There are three groups of High Pressure Grease Fitting: vents, breathers, and relief vents. Breathers do not restrict airflow and allow the gearbox to “breathe” in and out. Vents are different from breathers because air is only allowed to flow in one direction, and the vent closes to prevent airflow in the opposite direction. Relief vents have a small interior valve that relieves pressure at prescribed pressure ratings.

Vents

Vents open and close within a predetermined pressure range: As internal pressures rise, a flat seal (typically composed of rubber) opens, allowing pressure to vent. As the pressure decreases, the seal closes. The rubber seal has the added advantage of sealing the port opening while closed, thus preventing dirt, water, and other contaminants from entering.

Breathers

Breather fittings feature specially designed ports that allow air to move inandout, thus creating the effect of “breathing.” They have a special cap which reduces contamination. For additional contamination protection, some breathers are equipped with a felt filter.

Relief Vents

Pressure relief vents open and close within a predetermined pressure range. as internal pressure rises, the plunger or check ball opens, allowing pressure to vent. As pressures decrease to below the minimum threshold, the valve closes. Relief valves are available in both a top vent and side vent design.

Over Lubrication

As components turn inside gearboxes, the friction of the moving parts produces heat, which in turn causes the interior liquids and gases to expand.

As the volume of the liquids and gases expand, pressure increases. If not controlled, the excess pressure can cause seals to break, resulting in damage to the gearbox components

Prevention

In the application below, the pressure relief valve on top of the gear box has successfully vented excess pressure. This pressure relief allows the gearbox to operate safely at a variety of atmospheric conditions.

Installation

In most applications, it is best to install pressure control fittings above the stationary fluid line. Be sure to have the proper Brass Injection Packers with the correct pressure rating for the application.