Finding the unseeable

When leak testing a component, measuring airflow is more accurate than backpressure sensing or continuity pressure testing. Backpressure sensing only detects blockages that are greater than 70%, and continuity pressure tests detect 99% or complete blockage. Involve Test & Control Inc. (ITC), a Shelby Township, Michigan-based designer and builder of leak test systems, relies on Flow Testing Technology and its VICATS flow test systems to detect obscure obstructions in critical coolant or oil passages of cast, machined, or molded components.

In 2005, a leading automotive manufacturer asked ITC engineers to find out why engine blocks and heads in a pre-machined state were not flowing properly. Conventional borescope testing was not detecting the problem location because invisibly small obstructions were streamlining the flow rates. ITC worked with the manufacturer, pioneering a flow test process with fixturing and automation to measure the restrictions and to see their effect on component performance.

Al Pike, vice president and general manager of ITC explains, “ITC is really one of the only leak test systems builders that have developed proven flow testing technology. Flow testing measures airflow and compares it to upper and lower flow limits, detecting parts with partially restricted passages that ultimately can cause problems for a customer. This analytical flow statistical analysis is truly a different approach to finding restrictions. With our VICATS system, users can detect down to a 2% restriction by measuring the actual airflow – critical for today’s complex heads and engine block water jackets.

“Our systems use shop air, set at very low-test pressure to accurately measure airflow in smaller passages. When testing large passages, the systems use an on-board air supply, minimizing noise and large consumption of plant air,” Pike adds. “We have designed and built successful flow test systems for transmission output shafts, transmission housings, front timing chain covers, cylinder blocks, cylinder heads, and exhaust manifolds. But the technology is now being tested for detecting broken drills and taps as well as detecting internal flashing or fin issues and even core and sand breakages.”
 

Detecting obstructions

One of ITC’s early flow testing applications involved the detection of coolant passage flow in automotive engine front covers. Figure 1 (page 46) shows how airflow is measured in the coolant neck, A, through the coolant pump passage and the coolant pump outlets C & D. The system detects flow restrictions by measuring airflow through an oil pump inlet, H, and from an oil pump outlet, F. In proving out the process to the customer, a borescope showed the unobstructed and obstructed flow conditions.

Recently, ITC used flow-testing to find obscure obstructions in integrated aluminum exhaust manifold cylinder heads. The combination head/manifold has become a preferred design by automakers to reduce weight and the number of components as well as improve packaging space. Performance advantages are improved head airflow, exhaust airflow, and emissions from locating the catalytic converter closer to the engine exhaust. However, added issues related to optimum air and coolant flow arise in what are now more complicated passages in one part.

ITC engineers were tasked to provide a testing system that could flow-test the water jacket passages in a partially machined head/manifold at desired production rates. The ITC VICATS-LTS, visual control and test system is a cost-effective leak and flow test system that provides fast cycle times with high repeatability and accuracy. Integrated fixture control eliminates the need for a programmable logic controller (PLC) and human machine interface (HMI).

It has multi-part flexibility for use with several fixtures and can easily integrate with a PLC for larger, more complex applications. It can be applied for electable mass flow or pressure decay methods as well as the ability to provide precision production flow testing.

Involve Test & Control Inc. (ITC)
www.itc-leaktest.com