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GRANT LAIDLAW
Grant Laidlaw is currently the owner of the Air Conditioning and Refrigeration Academy (ACRA) in Edenvale.
He holds a Bachelor of Business Administration and an associate degree in educational administration. He
has a National Technical Diploma and completed an apprenticeship with Transnet. He has dual-trades status:
refrigeration and electrical. He has been involved with SAIRAC for 17 years and has been a Johannesburg
committee member for the past eight (chairman in 2011 and 2012). Currently he is the treasurer
(Johannesburg council) as well as president (national council).
ALL ABOUT BEARINGS
By Grant Laidlaw
A look into the basic procedures applicable to bearings to see how
failure can be prevented.
Moses asks: Grant, I work in the industrial air-conditioning
industry. We deal with bearings on our pumps, cooling
towers, electric motors, and air handlers, but we don’t have
procedures for this and when we replace the bearings, the
new ones fail quickly. Can you help with a solution?
H
i Moses, yes I can help. I have previously discussed the
types of bearings used, but let us look into basic procedures
applicable to bearings. Of course, as a basic principle, always try
to determine the cause of the failure in the first place.
Let us begin with seals.
All installed bearings are sealed from the atmosphere in one
way or another. If they are carried in housings such as a plummer/
pillow block or a flange unit, the housing will be provided with the
seals. In some cases, the bearing itself is provided with an integral
seal or shield on one side, or seals/shields on both sides. In the
latter, the bearing is factory lubricated for the life of the bearing.
Often, you will find the bearing size followed by a ‘z’ or ‘zz’;
alternatively, the size is followed by ‘rs’ or ‘2rs’. This simply means
the following:
6202:
6202 z:
6202 zz:
6202 rs:
6202 2rs:
No shields or seals
Shield on one side
Shield on both sides
Seal on one side
Seal on both sides.
Bearing with shield
(z and zz).
Bearing with rubber
seal (rs and 2rs).
PRACTICES TO BE FOLLOWED
Always follow these practices with bearings, new or old:
• Never remove bearings from their packaging until the very
last minute (immediately before mounting).
• Inspect housing seals and replace if necessary. Always
replace a rubber seal.
• Leave rust-inhibiting coatings on new bearings intact,
except for wiping this away from the bore and from the
outside of the outer ring.
• Work only in a clean environment; do the job away from
any other operation (grinding, drilling, and so on) that is
contaminant producing.
• Cover and protect all bearings during standing time or
breaks.
• Thoroughly inspect used bearings that are being reused, as
well as new bearings which are being taken from previously
opened packages or from damaged packaging.
• Clean and dry all components.
• Do not spin bearings with compressed air. Although
entertaining, this is an extremely dangerous practice, as
the bearing may disintegrate or be ricocheted at high
speed, creating a high likelihood for injuries.
Continued on page 63
www.hvacronline.co.za
RACA Journal I January 2019
61