
and the upstream pressure Ha input via the upstream pressure detector Mu, and using the formula instead of formula (2), the valve 2. Loss factor of valve 3 4.2. is calculated, and then the valve opening degree e and 0. is determined and output from the valve opening signal output device C4, and the valve actuator.

Mu, through the valve! and operate valve 3.

When such constant downstream pressure control is performed, there is no need to input the pressure detection signal from the downstream pressure detector to the microcomputer CK.

There is no need to provide a signal transmission line for this purpose. Similarly, when constant upstream pressure regulation control is performed, a line for transmitting the upstream pressure detection signal to the microcomputer CK is not required.

As described above, according to the present invention, the cavitation coefficients of all the valves can be made equal using detection signals from pressure detectors of at most two valves connected in series. Also, based on the opening information of the valves operated by the pressure signal of two or less and the operation signal trap from the outside, the opening of the remaining numerous valves is determined depending on the opening of the valve, so it is controlled. The properties are also improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional valve operating method in a piping system including two or more valves connected in series. Second
The figure is a block diagram of a valve operating method according to an embodiment of the present invention in a piping system including two or more valves connected in series, and FIG. 3 shows this operating method. FIG. 2 is a block diagram of an embodiment applied when constant pressure control is performed in the downstream part of the piping system. 1.3～n...valve M,～mui...valve actuator Md...downstream pressure detector Mm...
・Upstream pressure detector M#...Valve opening detector C
...Microcomputer C1...Pressure signal input device C3...Valve opening signal input device C1...
・Arithmetic storage device Ca...valve signal output device C
3...Target pressure setting device G,...Constant pressure control device stirrup. Patent applicant: Ebara Corporation

Claims (2)

[Claims] (1) In a piping system including two or more valves connected in series, pressure detectors are provided in the upstream and downstream parts of the piping system to detect the pressures in the upstream and downstream parts. In addition, one of the valves included in the piping system is operated from the outside, and the valve opening degree is detected by a valve opening degree detector, and the detection signals from those detectors, the characteristics of each valve, etc. Using the cavitation conditional formula, we can find that the cavitation coefficient is actually negative for a valve that is operated from the outside.
The valve opening degrees of the six valves are calculated by a microcomputer,
A valve operating method characterized in that the information is used to control the opening of a valve other than a valve operated from the outside. (2) i! In a piping system including two or more valves connected in a row Km, a pressure detector is installed in the upstream or downstream part of the piping system to detect the pressure in either the upstream or downstream part, and the pressure in the piping system is One of the valves is operated from the outside, and its valve opening is detected by a valve opening detector, and the detection signal from those detectors, the characteristics of each valve, and the equicavitation condition equation are used to detect the valve opening from the outside. A microcomputer calculates the valve openings of the six valves that will result in a substantially stronger cavitation coefficient than the operated valves, and a constant pressure control target value is set as a constant in the microcomputer, and this information is used to A valve operating method characterized by controlling a constant pressure by operating a part of a valve other than a valve operated from the outside.