Webinar highlights

14.09.2020

Итоги вебинара

In June, Kharkov Bearing Plant held another webinar on the topic: "Rules for mounting and operation of bearings. Reasons of failures".

After the webinar, HARP received a lot of emails with questions and feedback from customers and partners of the company.

HARP decided to publish the most interesting and popular questions and answers to them.

Explanations are given by the Head of the Product Development Department, leading technical specialist of HARP – Vitaliy Poletaev.

It would be interesting to learn about the experience of operating bearing units manufactured by HARP. We are interested in the main reasons of failures, damages to bearings and their reasons (wear, dents, tearing, holes, cracks, color changes, etc.).

These questions will be discussed during next webinars. We have already reviewed the damage during mounting in the previous webinar. Next, we plan to analyze operational wear.

Method of selecting HARP bearings for mounting on existing equipment, and comparing them with analogues from other manufacturers.

HARP bearings are manufactured in accordance with the requirements of international standards ISO and GOST, so their selection and calculation does not differ from the bearings from other manufacturers. If you are referring to the selection of an analog instead of imported bearings, you can use an electronic catalog https://harp.ua/products/.

Quality of HARP bearings has been constantly monitored. Compared to analogues manufactured by competitors, HARP bearings are at a decent level, and a number of positions have much higher quality than bearings of well-known world brands. Quality indicators of supplied HARP bearings correspond to PPM 100 ... 200 (PPM – number of defective parts per 1 000 000 pcs. in delivery), reliability of particular bearing groups was discussed in the previous webinar:

·video

presentation in PDF format

We would like learn more about lubrication of HARP bearings, selection of lubricants, recommended manufacturers.

We will discuss thesequestions during next webinar. For brief overview of the lubricants used in HARP bearings, see the HARP catalog, page 47

Marking of HARP bearings and their design features.

For marking see HARP catalog, pages 42-47. There is also information about the product range. In general, we recommend you watch two webinars to learn more about HARP products:

video 1 and video 2

presentation 1 and presentation 2

What software does HARP use to calculate shafts/bearings?

HARP carries out all design developments through its own powerful engineering centers of UKTBPP (Ukrainian Bearing Industry Design and Technology Bureau) and Joint Engineering Center of UPEC based on integrated CAD/CAM/CAE solutions of the Pro/ENGINEER system.

Calculations are also carried out according to GOST (ISO), in particular GOST 18854-2013 (ISO 76:2006) – static load capacity, GOST 18855-2013 (ISO 281:2007) – dynamic load capacity.

Bearing clearances and measurement methods (especially for deep groove ball bearings).

Clearances in HARP bearings are performed in accordance with the requirements of GOST 520, 24810, ISO 5753. Measurement methods are described in detail in pt. 9.39 of GOST 520-2011, as well as in OST VNIPP.006-00, where the values of radial clearances under the measuring load of the device are given

Mounting of angular contact bearings (preload, adjusting axial play, mounting duplexes and triplexes).

From practice: for angular contact bearings, a minimum preload is required, which ensures that there is no free movement (backlash) under working loads. In this case, the bearing must rotate without jamming, wedging. It should also be noted that ball bearings are less likely to receive excess tightening force, and tapered roller bearings – loosening. Accordingly, the setting is performed according to the feelings – this is the skill of a mechanic, repairman. It is common to monitor the tightening torque of fasteners in bearing units, such as car hubs (min/max values). In critical cases, to control the assembly, it is necessary to check the maximum torque of the bearing (shaft) without load (no more than the specified value).

Several instructions for mounting bearings are available on our website, in particular for railway bearings – Duplex, double-row angular contact bearing of the front wheel hub of the car

Please explain some features of the rollers in bearings H0-32330M produced by HARP. The fact that during visual inspection of these bearings we noted the following: roller is grinded not perfectly straight along the length, as it waves, i.e. there is a fuzzy line of light reflection, as if two segments along the roller length has a different tolerance or roughness, or maybe the diameter differs by a few microns.

Please explain: is this the manufacturing technology of this bearing, or it may be incorrectly manufactured. It is not possible to make measurements with a micrometer, since this will require "removing" the roller from the cage.

Indeed, the roller is not made perfectly cylindrical according to our technology. This is done intentionally because the roller diameter is lowered to the edges (corners) (about 0.03-0.04 mm per diameter), which results in a significant reduction in contact stresses along the raceway compared to a perfectly cylindrical roller. In the bearing industry, this is a common practice and according to GOST, the designation of such bearings contains the letter M – modified contact. Accordingly, the service life of modified contact bearings is longer than that of conventional contact bearings.

Does the deviation from the hardness of the part under the bearing affect it performance? Can we check in some documentation requirements to the shaft hardness under the bearing and the hardness of the counterpart under the bearing?

We are not aware of such requirements.

In my opinion, the shaft hardness is not critical for bearing mounting. Compliance with the tolerance of shape deviation and roughness per diameter is critical. However, if there is a difference in hardness, then there may be a difference in diameter during machining, because with the same allowance, the cutting / abrasive tool can remove a different layer of material. In your case, you can check the mounting for saddle / barrel shape

Do you have a guide for mounting bearings on the adapter sleeve?

We provide all requirements according to TU VNIPP.016 where the requirements for design, mounting and operation are specified in sufficient detail. The requirements of domestic and foreign bearing manufacturers for recommended mounting are as follows. According to TU VNIPP.016-03 and recommendations for medium loading modes, mounting h7 is recommended – this value should be guided. Mountings h9 and h11 can only be used for low-load units with low rotation speed.

Since a guaranteed clearance on the shaft is required in your production, I can give the following recommendations from myself, taking into account the requirements of the technical specifications:

g6 – for units with medium and high load, i.e. more than 0.05 xS (S – static load capacity). For example, you use UCF210 with a load of approximately 8000 N (800 kgf), which is higher than 0.05 xS = 0.05 x 23300 = 1165 N (116.5 kgf), so the unit is highly loaded. Mounting of g6 for UCF210 is – 0.010...-0.025 mm.

f7 – for units with a low load, i.e. less than 0.05 xS (as far as I remember, you use UCFL205, UCF206, and UCF207 working in such conditions). Mounting f7 for UCF206 is -0.025-0.050 mm.

For easier mounting and reduced requirements for shaft accuracy (h9), HARP manufactures bearings with taper mounting bushings – series 680000, 1680000.

We have studied a sample of bearing 256907 HARP, our mechanics say that unlike those bearings that they used before this one is very tight, is there a competent explanation for this?

In bearings 6-256907AEK12L19 manufactured by HARP, the tightness is increased (high-quality protection against moisture and dirt) due to the use of a lip-type seal (lip seal with spring compression). In analogues of other manufacturers, conventional types of seals are often used, which have a low degree of tightness, weak pressure on the sealing surfaces of the bearing rings. Taken into account this fact, bearings 6-256907AEK12L19 manufactured by HARP in the free state (not installed in the unit and not run-in) can rotate tighter than their analogues.

It is important that the bearing rotates evenly (without jamming) after mounting in the hub. Also, the performance and service life of the bearing is affected by the process of dismantling the previous bearing and mounting a new one.

If the hub bearing is mounted correctly, the hub should not be very hot during the car movement. To check this bearing for operability, it is necessary to mount the bearing in the hub of the car and perform a test run-in of the bearing. The recommended test run is 10 km with a car speed of 60-70 km/h. After stopping the car, measure the hub temperature in the bearing area (the temperature should not exceed 60 °C).

Please clarify the requirements for P. P. M.

P. P. M. is short for "parts per million", the number of defective parts per million delivered to the customer. According to my estimation, this indicator is about 100 on average for all products. But for many bearings, it can be 0 (without complaints when delivered).

You should refer to official data from the Technical Control Department of HARP (OTK), they keep these statistics in accordance with IATF 16949. According to this document, the PPM for HARP ball bearings in 2018 was 49, and in the first quarter of 2019 – 17, i.e. it meets the requirements of the equipment manufacturer (no more than 50)

Dear friends, we are grateful that you share your difficulties and problems and will keep you updated on further events and activities of HARP.

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