As the overhaul of unit operating near the host, the host bearing life gradually almost to the maximum allowable time frame. Gradually screw axial and radial play almost at maximum design allowable values, makes the change between the screw and the screw, screw the host shell and large changes in the gap between the front and rear face. Host is safe to run, while still at this time, but had to be considering plans to host the time has come for a major overhaul. Because once the running time to cross after the overhaul period, SKF bearings clearance wear and host reached the limits of technical conditions allow, hosts at this time is in unsafe condition, serious consequences may occur at any time as follows:
　　1, run the host load increases, cause harm to the primary motor and electrical systems
　　Hosts between the screw and the screw and front and rear side, between screw and shell strong friction that may arise between the host will host load sharply increases, excessive wear of FAG bearings work load is enormous. As a result, the motor will overload the working condition, could seriously jeopardize the safe operation of the motor. In serious cases, if electrical protection device of air compressor unit is not responsive or fail, it can also lead to motor burn.
　　2, air compressor exhaust volume greater attenuation of the amplitude occurs.
　　Clearance increases the host will cause the host to significant degradation of efficiency, namely, air compressor exhaust volume of greater attenuation of the amplitude, gas production had a certain impact. Especially on those empty pressure machine exhaust volume configuration rich volume smaller of user, due to empty pressure machine exhaust volume attenuation, in with gas system with air relative stability of situation Xia, tube network compression air pressure on will reduced many, on may appeared with gas system equipment, cannot normal work or fundamental cannot work, to appeared effect units normal production or led to temporarily sexual of cut-off, to enterprise brings loss.
　　3, suddenly the most serious consequences, there was a host of "lock".
　　If this happens, if the reaction than the electrical protection system, or when the protection expired, also may bring severe damage to the main motor and the electrical system.
　　For a host of "locking", on the one hand than Roh overhaul maintenance cost to many expensive, on the other hand because the host component is damaged, so restored the host's performance would also overhaul the hosts less than normal. And if it's host damage severity has no fixed value or can't be repaired at all, you can only be scrapped off a new host, direct loss is greatest. Because the new host is usually the cost of buying the entire air compressors cost around one-third, far higher than normal cases the hosts overhaul costs and overhaul under normal circumstances qualified comprehensive technical properties of the host and the new host is very similar!
　　Comprehensive analysis on visible, host regular overhaul work is both a basic equipment maintenance requirements, but also enterprises to control normal equipment maintenance costs, to avoid unnecessary financial losses and safeguard enterprises ' normal production of the basic requirements!
　　Therefore, the hosts on time, according to the standard for a major overhaul of the air compressor is not only necessary, but also a must!
　　Screw air compressor mainframe requires a major overhaul of the judgment:
　　Specifically, host for a major overhaul of the NSK bearings service life expires should prevail, but in practice it is difficult to have an accurate indicator to determine if the service life of the bearing is about to expire or has expired, internationally renowned compressor manufacturers under its nearly a century of practice experience standards is 20,000 hours or 4 years after the compressor is running on the host for a major overhaul.
　　The pass criteria in addition to the above, on the basis of experience are also available from the following areas host a meaningful judgment:
　　1) voice a mount of the Lord, especially the TIMKEN bearings the same;
　　2) motor operating current, and in particular the difference between no-load operating current and standard values;
　　3) heads the INA bearings vibrations.



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