Source: Solar Atmospheres
Keep that furnace running! Obviously, a furnace leak can be quite counterproductive and make it troublesome or even impossible to keep it going. What can be done? Thankfully, there are several solutions. This best of the web article gives helpful measures in defining leaks, detecting leaks, solutions for effectively stopping a leak, and much more.
As you move through the post, you'll encounter a tutorial that starts with the basics. A furnace leak if defined with differences described between a normal leak and something such as an outgassing problem. Then, other information is presented with descriptions on the rate of the leak and possible locations for said leak. The article continues with methods for leak checking and wraps up with a check list of sorts for vacuum furnace users.
An excerpt:
Some operators or leak checking personnel will often use a stethoscope when checking for leaks, as its ability to transmit low-volume sounds and eliminate external noise is exceptional. Often in gross leaks or some smaller leaks, a standard paint brush and soapy wash solution is helpful. Brush the solution around suspected leak areas. Big leaks will blow big bubbles at the leak while smaller leaks will form very fine foam.
Read more: "Vacuum Furnace Leaks and Detection Techniques"