Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M3/00—Investigating fluid-tightness of structures
  • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
  • G01M3/26—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors
  • G01M3/32—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for containers, e.g. radiators
  • G01M3/3236—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for containers, e.g. radiators by monitoring the interior space of the containers
  • G01M3/3263—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for containers, e.g. radiators by monitoring the interior space of the containers using a differential pressure detector

Definitions

• the invention relates to a method and a device for tightness testing of a test object having at least two seoarate chambe separated by at least one partition wall.
• the Swedish patent specification 7412067-6 discloses a tightness testing method in which'a test object and a refe ⁇ rence container are filled with a test fluid at the same pre sure and are connected to each side of a pressure sensitive diaphragm mounted in a differential pressure sensor, the diaphragm being deflected when the pressure falls in the test object due to leakage in the same. hether the test object should be classified as "tight" or "leaking" is a re ⁇ lative concept in the sense that" a certain leakage can al- ways be detected if a sufficiently high pressure is applied and/or a sufficiently long measuring time is used. In serial production certain s.c. tightness requirements are therefore established, according to which a test object is considered tight if leakage (diaphragm deflection of a certain degree) cannot be detected at a given testing pressure within a pred termined measuring time.
• the main object of the present invention is to improve this method for test objects having at least two separate chamber separated by at least one partition wall.
• An example of such objects are internal combustion engines having separate chambers, i.e. chambers for fuel, a lubricant and/or a cool ⁇ ing medium.
• the improvement should in the first place invol a reduction of the testing time for each test object without jeopardizing the reliability.
• this object is achieved by a method and a device, respectively, wherein the tightness between the chambers is tested by applying to the two cham ⁇ bers different fluid pressures both exceeding or both being below (i.e. both lying on the same side of the ambient press the ambient atmospheric pressure, whereupon the pressure in the chamber having the lowestover-pressure or the highest under-pressure, respectively, is checked with regard to a possible pressure increase or decrease, respectively, indi- eating an internal leakage in the test object. In case of su internal leakage (upon application of over-pressure) the pre sure will rise in the low pressure chamber.
• the pressure in ⁇ crease indicates unambiguously that the leakage is internal, and the test operation can be concluded already at this: stag if, on the other hand, no internal leakage is indicated, the test is continued by a tightness test of each chamber with respect to a possible leakage towards the outside, i.e. a s.c. external tightness test.
• the tightness requirements for internal leakage can be set much lower than for external leakage.
• the testing time for the internal tightness test can be made shorter than that of the external tightness test.
• the time needed for each tightness test and, consequently, the total testing time per test object may be further reduced by a controlled change of pressure simulating a slight leakage, either by a controlled pressure increase on the high pressure side or by a controlled pressure reduction, e.g. by means of a well- defined gas-leak, on the low pressure side (high and low pressures here denote the pressures on each side of the dia ⁇ phragm of the differential pressure sensor) .
• t drawing is a schematical representation of a tightness testing device.
• test object T havin two chambers Cl and C2, which are separated from each other a partition wall M. It should be emphasized that the test object T is shown schematically only on the drawing, whereas in reality the test object is normally of a rather complicat configuration. Likewise, the test object may contain three or more chambers mutually separated from each other and each being pressure tight internally towards the other chambers as well as externally towards the environment.
• the two chambers C1,C2 of the test object T are connected by means of detachable connectors (not shown) and hoses or con ⁇ duits LI and L2 to a source of pressurized gas (not shown either, but indicated by the arrow PI to the left on the drawing) .
• a source of pressurized gas not shown either, but indicated by the arrow PI to the left on the drawing
• a branch conduit L3 which in turn communicates, via a hose or condui L5, with a first reference container Rl.
• a branch conduit L4 and a conduit L6 are connected between the conduit L2 and a second reference container R2.
• the reference containers Rl and R2 should each have a volume substantially of the same size as the volume of the chambers Cl and C2, respectively, of the test object T and these con- tainers may consist of the chambers of a test object care ⁇ fully tested in advance and found tight.
• each conduit L5 and L6 there are inser ted in each conduit L5 and L6 electrically controllable cut- off valves V2' , V3 and V5' , V6, respectively.
• the conduits are evacuated so that the pressu ized gas exhausts (arrows P2) into the ambient air or into a recovery tank (in case a pressurized gas other than air or highly purified air is used) .
• a pressure sensor TVl and TV2 res tively, is connected and arranged to close the valves VI and V4, respectively, when reaching a predetermined pressure.
• the cut-off valves V5 and V5' are controlled by two parallel connected time relays Tl and T3, which are described more fully below.
• D2 is connected, which is represented schematically on the drawing and is provided with a diaphragm which is exposed on each side to the pressure in the respective conduit Ll,L5
• the deflection of the diaphragm actuates an electrical conta included in series in a circuit containing a time relay T4 and a signal lamp which is lit when the actuated contact clo ses within a time period or measuring time determined_by th relay T4.
• two differential pressure sensors D3 and Dl are connected between the conduits L2 and L6 and each adapted to actuate a circuit having a time relay T5, T2, and a signal lamp for indicating a relative pressure red tion in the respective conduit L2, L6.
• controlled gas leaks r i.e. throttles S1,S2 and S3, are connected to the conduits Ll, L2 and L6,via electrically trolled cut-off valves V8, V9 and V7.
• the device also comprises electrical circuits for controllin and actuating the various valves etc., but these circuits ar of a conventional nature and, therefore, they do not need to be described here.
• the device operates essentially in the following way:
• valves V1,V2,V2' ,V4,V5 and V5' are open, whereas the remaining valves are closed.
• the conduits Ll, L5, L2 and L6 are thus connected via the pressure regulators TRl, TR2 to the pressurized gas source (arrow PI) , so that the system is filled with gas.
• the pressure sensors TVl and TV2 cause the valves VI and V4 to close.
• the valves V5 and V5' will close.
• valve V7 When the valves V5, V5' are closed, the valve V7 is opened to the controlled leak S3, and there follows a control measure ⁇ ment (internal measurement) of the tightness between the cha ber Cl exposed to a relatively high pressure and the chamber C2 exposed to a relatively low pressure.
• a possible pressure increase in the chamber C2 is detected by means of the diaphragm of the differential pressure sen ⁇ sor Dl.
• This measuring time period can be kept rather short because a slow, controlled pressure reduction is effected in the circuit L6, R2 by means of the control leak S3.
• the contact co nected to the diaphragm of the pressure sensor Dl closes the associated electrical circuit and lights the signal lamp to indicate internal leakage. In such a case the testing of the test object is concluded and the next test object is tested.
• the tightness test is continued by testing the tightness of each chamber Cl and C2 in relation to the outside, i.e. an external tightness test.
• the valves V5 and V5' are opened during a latively short stabilizing time determined by the time relay
• valve V7 and, after the stabilizing time, the valves V2, V2* , V5 and V5* are also closed.
• EJR! drop in the circuit L2, C2 ⁇ is detected by means of the differential pressure sensor D3.
• a possible leakage (indicat by the respective signal lamp) in each circuit must constitu an external leakage, since these testing measurements have been preceded by an internal tightness test.
• valves V2, V2' , V3, V5, V5 ' and V6 are opened to let out the testing pressure, whereupon the test object can be taken out and be replaced b the next one.
• differential pressure sensors D1-D3 can be replaced by inductive pressure sensors of the kind described in the Swedish Patent specification 7507483-1.
• the two pressure sensors Dl and D3 can be replaced by only one differential pressure sensor operating in both directions.
• vacuum can be used instead of a high pres sure.
• reduced pressures substantially below th ambient air pressure are applied in the two chambers Cl and Then, the chamber Cl or C2 having the highest pressure (clo ⁇ sest to the ambient pressure) is tested with regard to a pos le pressure drop caused by internal leakage to the other chamber.
• the signal lamps may be replaced or supplemented by other indicators and/or control means, e.g.for automatic control o the entire testing operation.
• the valves may be controlled in some other way than electrically.
• separate pres ⁇ sure or vacuum sources may be connected to the high pres ⁇ sure and low pressure circuits, respectively, in which case the pressure regulators TRl and TRl are no longer necessary,

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Examining Or Testing Airtightness (AREA)

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Publications (1)

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ID=20339962

Family Applications (1)

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Cited By (8)

Citations (6)

• 1980
  • 1980-10-24 JP JP55502397A patent/JPH0128329B2/ja not_active Expired
  • 1980-10-24 EP EP19800901978 patent/EP0063113A1/en not_active Withdrawn
  • 1980-10-24 WO PCT/SE1980/000258 patent/WO1982001590A1/en unknown

Patent Citations (6)

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