Bearings checking

Check the adequacy of the bearing to accommodate maximum horizontal displacement, using the AASHTO LRFD Method B design procedure Calculate shape factor of the bearing Check service load combination Check condition immediately before deck placement Evaluate stability of the bearing Determine required thickness of steel reinforcement Determine low temperature requirements for the constituent elastomer... 

Overloaded bearing Check alignment, side, and end thrust. 

Heat build-up Ensure frequent preventive maintenance checks due to worn or on bearings overloaded, Monitor and alarm bearing temperature bearings. Ensure proper belt tension CCPS G-12 CCPS G-23 CCPS G-29... 

Hot bearings pro- Avoid by regular preventive maintenance (PM) viding a source of inspections, lubrication and belt checks Ignition., Ugg improved lubrication CCPS G-23 CCPS G-29 CCPS G-34... 

We provide below a few guidelines for checking the suitability of the bearing and the motor shaft, when selecting a motor for these drives ... 

Check for bearing insulation (dealt with separately in Section I0.4.,S). 

The bearing insulation is thus determined by the manufacturer while checking the shaft voltage at the works. This forms a routine in-house test for all HT and large LT motors. 

Bearings make a churning noise or overheat Check condition and level of grease as well as any skin effects or watermarks on the races, balls or rollers. If there are watermarks, the bearings should be replaced. Otherwise wash and regrease them, as explained earlier. 

Check bearings and air gap during maintenance, at least once a year. 

Direct or rigid couplings Flexible couplings Delayed-action couplings Construction and principle of operation Belt drives Checking the suitability of bearings Suitability of rotors for pulley drives... 

Installation of bearings and pulleys Important checks at the time of commissioning Maintenance of electric motors and their checks Maintenance of bearings General problems in electric motors and their remedy Winding temperature measurement at site Analysis of insulation failures of an HT motor at a thermal power station... 

Third, you would. suppose that parallel pumps are identical, that they were manufactured and assembled together. But it is possible that one pump of the pair is the dominant pump and the other is the runt pump. If you start the dominant pump first in the parallel system, and then decide to add the runt pump of the pair, the weaker pump may not be able to open the check valve. The pump operator perceives that the flow meter on the second pump is stuck or broken. This is because the second pump might be dead heading against a closed check valve, maintained that w ay by the dominant pump. If this situation exists, it may re.sult in premature failure of bearings and. seals, leading maintenance and operations personnel thinking that parallel pumps are problematic. 

This dial indicator is fixed to the volute mounting adapter collar of the pump and the needle is on the shaft (Figure 14-21). The shaft should be moved radially by hand (see the arrows) up and down. Note the movement in the indicator. This is a check of the radial tolerance in the bearing. Some people use the word run out . Radial dellection causes misalignment of the rotating and stationary faces of the mechanical seal. This shortens the seal life by eausing drive pins and springs to wear and rub in relative motion. 

The turbine undergoes three basic tests, these are hydrostatic, mechanical, and performance. Hydrostatic tests are to be conducted on pressure-containing parts with water at least one-and-a-half times the maximum operating pressure. The mechanical run tests are to be conducted for at least a period of four hours at maximum continuous speed. This test is usually done at no-load conditions. It checks out the bearing performance and vibration levels as well as overall mechanical operability. It is suggested that the user have a representative at this test to tape record as much of the data as possible. The data are helpful in further evaluation of the unit or can be used as base-line data. Performance tests should be conducted at maximum power with normal fuel composition. The tests should be conducted in accordance with ASME PTC-22, which is described in more detail in Chapter 20. 

If the turbine is not out of alignment, or the shaft bowed as determined by the vertical and horizontal clearance checks or the appearance of the bearing surfaces, it is not recommended that the rotor be removed. Some turbine designs, however, may require removal of the rotor to facilitate the removal of some bottom sections of the diaphragms or inlet vanes. If the rotor is... 

For tilting-pad bearings, blue-shoe the pivot surface, and check for contact area and position. The contacting surface must be in the center only and at the bottom portion of the pivot bore in the retainer. Check to be sure that pins do not bottom-out in pads. 

Operation empty to check for vibrations and heating of bearings. 

Beyond these items, the balance of the maintenance procedure should include the customary bearing and seal checks. 

Examination of the drive ratios shows that if both motors have ISOOrpm synchronous speeds that the pony motor is made to operate near 3600rpm when the big motor is operating. This is typically not a problem as to rotor balance or bearing duty because manufacturers make 3600 rpm versions of these same motors. Nevertheless, the duty should be checked and if this is a problem, the small motor can be changed to a 900 rpm model and the synchronous speeds of each motor will not be exceeded. 

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