Metal Face Seals - Installation and Maintenance

Installation Method

1. Ensure that the inside of the housing is clean, free of burrs, scratches and dust.  The load ring must be correctly fitted on the seal and be free from distortion (see Figure A).

2. Install the seal with load ring in the housing (Figure B). At this time, confirm that the end of the housing (1) will be parallel to the lapped surface of the seal (2). If the seal becomes out of alignment, even partially (Figure C) the seal shall have abnormal wear the o-ring will become distorted and will eventually fail prematurely.

3. After insertion, make sure that the precision lapped surfaces are absolutely free of foreign matter, then lightly apply lubricant oil to the mating surfaces.  Upon competition of the seal installation, reassemble the housings to the correct setting gap (see below) and fill with lubricating oil.

When properly installed, the two mated metal surfaces seal against each other, a thin film of lubrication between these two surfaces minimises wear, and the load rings provide pressure to ensure positive sealing.

Metal face Seals Installation

Setting gap

The setting gap (A) determines the amount of axial pressure on the sealing faces and the compression applied to the elastomeric rings.  Pioneer Weston seals are designed so a setting gap A of 3.0-0.5mm will provide adequate sealing force for the majority of applications. However if the seals are required to work at a continuous high peripheral speed the setting gap should be adjusted in order to prevent an excessive loading of the lubricating oil.

This will reduce surface pressures and can be done by increasing the setting gap A .In this case tests should be conducted to find the most suitable setting.


Correct installation will count for very little if the lubrication regime is overlooked or incorrectly administered. The seals will have a far greater operating life when provided with good lubricating and heat dissipating qualities when oil is used as opposed to grease.


Transmission oils, grade SAE 80 and SAE90 are recommended. If necessary, lower viscosity lubricants such as engine oil 20W 20 can also be used. In cases where hydraulic fluids / Bio-oils are to be used, please contact Pioneer Weston direct for advice. The oil level should be between the axis centre line and 2/3 of the seal diameter. When filled to the correct level, the oil will generally suffice for the lifetime of the seal.


Although grease can be used as a lubricator it is not recommended due to the fact it will not centrifuge to the wedge gaps in the seal faces during dynamic conditions. If grease is used it will result in higher wear, shorter lifetime and can only run at slower sliding speeds.

The seal should, on no account, be regreased with a grease gun, as the high pressure of the gun can dislodge the o rings and ultimately destroy them.