A fuel tank is a secure container used for storing flammable fluids. The term fuel tank is typically used for the part of an engine in which the fuel is stored and is later propelled or released to feed the main engine. The tanks differ largely in size and complexity. You can find tanks varying in complexity from small plastic tanks for butane lighters to external multi-chambered cryogenic space shuttle tanks.
Leak testing of fuel tanks can be complex as the pressure of the test part has to be critically observed. Improper monitoring may result in the complete damage or partial distortion of the tank. The water dunking test is also used but it may cause damage to metal tanks with rusting and the volume of fuel tanks is too large for air decay tests. So the Helium leak test is commonly used for leak testing.
Many companies like Mikro Innotech build innovative and customizable leak testers that suit your fuel tanks.The general steps that are followed by them for the Helium leak testing of fuel tanks are:
- The fuel tank is mounted on a supporting cradle and placed in the chamber of the tester. The chamber usually has shielded safety doors that do not allow the Helium to escape out.
- Once the doors are secured the chamber and test tank are pumped down or pressurized to a pre-set pressure and the tank is isolated from the chamber.
- The pressure of the chamber is further reduced and during this time the pressure in the tank is monitored to check for gross leakage.
- Once the chamber pressure comes down to the desired value helium is introduced into the test tank and allowed to disperse.
- After a certain time, the chamber is sampled for Helium leakage using a mass The spectrometer measures the Helium in the sample and gives the size of the leak.
- Some leak testers have the provision for probes and sniffer probes can be used to locate where the leak is in the tank.
- Once the tank has been tested both the tank and chamber are evacuated.
The typical specifications of a 75-litre plastic fuel tank for leak testing are:
Throughput: 48 seconds
Test Pressure: 3 psi (200 mbar)
Helium Usage: 8000 tanks/ standard cylinder (i.e. one standard sized cylinder can be used to test 8000 tanks)
Pass/Fail Limit: 0.1 mm³/sec (10-4 mbar/sec)
Some Helium leak testers have additional features like tracer gas reuse and recovery systems that ensure that only a small amount of the gas is wasted. The sensitivity of these testers is equivalent to the water dunk test. These tests are highly sensitive, fast and reliable. Since the testing is done with Helium gas it is completely dry and does not cause any water damage to the fuel tank. You also do not incur any additional drying costs to dry the inside of the tank thoroughly. Mikro Innotech offers completely automated leak testing machines for fuel tanks. These systems are suitable for the testing of both metal and plastic tanks.