Category: Newsletter

SKF Brazil, one of the largest bearing manufacturers in the world, mentions NILOS RINGS in their Technical Communication Newsletter #06 concerning the appropriate sealants to prevent contaminants and to prevent leakage of lubricated bearings:

“Another type of very simple and efficient contact seal is the NILOS RING. It consists of a piece of steel sheet with an edge that rubs against one of the bearing rings. It can grind against the internal or external rings. As the edge is pressed against the ring, after some time of operation it creates a groove which provides an excellent seal.”

Still on the references that SKF makes about NILOS RINGS, we also cite the latest edition of its General Catalogue, which, in matters concerning seals, SKF says on pages 146 and 147, the following characteristics of great importance and that differentiates our seals from the others, as their efficiency, being:

“The elastic sealing rings provide simple, economical and space-saving solution… After a break-in period, these contact seals (NILOS) become contact-free seals…”

This observation made by SKF is a technical curiosity, it confirms that NILOS RINGS never lose their sealing effect, as they wear out after their sealing edge after a certain period of operation, they become non-contact seals , which will seal indefinitely.

NILOS do BRASIL manufactures special seals for bearings that operate mainly in polluted and aggressive environments where common or generic seals fail.

Nilos Rings are widely used and recommended:

1 At high temperatures or in places where there is quick and / or abnormal wear of bearings. These are the preferred situations and where NILOS RINGS excel. Their main technical feature is that they NEVER lose their sealing effect, because the secret, now revealed, is that their function of sealing by contact makes a narrow groove passage (micro-maze) which remains throughout the bearing life.

2 On the other hand, if a machine is already worn-out, was poorly built or badly designed, the wear on the bearings is huge and, in these cases, besides the high wear on the bearings, tons of lubricants are wasted trying to solve the problem caused by excessive friction. But even in these cases the situation can be minimized using NILOS RINGS, which have sufficient elasticity (contact seals) or axial and radial clearances (labyrinth) that can compensate for equipment vibrations and oscillations, and allow continuous or periodic lubrication.

3 Common seals require a very polished seal surface, trimmed, heat-treated and even coated with hard chrome. However, NILOS RINGS seal directly on the sides of the bearing without any need for finishing, grinding, polishing and heat-treated rings because the bearings already have a suitable surface for the sealing effect.

1. PREFIXES: REFER TO BEARING COMPONENTS.
Examples of prefixes:
K	Cage
L	Removable Ring
R	Detachable bearing
N / NU / NUP / NJ	Types of internal and external rings

 

2. SUFFIXES: REFER TO INTERNAL AND EXTERNAL BEARING CONSTRUCTION.
Examples of suffixes:
A / B / C / D / E	Different and modified internal construction.
X	Modified dimensions
RS / LS / 2RS / 2LS	Shielding (seal)
N	Groove for retaining ring
NR	With snap ring groove
Z / ZZ	Protective plate
ZN	Protective plate on one side and groove on the other
ZNR	Protective plate and groove on both sides
C1 / C2 / C3 / C4 / C5	Internal clearance in ascending order
MT	Average grease temperature in shielded bearings
LT	Grease for low temperature shielded bearings
HT	Grease for high temperature shielded bearings
LHT	Grease for high and low temperature for shielded bearings

Bearings are robust mechanical components that last for a long time if:

• They are mounted correctly;
• Have good maintenance;
• Have efficient sealing;
• Are lubricated correctly.

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Maximum shelf life

• Bearings with protection plate (ZZ) ……………………… 2 years.
• Bearings with sealing plates (2RS) ………………………………….. 3 years

This time limit must be observed in order to keep the grease from hardening.

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Storage

Bearings must be maintained clean, bathed in oil or grease and wrapped in paraffin paper.

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Bearing check-up

Disclaimer: please note that the following checks must be carefully performed by qualified personnel only.

1) Listen

Hold a wood stick, screwdriver or a similar object against the bearing or as close to its bushing as possible. Get your ear close to the object’s end. A uniform metallic sound indicates the bearing needs lubrication. In case the bearing is already damaged, the sound will be characteristic of wobbling parts hitting each other.

2) Feel

Check the temperature of the bearing by holding a thermometer or heat sensitive chalk to the bushing’s compartment. If the temperature seems higher than usual or varies abruptly, one or more of the following situations could be happening:

• No lubrication, little lubrication or excessive lubrication;
• Presence of impurities due to lack of appropriate sealing;
• Excessive sealing pressure;
• Damaged bearing;
• Overloaded bearing;
• Bearing wrongly specified for application;
• Not enough internal slack on the bearing.

However, please remember there will be an increase in temperature for one or two days after the bearing is lubricated.

3) Observe

Make sure the lubricant is not leaking through inefficient and/or damaged seals or incorrectly fastened stoppers. The lubricant will present a change in its coloration under the presence of impurities or other contaminants. Automatic lubrication systems must also be checked regularly.

4) Lubricate

4.1 With grease: oils that contain thickening agents in soap form.

Three factors must be taken into consideration when selecting the type of grease to be used:

• Consistency (classified according to the NLGI scale – National Lubricating Grease Institute)
• The range of operation temperature
• Anti-corrosion properties
• Generally, soap-based greases used in bearings have consistency 1, 2 or 3

4.1.1) Calcium-based greases

Maximum temperature of 60 Celsius
Contain lead soap additives and are recommended for humid applications, including salt water.

4.1.2) Sodium-based greases

Temperature ranging from –30 to +80 Celsius
Offer protection against corrosion because they absorb humidity. If humidity is excessive, the grease might leak out of the bearing.

4.1.3) Lithium-based greases

Temperature ranging from –30 a 110 Celsius
Contain lead soap additives and are recommended for humid applications, including salt water.

4.1.4) Molybdenum-bisulfate-based greases

recommended for extremely high loads and pressures.

4.1.5) Greases for temperatures above 110 Celsius

Generally, they do not contain thickening agents in soap form, like silicone greases, for instance.

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Required amount of lubricant in bearings

1) Grease

Taking rotation into consideration, the bearings’ available space must be filled as follows:

• High rotation: must fill less than 1/3 of available space.
• Medium rotation: must fill 1/3 of available space.
• Low rotation: must fill ALL available space.

Note: When requirements are not specified, the ideal amount of grease in the bearing can be calculated applying the formula below:

G = 0,005 DB

G is the quantity (in grams)
D is the bearing’s outer diameter (in millimetres)
B is the width of the bearing (in millimetres).

2) Oil

2.1) Mineral oils

refined and with solvents can be use to lubricate bearings. Normally, mineral oils of medium to high viscosity are used, allowing the formation of an oil film thick enough to lubricate bearings operating in medium and high rotations.

2.2) Synthetic oils

Temperatures above 125 Celsius (polyglicol type). Please refer to the manufacturer’s instructions for other types of synthetic oils.

In high rotations, it is recommended to use low viscosity oils in order to keep the bearing’s temperature low.