Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/120548
Grease Fittings Grease fittings have several names such as a Zerk fitting, grease nipple or Alemite fitting. This is the lubrication point where the grease connector is attached. Standard Button-head Hydraulic Fitting The standard hydraulic Grease Fitting grease fitting is most commonly used for standard applications. It can be either upright or angled. The button-head Flush-type fitting is ideal for good Grease Pressure-relief coupler engagement when Fitting Vent Fitting large volumes of grease are being added. A flush-type grease fitting is preferred when space is limited for standard protruding fittings, while the pressure-relief vent fitting helps prevent higher pressures that could lead to damaged seals. Machine Health Risks Associated with Grease Guns High Grease Gun Pressure A high-pressure manual grease gun is designed to deliver from 2,000 to 15,000 psi. Applying too much pressure while greasing will damage the bearing seals, which rarely handle more than 500 psi. Symptoms of high grease gun pressure include collapsed bearing shields, damaged bearing seals, grease driven into electric motor windings, and safety and environmental issues. Regreasing Frequency Managing regreasing frequencies to optimal conditions is necessary to avoid long-term machine health problems. If the frequency is too long, symptoms may include lubricant starvation, which promotes wear, friction and grease contamination. If the frequency is too short, excessive grease consumption and safety and environmental issues may occur. Overgreasing and Undergreasing It is important to know the exact amount of grease necessary for your greasing application to avoid overgreasing or undergreasing. Symptoms of overgreasing include damaged seals and motor windings, environmental issues, and fluid friction, which leads to increased heat generation, higher grease oxidation rates and higher energy consumption. Symptoms of undergreasing include bearing starvation, which results in friction wear and increased contamination. How Output is Measured It is common for maintenance departments to have a wide variety of grease gun types, makes and models. This can cause greaserelated disorders due to cross-contamination and inaccurate knowledge of each grease gun's output per stroke. Grease guns are known to vary in the amount of grease that is output from 0.5 grams to more than 3 grams. This inconsistency depends on factors such as the type, model and age of the grease gun. To overcome this problem, it is necessary to calculate the amount of grease that is released from a grease gun per stroke. To do this, use a calibrated scale and consistently pull 10 strokes of grease onto the scale. Once this value is known, divide by 10. Grease Gun Best Practices • Calculate the proper amount of grease needed for the relubrication of bearings based upon the calibrated delivery volume of the selected grease gun. • Use a vent plug on the relief port of the bearing to help flush old grease and reduce the risk of too much pressure on the bearing. • Use extreme caution when loading grease into the grease gun to ensure that contaminants are not introduced. If using a cartridge, be careful when removing the metal lid so that no metal slivers are introduced into the grease. • Make sure the grease gun is clearly marked to identify the grease with which it should be charged. Do not use any type of grease other than that which is identified. • Always make sure the dispensing nozzle of the grease gun is clean before using. Pump a small amount of grease out of the dispensing nozzle and then wipe the nozzle off with a clean rag or lint-free cloth before attaching it to the grease fitting. • Clean the grease fitting of all dirt before attaching the grease gun. Inspect and replace damaged fittings. It is helpful to use grease-fitting caps to keep them clean, but still wipe fittings clean before applying grease. It is essential that the proper grease gun operation is understood and managed by lubrication technicians for bearing and machine reliability. • Ensure that the proper grease is used at every grease point. Applying the wrong grease can cause an incompatibility problem, which can quickly cause bearing failure. Lubrication points should be clearly identified as to which grease is to be used. This can be done with colored labels, adhesive dots or paint markers. • Grease guns should be stored unpressurized in a clean, cool and dry area and in a horizontal position to help keep the oil from bleeding out of the grease. Grease gun clamps make storage easy and organized. Also, cover the coupler to keep it free from dirt and contaminants. • Calibrate grease guns regularly to ensure the proper delivery volume. About the Author Bennett Fitch is a technical consultant with Noria Corporation. He is a mechanical engineer who holds a Machine Lubricant Analyst (MLA) Level I certification through the International Council for Machinery Lubrication (ICML). Contact Bennett at bfitch@noria.com. www.machinerylubrication.com | March - April 2013 53