This section is from the book "A Practical Treatise On Friction, Lubrication, Fats And Oils", by Emil F. Dieterichs. Also available from Amazon: A practical treatise on friction, lubrication, fats and oils.
The many contrivances commonly called "lubricators," by which lubricants are applied to machinery, are often much trouble to engineers, as the adoption of these contrivances is, with many, as much a consideration of price only as it is in the purchasing of lubricants; but with lubricators as well as with lubricants the best are always the cheapest. It is a great oversight to make the lubricant subject to the manner of applying it, as it is the lubricant that is to do the work and not the mechanical contrivance through which it is forced to do it. There are numberless such contrivances, many very ingenious ones and others of faulty construction, rather interfering with, than assisting, the lubricant to do its work properly.
Cylinder oils are applied by the hand-pump, by the automatic pump, or through the well known sight-feed lubricators.
The hand-pump admits the oil too irregularly, too much at one time, not enough at another, either from neglect or oversight.
The automatic pump, such as the first and well-known "Moses Pump," and the later improved styles, are the best means for applying oils to cylinders with proper regularity. With the automatic pump the oil is not brought in contact with water or steam before entering the cylinder. It supplies the oil with the starting of the engine and ceases to do so when the engine is stopped, and all the attention that is required is to keep the pump supplied with oil. Any kind of oil, if clean and free from grit, can be fed through these pumps, and the amount to be fed is easily regulated by the shorter or longer stroke that is given at its connection with the engine.
The proper feeding of cylinder oil through the modern sight-feed cup, now generally used, depends entirely on the intelligence of the engineer as how to use it properly. All the many sight-feed cups are devised on the principle of displacing the oil from the cup, drop by drop, by the water condensed from the steam before the latter reaches the cup. It requires a little time and patience when starting or refilling these cups, to wait until sufficient steam has been condensed and enough water been accumulated to operate the cup properly and get the oil to feed with proper regularity; otherwise the steam will churn the oil. Introducing some water in the cup before filling with the oil, and slowly turning on the steam and regulating the feeding, will prevent overheating and allow of regulating at once the proper condensing of the steam and the regular displacement of the oil.
The use of impure oils should be carefully avoided and the cleaning of the cup not attempted by blowing live steam through it, as thereby the fatty deposits from the oil, in connection with impurities in the water used for the steam, are baked to the sides and openings of the tubes in successive layers by the latent heat held there by the metal, in precisely the same manner as the scale in boilers is produced from the slimy, earthy deposits of the water, by baking and incrusting them on the iron by the latent heat under the prevalent and injudicious practice of "blowing off boilers." Sight-feed cups should be taken off from time to time and carefully cleaned with benzine or coal oil and a swapper.
It is, however, not a question alone of merely getting the oil into the cylinder, but the oil must possess sufficient power to cling to the metallic surfaces of the cylinder and the valves, in order to resist its being blown out with the exhaust before its work has been done.
An oil that does its work satisfactorily when applied direct with a pump, but will not do so through any of the many patent sight-feeding devices, proves conclusively that the lubricator or the wrong handling of it should be blamed, not the oil.
There is an endless number of cups of all kinds of construction to apply lubricants to the bearings of shafting and all kinds of machinery. For feeding oils, those will command the most attention that will allow the operator to see at a glance if the feeding is regular and uninterrupted. They all require more or less adjusting to properly regulate the amount to be fed and allow the oils to pass through the aperture, according to their limpidity or viscosity.
In some of them the flow of oil is regulated by controlling the width of the aperture with opening and closing devices; in others a wick is placed over the aperture, to secure regular and slow feeding on capillary principle, and still in others a rod, with flattened side, is placed to prevent a too rapid flow of the oil. If they are properly handled and attended to and proper judgment is used in adjusting them, in accordance with the characteristics of the oil used, most of them will answer their purpose satisfactorily.
In those cups which feed with a wick, it is important that the number of strands in the wick should be in proper proportion to the limpidity or viscosity of the oil used, and in those cups separated with a metallic stem with a flattened side, the latter should be filed still flatter or the stem removed entirely when a change is made from a limpid and easy-flowing oil to one which has a heavy body of uniform consistency.
In all cups exposed to varying temperatures, only such oils should be used as will not congeal and thereby become unable to flow and feed through the aperture. Frequently when changing from one oil to another, and especially when the oil first used was of a gummy character, and the new oil does not possess this objectionable quality, the oil may at first feed well enough through the aperture, without the necessity of changing its adjustment, but on account of its gradual loosening the almost imperceptible coating or gummy film on the sides of the cup, the latter is apt to obstruct the opening and the oil will be unable to force its passage through, and the bearing running warm, the oil will unjustly be condemned as being a poor lubricant.
Cups especially designed for feeding grease are also of varied construction and character. These cups should also have apertures proportionate to the melting quality of the grease used.
There are cups where it is intended to force the grease down by pressure or by springs, which consequently require much attention and adjusting and cannot be considered automatic feeders.
Those cups provided with metallic steins, resting on the shaft, to work on the principle that the frictional heat conveyed through these stems will melt the grease and make it limpid enough to flow down on them, also fail to secure perfect lubrication, as they can only begin and continue to lubricate after sufficient heat has accumulated by which to keep the grease melting.
As running machinery under increased heat means expansion of the metal, abrasion of the parts and waste of power, the deficiency of grease lubrication is apparent. The only reliable lubricating with grease is through long-slotted apertures in the box, which allow the grease to lay directly on the parts in motion.
When lard oil and tallow oil were the only means for lubricating locomotive engines, these oils would readily solidify in their feeding cups in cold weather, and all the cups had to be equipped with steam mantles to keep the oil in a fluid condition. When the petroleum oils came into use they were applied with oil pumps and through sight-feed lubricators and the use of the latter became almost universal.
Some promoters of grease lubrication conceived the idea to apply grease to cylinder lubrication, and constructed special sight-feed cups intended to allow the grease kept liquid by steam to be carried drop by drop with the steam into the cylinder.
Disregarding all theory as to the process of lubrication, they had grease compounds made of petroleum steam-refined cylinder stock and tallow oil. Lubricating cylinders with tallow having long ago been abandoned on account of the injurious action on the metal of the cylinders, the tallow combined now to form in conjunction with the impurities contained in steam-refined stock and the metallic abrasions, gummy deposits that accumulated in the cylinders and impeded the power. The application of grease for lubricating cylinders in this manner was also found inconvenient when the engine was stopped, and when the lubricant was exposed in winter to severe cold the grease became congealed and failed to flow until again liquified by the steam.