Page 131 - Reciprocating Compressors Operation Maintenance

118 Reciprocating Compressors: Operation and Maintenance

The formulas are based on 40,000 drops per gallon and lubrication of
600 square feet of swept surface per drop.
The drops per minute must be divided between the number of oil feeds
to the cylinder. Do not count the feed to the rod packing when making
this distribution. The packing must be considered as a separate cylinder
for lubrication purposes.
Rates of oil feed will generally fall between the limits shown in Table
3-1. These rates should be increased for dirty or wet gas conditions and
also for the initial running of new compressors. Oil feed rates can also be
obtained from Figure 3-5.
A practical and frequently used method to determine whether the prop-
er amount of oil is being fed consists of removing the discharge valves

TABLE 3-1
RATES OF OIL FEED

DROPS OIL PER MINUTE (Total for cylinder and packing)*
2
Cylinder Discharge Pressure of Cylinder, psi (kg/cm ) gauge
Diameter, 25-75 75-150 150-250 300-600 600-1500 1500-3000
in. (cm) (1.8-5.3) (5.3-10.6) (10.6-17.6) (21.1-42.2) (42.2-105.6) (105.6-211)
6-8(15-20) 3-6 5-8 6-9 7-12 9-16 12-18
8-10 (20-25) 4-7 6-9 8-11 10-15 12-20
10-12(25-30) 5-9 7-11 9-13 12-18
12-14(30-36) 6-10 9-12 11-16 14-21
14-16(36-41) 7-12 10-15 13-18
16-18(41-46) 8-13 12-17 15-20
18-20(46-51) 9-15 13-19 17-22
20-22(51-56) 10-17 15-21 19-24
22-24(56-61) 11-18 17-23 21-26
24-26 (61-66) 12-20 18-25 23-28
26-28(66-71) 13-21 20-26 25-30
28-30(71-76) 14-23
30-32(76-81) 16-24
32-34 (81-86) 17-26
34-36 (86-92) 18-27
38-40(97-102) 19-28
36-38 (92-97) 20-30

*The figures given are for gravity and vacuum type sight-feed lubricators. For glycerine
sight-feed lubricators, the figures given should be divided by three. Feeds to cylinder
bores should never be less than one drop per outlet per minute under any conditions.
The quantities given are based on an average of 8,000 drops per pint (16,900 drops per
liter) of oil at 75°F (24°C). (Reprinted from Compressed Air and Gas Handbook, Fifth
Edition, John P. Rollins, editor. New Jersey: Prentice Hall, 1988.)