CN1140837A - Determinating method for pressure leakage - Google Patents
Determinating method for pressure leakage Download PDFInfo
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- CN1140837A CN1140837A CN 96102299 CN96102299A CN1140837A CN 1140837 A CN1140837 A CN 1140837A CN 96102299 CN96102299 CN 96102299 CN 96102299 A CN96102299 A CN 96102299A CN 1140837 A CN1140837 A CN 1140837A
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- 230000008859 change Effects 0.000 claims abstract description 27
- 230000009467 reduction Effects 0.000 claims description 69
- 238000003556 assay Methods 0.000 claims description 20
- 238000005259 measurement Methods 0.000 claims description 12
- 238000009530 blood pressure measurement Methods 0.000 claims description 6
- 238000004904 shortening Methods 0.000 abstract description 2
- 239000007789 gas Substances 0.000 description 15
- 230000008676 import Effects 0.000 description 7
- 238000004364 calculation method Methods 0.000 description 5
- 238000001514 detection method Methods 0.000 description 5
- 230000009471 action Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 238000007429 general method Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
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- 239000002699 waste material Substances 0.000 description 1
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Abstract
The invention provides a measuring method to measure pressure leakage. A point MP4 can be used as the point where average pressure difference change per unit time is at a fixed value no matter the point MP4 has pressure leakage caused by a measured work piece or not, that is the point at which the quadratic differential value of the curve drawn according to the measured values of the pressure difference is zero. When reaching the point MP4, the pressure leakage of the measured work piece can be worked out by measuring the average change of the pressure difference per unit time. The point where the pressure is stable is accurately worked out, thus, shortening measuring time.
Description
The present invention relates to a kind of assay method of pressure leakage, especially to the inside of measured workpiece and the confined space that is used for measuring reference import the gases at high pressure of authorised pressure, change the pressure leakage assay method of measuring the pressure leakage that measured workpiece produces by measuring after this pressure reduction between the two.
For the sealing of measured automobiles engine with cast blank etc., the general method that adopts is: import high pressure gas bodies such as pressurized air from high-pressure air source such as air compressor to the inside of measured workpiece, measure the pressure leakage that measured workpiece produces.
At this moment, by the absolute value of pressure transducer measurement measured workpiece internal pressure, measure pressure leakage by this measured value, this mode can not be carried out the mensuration of high-precision pressure leakage because of the restriction of the sensor measurement precision that is stressed.Therefore developed such assay method, be exactly: preparation and measured workpiece be confined space-mensuration verifying unit (hereinafter to be referred as " verifying unit ") independently, as carrying out the device that high-precision pressure leakage is measured, connect this verifying unit and measured workpiece by the pressure differential detection instrument, change by the pressure reduction that detects between the two, measure the pressure leakage that measured workpiece produces.
And aspect the object lesson of the pressure leakage assay method realized, for example special invention of opening the pressure leakage determinator that flat 4-221733 communique put down in writing is arranged according to such differential pressure measurement.As for the technology of being put down in writing in this communique, be by the pressure differential detection instrument, connect the mensuration almost identical, that volume is identical verifying unit and measured workpiece with the measured workpiece shape.In measured workpiece and verifying unit, import pressurized air then, reach the timeliness of measuring pressure time point pressure difference afterwards by measurement and change, carry out the mensuration of the pressure leakage of measured workpiece generation.
Also developed the part of closed conduit in addition, substituted the mensuration verifying unit almost identical, that volume is identical, carried out the pressure leakage method for measuring by the pressure reduction of this airtight part and measured workpiece relatively with the measured workpiece shape.
Under the situation of the pressure reduction of the internal pressure of the internal pressure of measuring measured workpiece and verifying unit, it is generally acknowledged, when the internal pressure of measured workpiece and the internal pressure of verifying unit equate, stop the importing of gases at high pressure, directly measure the pressure reduction that produces then between the two, yet in fact this is not all right.
Usually import the gases at high pressure of verifying unit,, also it is not released to atmosphere though be that the mensuration of 1 measured workpiece is through with mostly.This is because there is no need it is released in the middle of the atmosphere, is because if each mensuration is released to it in the middle of atmosphere, gases at high pressure have been wasted in addition.But for measured workpiece, when the measured workpiece that will measure end when determinator disassembles, gases at high pressure will be released in the middle of the atmosphere, again gases at high pressure be imported in the measured workpiece of wanting to measure then.At this moment, because of existing general air in the measured workpiece, so this air is pressurized, adiabatic compression, temperature raise.Therefore, when the gases at high pressure of authorised pressure were imported into measured workpiece and verifying unit, the temperature of measured workpiece mesohigh gas was mostly than the temperature height of the gases at high pressure in the verifying unit.Under such situation, along with the temperature of the gases at high pressure in the measured workpiece is cooled, even measured workpiece does not leak, the pressure of measured workpiece one side also can reduce, and produces pressure reduction.If this situation takes place, although do not leak, the pressure reduction of measured workpiece internal pressure and verifying unit internal pressure also can increase, and just will be judged to be to exist to leak.
In case common in addition mensuration is that verifying unit and measured workpiece are communicated with, pressure just becomes equal, cuts off connection between the two under this state, measures the pressure reduction that produces after this.This moment is because the action of the solenoid valve that cut-out is communicated with etc. also can produce pressure reduction sometimes.
Fig. 3 is the curve map of an example of the such pressure reduction variation of expression, and pressure reduction increases the state that a side represents that the measured workpiece internal pressure is higher.At Fig. 3, pressing time, T1 represented to import the time of gases at high pressure in measured workpiece.Besides gases at high pressure have been imported in the verifying unit.At this moment, as described above, the temperature rises in the measured workpiece.After pressing time, T1 finished, verifying unit and measured workpiece were connected, and pressure reduction is zero.During the pressure reduction vanishing, the connection of measured workpiece and verifying unit is cut off (time limit t2), at this moment, for example owing to cut off the action of the valve that is communicated with, produces pressure reduction sometimes.Fig. 3 represents because the action of the valve that cut off to be communicated with, the situation that the pressure of measured workpiece one side has raise.At this moment, if the temperature of gases at high pressure in the measured workpiece higher, also be in the cooling procedure, the pressure in the measured workpiece descends along with the cooling of temperature.Solid line is just represented this situation among the figure.Under the situation of Fig. 3, time limit t4 represents that the temperature in the measured workpiece becomes with environment temperature and equates the time limit that pressure no longer changes.Have, dotted line and dot-and-dash line represent to exist the situation of leakage again.
As what expressed by above-mentioned reason, the measured value among Fig. 3 before the time limit t4 lacks reliability, the mensuration that must adopt the later measured value of time limit t4 to leak.
But problem is not know when to be time limit t4.Under the situation with the same terms repeated measurement, it is feasible measuring time limit t4 with the form of prior mensuration.Yet if measured workpiece is of all kinds, kind is more, time limit t4 is also more various.Fig. 4 represents the difference because of pressurized conditions, and pressure reduction reaches the stable situation of change of required time before, and it is different reaching the stable time.
In existing technology, measure in advance and stablize needed maximum time, after this effluxion, the mensuration of leaking (limit MP3 measures later in the curve map of Fig. 1 hereinafter).This mode must not be taked then for guaranteeing measuring reliability, but just can reach with short time pressure reduction under the stable situation, and Measuring Time becomes a kind of waste, and determination efficiency has been reduced.
Therefore the present invention realized pressure reduction stable, once the technology that changes the mensuration that can will begin in a minute in the time of can accurately measuring to the pressure reduction of following leakage.Here said pressure reduction stable status only just can obtain under leak free situation, in fact can not be applied to find out the time limit that pressure reduction has been stablized.If this processing mode is applied in the middle of the reality, having under the situation of leakage unstablely all the time, be measured to and when also can not realize.
Therefore, method of the present invention is: the gas of authorised pressure is imported in the inside and confined space of measured workpiece, cut off the inside of this measured workpiece and the connection of this confined space then, measure the internal pressure of this measured workpiece after this and the pressure reduction of this confined space pressure, measure the pressure leakage that this measured workpiece produces, the unit interval mean change amount that it is characterized in that obtaining above-mentioned pressure reduction is the time point of definite value, after this time point, and the mensuration that adopts the pressure reduction measured to leak.
The inventor has two class factors to repeat in the variation model of discovery pressure reduction after deliberation.The 1st class factor is followed leakage and is produced, and the 2nd class factor is to change even without leaking the pressure reduction that also produces.The inventor after deliberation in this respect, its pressure reduction unit interval mean change amount of pressure reduction variation model that has confirmed the former is certain, just represented to the time limit t4 of the curve map of dotted line as the dot-and-dash line of Fig. 3, there is the relation of pressure reduction and time while linear change.Confirmed the latter's pressure reduction variation model on the other hand, the unit interval mean change amount of its pressure reduction diminishes gradually, is not definite value, and just represented as curve map before Fig. 3 time limit t4, pressure reduction and time relation are not straight line.
Method of the present invention is to serve as according to proposing with such understanding, the unit interval mean change amount that detects pressure reduction is the time limit of definite value, just under leak free situation, shown in the solid line of this after image Fig. 3 like that, the time limit that pressure reduction no longer changes, perhaps under the situation of exist leaking, as the dotted line of Fig. 3 to shown in the dot-and-dash line, time limit t4 of pressure reduction linear change after that, measured value after this are used for measuring.
Adopt under the situation of this method, can calculate leakage rate according to the unit interval mean change amount of the pressure reduction of measuring after the above-mentioned time point.In this case, can measure leakage rate with short temporally precise.
In addition, adopt under the situation of this method, can be according to the pressure reduction of measuring at above-mentioned time point and the amplitude of variation of pressure reduction two pressure reduction when after this passing through the stipulated time, measure leak whether good.In this case, can make judgement accurately with the short time.
Have again, this method is after the time point that is communicated with of the inside that has cut off this measured workpiece and this confined space, with short time interval repeated measurement pressure reduction, the input computing machine, analogy by the differential pressure measurement value of charging to computing machine, the unit interval mean change amount of obtaining pressure reduction is the time point of definite value, and the result is satisfactory.As if this method of employing, can realize the automatic mensuration of computing machine.
Fig. 1 is the synoptic diagram by the measured concrete measurement result of an embodiment of pressure leakage assay method related to the present invention.
Fig. 2 is the mensuration sequential schematic of an embodiment of piezometry method of the present invention.
Fig. 3 is the concrete measurement result synoptic diagram of being measured with existing pressure leakage assay method.
Fig. 4 is the concrete measurement result synoptic diagram of being measured with existing pressure leakage assay method.
Just realized one embodiment of the invention below, be described further with reference to Fig. 1 and Fig. 2.At first, just, make an explanation with reference to Fig. 1 according to the measured concrete measurement result of the pressure leakage assay method of present embodiment.Fig. 1 is the curve map of expression according to the measured pressure reduction situation of change of the pressure leakage assay method of present embodiment.
As shown in Figure 1, the pressure reduction that produces along with solenoid valve is switched, measured workpiece and verifying unit are cut off changes with pressure variation simultaneously gradually.Here, the time that produces (not causing because of the leakage) pressure variation that is caused by reasons such as adiabatic compression is the scope of time Δ T2.Under leak free situation, pressure reduction does not change after the time Δ T2.On the other hand, under the situation of exist leaking, in the time of this range delta T2, as pressure difference, detect pressure differential deltap P that the measured workpiece that causes because of pressure leakage produces add by and the unprovoked value of leaking the pressure differential deltap PO that the pressure variation that causes produces.After the time point MP4 that time Δ T2 finishes, the value of the pressure differential deltap P that the measured workpiece that detection causes because of pressure leakage produces is as pressure difference.In the pressure reduction variation model before time point MP4, the pressure reduction that causes because of leakage and and unprovoked leak the pressure reduction that causes and mixed.The later pressure reduction variation model of time point MP4 reflects the value of the pressure reduction change that causes because of leakage.Therefore, the timeliness variation according to the later pressure difference of time point MP4 can calculate the pressure leakage amount that measured workpiece produces.Thereby owing to obtain a MP4 exactly, begin to measure from this time point, can measure with the shortest time.
This time point MP4 is that no matter whether measured workpiece produces pressure leakage the unit interval mean change amount of pressure reduction all be the point of definite value, and just the second differential value of the curve of being drawn out by the measured differential pressure measurement value of differential pressure pickup is zero point.
In the present embodiment, when the unit interval mean change amount of asking pressure reduction is the point of definite value, the measured value that need not record by differential pressure pickup, but adopt its moving average, this is in order to eliminate the cause of the error that produces because of determination data is at random.
Specifically, from the measuring-signal of differential pressure pickup, in each predefined sampling time, all as measured value X1, X2 ... deposit computing machine in.With each this measured value X1, X2 ... moving average calculate number N
PMoving average calculation P, the moving average P that calculates be as detected value Xp (1), Xp (2) ... deposit computing machine in.Use this detected value Xp,, calculate 1 subdifferential value D1 by following formula (1) at each predefined variable quantity unit of account time C1.
D1
(N)＝X
P(N)－X
P(N－C1) ··(1)
Calculate 2 subdifferential value D2 by following formula (2) then.
D2
(N)＝D1
(N)－D1
(N－C1) ··(2)
Further, calculate weighted mean value D2 by 2 subdifferential value D2 according to the method for weighted moving average
AVE, have this weighted mean value D2
AVEBe zero time point, with this time point as time point MP4.
So, be judged to be and arrive time point MP4, be used in the unit interval mean change amount of the pressure reduction of being measured after this time point MP4, can calculate the pressure leakage amount V of measured workpiece
LAspect the concrete grammar that calculates, can adopt various methods.For example by a MP4 and in addition the differential pressure measurement value X or the detected value X of the point-to-point transmission of a bit
PThe method of finding the solution, the method for finding the solution by the moving average of unit interval, method of finding the solution by the moving average of unit interval mean change amount (for example differential value D1) etc.
The amplitude of variation of pressure reduction two pressure reduction during by the pressure reduction of time limit MP4 with after this through the stipulated time just can judge exactly whether leakage is good below more than the setting still being.
As mentioned above, obtain the time point MP4 when not having pressure variation exactly, begin the calculating pressure leakage rate, can before beginning in the past detects time point MP3, begin to detect thus from this time point.Therefore T4 detection time that available detection time than in the past, T3 lacked calculates the pressure leakage amount, can shorten the minute of pressure leakage.
With regard to the mensuration order of the pressure leakage assay method of present embodiment, describe below with reference to Fig. 2.Fig. 2 is the flow chart of the mensuration order of expression present embodiment pressure leakage assay method.
When the step S10 at Fig. 2 measures beginning, at first import the parameter of (step S12) measured workpiece and verifying unit.Size, shape of the size, shape etc. of measured workpiece and verifying unit etc. are arranged aspect parameter.Then import the differential pressure measurement value X that (step S14) recorded by differential pressure pickup.
Whether good then moving average calculation P carry out judgement (step S16).Measured value X be input to only be the necessary number of moving average calculation before, when this judgement is not "Yes", return step S14, repeatedly input measurement value X.Having imported at measured value X only is the time point that calculates necessary numerical value of moving average, enters step S18, moving average calculation P.Like this, the value of the moving average P that calculates deposits computing machine (step S20) in as detected value Xp.
Then, calculate variable quantity, carry out whether good judgement (step S22).When through time of the unit interval C1 of predefined calculating variable quantity, this judgement becomes "Yes", and utilization detected value Xp is according to above-mentioned formula (1) and formula (2) calculating 1 subdifferential value D1 and second differential value D2 (step S24).
Then, calculate weighted mean value D2
AVE, carry out whether good judgement (step S26).2 subdifferential value D2 calculate only be calculate the necessary number of mobile weighted mean before, this judgement is not a "Yes", returns step S14, carries out said process repeatedly.Having calculated at 2 subdifferential value D2 only is the time point that calculates the necessary number of mobile weighted mean, enters step S28, calculates weighted mean value D2
AVESo, according to the weighted mean value D2 that calculates
AVEWhether be zero, carry out the whether stable judgement (step S30) of pressure.If weighted mean value D2
AVEBe zero, then this is judged as "Yes", and the judgement of step S32 also is a "Yes", carries out pressure leakage amount V
LCalculating (step S34).
The mensuration of pressure leakage finishes (step S36) in proper order thus.
In the present embodiment, though when computing, adopted the method for moving average and method of weighted mean, not necessarily only limit to these computing method.
In addition, the assay method of present embodiment can also be applicable to the part of closed conduit to make it become other forms such as separate space.
Content for other processes of pressure leakage assay method also is not limited in present embodiment.
In the present invention, because the assay method of the pressure leakage that proposes is: asking the unit interval mean change amount of pressure reduction is the time point of definite value, begin to result from the pressure leakage mensuration of above-mentioned measured workpiece from this time point, so, can obtain the time point of pressure stability exactly, can adopt the measured value of the pressure reduction that begins from this time point to carry out the mensuration of pressure leakage, can save the remaining stand-by period.
Therefore this is a kind of minute of pressure leakage and extremely practical pressure leakage assay method of shortening.
Claims (5)
1. a mensuration results from the method for the pressure leakage of measured workpiece:
The gas of authorised pressure is imported in the inside and confined space of measured workpiece;
Cut off the inside of this measured workpiece and the connection of this confined space then;
Measure the internal pressure of this measured workpiece after this and the pressure reduction of this confined space pressure, it is characterized in that:
The unit interval mean change amount of obtaining above-mentioned pressure reduction is the time point of definite value, the mensuration that adopts the pressure reduction of mensuration to leak later at this time point.
2. the pressure leakage assay method of claim 1 is characterized in that:
After above-mentioned time point,, calculate leakage rate by the pressure reduction unit interval mean change amount of measuring.
3. the pressure leakage assay method of claim 1 is characterized in that:
Whether according to the pressure reduction of measuring at above-mentioned time point with the amplitude of variation of pressure reduction two pressure reduction when after this passing through the stipulated time, it is good to measure leakage.
4. the pressure leakage assay method of claim 1 is characterized in that:
After the time point of the connection of the inside that has cut off this measured workpiece and this confined space, with short time interval repeated measurement pressure reduction, the input computing machine;
According to the analogy of the differential pressure measurement value of charging to computing machine, the unit interval mean change amount of obtaining pressure reduction is the time point of definite value.
5. the pressure leakage assay method of claim 4 is characterized in that:
After the time point of the connection of the inside that has cut off this measured workpiece and this confined space, with short time interval repeated measurement pressure reduction, the input computing machine;
According to the measured value of the pressure reduction of charging to computing machine, obtain 2 subdifferential values of pressure reduction, be zero condition according to this 2 subdifferential value, the unit interval mean change amount of obtaining pressure reduction is the time point of definite value.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP147684/95 | 1995-06-14 | ||
| JP14768495A JP3461973B2 (en) | 1995-06-14 | 1995-06-14 | Pressure leak measurement method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1140837A true CN1140837A (en) | 1997-01-22 |
| CN1080879C CN1080879C (en) | 2002-03-13 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 96102299 Expired - Fee Related CN1080879C (en) | 1995-06-14 | 1996-06-13 | Determinating method for pressure leakage |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JP3461973B2 (en) |
| CN (1) | CN1080879C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103808474A (en) * | 2012-11-14 | 2014-05-21 | 广州市特种承压设备检测研究院 | Method for checking sealing performance of safety valve |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8457908B2 (en) * | 2009-06-11 | 2013-06-04 | University Of Washington | Sensing events affecting liquid flow in a liquid distribution system |
| KR101527959B1 (en) * | 2014-01-06 | 2015-06-16 | 한양대학교 산학협력단 | Simulation system of Production well tubing |
| CN104913204B (en) * | 2015-06-15 | 2018-02-13 | 汉威科技集团股份有限公司 | Pipeline gas leak detecting device and its detection method |
| US10352814B2 (en) | 2015-11-10 | 2019-07-16 | Phyn Llc | Water leak detection using pressure sensing |
| US10094095B2 (en) | 2016-11-04 | 2018-10-09 | Phyn, Llc | System and method for leak characterization after shutoff of pressurization source |
-
1995
- 1995-06-14 JP JP14768495A patent/JP3461973B2/en not_active Expired - Lifetime
-
1996
- 1996-06-13 CN CN 96102299 patent/CN1080879C/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103808474A (en) * | 2012-11-14 | 2014-05-21 | 广州市特种承压设备检测研究院 | Method for checking sealing performance of safety valve |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH08338784A (en) | 1996-12-24 |
| JP3461973B2 (en) | 2003-10-27 |
| CN1080879C (en) | 2002-03-13 |
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Address after: Aichi Prefecture, Japan Co-patentee after: Feng Tong equipment engineering Limited by Share Ltd. Patentee after: Toyota Motor Corp. Co-patentee after: Ghost Head Industrial Co.,Ltd. Co-patentee after: Fukuda Co.,Ltd. Address before: Aichi Prefecture, Japan Co-patentee before: Fengtong Engineering Co.,Ltd. Patentee before: Toyota Motor Corp. Co-patentee before: Ghost Head Industrial Co.,Ltd. Co-patentee before: Fukuda Co.,Ltd. |
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