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PROBLEM
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SOLUTIONS (corrections)
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TRAPPED AIR IN GREASE. Grease can contain air bubbles (voids or segments of air)
that enter the grease when grease is manually stirred or transferred or during normal drum changes.
When present in the lubricant delivery tubes or hoses, these air bubbles compress as grease is
dispensing and begin to expand immediately after grease was dispensed. The type of drooling and dribbling caused by this will be intermittent and you may occasionally see the bubbles exit the nozzles.
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Remove air from grease and INSTALL A SNUFF-BACK DEVICE.
G. P. Reeves uses our patented equipment (US patent #6,053,285) to automatically remove air from grease.
Our equipment will remove air from grease prior to that grease being dispensed onto your product.
For more details about our patent, see:
http://gpreeves.com/cat/cat-patentedairdetect1.pdf
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TRAPPED AIR IN PLUMBING OR MANIFOLDS. Cross holes in manifolds may be drilled too deep causing blind cavities where air cannot be displaced by grease. Tube and pipe fittings may be trapping air in tapered pipe threads. “Tees” that trap air in their unnecessary outlets could have been substituted for elbows. Trapped air compresses during dispense and expands after dispense. As it expands, it slowly forces grease to extrude from the nozzle tip.
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Manifolds and plumbing can be designed to minimize or eliminate areas where air can be trapped. Air trapping areas of existing manifolds can often be filled with epoxy. Plumbing can be re-engineered. Tees can be replaced with elbows.
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OVERSIZED TUBING. Grease delivery tubing (between grease dispenser and nozzle) may be oversized causing much more grease volume than necessary. All grease is compressible to some degree and five times more grease than necessary will compress five times more than necessary. Compression during dispense always results in expansion after dispense. That expansion causes grease to extrude from the nozzle tip.
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Replace oversized tubing with smaller inside diameter tubing. A minor decrease in diameter can cause a major decrease in grease volume. Example: 1/4” ID tubing has a volume of .589 cubic inch (9.68 cc) per lineal foot. 3/16” ID tubing has a volume of .331 cubic inch (5.42 cc) per lineal foot.
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COMPRESSIBILITY OF GREASE Grease (even without visible air) is often compressible by as much as 1% of its volume for every 500 p.s.i. of dispense pressure. Even low pressure grease dispensing causes some compression during dispense. Compression during dispense always results in expansion after dispense. That expansion causes grease to extrude from the nozzle tip.
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Increase the inside diameter at the grease nozzle tip. Carefully select the grease delivery tubing to assure that its inside diameter is not causing grease flow resistance causing an unnecessarily high dispense pressure. INSTALL A SNUFF-BACK DEVICE.
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HIGH DISPENSE PRESSURE is often caused by selection of dispensing components that were originally designed for maintenance greasing and require high pressure for operation. Dispensing at 2,500 p.s.i. can cause much more drooling and oozing than dispensing at 500 p.s.i.
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Select components designed for operation at lower pressure. G. P. Reeves has grease dispensing equipment that will function at less than 500 p.s.i.
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GREASE DISPENSER LOCATION Grease dispensers can rarely be mounted at the dispense point or nozzle. Grease contained in dispense tubing will compress during dispense and slowly expand to its original size after grease has been dispensed. That expansion causes grease to extrude from the nozzle tip.
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Install the grease dispensers as close to the nozzles as practical and possible. INSTALL A SNUFF-BACK DEVICE.
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BALLOONING OF HOSES Flexible tubing or hose may balloon (increase in diameter) as grease pressure in the hose or tubing increases while grease is being dispensed. After grease has been dispensed, pressure returns to normal allowing the hose or tubing to return to original size. The hose or tubing has more grease volume during dispense than after dispense. As the hose or tubing returns to original size, that extra volume of grease extrudes from the nozzle tip.
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Select tubing that doesn’t expand with the anticipated dispense pressure. Use hose rated for 3000 p.s.i. even when dispense pressure is expected to be less than 500 p.s.i. Even a small increase in hose or tube diameter will result in an increase in volume that must be snuffed back. Example: Two feet of 3/16” ID hose has a normal volume of .662 cubic inch. When under pressure and expanded by .002”, its volume increases to .667 cubic inch. That is an increase of .005 cubic inch or enough to extrude almost 1/2 inch of grease out of a 1/8” diameter nozzle orifice.
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BENDING OF HOSES Flexible hose or tubing is often used because the grease nozzle must be moved to and from the part being greased. Often the hose has more of a bend after dispense than it did during dispense. As the hose is bent, its internal volume decreases causing grease to extrude from the nozzle tip.
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Carefully select the grease delivery tubing to assure that its inside diameter is as small as possible without causing grease flow resistance causing an unnecessarily high dispense pressure. Keep bend radii as large as practical. Install “constant swivel” fittings to minimize hose bending. INSTALL A SNUFF-BACK DEVICE.
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Nozzle
Nozzle