Helium Leak Testing Services

 

Helium Leak Testing Services

As a vacuum heat treater, Solar Atmospheres is ever cognizant of the integrity of its vacuum chambers. As a routine, a “leak-up” is performed on every vacuum furnace. Helium leak testing services involve pumping the furnace down to a deep, or “high” vacuum level (about .01 microns of mercury (µHG residual gas) and isolating the chamber from the pumping system. Bear in mind, room pressure is about 760,000µHG. The vacuum level is then monitored via calibrated gauge and a “rate of rise” is determined as a rate per hour. The usual requirement for the helium leak testing service is for the vacuum to deteriorate no more than 20µHG per hour. As a perspective, if a furnace has a leak of this size, and the leak rate was linear, it would take a furnace over four years to leak up to room pressure! If the leak rate is determined to be higher than this, a helium mass spectrometer may be used to detect the leak. This involves connecting a helium mass spectrometer to a furnace and releasing helium gas around the outside of the furnace in the suspect area. If a leak is present, the helium passes through the leak, into the furnace chamber, and is subsequently detected by the unit. In reality, the helium mass spectrometer is capable of detecting leaks far smaller than what is required to produce an effective vacuum heat treatment process.

The Value of Helium Leak Testing Services

The helium leak testing services are very sensitive. Therefore, it is a valuable test in searching for leaks in brazed assemblies. After brazing, an assembly is placed directly on the unit and the unit’s pumps evacuate the area within the assembly to the necessary low vacuum level. Helium gas is then released around the outside of the assembly. If a leak is present, the unit alarms and the leak point identified. With standard helium leak detection equipment a leak rate as low as 1x10-9 cc/second can be detected.

Vacuum technology is a complex technology. Understanding the laws of gas and the nature of leaks is critical in detecting and preventing them. The ultimate goal is to add as much value as possible to the vacuum heat treating experience at Solar Atmospheres.