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Selection of Injection Machine Hydraulic oil & Lube

Author:Haifly Injection Molding Machine Date:2011-12-28 20:25:54
Selection of Injection Machine Hydraulic oil & Lube
9.1 Injection Machine Hydraulic Oil
l        Properties required
Ø        Free flowage in operational conditions;
Ø        Form proper sealing among movable components;
Ø        Little physical and chemical change in use;
Ø        Rustproof &anticorrosion
Ø        Load bearable to reduce abrasion of movable parts
Ø        Able to instantly separate water, dirt and other foreign substance to delete them from Injection molding hydraulic system when in stationary state
Ø        Suitable for sealing in use
Ø        Flame resistance for different use
Ø        Not prone to form foam.
 
l        Types of Injection molding hydraulic oil
There are roughly two types of hydraulic oil, one is mineral hydraulic oil and the other is anti-flaming hydraulic oil. The former one is commonly used now with rather broad scope of application.
l        Selection of Injection molding hydraulic oil
Normally, selection of hydraulic oil focuses on four aspects, namely, the type, viscosity, lubricating performance, and other quality elements including oxidation stability, shear stability, flame retardance and impact on sealing material.
 
l        Maintenance of hydraulic oil
Ø        Maintenance items are classified as follows:
    Foreign substance in hydraulic oil could be identified by viscosity, total acid value and color;
    Exotic pollution could be identified by weight or calculating;
    Appearance could be identified by color.
    However, the quality of hydraulic oil could be identified by observing the changes in its viscosity and total acid value and checking water in oil, color and contaminated degree.
Ø        Running-related control shall be done to the following items in daily inspection:
    Oil level: Make sure that minimum oil level over the mid line of level gauge. Too low oil level could hardly separate contamination in finely ground particles, water and foam. At the same time, record the oil level in oil tank during regular inspection for comparison against oil level control chart.
    Oil temperature: Conduct empty running before operation starts in case of low oil temperature. Adjust cooler to ensure oil temperature do not exceed 550C under normal operation.
    Oil pressure: Make sure of normal pressure reading. If not, clogging in filter may occur and air will be suctioned into working oil. Check pump and pressure gauge.
    Filter: Pay attention to pressure change of filter and clean filter regularly. If many foreign substances are found in oil, check to see how they entered.
    Noise of pump: Abnormal noise is caused by filter clogging, air suction, over high oil viscosity or entry of foreign substance into pump.
    Leakage: Check if any leakage at joint, flange and flexible hose that is caused by seals deterioration.
 
Ø        Maintenance of Injection molding hydraulic equipment
    Oil tank filling and supply:
a)      Fill the oil via suction filter. Remove the cap and cover during oil filling and put them away from the position where dust and filament may stick to.
b)      Make sure not to have 100-mesh filter clogged up which will lead to reverse flow of oil dropping to the floor. In case of no use of the filter, make sure the oil during filling has not been contaminated by foreign objects.
c)      Fill the oil via minimum 100-mesh filter in case of no use of suction filter, and make sure all devices into which oil is contained completely clean. Purging of device prior to oil filling is recommended.
d)     Consult comments from oil supplier and get their help in both cases of first oil filling and supply with new oil.
 
Have Injection molding hydraulic oil be in stationary state for 3-5 hours after replacement of
oil so as to delete air bubble and have floating objects deposited before pump
motor is started up.
 
    Regular test of oil properties
If oil is blemished or deteriorated, it will lead to shortened service life of machine with possible failure. Therefore, it’s absolutely necessary to test oil regularly to see any change in its properties. The test can be conducted either by end user or by oil company.
a)      Test by end user
¨         Visual test: Put new oil sample and one in use into respective test-tube, and compare respective color clarity, inside floating objects and water deposited at the bottom of test tube.
¨         Drop test: Have one drop of oil onto the filter paper and observe 2-3 hours later to see any contamination.
 
b) Test by oil company
If the above two cases suggest abnormity of oil, then it requires further test in the lab by oil company.
 
   c) Period for regular test
One day per month for visual test or drop test. Every three months for test by oil company.
 
    Limits for hydraulic use
Two items could be considered in identifying use limits of hydraulic
oil for overall judgment, they are oil deterioration and contamination
degree.
 
    Flushing
 
    Objective & Procedure
Firstly flush away prill, dust and sand that might have entered oil tank and pipe during machine manufacturing, assembling or installation. Then clean the hydraulic equipment after it has been used for some time. It’s recommended to invite maintenance experts from oil company to flush in your company with their flushing device.
 
    Flushing at oil exchange
Firstly discharge all the oil, clean the oil tank with sponge, and flush with
the same viscosity oil by a flushing equipment under low pressure. After 4-8
hours flushing, all prills, grease or dirt could be removed.
 
    Flushing may be also taken in case of serious contamination of original oil by water or chemicals after consulting our maintenance expert.
 
9.2 Injection molding Lube & Grease
l        Selection of lube
Lube includes gear oil and lubrication grease. Please refer to recommended oil type and viscosity in Chapter 3 when selecting lube.
 
l        Maintenance of lube
Hydraulic oil could be purchased and even replaced immediately, but lube is different that it must be stored for long time, and must be taken caution in its maintenance and storage as follows:
    Oil drum must be placed on wood floor;
    Keep the drum tight with water proof paper or other proper cover to seal it if possible;
    Make sure no direct sun beat onto oil container;
    Ensure ambient temperature no higher than 400C for oil;
    Lubricate frequently after some time, and clear up the grease if it becomes dark and hard.