Do Mechanical Seals Leak?

To answer your question simply, yes. All mechanical seals leak. There is simply no way around it. However, there is more to it than that.

Continue reading to learn more about how mechanical seals work, why they leak, and why these “managed leaks,” as they are called, are important to your pump’s performance.

What Is a Mechanical Seal?

Mechanical seals are used to contain fluid within vessels (typically something like a centrifugal pump) that features a rotating shaft that passes through a stationary housing (or sometimes it’s the opposite and the casing rotates around the shaft).

When sealing a centrifugal pump, the goal is to prevent large volumes of fluid from escaping when the rotating shaft enters the “wet” area of the pump. The seal is put in place between the pump shafts and the pump housing to achieve this goal.

The sealing needs to be able to contain the pressure created by the pumping process and withstand the friction caused by the two components rotating against each other.

What Is a Managed Leak?

All mechanical seals leak. They actually have to in order to maintain a fluid film over the entire mechanical seal face. This mandatory leakage is what is referred to as a managed leak. Managed leaks are completely different from outright mechanical seal failure, which is one of the leading causes of pump failure.

The leakage from a managed leak is extremely low. For example, the leakage in a hydrocarbon is measured by a volatile organic compound (VOC) meter in parts per million. Needless to say, it’s almost negligible.

However, some leaks are more harmful to humans and the environment than others. If a leak could pose a threat to the surrounding environment, it is crucial that the leak is maintained as effectively as it can be.

For instance, a hydrofluoric acid leak is obviously an environmental issue, so leakage can be very damaging. The same goes for propane. Propane is very flammable, as it is liquefied natural gas, so an excessive amount of leakage could end up causing an explosion.

In these more dangerous cases, we would recommend that you resort to a seal-less design for the pump that prevents any fluid from ever leaking out. Our solution would be to use a magnetic drive, which prevents any fluid from coming into contact with the atmosphere at all.

The application of the pump has to be taken into account as well. Some fluids are much more difficult to seal than others. For example, crude oil is very slick and lubricating, making it much harder to seal effectively than something like water. Water is non-lubricating, so it’s much easier to seal.

The important thing to remember is that yes, mechanical seals do leak, but these leaks are important to their overall functionality.

Causes of Mechanical Seal Failure

Not all leaks are the good kind, unfortunately. Uncontrolled mechanical seal leaks are some of the leading causes of industrial pump failure. The following are common causes of mechanical seal failure.

Operational Failures

Every pump is designed with specific operating conditions in mind. These conditions are referred to as the pump’s best efficiency point (BEP), which is the point at which your pump operates at its peak efficiency.

Operating your pump outside of these conditions can lead to serious problems, including insufficient net positive suction head (NPSH) and low vapor margin.

Mechanical Failures

Mechanical failures occur when your pump’s components are faulty to begin with or start to malfunction over time. Typical examples of mechanical failures include shaft misalignment and coupling and impeller imbalance. Other components of your pump that you should check to make sure they are satisfactory include its base, pipes, and bearings.

Seal Component Failures

In addition to the failings of your pump’s mechanics, you also need to keep an eye on the seal itself. The seal features several components that can fail if they are not properly attended to. You need to be aware of your seal’s material quality, secondary seals (such as gaskets and o-rings), and springs. Make sure to check your seal for heat distortion on a regular basis.

Design Failures

If there are problems with the way your pump skid was designed or installed, these problems could lead to mechanical seal failure. Always make sure to have your pump assembled and installed by a reputable company or someone with the proper knowledge and experience.

You Can Rely on C&B Equipment!

At C&B Equipment, we are a reputable distributor of several types of industrial equipment, including industrial pumps and mechanical seals. We specialize in the repair, installation, and maintenance of industrial equipment so that you don’t have to worry about it yourself.

Having one of your industrial pumps break down is a major hassle, but with our preventative maintenance programs, this possibility will become a non-issue. Whether it’s a problem with the mechanics of your pump or your mechanical seal is failing, we’ve got you covered!