Contain Oil Vapor for Better Reliability

In a boiler feed pump, an air breather is used to vent the enclosed air space on the bearing housings. With increasing heat and thermal expansion, oil vapors form in the bearing housings and migrate through the air vents. The vapor then condenses in the air filter media saturating the filter with oil. The air breather becomes ineffective, which affects mechanical seals and the overall reliability. In addition, oil droplets form and run down the outside surface of the vent post (Figure 1), creating a slick and oily surface in the surrounding area.

Figure 1. Boiler Feed Pumps Showing
Oil Stains on Machine and Floor

These problems related to oil vapor loss create maintenance, safety, environmental and housekeeping issues, indicating the need for a product that will contain oil vapor without causing damaging saturation and leaks.

A Productive Solution

JLM Systems Ltd. developed the OILMISER™ Vapor Guard to reduce oil consumption, improve mechanical reliability, extend air filter life and to keep the surrounding areas in the plant contaminant-free.

The original air breather is removed from the vent port on the bearing housing and replaced with a Series 6200 OILMISER™ vapor guard. A clean, uncontaminated air filter is reinstalled into the top port of the vapor guard. The vapors now accumulate in the vapor guard and return to the bearing housing without contaminating the air filter and surrounding areas.


The vapor guard is designed for lubricated machinery with an enclosed headspace that is vented to the atmosphere. The most common applications involve rotating machinery such as gearboxes, bearing housings, speed reducers and hydrostatic transmissions.

The OILMISER is also an effective splash guard. On high-speed rotating machinery, oil vapor can be compounded by the spray of oil from internal moving parts. The vapor guard acts as a collection chamber, preventing the oil from escaping into the outside surroundings as well as to the air filter.

Vented reservoirs used on closed- and open-loop motor circuits can also benefit from the vapor guard. Generally, volumetric changes within the reservoir are the result of heating and cooling. In these applications, oil cleanliness is crucial while an ineffective air breather is potentially catastrophic.

The Working Details

  • A central diffuser post is located on the inside of a sealed aluminum containment chamber.

  • The central diffuser slows the escaping vapors by dispersing them within the containment chamber, which has a top exit port vented to the atmosphere (Figure 2).

  • The migrating vapors condense on the diffuser post and the inside walls of the chamber.

  • As the condensation builds, it runs down the diffuser post and walls of the chamber, collecting at the bottom.

  • The oil accumulates in the containment chamber and is channeled into the bearing housing through “bleed-back” holes located at the bottom of the diffuser post.

Figure 2. Typical Vapor Guard Construction
Including Diffuser Post, Bleed-back Holes
and Sealed Containment Chamber


Features and Benefits

Air quality is a major consideration for both the reliability of the machinery and the safety and protection of the outside environment. A unique feature of the vapor guard is its flexible design, which allows numerous top port options. This enables it to easily integrate with systems designed by the original equipment manufacturers and service contractors.

Filter elements are available separately from the initial OILMISER™ standard vapor guard package, which features several port configurations combined with a variety of top-end adapters. The vapor guard accepts most of the conventional air filters, spin-on filters and desiccant breathers.

The basic model of the Series 6200 uses a three-inch long diffuser post and a 3¾-inch containment chamber. Also available is a 6220 OILMISER vapor guard featuring a double-length diffuser post and an extended containment chamber. In various applications, the longer dwell time in the chamber will increase the amount of condensation removed from the migrating vapors.

Vapor Guard is designed for lubricated machinery with an enclosed headspace that is vented out to the atmosphere. The most common applications are on rotating machinery such as gearboxes, bearing housings and hydrostatic transmissions. Some vented reservoirs can also use the OILMISER™ vapor guard when volumetric changes within the reservoir are the result of thermal expansion.

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