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  • Periodic Reporting for period 1 - LeakFree (Development of a reliable quality control system using advanced Non-Destructive Evaluation (NDE) technologies for the production environment of leak-free fuel tanks from plastics and composites)

LeakFree Report Summary

Project ID: 673155

Periodic Reporting for period 1 - LeakFree (Development of a reliable quality control system using advanced Non-Destructive Evaluation (NDE) technologies for the production environment of leak-free fuel tanks from plastics and composites)

Reporting period: 2015-06-01 to 2016-02-29

Summary of the context and overall objectives of the project

There is an increasing demand by consumers towards more fuel-efficient cars and the car companies respond to this demand through the development of plastic car components. Over the years, the usage of Plastic Fuel Tanks (PFTs) has dominated over steel tanks as they offer numerous advantages such as lower weight, higher corrosion resistance, improved fire resistance, recyclability, lower total system costs, better crash performance and improved waste disposal.

The LeakFree project aims to develop a low cost leak detection technology that will be fast, accurate, traceable and automated to be applied within mass production environments. Major factors in automotive industry are security, protecting the environment and quality assurance. Therefore, suppliers to the industry must adjust themselves to the high quality assurance systems. The solution in the project will be primarily developed according to the needs and requirements of the fuel tanks production industry.

Since the leakage from the fuel tanks is a major concern for the industry, the fuel tank producers should make 100 % leakage tests after production. There are many different methods of detecting leakage from the tanks. However, the complexity and high cost of some systems make it not feasible. Although leakage detection of fuel tanks is a major issue in automotive industry, there is no consensus among the OEM’s how to detect leakage. There is not a standard measuring system of detection, making every supplier take a different road.

Leakage inspection of fuel tanks in automotive industry is mostly done by pressurizing the tank to 0.3 atm and

a) Monitoring the pressure drop in the tank after it has reached pressure equilibrium
b) Monitoring the airflow into the tank, after it has been pressurized to 0.3 atm., which shows leakage
c) Monitoring the evolving bubbles from the tank, which has been dived into water, by trying to see the bubbles, with human eye.

Monitoring pressure drop in the tank and monitoring airflow into the tank after pressure equilibrium is not precise for plastic tanks, as the expansion of plastic makes it hard to distinguish if the pressure drop in the tank / air flow into the tank is caused because of leakage or because of material expansion. The traceability and accuracy need of the automotive industry is not fulfilled if the bubbles from the tank dived into the pool are inspected manually by subjective judgement of the QC operator, which very much is effected by their physical conditions and fatigue-level.

The LeakFree project aims to develop a low cost leak detection system in a nutshell that will be fast, accurate, reliable, reproductive, with data acquisition to the supplier’s QC and logistics ERP system, making the data produced traceable. It should also be automated within mass production environments. The solution will be primarily developed according to the needs and requirements of the automotive industry and their fuel tanks suppliers. The system will be feasible to buy and to use for the suppliers to the OEM’s.

The LeakFree system’s philosophy is to listen to the bubbles evolving from pressurized tank dived under water using hydrophones. For this, precise hydrophones should be placed into the pool where the pressurized tank rests for a certain time, listening to bubble noises. Environmental sound should be filtered out, to have an accurate, reliable and reproducible result.

A software is to be developed to communicate the results of the leakage detection system with the ERP system of the company. The tank to be tested, the QC personnel making the test, the pressure, the time, the result – leaking / not leaking – barcode for the result shall be controlled by this software.

Some hardware shall be constructed to make the tests possible. For this:

1) An automated, diving system of the tank to be tested into the pool is to be constructed. This system shall be able to test tanks of various sizes. As the tanks vary between 20 to 500 liters, this requires careful planning of the diving system. The system is to be fast enough, to fulfill the capacity needs of the manufacturer.

2) Welding systems for plastic parts, to weld to the other plastic parts, sensors and accessories airtight to them. The welding parameters are to be adjusted to achieve parts accepted as “airtight, by mostly the automotive industry. These welding parameters are time, temperature, distance, pressure.

As there is no standard / common regulation for the leakage detection system of fuel tanks in automotive industry, the most important aim will be to persuade various OEM’s on one single system, meaning LeakFree system, which will elevate many weaknesses of the conventional systems used. As Floteks is producing for many OEM’s, using all the leakage detection systems a) b) and c) mentioned above, the dissemination of the acoustic detection of leakage system will rather be easy, if the project achieves its goals when completed.

The development of an automated hotplate and spin welding is also a side product of this project and if a perfect welder is developed, it can have a chance in the market for rotomoulders, mostly in automotive business.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Work Package 1 and most of the jobs in Work Package 2 is done and so far 2 Deliverables are submitted, namely :

1. Specification Document of the LeakFree system (D1.1),
2. Leakfree Hardware System Components (D2.1).

3 project meetings were held at Floteks premises by the participation of Brunel and IKH technical personnel and every aspect of the project was discussed thoroughly. The Meeting Notes are attached as PDF files.

In the first 2 months of the project, “Technical and Operational Specifications of the LeakFree System” is decided after detailed analysis of the tanks and the production environment at the Floteks production grounds was made.

After the Specifications were clarified, than “The LeakFree demonstration and validation phases” were planned.

The Design and development of the Hydrophone array was done by BIC guided by Floteks. Development of the leakage detection algorithm is done by BIC again with tests on the ground, Floteks production area and laboratory.

In order to accomplish all these,

A) Welding equipment for welding the accessories of different Polyethylene types (HDPE, LDPE, LLDPE, each with different MFI’s and Densities) to the rotomolded articles is designed and assembled. There were 4 types of welds to be prepared and tested, 1) Automatic Hotplate welding 2) Automatic Spin welding 3) Manual hot gas welding d) Manuel extrusion welding. The reason for welding is to check the leakage after welding the parts together, using different parameters of welding technology.
B) The main pool for diving the welded parts into and preparing the environment for measuring the sound caused by the leaking bubbles is constructed.
C) Automatic pressurizing and diving system with special mechatronics hardware and software is prepared to sink the welded parts into the pool by controlling all the parameters, which also contained the hydrophones brought and adjusted by Brunel Innovation Center.

BIC has accomplished,

A) Designing the sound tracking system for bubbles
B) Choosing the suitable hydrophones for listening to the evolving bubbles, if any leakage
C) Connecting the hydrophones via interfaces to a computer, to collect data
D) After collecting the data for bubbles and of the environmental sounds, filtering out the unwanted noise, to detect the bubble sound, tried to measure the bubble noises evolving because of different sized holes. For this, different injectors were used,

by the guidance of Floteks.

IKH has accomplished,

A) The project web page,
B) The software coding of the developed algorithm. The software is being developed based on the principles of Object Oriented programming.(OOP)
C) Two way data communication between Floteks ERP system and the control software; this was implemented under the guidance of Floteks.
D) Communication of the Leakfree software with the automatic diving system.

Summary of the results achieved:

Until the first meeting in Bursa, Floteks had started developing the automatic diving system and the necessary pool. The pool constructed was of transparent 15 mm thick Polyacrylic plates, glued together and sealed leak-free with silicone. The tests were made for 3 days in the laboratory environment of Floteks and the bubble detection was successful. However, after BIC has measured the environmental the sounds from the factory, it was observed that the sounds in factory conditions would not allow a precise Leak detection. So, the Leakfree team has decided that the pool had to be soundproof, to get better results. This soundproof pool was to be constructed by Floteks, till the next meeting in March, again in Floteks / Bursa. During the first meeting, IKH, Floteks and BIC have discussed the software issues as well, giving IKH details of the program they have to write, to have the Leakfree system communicate with the ERP system of Floteks. The discussions needed to proceed, as the info given to IKH at the first meeting was not sufficient. The preparation of the web site for Leakfree, which is the IKH’s responsibility, was also discussed during the meeting. It was decided that the web site had to be ready within a few weeks after the first meeting.

The second meeting was held in March 2016. By that time,

1) Prepared the soundproof pool to dive the plastic products to be tested.
2) Prepared the sample products to be tested
3) Assembled and prepared the Extrusion welder, hot gas welder, hot plate welder and spin welder functioning, with some minor points still missing.
4) Finished minor missing points of the automatic diving system

1) Provided new hydrophones for testing
2) Provided new amplifier for 3 channels
3) Worked on filtering the factory sounds
4) Worked on a better and more precise algorithm for detection,

1) Developed the web page for the Leakfree Project,
2) Worked on establishing the overall architecture of the Leakfree software,
3) Incorporated the leakage detection algorithm to the software,
4) Worked on the interface of the Leakfree software with Floteks’ ERP system,
5) Worked on the interface of the Leakfree software with the automatic diving system.

The tests during the second meeting have shown that
a) The soundproof pool prepared was rather successful, but needed a better lid to close automatically during test period.
b) Filtration of the factory noises was successful to detect the bubbles evolving.
c) The bubbles evolving from different injectors were measured, so that the computer would be able to analyze the hole diameter causing the leakage.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The tank suppliers to the automotive industry today are using mostly the system of pressurizing their tanks under water, then watching the building and escaping of the bubbles. The work done up to now for Leakfree shows that as planned, the bubble formation does not need to be seen; it can be detected by hydrophones, after filtering out the environmental sounds. The data coming from the hydrophones through amplifiers to the computer can be filtered out and single bubble formation can be detected as graphical peaks on the screen, also interpreted by the software. As a result, this interpretation will be sent to the ERP system of the company, with data required by the automotive company, a pass / no pass barcode will be produced by the system thus the quality control becomes human independent, on the contrary to today’s common approach.

The hot plate welding and spin welding stations under development are also above the common practice today, although the system partially exists today. In the hotplate and spin welding station, a software has been developed, where the time, temperature, heating pressure, welding pressure and the distance traveled of the parts can precisely be adjusted via Mitsubishi PLC’s. The more developed hotplate welding machine constructed can also position the product and the accessories to be welded correctly so that the welding is quality assured. This is of utmost importance, as the accessories to be welded are more expensive than the tank itself and if the scrap rate of welding is high, Floteks (or any other company doing welding) will get high reject costs. Besides, achieving a perfect quality assurance could mean that the 100 % leakage tests may become obsolete in the future. For this, currently many tests have to be done.

The March meeting has shown that almost all the hardware is ready to be used in the production, except for a few corrections on soundproofing walls of the pool and fine adjustment of the automatic welding stations, to weld leakfree specimens.

Related information

Record Number: 190281 / Last updated on: 2016-11-14
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