EP2724137A1

EP2724137A1 - Method for checking the leakproofness of safety valves

Info

Publication number: EP2724137A1
Application number: EP12729636.6A
Authority: EP
Inventors: Alois QUATMANN; Ulrich Engelmann; Oliver Borgmann
Original assignee: Elster GmbH
Current assignee: Elster GmbH
Priority date: 2011-06-27
Filing date: 2012-06-26
Publication date: 2014-04-30
Also published as: US9080923B2; EP2541224B1; KR101963217B1; ES2462005T3; WO2013000921A1; JP5925305B2; KR20140048937A; CN103782148A; US20140174158A1; JP2014522967A; EP2541224A1; CN103782148B

Abstract

Method for checking the leakproofness of safety valves. Method for testing the leakproofness of two controllable valves (V1, V2), wherein the valves are arranged at opposite ends of a test volume (10). An inlet pressure pe is present upstream of the test volume, in front of valve V1, and an outlet pressure pa is present downstream of the test volume, behind the valve V2. A control device controls the valves to open and close, and the control device is coupled to at least two pressure switches (26, 27) which are both operatively connected to the test volume (10) in order to monitor the pressure. The first pressure switch is set to a first triggering threshold d₁, wherein d₁=pe/x, where x>3. The second pressure switch is set to a second triggering threshold d₂, wherein d₂=pe(1-1/x). A valve is controlled in order to open the valve for a period of time t_L1 and then to close said valve. The process then waits for a measurement period t_M1 and a first pressure switch is checked. The second valve is then opened and closed again and the second pressure switch is checked. The functionality of the valves is indicated if the method has not been aborted owing to a pressure switch being triggered.

Description

Method for checking the tightness of safety valves

The invention relates to a method for the control of

Tightness of controllable valves in a gas line.

In particular, the invention relates to a method to

Detect leaks in gas valves, which are arranged along a gas line as redundant safety valves.

Various safety regulations and standards determine the design and configuration of safety devices on gas lines, as described e.g. used in industrial thermal processing plants. By way of example, the

Safety requirements for furnaces and

Fuel management systems gas-fired industrial

Thermoprocessing plants according to DIN EN 746-2 be called.

Regularly according to such regulations a pre-ventilation of a burner space in front of a burner (new) start is required. There are however permissible exceptions. For example, no pre-venting is required after the automatic switch-off during shutdown if the burner is equipped with two valves closing at the same time and a leak-tightness control device (valve monitoring system). The tightness control works as

Automatic monitoring system of a line section with shut-off valves to give a signal for checking, if the leakage of one of the valves exceeds the response limit.

According to the prior art, various approaches to

Check the tightness known. The valves of corresponding systems are along a gas line, on two

different positions, upstream and downstream of a test volume arranged. Both valves are controllable to block or release the gas passage

enable .

Applicant has long used various methods to ensure tightness control. It will

Usually a pressure switch is used in the gas line between the valves, which has a trigger point in the pressure range between the upstream adjacent inlet pressure and the downstream adjacent outlet pressure. One

The corresponding prior art method will be explained in more detail below with reference to the drawings.

In addition, methods are known in which two pressure switches are used in the gas line between the valves, which may also have different release pressures.

The prior art therefore provides methods for checking a tightness of two controllable valves, wherein the

Valves are arranged at opposite ends of a test volume. On the input side, ie upstream of the test volume, in front of a valve VI, an input pressure p _{e is applied} . On the output side, ie downstream of the test volume, behind valve V2, is located

Output pressure p _a on. In incinerators applies that the

Input pressure is greater than the outlet pressure, so p _e > P _a and the pressure in the test volume is equal to p _z . That's it

Size ratio p _e ^ p _z -Pa-

A control device is coupled to the valves for controlling the opening and closing, the control device is coupled to at least two pressure switches, both for

Pressure monitoring with the test volume in operative connection.

In a method for leak testing of gas valves according to the document DE19831067 at least a second gas valve at start and at least a first gas valve when switching off the burner is checked for leaks.

The US6057771A suggests a stretch between two

Monitor valves with pressure switches to detect leaks in the valves. The fluid, which is trapped in the path with valves locked, leads to an increase in pressure when heated by ambient heat. Will not this

detected, may indicate a lack of blocking of the valves

be inferred.

However, a disadvantage of said methods is their test times, which are caused by the technical equipment.

Especially with large volumes and larger systems, the test period can take considerable time to on the one hand, the volume between the valves to the inlet pressure act on the other hand, the pressure in the test volume downstream drain. These operations are required to verify proper valve disabling functions.

The object of the invention is to provide an improved method for tightness control, which provides an unchanged high security with a shorter test time.

This object is achieved by a method with the

Features of claim 1.

The method according to the invention of the type mentioned initially pursues an optimized approach to tightness control.

First, the first pressure switch is on a first

Trigger threshold di set, where with x> 2. Of the

Parameter x indicates a fraction of the input pressure and can have any value, so it does not need to be an integer value.

The second pressure switch is set to a second trip threshold d2, where d2 = p _e (1 ^~ 1 / x). The trip thresholds are selected to be substantially symmetrical about half the input pressure, one by one half the input pressure

reduced and increased by the same amount compared to the half input pressure. This symmetrical arrangement can not be maintained mathematically exactly in practice, but it is within the usual tolerances to choose a corresponding value with associated triggering thresholds. This setting can be made once, when the system is set up, and does not need to be repeated each time the procedure is performed.

At the beginning of each tightness check both valves are in blocking position.

Alternatively, according to the invention, one of the following two

Completed step groups, the step sequences contain the same steps, but these in different

Process order. Basically, both sequences of steps are therefore equivalent, but an initial selection can, depending on the chosen sequence of steps, provide additional time savings. According to the first sequence of steps, first valve VI is actuated in order to open it for a period of time t _L i and then to lock it again. Waiting for a measuring time t _M i and then querying the second pressure switch. If p _z <d 2, an impermissible pressure drop has occurred between the valves VI and V2 and the process is terminated with detection of the leakage of the valve V2.

If the evaluation shows that p _z d2, the pressure in the

Test track thus above the triggering threshold of the second

Sensor is held, the proper function of the

Valve V2 detected. Subsequently, a control of the valve V2 to open this for a period of time t _L 2 and connect to lock. Again, a measurement duration t _M 2

waited and then queried the first pressure switch. If p _z > di, aborting the method with detection of the leakage of the valve VI. In this case, there was an increase in pressure above a permissible value despite the previous pressure relief valve V2.

If applicable, however so the tightness control is successfully completed.

According to the second sequence of steps, the process is run in a different order.

First, valve V2 is driven to open this for a period of time t _L 2 and connect to lock. To

Waiting for a measuring time t _M 2 of the first pressure switch is queried and aborted the method with detection of the leakage of the valve VI if p _z > di.

Otherwise, if Valve VI is actuated to open this for a period t _L i and connect to lock. Again, a measurement period t _M i is awaited.

Subsequently, a query of the second pressure switch and abort the process with detection of the leakage of the valve V2 if p _z <d2.

The indication of the functional efficiency of the valves takes place, if no abort of the procedure took place.

It is essential that the measurement times t _M i and t _M 2 according to the inventive method over the known concepts can be shortened significantly. These are regularly

Measuring times identical t _M i = t _M 2 ⁼ t _M , since the tripping values of the sensors are selected symmetrically by half the input pressure. By placing two pressure switches in the test volume between the

Safety valves are arranged, and these have different, substantially symmetrical switching points with respect to the half input pressure, a faster leak test is possible. So if, for example, the first pressure switch one

Triggering threshold, which is H of the input pressure, according to the invention, the second pressure switch has a value of about Ή of the input pressure. It is immediately apparent that the approach of the tripping thresholds to the input pressure on the one hand and to the output pressure on the other hand allows a higher sensitivity of the detection with the pressure switches. If there is a leak in the system, the above thresholds are exceeded or undershot faster than in the system with a single pressure switch or more

redundant pressure monitors is the case. The measuring time t _M can therefore be significantly reduced.

Preferably, the sequence of steps is determined depending on the state of the system at each tightness check.

It is first checked if at the beginning of

Tightness check the first pressure switch indicates that the first triggering threshold has been exceeded, ie p _z > di. In this case, the first sequence of steps is run through.

If at the beginning of the tightness control the first

Pressure monitor does not indicate exceeding the first tripping threshold, ie this is the second step sequence

run through .

Since the sequence of the valve tests is determined at the beginning of the method, depending on the state of the system, a time saving without impairing the

Security guaranteed. Depending on the pressure conditions between the valves, first the tightness of valve VI or, secondly, the tightness of valve V2 is checked. For this purpose, one of the pressure monitors is used to check whether the test volume moves approximately at the pressure level of the outlet pressure. Is this In the case, first, the tightness of the upstream and acted upon by the inlet pressure valve VI is checked. However, if the pressure in the test volume is already significantly higher than the initial pressure, the pressure tightness of the downstream,

tested against the output pressure blocking valve V2.

Depending on the choice of trigger levels can be a significant

Shortening of the measurement duration can be achieved, in which case, when the triggering thresholds of the pressure monitors approach ever closer to the pressures beyond the valves, the risk of

Error detection exists.

It is therefore particularly advantageous if in the

inventive method, the pressure thresholds with a

Parameter x <10 can be set. Depending on the design of the system and the system can be this factor and the so

linked measuring duration t _{M be} adjusted. The measurement time is shorter, the larger the factor x is selected.

It is prescribed by the specifications and technical standards to be complied with that the leakage on a gas-carrying system must not exceed certain limit values. The

Measuring time t _M is taking into account the switching accuracy of the pressure switch, the volume between the safety valves, the pressure difference between input and output

Outlet side and the cable cross-sections and the other interpretation of the system to determine. In any case, however, a much faster leak control procedure is achieved, as the symmetrical selection of the tripping thresholds of the

Pressure monitor reports an excessive increase or decrease in the pressure in the test volume much earlier than in a pressure monitor, which is functionally tuned approximately midway to a pressure value between input and output value.

From the wording of claim 1 shows that the measurement duration and opening times of the valves may be different depending on the currently switched valve. However, it is also possible for both valves identical measuring times and

Opening hours are chosen. In this case, the Configuration of the system extremely simple, since only a few

Parameters are to be set.

The invention will now be explained in more detail with reference to the accompanying figures.

Figure 1 describes a method and a structure according to the

Prior art, wherein a pressure switch is used.

FIG. 2 shows a flow chart of the method with the means from FIG. 1.

FIG. 3 shows a system construction for tightness control according to the invention.

FIG. 4 shows a flow diagram of a method according to the invention for using the device from FIG. 3.

FIG. 1 shows a device for checking the tightness of two shut-off valves VI and V2. Between the shut-off valves VI and V2, a test section 10 is formed. On the inlet side of the device, a supply line 15 is arranged so that the valve VI sits between the test section 10 and the supply line 15. The valve V2 is located between the test section 10 and the outlet 20, which leads to a gas consumer, e.g. one

Burner device leads.

In the supply line 15 is an input pressure p _e . With the volume of the test section 10, a pressure sensor 25 is coupled. In this device according to the prior art, the

Switching point for the pressure sensor to the half input pressure ρ _θ / 2 set. The pressure in the test section 10 is designated by p _z .

FIG. 2 shows the sequence of a test program, as can be carried out according to the device of FIG. This test procedure according to the prior art takes place in three sections, an initial waiting time, a valve opening time and a test time.

After the start of the program first passes

Waiting time t _w at step 50. Subsequently, the status of the pressure monitor 25 is queried, if the pressure prevailing in the test section 10 p _{z is} greater than half the input pressure p _e , the program flow A continues to proceed if the Pressure is not greater than half the input pressure, is transferred to the program branch to program B.

If the pressure in the test section after the expiry of the waiting time is greater than half the inlet pressure is at

Step 60a found that the pressure valve V2 downstream of the test section is intact. This valve V2 is activated in step 65a to the open position, then an opening time t _L of a few seconds, here waiting for about 2 seconds and the valve in step 75a back into the

Closed position activated. In step 80a, the measurement time t _{M is} awaited and then, in step 85a, it is determined whether the pressure in the test section is greater than half the input pressure. If this is the case, it is determined in step 90a that the valve VI is defective, since a pressure increase of the test section has taken place through this valve. Is the pressure of

Test track continues to be less than half of the inlet pressure, the functioning of valve VI is determined at step 95a.

The program B, which is selected at the initial exceeding of the pressure in the test section from half the inlet pressure, proceeds analogously, however, in step 60b, the proper functioning of the valve VI is first of all concluded. After opening and closing the valve VI in steps 65b, 70b and 75b, the measuring time 80b is completed and then checked whether the valve V2 meets the tightness requirements and the pressure in the test section is maintained.

It can be seen that the tightness control due to the use of a pressure switch, set to half

Input pressure can take a considerable amount of time, especially when larger volumes are to be checked.

According to the invention, therefore, that shown in FIG

Concept proposed, which uses two pressure sensors, which are set symmetrically about half the input pressure with their switching points. In this example, one pressure sensor 26 is set at a switching point p _e / 4 while the other one

Pressure sensor 27 is set to the switching point 3 / 4p _e . FIG. 4 shows a corresponding sequence of FIG

inventive method. After starting the method, it is checked in step 150 whether the pressure sensor 26 indicates that the prevailing pressure in the test volume V _P p _{z is} greater than 1/4 of the input pressure p _e . If so, the program continues in the left branch of the program.

In this case, the valve VI is opened at step 160a, kept open at step 165a for an opening duration t _L i (eg, for a few seconds), and closed again at step 170a. Subsequently, a measurement period t _M i elapses at step 175a. This measuring time will depend on the structure of the

Institution and the applicable regulations. In

Dependence on the maximum volume flow through the

Gas supply, from the inlet pressure and other parameters is determined when specifying the measurement duration, which pressure drop per time is compatible with legal requirements. These

timing is applied to the switching points of the device which are symmetrically applied at half the input pressure,

converted. Corresponding calculation methods are known to the person skilled in the art. The measurement duration t _M i in step 175a is therefore a measurement duration significantly shorter than the measurement duration of FIG. 2 in steps 80a and 80b, since only a smaller absolute pressure change is monitored. Will in step 180a

If the pressure p _z prevailing in the test volume is still greater than 3/4 of the inlet pressure, the faultless function of the valve V2 is determined at 185 a, because a defective valve V2 would have been in the measuring time t _M at the

applied pressure differential between p _z and p shown _a leakage which p would have to drop the pressure below the value of _z Ή p _e. However, if the criterion is not met in step 180a, the malfunction of V2 is detected at 190a and the method ends with an error message.

After step 185a, in step 195a the valve V2 is actuated to open and the opening in step 200a is activated

Opening duration t _L 2 (eg 2 seconds) held to a

To allow pressure equalization between the volume V _P and the output side. In step 205a, the valve V2 becomes again closed and a measuring time t _M 2 is waited in step 210 a. Now, it is determined by means of the sensor 26 whether the pressure present in the test volume is greater than H of the

Inlet pressure, which would indicate a defective valve VI. But since here the pressure increase of H of the inlet pressure

is detected and not, as described above, of the half of the input pressure, the measurement time T _M 2 in step 210a again significantly less than the time required in Figures 1 and 2 measurement time t _M.

It should be clarified that the shortening of the measuring time with constant safety is due only to the arrangement of several pressure sensors, which have symmetrically distributed by half the input pressure switching points.

The right branch of the method in Figure 4 is completed when initially the presence of a low pressure in

Test volume was determined. It is then started with the test of the valve VI and subordinate checked the functioning of the valve V2. Steps 195a to 210a correspond to steps 160b to 175b. On the other hand, steps 195b to 215b correspond to steps 160a to 180a.

It can be seen that the procedure according to the invention brings about a significant shortening of the leak-tightness test method, without abandoning the observance of the safety guidelines or impairing their testing. Rather, the entire system becomes more sensitive and responds more reliably to the presence of leaks. It is clear to the person skilled in the art, in view of FIG. 3 and FIG. 4, that a pressure increase, for example in the case of a leaking valve VI in the volume V _P to 1/4 of the inlet pressure, is faster than from 1/4 to 1/2 of the

Input pressure. The duration for pressure equalization depends on the difference of the pressures to be compensated. Therefore, with the described method according to the invention an extremely sensitive and reliable, set to the individual functions of the system leak test can be ensured.

Claims

claims

1. Method for checking a tightness of two

controllable valves, wherein the valves are arranged at opposite ends of a test volume, upstream of the test volume, upstream of valve VI, an input pressure p _e and wherein downstream of the test volume, behind valve V2, a

Output pressure p _a , where p _e > P _a and where the pressure in the test volume is equal to p _z ,

wherein a control means the valves for opening and

Closing activates and wherein the control device is coupled to at least two pressure switches, both of which are operatively connected to the pressure monitoring with the test volume,

characterized by the steps

Setting the first pressure switch to a first

Triggering threshold di, where

Setting the second pressure switch to a second

Triggering threshold d ₂ , where d ₂ = p _e (ll / x),

with each tightness control alternatively one of the following two step groups is processed:

first step sequence:

actuating the valve VI in order to open it and to lock it for a period of time t _L i, wait for a measuring time t _M i,

Interrogation of the second pressure switch and termination of the method with detection of the leakage of the valve V2 if p _z <d ₂ ,

- Actuation of the valve V2 to open this for a period t _L 2 and connect to lock,

wait a measuring time t _M 2,

- Polling of the first pressure switch and abort the method with detection of the leakage of the valve VI if p _z >di;

second step sequence: - Actuation of the valve V2 to this for a

Duration t _L 2 to open and then lock,

Waiting for a measuring time t _M 2,

- Queries of the first pressure switch and abort of the

Procedure with detection of the leakage of the valve

VI if p _z > di,

- Actuation of the valve VI to this for a

Duration t _L i to open and then lock,

Waiting for a measuring time t _M i,

- Queries the second pressure switch and abort the

Method with detection of the valve V2 leakage if p _z <d2,

Indication of the functioning of the valves, if no abort of the procedure took place.

2. The method according to claim 1, wherein then,

if at the beginning of the tightness control the first

Pressure monitor indicates an exceeding of the first triggering threshold, ie p _z > di, the first step sequence is processed and then,

if at the beginning of the tightness control the first

Pressure monitor does not indicate exceeding the first tripping threshold, ie the second step sequence is processed.

3. The method of claim 1 or 2, wherein x <10.

4. The method according to any one of claims 1 to 3, wherein for the measurement periods applies t _M i = t _M 2 and wherein for the opening times applies t _L i = t _L 2.

5. The method according to any one of claims 1 to 4, wherein after setting one of the pressure monitor an automatic

Adjustment of the other pressure switch with identical

Parameter x takes place.