EP0898112A1 - Pipeline system for the controlled distribution of a fluid and method for the operation of such a system - Google Patents

Abstract

The pipeline system (10) includes a main pipeline (11), which at a branching point (12) is branched in multi-branch lines (13-15). Each branch line has a variably adjusted valve (V1,V2,V3) to alter the mass flow in each of the branch lines. A first pressure measuring unit (PM1,PM2,PM3), measures the pressure drop of the flowing medium at the respective valve. For the reaching of a redundancy or reserve concept in the pressure measuring, at least one second pressure measuring unit (PM10, PM11 or PM12) is arranged between two of the branch lines (e.g. 13 and 14), in the flow direction behind the control valves.

Description

TECHNICAL AREA

The present invention relates to a piping system for Distribution of a flowing medium, comprising a main line, which at a branch point into a plurality branched from branch lines in each of the branch lines a variable throttle, with which the mass flow is adjustable in each of the branch lines, as well as for each Throttle point a first pressure measuring device with which the pressure drop of the flowing medium at the respective Throttle point is measured.

The invention further relates to a method of operation of such a piping system.

STATE OF THE ART

In power plant technology or other areas of application there is often the task of a large number of consumers with a mass flow of a compressible or incompressible Medium (e.g. cooling water, steam, oil or the like) supply. The supply system used for this typically exists from a network of pipelines, which itself characterized by branching points (nodes) at which a main line (a main flow of the medium) into two or more branch lines (branch streams) which branch to individual consumers or groups of consumers. In many cases it is necessary that the mass flow in each individual branch line according to the requirements of the consumer (s) is controlled. This can For example, a control valve is arranged in the branch line whose stroke is set so that the desired one Mass flow flows through the valve.

A simple way, the mass flow of the medium To control by a control valve is to lift the valve to calculate who to achieve the given Mass flow is needed. The calculation of the valve stroke is typically based on that measured on the control valve Pressure loss (pressure drop), the characteristic of the valve and the properties of the medium. In the simplest case results then (e.g. for the fuel supply system of an industrial Gas turbine) a piping system as it is in Fig. 1 is shown. In the piping system 10 of FIG. 1 a main line 11 branches at a branch point 12 in (for example) three branch lines 13, 14 and 15. In each of the branch lines 13, 14, 15 is a valve V1 or V2 or V3 provided, by means of which the mass flow can be set (controlled) by the respective branch line can. There is one parallel to the valve V1, V2, V3 Pressure measuring device PM1 or PM2 or PM3 arranged, the measures the pressure drop across the valve.

If the valve lift of the valves V1, .., V3 is denoted by h, then h is a function of the valve characteristic K _V , namely h = h (K V ).

For a compressible medium (eg the fuel gas for the gas turbine), the size K _V results for subcritical flow conditions K V = α (dm / dt) [T M / (p M -Δp)] 1/2 [1 / Δp] 1/2 , with the constant α, the mass flow dm / dt, the pressure p _M and the temperature T _M at the branch point 12 or in the main line 11, and the pressure drop Δp at the valve. For a given mass flow dm / dt, the quantity K _{V can be determined} on the basis of the measured quantities T _M , p _M and Δp according to equation (2). The valve stroke can be calculated from the specified valve characteristic K _V (h). A comparable determination can also be carried out for incompressible media.

The most important variable for the calculation of the valve stroke is the pressure drop measured at valves V1, .., V3. If if this measurement becomes faulty, this leads to an unacceptable one Failure of the supply system (and in the case of one Gas turbine for a quick shutdown) or even (e.g. in Case of a cooling water system) to a security risk. It is therefore desirable in many cases, the measurement of the Pressure drop across valves V1, .., V3 redundant, making an error in a single measurement of pressure drop Δp not the continuous, safe operation of the system touched or impaired (availability requirement or Availability Requirement AR).

The purpose of a redundancy concept is twofold: (1) The occurrence of a measurement error should be recognized and the faulty one Measuring device or the faulty measuring channel should be identified. (2) The (not) usable measured values are to be replaced by redundantly determined measured values.

Gemeldete Fehler (Notified Failure NF): Diese Fehlerart umfasst alle Fehler, die vom Sender oder einer anderen I/O-Einrichtung durch ein Bad-Data-Quality(BDQ)-Signal an das Steuerungssystem gemeldet werden. Aufgrund des BDQ-Signals weiss das Steuerungssystem, welche Δp-Messung fehlerhaft ist. Dies passiert typischerweise, wenn eine Messleitung unterbrochen ist oder ein Fehler in einer Komponente in der Messkette auftritt.

Drift in der Messung: Diese Fehlerart beschreibt die schleichende Verschlechterung des Messignals, so dass die übertragene Information nicht länger eine gültige Messung des Druckabfalls ist. Sie kann nicht detektiert werden und wird dementsprechend auch nicht an das Steuerungssystem gemeldet. Es müssen daher andere Wege beschritten werden, um diese Fehlerart zu handhaben.

There are two basic types of errors to consider:

Reported errors (Notified Failure NF): This type of error includes all errors that are reported to the control system by the sender or another I / O device using a bad data quality (BDQ) signal. Based on the BDQ signal, the control system knows which Δp measurement is faulty. This typically happens when a measuring line is interrupted or an error occurs in a component in the measuring chain.

Drift in the measurement: This type of error describes the gradual deterioration of the measurement signal so that the transmitted information is no longer a valid measurement of the pressure drop. It cannot be detected and, accordingly, is not reported to the control system. There are therefore other ways to deal with this type of error.

The redundant measurement of the pressure drop can be carried out according to FIG. 2 be done with double redundancy. In the case double redundancy is already per valve in addition to that existing pressure measuring device PM1, .., PM3 each one second pressure measuring device PM4, .., PM6 arranged in parallel. If one of the two pressure measurements (per valve) is faulty, can be switched to the other pressure measurement. This is only possible for reported errors where the incorrect measurement can be detected by the BDQ signal can. A drift of the measurement can be doubled Redundancy cannot be mastered because only two are independent Measurements per valve cannot be decided which of the two measurements is disturbed (or drifts).

The redundant measurement can be used to overcome this problem 3 with a triple redundancy be performed. In the case of triple redundancy, pro Valve next to the existing pressure measuring device PM1, .., PM3 each have a second pressure measuring device PM4, .., PM6 and a third pressure measuring device PM7, .., PM9 arranged in parallel. To determine the incorrect measurement in the case of a drift, the 2-out-of-3 choice principle is used. The 2-out-of-3 choice principle assumes that if 2 out of 3 Measuring channels deliver the same measured values, these measuring channels work correctly while the third measuring channel is faulty is.

Both with the double redundancy shown in FIG. 2 as well as in particular the triple shown in FIG. 3 Redundancy has the disadvantage of being very independent Pressure measuring devices PM1, .., PM6 or PM1, .., PM9 must be used, which is particularly the case with triple Redundancy with 3 pressure measuring devices per branch line leads to considerable effort.

PRESENTATION OF THE INVENTION

It is an object of the invention to provide a piping system to improve the type mentioned at the outset in such a way that a increased fault tolerance with comparatively little additional effort is achieved in the acquisition of measured values.

The task is the beginning of a piping system mentioned type solved in that to achieve redundancy in the pressure measurement at least between two of the branch lines in the direction of flow behind the throttling points second pressure measuring device for measuring the differential pressure is arranged between the respective branch lines. By adding the second pressure measuring device in the specified Way for measuring the pressure drop to the Throttling points of the two affected branch lines one double redundancy achieved. The three pressure measuring devices measure the differences between a total of three pressures (the Pressure in the main line and the pressures in the two Branch lines behind the throttling points), each of the three pressures each from two pressure measuring devices as a reference value is taken. If the measurement is error-free hence the three measured values of the three pressure measuring devices linear dependent: the sum of the measured values must (if correct Choice of sign) must be zero. Any pressure reading for a branch line can therefore be divided into two Determine wise (double redundant): First as direct Measured value of the associated first pressure measuring device, and others from the sum of the measured values of the other two pressure measuring devices. The invention allows three Pressure measuring devices for two branch lines one double Realize redundancy while using the scheme from Fig. 2 four pressure measuring devices would be necessary.

The dual redundancy is to be implemented for all branch lines according to a first preferred embodiment the invention between each branch line and each another branch line a second pressure measuring device to measure the differential pressure between the respective Branch lines arranged. With n branch lines, n-1 Pressure measuring devices required.

The saving becomes even clearer if the principle of Invention triple redundancy is to be achieved. According to a second preferred embodiment of the invention this is achieved in that between each branch line and two additional branches each have a second one Pressure measuring device for measuring the differential pressure between the respective branch lines is arranged.

The method according to the invention for operating the pipeline system is characterized in that for each pair of Branch lines the associated first pressure measuring devices and that arranged between the pair of branch lines second pressure measuring device each grouped together be, with the proper functioning of the Pressure measuring devices for each group of pressure measuring devices the sum of the pressure readings is zero, and that if one of the first pressure measuring devices within a group fails, the associated pressure reading from the Pressure measurement values of the other two pressure measuring devices of the Group is determined.

A preferred embodiment of the method according to the invention is characterized in that each first pressure measuring device each in two groups of pressure measuring devices is represented, and that the pressure readings from the first Pressure measuring device to be treated as faulty if those from the other two pressure gauges each of the the two groups determined associated pressure measurements with each other, but not with those from the first pressure measuring device pressure readings match.

Further embodiments result from the dependent claims.

BRIEF EXPLANATION OF THE FIGURES

Fig. 1

ein Rohrleitungssystem mit drei Zweigleitungen nach dem Stand der Technik mit einer Druckmesseinrichtung pro Drosselstelle (Ventil);

Fig. 2

das System aus Fig. 1 mit zwei Druckmesseinrichtungen pro Drosselstelle (Ventil) zum Erreichen einer zweifachen Redundanz;

Fig. 3

das System aus Fig. 1 mit drei Druckmesseinrichtungen pro Drosselstelle (Ventil) zum Erreichen einer dreifachen Redundanz; und

Fig. 4

ein bevorzugtes Ausführungsbeispiel der Erfindung, welches ein Rohrleitungssystem gemäss Fig. 1 zugrunde legt und im Unterschied zu Fig. 3 die dreifache Redundanz durch (wenige) zusätzliche Druckmesseinrichtungen zwischen den Zweigleitungen erreicht.

The invention will be explained in more detail below on the basis of exemplary embodiments in connection with the drawing. Show it

Fig. 1

a pipeline system with three branch lines according to the prior art with one pressure measuring device per throttle point (valve);

Fig. 2

the system of Figure 1 with two pressure measuring devices per throttle point (valve) to achieve double redundancy.

Fig. 3

the system of Figure 1 with three pressure measuring devices per throttle point (valve) to achieve triple redundancy. and

Fig. 4

a preferred embodiment of the invention, which is based on a piping system according to FIG. 1 and, in contrast to FIG. 3, achieves triple redundancy by (few) additional pressure measuring devices between the branch lines.

WAYS OF CARRYING OUT THE INVENTION

4 is a preferred embodiment of the inventive Piping system reproduced, which at one main line and three branch lines have triple redundancy with only three additional pressure measuring devices. The pipeline system 10 comprises a main line 11, which is at the branch point 12 in the three branch lines 13, 14 and 15 branches. In each of the branch lines is a controllable throttle valve V1, V2 and V3 built-in. The pressure drop (pressure loss) at the valves V1, V2, V3 is initially directly through a parallel to the valve arranged first pressure measuring device PM1 or PM2 or PM3 measured. For this - as shown in the figures - on both Sides of the valve from the branch piping to the pressure measuring devices. It is also just as conceivable, pressure transducers directly on the branch lines Arrange in front of and behind the valve and signal lines from the pressure transducers to the actual pressure measuring device respectively. In this respect, the system from FIG. 4 is direct comparable to the system from FIG. 1.

In contrast to FIG. 1 (and also FIG. 3), in the example of FIG. 4 there are three second pressure measuring devices PM10, PM11 and PM12, which are each arranged behind the valves V1, V2 and V3 between the branch lines and the pressure difference between each Measure two of the branch lines 13, 14 and 15. The pressure measuring devices PM1, PM2 and PM3 thus measure the pressure drop Δp1, Δp2 and Δp3 at the valves V1, V2 and V2. The pressure measuring devices PM10, PM11 and PM12 measure the differential pressures Δp10, Δp11 and Δp12 between the branch line pairs 13/14, 13/15 and 14/15. Since the pressure upstream of valves V1, V2 and V3 must be the same in all branch lines, the differential pressures are not linearly independent, but must (according to the mesh and knot rule in electrical networks) satisfy the following equations: c1 = Δp1 + Δp10 - Δp2 = 0 c2 = Δp2 + Δp12 - Δp3 = 0 c3 = Δp3 - Δp11 - Δp1 = 0 c4 = Δp11 - Δp10 - Δp12 = 0

These equations define conditions (constraints c1 to c4), from which the redundant printing information is derived can be. For example, the pressure difference (the pressure drop) Δp1 on valve V1 in branch line 13 to three different ones Ways to be determined independently, namely (i) directly through the pressure measuring device PM1, (ii) indirectly with the pressure measuring devices PM2 and PM10 Using equation (3), and (iii) indirectly through the pressure gauges PM3 and PM11 using equation (5). The same applies to the pressure drops at the other valves V2 and V3.

As long as the pressure measuring devices and the associated channels work properly, equations (3) to (6) and the associated conditions are fulfilled, ie, c1 = c2 = c3 = c4 = 0. As soon as a pressure measurement is faulty, one or more of the constraints c1 to c4 ≠ 0 and the associated conditions are violated. For example, if the pressure measurement of Δp1 is incorrect, then c1 ≠ 0 and c3 ≠ 0 apply. For the various cases in which an incorrect pressure measurement leads to the violation of certain conditions, the following systematic logical table can be drawn up: condition Δp1 Δp2 Δp3 Δp10 Δp11 Δp12 c1 = Δp1 + Δp10 - Δp2 = 0 1 1 0 1 0 0 c2 = Δp2 + Δp12 - Δp3 = 0 0 1 1 0 0 1 c3 = Δp3 - Δp11 - Δp1 = 0 1 0 1 0 1 0 c4 = Δp11 - Δp10 - Δp12 = 0 0 0 0 1 1 1

Each of the conditions ci, i = 1, .., 4 defines a row of one Matrix and each pressure measurement Δpj, j = 1, .., 3,10, .., 12 defined a column of the matrix. For an incorrect pressure measurement Δpj is the violation of the condition ci by a matrix element "1" is displayed in the jth column and the ith row. Conditions that are not violated are indicated accordingly a matrix element "0" is displayed. As in the above Example the Measurement of Δp1 incorrect, the conditions according to the table c1 and c3 violated (matrix elements are "1"). The Conditions c2 and c4 are not affected by this error (Matrix elements are "0").

Conversely, the table specified allows from the injured Conditions to conclude the faulty pressure measurement. The faulty measurement can then be resolved affected equations derived from the other pressure measurements become.

Example:

During the measurements it turns out that the conditions c2 and c3 are not satisfied (c2 ≠ 0; c3 ≠ 0). From the above Table can be derived that the pressure measurement of Δp3 is incorrect (matrix value "1" in the one belonging to Δp3 Column). The missing measured value for Δp3 can now be calculated using the equation (4) from measurements of Δp2 and Δp12, or above Equation (5) derived from the measurements of Δp1 and Δp11 become.

The procedure explained is applicable if only one of the pressure measurements is faulty. It is different Case when several (two or more) pressure measurements at the same time are faulty. The assignment - as above in the form of Table has been drawn up - is then no longer clear. Although it can (due to a violation of the terms c1 to c4) it is found that incorrect pressure measurements are available, but it cannot be clearly determined which of the pressure measurements are faulty.

Example:

If the conditions c1, c2 and c3 are violated (c1 ≠ 0; c2 ≠ 0; c3 ≠ 0), the measurements of Δp1 and Δp2, or the Measurements of Δp2 and Δp3, or the measurements of Δp1 and Δp3, or the measurements of Δp1, Δp2 and Δp3 incorrect be. Are only two measurements incorrect and can, for example the measurements for Δp1 and Δp3 by a corresponding one BDQ signal can be identified as faulty Δp1 by solving equation (3) from Δp10 and Δp2, or Δp3 calculated from Δp2 and Δp12 by solving equation (4) become.

If 3 measurements are faulty at the same time, the faulty ones Measurements on valves V1, V2 and V3 only then reconstructed if at least one of the measurements Δp1, Δp2 and Δp3 is error-free.

Example:

If the pressure measurements of Δp1, Δp2 and Δp10 are incorrect, can calculate Δp1 using equation (5) from Δp3 and Δp11, and Δp2 using equation (4) from Δp3 and Δp12 can be calculated.

Only if Δp1, Δp2 and Δp3 are faulty at the same time can these values are not calculated from the other measured values because the system of equations (3) to (6) in this case is singular. This corresponds to the (physical) circumstance that the differential pressures between the branch lines 13, 14, 15 taken by itself no information about the pressure drops included on valves V1, V2 and V3.

(a) die Detektion und Identifizierung der fehlerhaften Druckmessung und die Anleitung des richtigen Messwertes, wenn eine einzelne Druckmessung durch eine Drift fehlerhaft wird;

(b) die Detektion der fehlerhaften Druckmessungen und die Anleitung der richtigen Messwerte nach einer Identifikation der fehlerhaften Messungen z.B. durch ein BDQ-Signal, wenn zwei beliebige Messungen gleichzeitig fehlerhaft sind; und

(c) die Detektion der fehlerhaften Druckmessungen und die Anleitung der richtigen Messwerte nach einer Identifikation der fehlerhaften Messungen z.B. durch ein BDQ-Signal, wenn drei beliebige Messungen gleichzeitig fehlerhaft sind; ausgeschlossen ist dabei der Sonderfall, dass alle drei Druckmessungen an den Ventilen gleichzeitig fehlerhaft sind.

Overall, a system according to FIG. 4 enables the following corrections:

(a) the detection and identification of the faulty pressure measurement and the guidance of the correct measurement value if a single pressure measurement becomes faulty due to a drift;

(b) the detection of the faulty pressure measurements and the guidance of the correct measured values after identification of the faulty measurements, for example by means of a BDQ signal, if any two measurements are faulty at the same time; and

(c) the detection of the faulty pressure measurements and the guidance of the correct measurement values after identification of the faulty measurements, for example by means of a BDQ signal, if any three measurements are faulty at the same time; The special case that all three pressure measurements on the valves are faulty at the same time is excluded.

In the example discussed above, the three branch lines are sufficient 3 additional pressure measuring devices PM10, PM11 and PM12, to get largely the same redundancy as one 3. Additional branch lines are added, two additional pressure measuring devices per additional branch line needed between the additional Branch line and any two other branch lines arranged become. The maximum savings on pressure measuring devices compared to the arrangement of Fig. 3 results in the case of three branch lines.

LIST OF DESIGNATIONS

10th

Piping system

11

Main line

12th

Branch point

13, 14, 15

Branch line

PM1, .., PM12

Pressure measuring device

V1, V2, V3

Valve

Claims (7)

Pipe system (10) for the controlled distribution of a flowing medium, comprising a main line (11), which at a branch point (12) into a plurality branched by branch lines (13, 14, 15) in each of the Branch lines a changeable throttling point (V1, V2, V3), with which the mass flow in each of the branch lines (13, 14, 15) is adjustable, as well as for each throttle point (V1, V2, V3) a first pressure measuring device (PM1, PM2, PM3), with which is the pressure drop of the flowing medium at the respective Throttle point (V1, V2, V3) is measured, characterized in that that to achieve redundancy in the Pressure measurement at least between two of the branch lines (13, 14 or 13, 15 or 14, 15) in the flow direction behind the Throttling points (V1, V2 or V1, V3 or V2, V3) a second Pressure measuring device (PM10 or PM11 or PM12) for measurement the differential pressure between the respective branch lines (13, 14 or 13, 15 or 14, 15) is arranged. Pipe system according to claim 1, characterized in that between each branch line (13, 14, 15) and a different branch line (14 or 13 or 14) one second pressure measuring device (PM10 or PM12) for measuring the Differential pressure between the respective branch lines (13, 14 or 14, 13 or 15, 14) is arranged. Pipe system according to one of claims 1 and 2, characterized in that between each branch line (13, 14, 15) and two further branch lines (14, 15 and 13, 15 or 13, 14) each have a second pressure measuring device (PM10, PM11 or PM10, PM12 or PM11, PM12) for measuring the Differential pressure between the respective branch lines (13, 14, 15) is arranged. Pipe system according to one of claims 1 to 3, characterized in that the throttling points as valves (V1, V2, V3) are formed. Pipe system according to one of claims 1 to 4, characterized in that three branch lines (13, 14, 15) be used. Process for operating a piping system according to Claim 1, characterized in that for each pair of Branch lines (13, 14 or 14, 15 or 13, 15) the associated first pressure measuring devices (PM1, PM2 or PM2, PM3 or PM1, PM3) and that between the pair of branch lines arranged second pressure measuring device (PM10 or PM12 or PM11) are grouped together, whereby with proper functioning of the pressure measuring devices for each group of pressure measuring devices the sum of the pressure measured values is zero, and that if within a Group one of the first pressure measuring devices (PM1 or PM2 or PM2 or PM3 or PM1 or PM3) fails, the associated Pressure reading from the pressure reading of the other two Pressure measuring devices of the group is determined. A method according to claim 5, characterized in that each first pressure measuring device (PM1, PM2, PM3) each is represented in two groups of pressure measuring devices, and that the pressure measurements from the first pressure measuring device be treated as faulty if those from the other two Determine pressure measuring devices of each of the two groups associated pressure readings among each other, however not with those delivered by the first pressure measuring device Pressure measured values match.

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