JPS5823294A - Pumping condition supervisory system - Google Patents

Abstract

PURPOSE:To enable fine and highly efficient pumping in such a way that pumping operation is done by means of a microcomputer using suction pressure and discharge pressure, or detecting signals of the number of revolution and pumping characteristic curves. CONSTITUTION:In a constant-speed or variable-speed turbo pump 1, pressure detectors 3, 4 are provided on the suction side and on the discharge side of the pump. Besides, in the variable-speed pump, further a revolving number detector 5 is provided for detecting the suction pressure, discharge pressue, and the number of revolution of the pump. By using their detecting signals and pumping characteristic curves, a microcomputer 6 finds the present value, upper limit value, lower limit value, value in the maximum efficiency point of the flow rate, and the present value, upper limit value, lower limit value, value in the maximum efficiency point of the discharge pressure, and computes those values.

Description

[Detailed description of the invention] The present invention relates to a pump operating state monitoring system.

Conventional pump operating state monitoring systems mainly display state quantities that can be directly detected by a detector, but rarely display state quantities that can be derived using pump performance characteristics. For example, by detecting pump suction pressure, discharge pressure, and rotational speed, useful information regarding pump operation such as flow rate, pump efficiency, and required NP8H (net positive suction head) can be obtained from pump characteristics, but conventional monitoring The method did not output this information.

Furthermore, when monitoring whether or not the pump is being operated within a proper operating range, conventionally one of the following methods has been used.

The first method is to determine whether the flow rate or pressure deviates from a preset tolerance value. The second method, as shown in FIG. 1, uses limit lines 101 and
02, the limit line 103 corresponding to the upper limit of rotation speed and the limit line 104 corresponding to the lower limit of rotation speed are stored in the monitoring device, and the flow rate and pressure exist within the area surrounded by limit lines 101, 102, 103, and 104. This is a method of determining whether or not.

As shown in FIG. 2, the limit lines 101, 102, 103, and 104 shown in FIG.
The rotation speed and flow rate are at the limit line 101/5102', 103
There is also a method of determining whether or not it exists within the area surrounded by ', 104', but this method is based on
This method can be considered essentially equivalent to the above method.

All of these conventional methods for determining appropriate driving have the following drawbacks. That is, although the permissible operating range of the pump varies greatly depending on the pump suction pressure Ps, and also varies depending on the pump rotation speed N in the case of a variable speed pump, in the first determination method described above, the pump suction pressure Ps and The permissible value is set without considering the change in the pump rotational speed N, and the limit line is determined in the second determination method without considering the change in the pump suction pressure PS.

Therefore, the first determination method is for a constant speed pump and for suction pressure P.
This is applicable only when the change in s is small, and the second determination method is only applicable when the change in suction pressure Ps is small.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional pump operating state monitoring method and to provide a pump operating state monitoring method that can accurately monitor even when there are fluctuations in pump suction pressure PS. .

Therefore, according to the pump operating state monitoring method of the present invention, pressure detectors are provided on the suction side and discharge side of the pump for constant speed or variable speed turbo pumps, and for variable speed pumps, pressure detectors are provided on the pump suction side and discharge side. A detector is provided to detect the pump suction pressure Ps, the discharge pressure Pd, and, in the case of a variable speed pump, the pump rotation speed N. A known microcomputer uses these detection signals and pump characteristic curves to
The current value Qss of the flow rate, the upper limit Q2, the lower limit Q11, the value Q4 at the highest efficiency point, the current value P11 of the discharge pressure, the upper limit PtS, the lower limit P3%, the value P4 at the highest efficiency point are determined, and these values are output.

If necessary, it also outputs a lot of information, such as the cumulative flow rate, total head, effective NPSH, required NPSH, pump efficiency, etc., which can be obtained incidentally from the above-mentioned output values.

This enables detailed monitoring and appropriate and highly efficient pump operation using these output values. In other words, by manipulating the pump flow rate control valve or the pump rotation speed to keep the current value within the upper and lower limits, proper operation that does not cause cavitation, etc. can be achieved, and the current value can be adjusted to the value at the highest efficiency point. By bringing the value close to υ, it becomes possible to perform highly efficient operation.

Furthermore, according to the monitoring method of the present invention, the upper and lower limits of the pump's permissible operating range are determined by considering the suction pressure Pa and, in the case of a variable speed pump, the rotational speed N, and these values are used to detect deviations from the permissible operating range. Determine. Therefore, accurate determination is possible even when there are fluctuations in the suction pressure ps.

Further, according to the monitoring method of the present invention, the deviation between the current value Q of the flow rate obtained from the flow rate detection and the pump characteristic curve and Q4 is determined, and it is determined whether the deviation is greater than the allowable deviation. This makes it possible to monitor the presence or absence of factors that degrade pump performance, such as foreign matter or air getting into the pump, or wear on the pump liner ring.

The pump operating state monitoring system of the present invention will be described in detail below.

First, the pump characteristic curve used in the monitoring method of the present invention will be explained. A curve 111 shown in FIG. 3 is a pump head curve obtained by performing a pump performance test. Curve 112 is an excessive flow limit line that indicates that it is impossible for the flow rate and head to be on the right side of this curve considering the purpose of use of the pump, and curve 113 is an under flow limit line determined from the minimum flow limit of the pump. It is.

A curve 114 shown in FIG. 4 is the required NPSH curve of the pump, and is a characteristic uniquely determined for each pump.

When n = N / No (1), the flow rate at the intersection of the pump head curve 111 and the curve 112 corresponding to each rotational speed ratio R is represented. Similarly, the curve 113' is the pump head curve 11 corresponding to each rotational speed ratio R.
1 and the flow rate at the intersection of curve 113.

A curve 115 shown in FIG. 6 is a pump shaft power curve obtained by conducting a pump performance test.

When the curves 111, 112', 113', and 114, 115 are expressed as functions regarding the flow rate Q7 and the head H1 required NP SRM s shaft power W, the following results are obtained.

H= fH(Q) (2)Q=fu
(R) (3) Q = fL (R)
・(4)1111= , fR(Q)
(5) W = fW (Q) (6
) and the inverse functions of equations (2) and (5) Q-ba(machi (7) ). Even when input in the form of a table, these continuous functions can be easily approximated by using an interpolation method or the like.

In addition, as shown in FIG. 7, a suction pressure detector 3 is provided on the suction side of the pump 1, and a discharge pressure detector 4 is provided on the discharge side, and the measuring point height from the pump axis to the suction pressure detector 3 is Difference Zs
The measurement point high pressure Zc+ at the four discharge pressure detector trenches, the pipe cross-sectional area As of the suction pressure detection point, and the pipe cross-section 8jAd of the discharge pressure detection point are stored in the microcomputer 6.

Further, the atmospheric pressure PR, the average value of the specific weight γ of the liquid handled by the pump and the vapor pressure Pv, and the flow rate Q at the highest efficiency point of the pump at the rated rotation speed No. 1 of the pump. and lifting height FL are stored in the microcomputer 6.

Next, a monitoring procedure will be explained according to the apparatus shown in FIG.

First, the detection signals of the suction pressure detector 3 and the discharge pressure detector 4 are input to the microcomputer 6, and the suction pressure Ps
1 to obtain a discharge pressure Pd. In addition, when a variable speed pump is targeted, a rotation speed detector 5 is provided in the drive machine 2, and the detection signal of the rotation speed detector 5 is inputted to the microcomputer 6 to obtain the pump rotation speed N, and formula (1) is calculated. Use this to find the rotation speed ratio. In the case of a constant speed pump, the rotation speed ratio is always set to 1.

Also, find . Here, g is the gravitational acceleration, and Q,
is the flow rate obtained one time before using the α formula described below.

Using the above data, calculate the pump total head H and effective NPSHhs from the following equations 00) and 00.

)(,=(P,+-Ps)/r+D
QO)hs=(Pa-Pv+Ps)/r+Zs+Ql
v'(2gAs'') (11) Also, calculate the current value Q of the flow rate and the value at the highest efficiency point using the 02 formula and the θ■ formula.

QI=R”f; (HIAL”) az
Q4=RQO (13) Also, the current value P1 of the discharge pressure and the value P4 at the highest efficiency point are determined from equations 04) and 05).

P, = Pd α (I) P, = Ps + γ (几2HO-D)
(15) Next, the required NP8H curve 1 shown in Figure 4
The upper limit flow rate Qu corresponding to the intersection of 14 and effective NPSHhs
and the lower limit flow rate qL are determined from the αω formula.

Qu or qL=R-f”(hs/R”)
aQ Also, curve 112' and curve 113' shown in FIG.
The lower limit flow rate Qu' and the lower limit flow rate qL' determined from the above are obtained from the 07+ formula and the 0-kage formula.

qu'=fu(R)'
(lηqL'-ft(R)
(The smaller of qll and qu' is the upper flow rate Q, and the larger of qL and qL' is the lower flow rate Q3. That is, Q2 = MIN (qu + qu')
01Qs = MAX (q r, + q
Next, the upper limit value P2 and the lower limit value Pse of the pump discharge pressure are determined using the equation (21) and the equation (21).

P2=Ps+γ(R”fu(Qs/R) D)
(21) Ps=Ps+r (R2・fu(Qt/R)
-D) (Q obtained 23 or more, , Q,
, Q, , Q, and “I rPt + P3y
P4 is output from the microcomputer 6 to the output device 7.

It also determines whether or not equation (to) or equation I24 is satisfied, and outputs the result to the output device 7.

Q, <Q, <Q, 23) Ps
< Pt < Pt (goods)
If formula (c) or formula (24) is satisfied,
This means that the pump is being operated within the permissible operating range.Furthermore, it is also possible to obtain the required NP8Hhr< and pump efficiency η from equations (e) and (a) and output them to the output device 7.

hR= ”'fn (outside Qt) (c) η
= 0.163QIH+/(R″-fL(Q4))
@It is possible to monitor the pump operating state by obtaining the state quantities from time to time without repeating the above procedure. Further, by numerically integrating the flow rate Q with respect to time using the microcomputer 6, the integrated flow rate can be determined and output.

Further, since the flow rate Q is calculated from the performance curve that the pump should originally have, it should match the meteor Q: measured by the hook flowmeter, which does not change the pump performance. Q, and Ql
If the deviation is large, there is a possibility that the pump performance has deteriorated due to foreign matter or air entering the pump, wear of the impeller or lychee ring, etc.

Then, by additionally inputting the detection signal of the flow rate detector to the Microcomputero, we obtain the measured flow flQζ, find the deviation from Q, and check whether it exceeds the allowable deviation preset in the Microcomputero. By making a determination and outputting the result from the microcomputer 6 to the output device 7, it is possible to know whether or not the performance of the bomb has deteriorated.

As explained above, the pump operation status monitoring method of the present invention monitors the pump and performs pump operation based on a large amount of information, so it is possible to perform detailed pump monitoring and appropriate and highly efficient pump operation. It becomes possible. In particular, the pump operating state monitoring method of the present invention takes suction pressure into consideration when monitoring the pump and determining deviation from the allowable operating range, so even if there are fluctuations in suction pressure, accurate monitoring and determination can be performed. It can be performed.

[Brief explanation of drawings]

FIGS. 1 and 2 are limit diagrams of flow rate-pressure and rotation speed-flow rate in the case of a conventional determination method. Figures 3 to 6 show pump characteristic curves used in the monitoring system of the present invention, where Figure 3 shows the flow rate vs. head, and Figure 4 shows the flow rate vs. NPSH.
, FIG. 5 shows the rotational speed ratio-flow rate curve, and FIG. 6 shows the flow rate-shaft power curve. FIG. 7 is an explanatory diagram showing the difference in measurement point height from the pump axis to the suction pressure detector and the discharge pressure detector, and the pipe cross-sectional area at the suction pressure detection point and the discharge pressure detection point. FIG. 8 is a block diagram showing the monitoring system of the present invention. 1 pump, 2...driver, 3...suction pressure detector,
4...Discharge pressure detector, 5...Rotation speed detector, 6
...Microcomputer, 7...Output device Patent applicant Ebara Corporation Representative Patent attorney Satoshi Takahashi

Claims (2)

[Claims] (1) In constant speed or variable speed turbo pumps,
Pressure detectors are provided on the suction side and discharge side of the pump, and a rotation speed detector is also provided for variable speed turbo pumps, and the detection signals of these detectors and the pump characteristic curve are used to create a microcomputer. Current value of flow rate Q1
, upper limit value Q2, lower limit value Q3, value at the highest efficiency point,
and current value P1, upper limit value P2, lower limit value P of discharge pressure
A pump operating state monitor characterized by determining a value P4 at the Ss maximum efficiency point, outputting those values, determining whether the current value is between an upper limit value and a lower limit value, and outputting a determination result. method. (2) Install a flow rate detector and additionally input the detection signal of the detector to obtain the measured flow iQ, and check whether the deviation from Q is within the tolerance set in advance in the microcomputer. A pump operating state monitoring system according to claim 1, characterized in that the system makes a determination and outputs the determination result.