Overview of methods for leak testing in APT

APT deals with various areas from the test and Testing technology. Some of these areas require certain physical background. In the following, Test methods and systems used with their primary use (Leakage testers and flow testers for compressed air) and vacuum).

Application	PMD02-Relative pressure system	PMD02-Differential pressure system	PMD02-Massflow system	PMF01-Massflow system
Testing	Differential pressure measurement in closed test volume The loss of pressure or increase of pressure is measured Continuity test of drilling's Result output in pressure per time or volumetric current per time	Differential pressure measurement in closed test volume The loss of pressure or increase of pressure is measured Continuity test of drilling's Result output in pressure per time or volumetric current per time	Pressure overflow and flow out with big cross sections from buffer volume Measurement of the flow out mass flow Result output in mass flow per time	Flow out by using a precision pressure regulator at the pressure supply Measurement of the flow out mass flow Result output in mass flow per time
Execution	1 channel to 4 channel instruments Autonomous test channels Over pressure and vacuum (also combinable) Different pressure ranges	1 channel to 4 channel instruments Autonomous test channels Over pressure and vacuum (also combinable) Different pressure ranges	1 channel to 4 channel instruments Autonomous test channels Over pressure and vacuum Different pressure ranges	1 channel to 8 channel instruments Only coherent check is possible Over pressure or vacuum Different pressure ranges and different flow ranges possible
Sensoric	Relative pressure sensor: Resolution 10 - 100 Pa, dependent of the pressure range Relative pressure sensor / regulator: Different ranges (Vacuum, 100kPa, 600kPa, 800kPa and others)	Differential pressure sensor: Resolution 0,1 Pa, Range -350...+3500 Pa (others possible) Relative pressure sensor / regulator: Different ranges (Vacuum, 100kPa, 600kPa, 800kPa and others)	Massflow sensor: Resolution max 0,001Nccm/min, Ranges 4, 25, 50 or 100Nccm/min (others possible) Relative pressure sensor / regulator: Different ranges (100kPa, 160kPa, 600kPa, 1000kPa)	Massflow sensor: Resolution max. 0,0005Nccm/min Ranges from 20Nccm/min to 100Nl/min Relative pressure sensor / regulator: Different ranges (Vacuum, 50kPa, 100kPa, 400kPa, 1000kPa and others)
Ranges of application	Leak testing in smaller to middle test volumes with short to middle cycle times Test of drillings Fully automatic, semiautomatic and manual applications Examples: Test pieces with greater limits	Leak testing in smaller to middle test volumes with short to middle cycle times Test of drillings Fully automatic, semiautomatic and manual applications Examples: Cylinder head, water pump, oil channels, oil pumps, lids, dust covers etc.	Leak testing in middle to big test volumes with very short to middle cycle times Fully automatic, semiautomatic and manual applications Examples: Oil room without pressure, crank cabinet, to suction pipe (metal or plastic), oil pans, complete engines, complete gears etc.	Flow check with bigger throughput Function tests Fully automatic, semiautomatic and manual applications Examples: Valve seat check, oil drilling check in crankshafts, cross section check in drillings and lines, easy leak testings etc.
Comparative considerations	Bigger test volumes: Only interesting for bigger test pieces with greater leakage limits and a longer test cycle time. Smaller test volumes: Possible using with small test pieces and greater leakage limits and a longer test cycle time. Result Ideal for precision measurements with small test pieces and longer test cycle times. For bigger test volumes only to a limited extend usable.	Bigger test volumes: Test volume: oil room of a complete engine Volume = 20000ccm Test pressure = 20kPa Cycle time = 25sek Measuring time = 5sek Dispersion of the overall 5Pa => min. leakage = 11,9ccm/min Test volume: plastic-suction pipe Volume = 2800ccm Test pressure = 200kPa Cycle time = 35sek Measuring time = 5sek Dispersion of the overall 5Pa => min. leakage = 1,7ccm/min Smaller test volumes: Test volume: water room of a cylinder head Volume = 800ccm Test pressure = 200kPa Cycle time = 20sek Measuring time = 5sek Dispersion of the overall 5Pa => min. leakage = 0,5ccm/min Result Ideal for precision measurements with small test pieces and short test cycle times. For bigger test volumes only to a limited extend usable.	Bigger test volumes: Test volume: oil room of a complete engine Volume = 20000ccm Test pressure = 20kPa Cycle time = 15sek Measuring time = 1sek Dispersion of the overall 0,1ccm/min => min. leakage = 1,2ccm/min Test volume: plastic-suction pipe Volume = 2800ccm Test pressure = 200kPa Cycle time = 20sek Measuring time = 1sek Dispersion of the overall 0,6Nccm/min => min. leakage = 1,7ccm/min Smaller test volumes: These processes brings with test volume less than 1,000 to 1,500 ccm no lasting advantage. Here, hence, it is not mostly used. Result Ideal for precision measurements with bigger test pieces and short test cycle times. For bigger test volumes only to a limited extend usable.	This application can be used either in bigger test volumes with very long cycle times (> 30-60sek) or in very small test volumes with very short cycle times (<10sek). Result The insertion in normal leak test tasks is possible only partly. Because all test channels work parallel, bigger leaks on one channel influence the other test channels. The ability for reproduction depends very strongly on the application. It is reached with very small leaks not the precision of the PMD02 system.
Cost comparison	Exact standard application for an affordable price with many functions.	Exact standard application for an affordable price with many functions.	Exact standard application for the approx. 1.5-fold price of the differential pressure application.	Inexpensive multi channel solution for easy test tasks.

Differences in the leak test: PMD02 and PMF01 in comparison

Our leak test and flow meters are suitable for different processes and applications. A leak test with the relative pressure, differential pressure or mass flow method can be carried out without any problem with our PMD02 series leak test devices. The device has one to four autonomous test channels. Depending on the test method chosen, the respective sensors differ with respect to the possible pressure ranges. The PMF01 flowmeter also works with the mass flow principle, but does not achieve the precision of the PMD02 in the case of smaller leakages because the test channels work in parallel and influence each other.

The comparison of the individual test methods reveals that the relative pressure method is particularly suitable for small test volumes, but the test times are relatively long, in contrast to the differential pressure method. Both methods are only conditionally applicable for larger test volumes. In this case, the mass flow method is the right choice. In a short test time, precise measurements can be carried out with the PMD02.

Conclusion: Our leak detector PMD02 is a cost-effective and precise standard application and offers you an extensive range of functions. For simple test tasks, our PMF01 flow-through tester is particularly suitable as a cost-effective multi-channel solution.

APT finds the right method for your leak test.

If necessary, it is always sensible to present the test task with all boundary conditions. Do you have any questions about leak test? We stand by you as a professional consultant and find the right procedure for you. We select the appropriate test technology for your requirements and determine the optimal cost-benefit strategy. Take advantage of our competence and get in contact with us!

Note: Please note our test conditions!

Importand

The compressed air supply should follow for all test systems in DIN ISO8573-1, the following classification:

Particle class 2 (<= 5µm)
Water class 3 (pressure dew point -20°C)
Oil class 2 (<= 0,1mg/m³)

For pollution by liquids or solid particles in the pneumatic circuits and the resulting damage to the pneumatic components and damage the pneumatic components by applying an external pressure on the test item connection no warranty or liability is accepted. This also applies for any consequential damages in test or test parts.

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