Page 291 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Power Transmission Gears 271

drives when splash lubrication cannot be used due to gear arrangement.
A simple forced-feed system consists of a pump with a suction line and
supply lines to deliver the oil; the gear housing serves as the reservoir. In
contrast to this simple arrangement, more complicated lubrication supply
systems for high speed drives may include many of the following compo-
nents :

1. Large reservoir
2. Filters (duplex or single)
3. Shaft-driven pump
4. Auxiliary pumps (motor- and steam-driven)
5. Heat exchangers (single or duplex)
6. Accumulators
7. Pressure control devices
8. Safety alarms and shutdowns (temperature and pressure)
9. Temperature regulators
10. Isolation valves
11. Heaters (steam or electric)
12. Purifiers (to remove water and oxidation products)
13. Flow indicators
Many of these lubrication systems are well designed and constructed not
only to lubricate the gears and bearings of the gear unit but also to enhance
performance of the driving machine, gear unit, and driven machine. Figure
6-34 illustrates one such system.

lntermlttent Lubrication
Intermittent lubrication is exactly that: a system in which the lubricant
is not available continuously but is supplied periodically to the gears or
bearings, or both. This type of lubrication system is the least common
and is primarily suited for low speed applications. Of the three methods
of applying the lubricant-brushing or pouring, hand spray, and mechan-
ical spray-mechanical spraying is by far the most commonly used.

1. Brushing or pouring: In this method an extremely heavy lubricant is
brushed or poured on the gears by hand. It is used when a pan or
any form of flooded lubrication is impractical for gears operating at
very low tip speeds. This lubricant can be applied either cold, if the
viscosity allows, or hot when preheating is required for application.
2. Hand spray: Pressure lubrication is obtained when the lubricant is
placed in a container and sprayed similar to applying paint. This
method is better than the brushing or pouring application as it pro-
vides more uniform distribution of the lubricant.