Finding Leaks in Your Vacuum Furnace – Part X

In our previous post on inert gas leaks, we discussed the causes and effects of both external and internal inert gas leaks in relation to the vacuum furnace, such as part discoloration. Today, we will discuss how to determine whether the furnace or the pumping system is the root cause of any vacuum-related issues.

All too often, we start to experience outgassing, dirty parts, performance issues, etc. and immediately assume there is something wrong with the furnace. While it’s true that the furnace can be the source of the problem, sometimes there’s actually something wrong with the capabilities and performance of the pumping system.

pumping system

For example, you may know that the furnace frequently outgasses when it’s heated. To put this into perspective, think of the furnace as running on a scale of 1 to 10. When the normal load is outgassing, the scale goes up to a 4. So you run this process a thousand times and it always gets up to 4 out of 10; however, all of a sudden, it’s going up to 9.

Your first instinct might be to blame the furnace and assume that there must be a leak as the outgas load is significantly higher than it used to be and the parts are coming out dirty. While it’s true that there could be something wrong with the furnace, you don’t want to waste valuable time going through all of the steps of leak checking the furnace only to be unable to figure out what’s wrong because the real problem could be the pumping system.

What could actually be happening is that the pump isn’t tolerating the normal percentage of outgassing as fast, resulting in the percentage reaching higher levels than you’re accustomed to seeing. In addition, the parts per million (PPM) of exposure of the parts to contamination is a higher percentage for longer periods of time. As a result, you are seeing dirty work come out of the furnace, but the real culprit isn’t the common suspects – the furnace, process or braze alloy – it’s the pumping system, which just isn’t doing its job correctly.

So how do we determine which is the true guilty party – the furnace or the pumping system?

For this situation, imagine the furnace and the pumps are children. When they do something wrong, you need to separate the two and go after the one most likely to confess to what they did (i.e., the easy one) first. In this case, it’s the pumping system.

Step 1: Make sure the pumps are doing their job. Determine this by leak checking the pumps, as well as doing blank-off performance testing, flow testing, etc.

Step 2: If the pumps pass the necessary tests, then it’s time to take a look at the furnace. Only once you have ruled out the pumping system as the potential culprit should you move onto leak checking the entire furnace.

Step 3: If both the pumping system and the furnace pass the necessary tests, then the next recommended step is to question the validity of the vacuum gauge system. Are the sensors calibrated? Dirty? Not presenting accurate vacuum data?

If you encounter a situation where you require further information or assistance, please call Ipsen’s Aftermarket Support Helpline at 1-844-Go-Ipsen (Toll Free: 1-844-464-7736; International: +1-815-332-2530) or email

In our final post in the series, Finding Leaks in Your Vacuum Furnace – Part XI, we will discuss the different leak detection methodologies that can be utilized.