Additional Resources

How Big is a Drop of Oil?

In the days of sight-feed lubricator pumps, delivery rates were expressed in “drops/minute.” But there were two types of pumps, vacuum and liquid-filled, and drops in one were three times the size of the other!

So, here are the conversion values, assuming 30 or 40 weight oil at room temperature.

For vacuum sight glasses
1 drop = .002 cu.in.
14,115 drops = 1 Pint
10 drops/minute = 1 Pint/24 Hours
For liquid filled
1 drop = .006 cu.in.
4,705 drops = 1 Pint
10 drops/minute = 3 Pints/24 Hours

Keep in mind that the above are estimates, since, due to surface tension, a drop of kerosene isn’t as big as a drop of gear oil, and a drop of 30 weight oil at 0 degrees is larger than one at 150 degrees.

When you think about it, that’s a good reason to have a positive delivery lubrication system like our Watchman Lubrication System rather than multiple pump lubricators. And you get protected delivery as a bonus!

By the way, if you still have the older style liquid-filled glasses, get rid of them! They can become pressurized and explode if air is present in the glass or the lube line. Replace them with vacuum glass type pumps which present no safety risks.

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