InterTech M1075 – for unsurpassed leak testing speed and accuracy

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An InterTech Design Report

Our diesel engine mass flow technology shortens test cycle time by finding leaks faster to enhance manufacturing efficiency and process – significantly. Download the full report in a PDF format at:DR129_R1

The Challenge

Develop a production line solution to detect and repair leaks prior to hot testing. Eliminate the possibility of leak-associated defects getting through the system. Deliver accurate results in seconds, while not wasting time and money on hot test repeats.

InterTech M1075 – for unsurpassed leak testing speed and accuracy - using Mass Flow, Pressure Decay & Differential Pressure Testing

InterTech M1075 – for unsurpassed leak testing speed and accuracy

The InterTech Solution

InterTech M1075 dry air tests both the water side and the oil side of an engine block at the same time, up to twice as fast as other available options.

The water side includes engine block passages, water pump, heater housing, thermostat housing, associated hoses and the coolant half of the lube-oil cooler, creating a cavity of about 12 liters. The oil side includes engine block passages plus, front and rear gear fly wall housings, crankshaft seals, oil pan, intake manifold and the oil half of the lube-oil cooler.

This creates a cavity of up to 180 liters depending on engine model. The InterTech testing system avoids problems of pressure fluctuation in the supply line by using isolated air reservoirs. Because it is independent of plant air supply, it provides a direct and stable measurement of leakage.

The InterTech system simultaneously pressurizes both cavities and the reservoirs: the oil cavity to 2.5 psi with a reject limit range of .2 lpm to1.4 lpm (user selectable); and the water cavity to 10 psi with a reject limit of 25 sccm.

Any leakage causes the leaking cavity to lose pressure and the InterTech mass flow transducer reads the flow rate.

 

For a customised quote for your leak testing problems, contact our Indian office in Chennai at 044 – 4211 2525 / +91 994 032 0718 / +91 98409 14544

You may also email our Sales Reps in India at ajay@intertechdevelopment.com / ram@intertechdevelopment.com

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Leak Testing 101 – Part 4

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In parts onetwo, and three of this “Leak Testing 101” series, we discussed three methods of dry-air leak testing—pressure decay, differential pressure decay, and mass-flow leak testing—including the pitfalls and hidden costs inherent in two-step pressure testing methods and the higher accuracy of single point measurement mass-flow leak testing techniques.

 Is mass-flow leak testing always the best leak testing method? Absolutely not. When accuracy and cycle time requirements are not that stringent, pressure decay testing or differential pressure decay testing can be a better application match because test instrumentation does not require as much specialization and related cost. At the other extreme, when very small leaks of less than 0.01 standard cubic centimeters per minute (sccm) must be detected, helium mass spectrometer leak testing methods may be required. It is the only reliable method when an application requires detecting leaks as small as 10–4 standard cubic centimeters per second (sccs) or less.

There are several different helium leak detection methods:

Sniffer—The test item is pressurized with helium and an operator moves a sniffer probe connected to the mass spectrometer to localize the leak. This method is slow, nonquantitative but has the advantage of localizing the leak.

Accumulation—The test item is placed in a chamber and charged with helium. Helium leaking from the part accumulates in the chamber and after a certain amount of time, a sniffer probe checks for the presence of helium, i.e., a leak. While apparently inexpensive, this method has a number of shortcomings: presence of tracer gas from prior tests, lack of adequate circulation in the chamber, and long test times due to background effects. As a result, it will be difficult to provide quantitative testing with this method.

Vacuum leak testing with helium—Figure 1 shows how helium mass spectrometer leak testing proceeds. The part is pressurized with helium and the chamber is evacuated down to less than 0.1 mbar absolute to eliminate background effects. The presence of helium leaking into the chamber is then detected by the mass spectrometer.

Helium Mass Spectrometry Method of Leak Testing

Figure 1: Test item is pressurized with helium within a test chamber. The chmber is evacuated, drawing helium out of the leaking test item. Mass spectromter then samples the vacuum chamber.

Equipment costs, maintenance costs, extra time required to evacuate helium from test fixturing in between test cycles, and ever rising helium costs makes this method the method of last resort. Typical applications include: heating, ventilating, and air conditioning (HVAC) components; pace makers; aluminum wheels; and airbag components.

For these type applications where leaks of 10–4 sccs or less must be detected for product integrity or safety, helium has its well-deserved place in the repertoire of best-match leak test techniques to consider.

In the next part of this Leak Testing 101 series we will discuss miscellaneous other testing techniques including: hydrogen ultrasonic, bubble testing, and air under water.

If you would like specific questions on best practices for leak testing (and other testing topics) answered in future articles, please send me your questions at jhoffmann@intertechdevelopment.com.

 

Note:  The above article has been reproduced from an article written by the author for Quality Digest

 

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Leak testing 101 – Part 1

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Not too long ago, when you wanted a product to be leak-proof, you simply put it under water, made sure it didn’t bubble, and thereby concluded there were no leaks. Such “bubble testing” takes time and depends on the operator’s ability, making it totally inappropriate for the modern production environment. Also, it doesn’t generate the quantitative measurements that are the lifeblood of quality assurance engineering.

Dry-air leak testing methods—some of which can detect leaks as small as 0.01 standard cubic centimeters per minute (sccm)—are the methods most commonly used today by a wide range of industries—from medical devices, to automotive, to appliances, and aerospace, among others. These dry air methods enable quality managers to define leaks quantitatively.

“No leaks allowed” standards are concepts of the past. There are a variety of dry air leak test methods and best-practice techniques for each type of method, which will enable compliance to ISO 9001 and comparable quality management standards to be achieved. Generally speaking, these dry air leak test methods include;

  • Pressure testing
  • Differential pressure-decay testing
  • Mass flow leak testing

In addition, tracer gas testing and especially helium mass spectrometer leak testing, are used in more demanding applications where leaks as small as 10-5 standard cubic centimeters per second (sccs) must be detected in a production environment. If one truly understands leak testing application requirements and best practice techniques for these various leak test methods, the selection of which type of testing to perform is a rather straightforward matter.

The first step in designing a leak testing solution is to correctly define what the leak limits are. Leak testing applications laboratories begin with an engineering analyses of a specific application to determine and quantify how much a product or component can leak. Often, correlation studies are performed to verify if it is possible to use dry-air test methods instead of hydraulic fluids. Sample parts are tested as part of an initial engineering analysis. These determine the production requirements and leak standards to be achieved so that quality engineering of test solutions can begin. The first step in this process is to select the leak testing method that is the best match to application requirements.

In this “Leak Testing 101” series we will discuss the various dry air leak testing methods and the issues and techniques that affect testing costs and gauge repeatability and reproducibility (GR&R).

First, let’s take a look at the pros and cons of pressure-decay testing.

The big plus of pressure-decay testing—or at least the thought behind it—is that the leak detectors for pressure-decay leak testing have the lowest upfront cost. It is probably for this reason that the method is still in use, although in many applications the real costs of pressure-decay testing are actually much higher than many realize.

In the pressure-decay method for leak testing (see figure 1), a part is pressurized, the test circuit is isolated, and the pressure drop associated with a leak is measured. A transducer reads the pressure change. Calculations then convert these time/pressure readings into a measure of leakage rate. The higher costs of pressure-decay testing stem from the difficulties inherent in the test methodology. Pressure-decay leak testing is relatively difficult because measurements are highly vulnerable to changes in testing conditions such as drafts or temperature and there are often difficulties in determining the volume of test parts and test circuits, which must be known in order to calculate results.

Pressure Decay Method of Dry Air Leak Testing

Pressure Decay Method

Also, pressure-decay leak testing requires two measurements of pressure with sufficient elapsed time between measurements. When speed of testing is an issue, this built-in delay makes the pressure-decay method less desirable. More important, the two measurements and the time lapse significantly increase the potential for measurement error. The amount of time you need to wait between measurements varies. Sometimes, long intervals between measurements can make for extreme accuracy, but these long wait times are typically not practical. The larger the part volume, the longer it takes to measure the pressure drop. Moreover, very large flows are also impractical with pressure decay, because when pressure drops very fast, it will probably not be measured accurately.

Thus, although pressure-decay leak testing instruments have a relatively low upfront cost, the extra time it takes to perform testing (if the results are reliable enough for the given application) is another expense that needs to be factored in to overall cost. It can still be the best leak test method for a specific application, but the trend lines are in the other direction. Most applications now require tighter GR&R even for very low leak rates, often with large volume parts, and with a desire to keep test cycle times to the bare minimum to cut overall testing costs.When you factor all these considerations in, it often leads one to use other leak test methods instead.

In the upcoming issues of this “Leak Testing 101” series I will discuss differential pressure-decay testing, mass-flow leak testing, temperature compensation issues, and many other topics. By the conclusion of Leak Testing 101, my goal is to bring all quality managers up to speed on the real factors that affect leak testing cycle times, costs, and reproducibility.

If you would like your specific questions on best practices for leak testing (and other testing topics) to be discussed in future articles, please leave your comments and suggestions in the Comments area below.

ABOUT THE AUTHOR

Jacques Hoffmann’s picture

Jacques Hoffmann

Jacques Hoffmann is founder and president of InterTech Development Co., a world leader in test-centric assembly specializing in automated leak and functional testing with mass flow, hydraulic, helium, or pressure decay technology (ISO-17025 accredited). InterTech Development Co.-engineered solutions are used by hundreds of quality management, product design teams, and manufacturers worldwide and the company’s worldwide support organization maintains offices in North America, Asia, and Europe.

Note:  The above article has been reproduced from an article written by the author for Quality Digest

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Real Time Monitoring Software

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For Optimizing Test Conditions In Leak Testing Applications

Real Time Monitoring software for optimizing test times and isolating problems in leak testing applications is now available from InterTech Development Company, arguably the world’s leading authority on test-centric assembly specializing in automated leak and functional testing. InterTech’s S3085 monitoring software helps provide users with the means to show real time traces of how their test instrumentation transducers are performing versus actual cycle times.

The InterTech S3085 Software enables data transfer between a PC and test instrumentation and can display test records from up to 8 InterTech M-10×5 test instruments. It has the facility to automatically calculate R&R percentages based on the number of trials performed. All data can be saved in a Microsoft Excel™ spread sheet file format, facilitating SPC analyses. Data can also be viewed on a monitor including data, shift, channel and test status. Fully Windows compatible with the ability to record two million test records, InterTech’s S3085 monitoring software costs US $1800.

Jacques Hoffmann, President and Founder of the worldwide InterTech Development Company comments that InterTech’s S3085 monitoring software provides users with the means to better understand and assess complicated testing phases in their applications in a real time manner. Hoffmann says, “Through InterTech’s leading edge approach to leak testing applications worldwide, we saw the need for software tools that could enable users to intuitively diagnose issues with their testing process through real time graphical displays, and this is why and how the InterTech S3085 monitoring software came to be developed.”

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Test-Centric Assembly

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Uptime Optimization Services

18 station chassis optimized for test centric assembly

Machine builders, automotive component manufacturers, and others seeking faster test-intensive assembly operations can now access InterTech Development Company’s Uptime Optimization consulting services that detail how to incorporate on-line calibration and validation of test technology, automation of temperature compensation during testing, and similar engineering that minimizes or eliminates previous needs to shut down test-centric assemblies for recalibrations. InterTech Development Company engineers estimate that a combination of solid state capabilities for online recalibrations can eliminate up to 60 minutes of assembly downtime in each 8-hour shift using machines with leak testing stations.

Jacques Hoffmann, President of InterTech Development Company comments that many assembly operations are straddled with mechanical type calibration and validation processes that are now obsolete. Hoffmann says, “Machine builders that are adding test technology as a secondary consideration in a larger assembly often do not know that they are using substandard leak testing technology that slows down production processes. One of the more straightforward ways to optimize production uptime is by adding electronically self-calibrating leak testers that automatically validate entire test systems while they are in operation. Another method is by using technology that can automatically adjust testing and interpret results correctly for parts testing at different temperatures, such that cooling of recently cast parts isn’t necessary. These are some of the ways in which InterTech Development Company can help machine builders and assemblers re-engineer processes to eliminate downtime.”

The world’s first production line leak detectors featuring electronic technology for self-calibration and system validation (CalVal) were introduced to assemblers by InterTech Development Company in 2004. Automated Temperature Compensation was developed and introduced by InterTech Development Company in 1995.

InterTech Development Company is a world leader in test-centric assembly specializing in automated leak and functional testing with mass flow, hydraulic, helium, or pressure decay technology (ISO-9001-2000 International Standards for Quality Management). IDC-engineered solutions are used by hundreds of automotive components manufacturers worldwide, among other assembly-intensive manufacturers. InterTech Development Company’s worldwide support organization maintains offices in North America, Asia, and Europe.

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