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COVER PAGE |
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IBT |
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ISG |
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ENGINEERING |
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MATERIAL HANDLING |
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PT |
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FLUID POWER |
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IBT MEDIA |
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SAFETY |
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LEAN SIX SIGMA |
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ELECTRICAL |
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IMT |
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LUBE |
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Grease Gun
Theory & Practice
By Paul Conley, Chief Engineer, Lincoln Industrial
The grease gun delivers lubrication to bearings, putting just the right amount, right where it is needed. To a shop maintenance professional, a good grease gun can be his best friend, saving time, saving money, preventing downtime and extending bearing life.
Grease fittings and the grease gun came out of the coal mining industry, used to lubricate wheels on coal cars. In 1900, there were 19,000 coal mines in the United States. To transfer the coal out of the mines, coal trams ran on railroad tracks. This number of mines required a large number of tram cars. With heavy loads on the wheels and some crudely design wheels and shafts, there were constant car wheel shaft and wheel failures. With a typical component life of 90 days, it was clear that something had to be done
Lubrication and its relation to friction and wear were not well understood in those days. As a result, they made initial progress initially through trial, error and experimentation.
Coal tram wheels had been designed without adequate provisions to lubricate the bearings. This problem led to the development of roller bearings for wheel shafts to reduce friction and wear. In addition, manufacturers began to design wheels with channels, so lubricant could be introduced to the bearings at frequent intervals from the outside.
The need for finding a way to deliver grease into the wheel hub led to the development grease gun. The first type of grease gun was a push-type that connected to a primitive grease fitting.
By 1917, coal car wheels that would work with a grease gun had been introduced to the coal mining industry with outstanding results. Coal car wheel and bearing life was extended from three months to two years; a fantastic success that did not go unnoticed by early car makers.
Car manufacturers began to improve on the design of chassis joints. They included channels to distribute grease to the chassis bearings. Alemite and Lincoln began to design and sell improved grease fittings and grease guns. By the mid-1920s, grease fittings and grease guns became standard tools in the automotive and mining industry.
Grease gun improvement began. The original push-type grease gun could normally generate 300 psi of pressure. Shaft and bearing tightness increased, creating a need for a grease gun that could produce more pressure. The development of a piston/plunger that was directly connected to a push handle followed shortly.
In the 1930s, the need to generate greater force led to the development of the lever grease gun Since the late 1930s, the lever grease gun has been industry standard
There are six standards a grease gun must meet:
- Capability to develop high pressure (8,000 psi )
- Ability to maintain prime
- Allow for bulk, remote and cartridge filling
- Have self-priming features
- Durability
- Contain a quality grease coupling
There are certain features a grease gun needs for top quality:
Hardened bushing and plunger with clearance metal-to-metal fits in the .0001 ( one ten thousandths of an inch ) Allows for the pressure to be developed and prevents bypass of lubricant during high pressure from the piston chamber.
Precise machined ball check and seat surfaces with coined or diamond-honed ball seats Prevents grease from back flowing into the piston chamber. If this occurs, the grease will not get to the bearing, and the grease gun will not prime.
Piston plunger travel to extend up to the ball check. Allows air to be expelled, thus the grease gun will not lose prime. This is an important feature when air is introduced in the grease; usually during the refill process.
Iron metal head casting. Allows sufficient hardness for the purpose of wear resistance to maintain tight clearances between the piston and plunger, extending the grease gun's ability to produce and maintain pressure over time.
Grease tube and seal design to accept three filling methods. Allows for bulk, remote and cartridge filling. An elastomer follower-type seal that is or can be configured to seal in two directions and accommodate a standard grease cartridge is ideal. For bulk and remote filling, the seal must prevent grease from bypassing the follower in the grease gun from the top. For cartridge use, the seal must accommodate the grease cartridge tube.
Adequate opening of grease from the cartridge to the piston chamber. An opening large enough so that it does not restrict flow of grease from the cartridge tube to the piston chamber is needed. This is especially important when operating the grease gun in cold weather. The size of the orifice must be large enough to allow for flow of grease under cold temperature conditions. See illustration below.
Heavy gauge steel construction of the grease tube Typically, .045 inch thick wall steel tubing or greater is needed to ensure a rugged design.
Three Jaw case hardened coupler (as opposed to a four jaw ) Provides reliable seal connection by gripping the ball of the fitting; and as more pressure is required to force the grease through the fitting, the tighter the seal will become, thus preventing leakage.
There are essentially two types of manual grease guns: the lever gun and the pistol grease gun. Grease guns can also be operated pneumatically and electrically
The lever grease gun has a mechanical advantage that develops high pressure. The need for precise-tolerance, hardened machined components is critical with this type of lever gun.
The pistol grease gun has less mechanical advantage, and develops less pressure. As a result, the need for precise metal-to-metal, close-tolerance fit is not as critical.
A lever grease gun typically can be configured with larger volume grease tubes ranging from 14 to 30 ounces. With pistol grease guns, the maximum size grease tube is 14 ounces.
Either type of grease gun can be configured to have a rigid tube or flexible hose. The benefit of a rigid tube is that it can withstand high pressure. High pressure sometimes is required to push grease through a restrictive or clogged grease fitting. The other benefit is that it is easier to maintain the coupler on the grease fitting during use, thus permitting two hands to operate the grease gun.
With a flexible hose, one hand is usually required to hold the coupler on the grease fitting. This makes it a little more difficult to operate the lever gun. A lever gun is usually equipped with a rigid tube, as using two hands is required to operate the grease gun. With a piston-type grease gun, a user can operate the grease gun with one hand, and the other hand is free to hold the coupler on the grease fitting.
The lever gun is the best option for heavy industrial use such as mining, cement, pulp and paper and steel. Today's lever guns provide high pressure or high output. There is a trade off. Lever guns can produce higher pressure with lower output per stroke or lower pressure with more output per stroke.
A lever grease gun with high output of grease per stroke but producing lower pressure is the best choice for applications involving large bearings that have more clearances for grease to flow. For industrial applications with smaller bearings, a lever grease gun that produces higher pressure but less output volume is ideal.
The pistol grip grease gun can be used for non-industrial applications such as for small tractors and automobile maintenance. The pistol grip grease gun usually provides lower pressure (500 psi) and lower output per stroke.
There are essentially three methods to fill a grease gun: bulk, remote and with a grease cartridge.
Bulk fill is performed by removing or unscrewing the grease tube from the grease gun head. Remote fill is performed by connecting a grease pump from a remote grease container to the top of the grease fill fitting. Cartridge fill is performed by removing or unscrewing the grease tube from the grease gun. In all instances, when refilling a grease gun, there is the possibility of air being introduced into the grease gun cartridge tube. For the grease gun to operate properly, the air must be expelled.
If the grease gun has a relief valve, the priming of the grease can be performed using this valve.
Grease guns can produce high pressure. It is essential to use an outlet hose or rigid extension pipe that is rated for the pressure the grease gun can produce. This is especially relevant for a hose. It would be improper to use a device such as a lever gun that can produce very high pressure of 8,000 psi with a hose this is rated less than 8,000 psi. It is important to know the pressure rating of the extension hose before using the grease gun. If you do not know, then a rigid pipe connection should be installed.
If an extension pipe or hose is not strong enough to withstand the pressure that is being developed, then the hose or pipe could burst, causing high pressure grease or fragments to release violently and cause injury or other damage.
When used properly - which means with the right lubricant, right fittings, and in a safe and careful manner - the maintenance pro can cut his lubrication jobs down to size while assuring increased intervals between major repairs and reducing unplanned downtime.
For as simple as it appears to be, the grease gun is an impressive and sophisticated tool.
For more information about lubrication including grease guns, automated systems, and maintenance services, contact Ron Puckett
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To learn more about lube products and services from IBT, contact us today!
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