Plummer Blocks

a) Anatomy of pulley plummer block assemblies

For the purpose of clarity the following diagram indicates the typical pulley assembly, showing the support bearing arrangement comprising bearings, plummer blocks and sole plates. Click on the thumbnail for larger image.

The conveyor pulley shell (1) is fixed to the pulley shaft (2) by means of locking elements (3). The shaft is supported in bearings (4) which are housed in plummer blocks (5) to enable the pulley to rotate freely. The plummer blocks are secured on sole plates (6) which are welded to the pulley support structure (7). The sole plates enable the pulley to be aligned by adjusting the jacking screws (8).

PIC

In more specific detail, a typical bearing and plummer block assembly (SKF) is indicated below (click on thumbnail for larger image):-

A tapered spherical roller bearing pulley bearing (1) is shown attached to the pulley supporting stub shaft (2) by means of an adapter sleeve (3) and lock nut (4). 

The plummer block or bearing housing (5) supports the bearing. Item (6) is a typical sealing arrangement and (7) is the end cap.

A number of variations to this arrangement are available, depending on the application, environment.

This section of the Ckit Handbook includes details of plummer blocks, their seals, end covers, locating rings, essential tables and much more.

b) Features and accessories of plummer blocks

The following is an extract from the SKF catalogue, edited for this Handbook.

- General

Bearing housings fitted with rolling bearings are economic, replaceable bearing units and require little maintenance.

SKF bearing housings are generally made of cast iron and the bearing seating of the housings is machined to tolerances such that a loose fit of the bearing outer ring is ensured.

For further details on seals, page down or click here.

SKF bearing housings are primarily intended for grease lubrication. In the majority of cases it is sufficient to charge the housings with grease on mounting and to replace this grease periodically when carrying out inspections.

Plummer block housings usually have no provision for re-lubrication since used grease can be easily replaced once the housing cap has been removed.

If shorter re-lubrication intervals are required a hole may be drilled and tapped to take a grease nipple or supply line.

Plummer blocks are designed for use with self-aligning ball bearings and spherical roller bearings where the bearing either has a tapered bore and be mounted on an adapter sleeve, or the bearing has a cylindrical bore.

Elongated bolt holes are provided in the plummer block housing base to permit slight adjustments to be made to the position of the plummer block during mounting.

Most housings are fitted with dowel pins to ensure correct location of the associated caps and bases, which are not interchangeable.

Plummer blocks are designed to accommodate loads acting at right angles to the base. If the direction of load is not perpendicular to the base, care should be taken to see that the housing, cap bolts and holding down bolts have sufficient strength to carry the loads involved.
Further details regarding loading of plummer blocks is outlined elsewhere in this section.

- Types of plummer blocks

The following is an extract from the SKF catalogue, edited for this Handbook.

SKF manufacture three different types of plummer block housings namely, the 'SNA', 'SN' and 'SD' plummer blocks.

i. Type SNA plummer blocks

SNA plummer blocks are designed for use with bearings mounted on adapter sleeves or with a cylindrical bore.

The housings of SNA plummer blocks are identical for both types of bearings, but are combined with different seals.

ii. Type SN plummer blocks

SN plummer blocks are designed for use with bearings mounted on adapter sleeves or with a cylindrical bore however, different housings are used for SN plummer blocks depending on whether the bearing is to be mounted on an adapter sleeve or has a cylindrical bore.

iii. Type SD plummer blocks

SD plummer blocks are for use with bearings mounted on adapter sleeves.

Plummer blocks can accommodate a number of specific features which should be considered for each application. These features are discussed in detail below.

- Lubrication

The following is an extract from the SKF catalogue, edited for this Handbook.

Pulley plummer blocks and bearings do not require frequent re-lubrication under most operating conditions however, where the environment is harsh, provision can be made for frequent greasing or oiling. This is outlined below.

If frequent re-lubrication is required, housings fitted with 'V'-ring seals should be selected (suffix TA). Excess grease can escape from the housing past the lip of the 'V'-ring and the risk of hot running because of over-lubrication is reduced.

The efficiency of re-lubrication can be much improved by mounting an extra perforated 'V'-ring inboard of the 'V'-ring seal washer at the side where grease is applied so that grease can only leave the housing at the opposite side.

Housings of series SNA 5 and SNA 6 with 'V'-ring seals are therefore available complete with an extra 'V'-ring, grease nipple and splash plate.

It should be noted that where possible, grease should be supplied to housings with these additional features (suffix TAV, e.g. SNA51OTAV) on the side away from the lock nut.

Housings with 'V'-ring seals can be adapted for oil lubrication; see adjacent illustration.

It is necessary to drill entry and exit holes for the oil and to supplement the seals. The holes should be drilled one at each side of the bearing so that oil must pass through it.

Good sealing is obtained if an extra 'V'-ring is mounted at each side of the housing in an inboard position with its lip against the steel washer. The extra V'-rings should be of the perforated type.

At peripheral speeds in excess of 7 m/s it may be necessary to locate the 'V'-ring axially.
If a wide bearing is used, the steel washer should be turned, for reasons of space, so that its rubber lip faces inwards.

SD plummer blocks can be re-lubricated. The plug in the lubrication housing base can be replaced by a grease nipple.

The grease penetrates the bearing via the lubrication groove and three holes in the outer ring (VJ33 feature).

The housings are also suitable for oil lubrication. Bosses indicate where holes can be drilled in the base and cap for entry and exit of the oil and also to take an oil level gauge and a drain plug.

Where circulating oil lubrication is used, the supply may be connected to the lubrication duct in the housing base.

SN plummer blocks of series SN 5 and SN 6 are coupled with felt seals only. End covers for housings to be mounted at shaft ends are available; further details are available on request.

For arrangements requiring frequent re-lubrication, housings with grease valves are available. The housing dimensions are in accordance with ISO/R 113. The bearing seating is machined to tolerance H7. 

SD plummer blocks of series SD 31 TS are designed to take large spherical roller bearings or Series 231 C. The housings are fitted with labyrinth rings. These have a clearance fit but a rubber 'O'-ring inserted between the ring and the shaft ensures that the ring rotates with the shaft and also permits slight axial displacements caused by thermal changes in shaft length. 

Housings for shaft ends are supplied with an end cover instead of one of the labyrinth rings; further details are available on request. The bearing seating is machine to tolerance H8.

- Housings

The following is an extract from the SKF catalogue, edited for this Handbook.

A variety of housings are available to suit different requirements and applications.

SNA plummer blocks are a development of the SN plummer blocks. The dimensions of both SNA and SN housings follow ISO/R 113 and the housings of series SNA 5 and SNA 6 are interchangeable with those of SN 5 and SN 6, respectively. The SNA housings have much greater strength however.

Where even greater strength is required SSNAD housings can be supplied. A standard range of housings from size 511-609 is available made of spheroidal graphite cast iron. The bearing seating is machined to tolerance H8.

These housings carry the designation prefix SSNAD, e.g. SSNAD 511 TA.

i. Drilling

The foot of SSNAD housings is solid and without bolt holes. These should be drilled according to the instructions given in the following table. SSNAD and SNA housings are otherwise identical and the same bearings and accessories may be used.

Table indicating base drilling dimensions.

For two holes

For four holes

Housing without seals Dimensions mm
For two holes For four holes

Designation

 J N1 J1 J2 N2
SSNAD 511-609 210 18 200 35 15
SSNAD 512-610 210 18 200 35 15
SSNAD 513-611 230 18 220 40 15
SSNAD 515-612 230 18 220 40 15
SSNAD 516-613 260 22 250 50 15
SSNAD 517 260 22 250 50 15
SSNAD 518-615 290 22 280 50 18
SSNAD 519-616 290 22 280 50 18
SSNAD 520-617 320 26 300 60 18
SSNAD 522-619 350 26 320 70 18
SSNAD 524-620 350 26 330 70 18
SSNAD 526 380 28 370 70 22
SSNAD 528 420 35 400 80 26
SSNAD 530 450 35 430 90 26
SSNAD 532 470 35 450 90 26

ii. Loading and strength of plummer block housings.

Plummer blocks are designed to accommodate loads acting at right angles to the base. If the direction of load is not perpendicular to the base care should be taken to see that the housing, cap bolts and holding down bolts have sufficient strength to carry the loads involved.

Approximate values for the breaking load for the housings and the yield point for the cap bolts are given in the tables below.

To obtain the permissible load, the values are divided by a factor selected with regard to safety requirements.

For general engineering purposes a safety factor of 6 is generally applied for the housings and a factor of 3 for the bolts.

Approximate values of the breaking load (P) for the housings, and the yield point (Q) for the cap bolts are given in the following tables for different radial directions of loading.

When the load acts at an angle of 55 deg. the cap bolts carry no load and 'Q' is always greater than 'P' when the load acts at an angle of 90 deg. 

In the axial direction the breaking load is approximately 65 % of P180 deg.

Table showing strength of SNA and SSNAD plummer blocks

Strength of SNA and SSNAD plummer block housing
Housing Breaking load for SNA housings * Yield point for the two cap bolts
SNA housings SSNAD housings
Size P55° P90° P120° P150° P180° Q120° Q150° Q180° Q120° Q150° Q180°
-- kN (1kN = 225lbf) kN (1kN = 225lbf)
505 130 80 60 50 65 90 50 45 -- -- --
506-605 140 85 65 55 70 90 50 45 -- -- --
507-606 160 95 75 65 80 90 50 45 -- -- --
508-607 180 110 80 70 90 90 50 45 -- -- --
509 190 115 85 75 95 90 50 45 -- -- --
510-608 220 130 100 90 110 90 50 45 -- -- --
511-609 230 140 105 95 115 130 70 65 290 160 145
512-610 250 150 110 100 125 130 70 65 290 160 145
513-611 280 170 125 110 140 130 70 65 290 160 145
515-612 340 205 155 135 170 130 70 65 290 160 145
516-613 360 215 160 145 180 230 125 115 290 160 145
517 400 240 180 160 200 230 125 115 290 160 145
518-615 460 280 210 180 230 440 240 220 540 300 270
519-616 480 290 220 190 240 440 240 220 540 300 270
520-617 520 310 230 210 260 620 340 310 850 470 425
522-619 620 370 280 250 310 620 340 310 850 470 425
524-620 720 430 320 290 360 620 340 310 850 470 425
526 820 490 370 330 410 900 500 450 1220 670 610
528 960 570 430 390 480 900 500 450 1220 670 610
530 1100 660 490 440 550 900 500 450 1220 670 610
532 1130 780 580 520 650 900 500 450 1220 670 610

* = SSNAD housings have approximately twice this strength.

Table showing strength of SN plummer blocks

Strength of SN plummer block housing
Housing Breaking load for the housings * Yield point for the two cap bolts
Designation P55 P90 P120 P150 P180 Q120 Q150 Q180
-- kN (1kN = 225lbf) kN (1kN = 225lbf)
SN505 -- 70 40 30 30 35 80 45 40
SN506 SN605 80 50 35 30 40 80 45 40
SN507 SN606 90 55 40 35 45 80 45 40
SN508 SN607 100 60 45 40 50 80 45 40
SN509 -- 110 65 50 45 55 80 45 40
SN510 SN608 120 70 55 50 60 80 45 40
SN511 SN609 140 85 60 55 70 140 80 70
SN512 SN610 150 90 65 60 75 140 80 70
SN513 SN611 170 100 70 70 85 140 80 70
SN515 SN612 190 110 85 75 95 140 80 70
SN516 SN613 220 130 100 90 110 240 130 120
SN517 -- 240 140 110 95 120 240 130 120
SN518 SN615 260 160 120 100 130 240 130 120
-- SN616 280 170 130 110 140 240 130 120
SN520 SN617 340 200 150 140 170 540 300 270
SN522 -- 440 260 200 180 220 540 300 270
SN524 -- 520 310 230 210 260 540 300 270
SN526 -- 620 370 280 250 310 760 420 380
SN528 -- 720 430 320 290 360 1000 550 500
SN530 -- 860 520 390 340 430 1000 550 500
SN532 -- 1100 660 490 440 550 1000 550 500

* = Housing series SN2 and SN3 have the same strength as those of series SN5 and SN6 respectively.

Table showing dimensions of SN plummer blocks

Shaft dia. Housing Dimensions Mass Designation
da db A A1 H H1 H2 J L N N1 G
mm mm kg --
130 145 190 130 290 150 50 380 445 35 28 24 28.5 SN226
140 155 205 150 305 150 50 420 500 42 35 30 36.0 SN228
150 165 220 160 325 160 60 450 530 42 35 30 43.0 SN230
160 175 235 160 345 170 60 470 550 42 35 30 49.5 SN232

Table showing strength of SD plummer blocks

Strength of SD plummer block housing
Housing Breaking load for the housings Yield point for the four cap bolts
Designation P55 P90 P120 P150 P180 Q120 Q150 Q180
-- kN (1kN = 225lbf) kN (1kN = 225lbf)
SD3134 2100 1000 760 680 850 1500 830 750
SD3136 2400 1150 850 760 950 1500 830 750
SD3138 2700 1300 1000 880 1100 2000 1100 1000
SD3140 3200 1600 1150 1050 1300 2000 1100 1000
SD3144 4000 1900 1400 1400 1600 2000 1100 1000
SD3148 4200 2000 1500 1500 1700 3200 1800 1600
SD3152 4700 2300 1700 1700 1900 3200 1800 1600
SD3156 5000 2400 1800 1800 2000 3200 1800 1600
SD3160 6000 2900 2200 2200 2400 3200 1800 1600
SD3164 7000 3400 2500 2500 2800 3200 1800 1600

Table showing dimensions of SD plummer blocks

Ref No. d1 Spherical Roller Brg. + Adaptor Sleeve. A H1 H2 H L A1 J J1 J3 J4 J2 V d2 B
SDX 31106 500 231 / 530 CAK/W33 + OH31106 484 500 980 1100 1140 450 980 320 70 54 35 80 870 19
0
SDX 3196 450 23196 CAK/W33 + OH3196 458 470 910 1030 1040 440 880 310 70 54 35 80 790 17
0
SDX 3192 430 23192 CAK/W33 + OH3192 450 470 890 1010 1040 440 880 310 70 54 35 80 760 16
5
SDX 3188 410 23188 CAK/W33 + OH3188 436 440 840 960 940 400 810 280 64 48 35 70 720 15
5
SDX 3184 400 23184 CAK/W33 + OH3184 434 440 840 955 940 400 810 280 64 48 35 70 700 15
0
SDX 3180 380 23180 CAK/W33 + OH3180 400 390 755 860 880 380 760 280 64 48 35 70 700 14
0
SDX 3176 360 23176 CAK/W33 + OH3176 385 390 742 850 880 380 760 280 64 48 35 65 620 13
0
SDX 3172 340 23172 CAK/W33 + OH3172 380 360 700 800 830 350 700 240 64 48 30 50 600 12
8
SDX 3168 320 23168 CAK/W33 + OH3168 380 360 690 790 830 350 700 240 64 48 30 50 600 11
0

 

- Plummer block seals

The following is an extract from the SKF catalogue, edited for this Handbook.

A marked improvement compared with earlier plummer blocks is that different types of seal can be used. The standard seals supplied by SKF are 'V'-ring and felt seals. They are delivered in special packages together with the housings. Fitting is very simple.

SKF bearing housings are always supplied complete with seals comprising 'V'-ring seals, felt seals (felt strips unless otherwise stated) or labyrinth seals.

'V'-ring seals are suitable for peripheral speeds of up to 12 m/s and operating temperatures of -40 to +100 deg. C. Felt seals are normally employed for peripheral speeds of up to 4 m/s and temperatures of up to + 100 deg. C. Before using felt strips, they should be soaked in hot oil for a few minutes. Labyrinth seals are universally applicable and not subject to wear.

The different seal types are outlined below :-

i. 'V'-ring seals

The 'V'-ring, which is of synthetic rubber, has a thin sealing lip, which functions in an axial direction. The ring also acts as a flinger as it rotates with the shaft.

This type of seal can be used with both grease and oil lubrication and is extremely effective under most operating conditions including high speeds.

The 'V'-rings in SNA plummer blocks seal against sheet metal washers with a rust preventive coating and placed in the grooves of the housing.

Each washer has a rubber lip bonded around its periphery and which bears against the housing. However, in plummer blocks SNA 205 to SNA 218 the 'V'-rings seal directly against the housing; in this case the side faces of the housings are machined.

SNA plummer blocks with 'V'-ring seals are given the suffix TA, for example SNA 505 TA.

The 'V'-ring seals consist of a 'V'-ring (1) and a sheet steel washer (2), which has been treated to prevent corrosion.

The 'V'-ring is mounted on the shaft (3) and seals against the washer, which is mounted in a groove (4) in the plummer block housing (5).

The washer has a bonded rubber lip and seals against the housing.

For exacting operating conditions, the 'V'-ring and felt seals of housings SNA 505 to SNA 518 and SNA 605 to SNA 615 may be supplemented by a light alloy collar (6).

The collar prevents the seals from becoming damaged and also enhances their sealing effect. The bore diameter tolerance is H10. The collar is designated TSNA B, e.g.: TSNA505B.

ii. Felt seals

The felt seal is a simple but adequate seal which can be used with grease lubrication and at peripheral speeds of up to some 4m/s.

Plummer blocks of series SNA 5 and SNA 6 are obtainable with split felt seals consisting of oiled felt incorporated in a light alloy ring in two pieces. These are pressed into the housing grooves after first inserting rubber 'O'-rings, which serve both as an effective seal between the housing and the light alloy ring and also to prevent this from rotating.

Plummer blocks SNA 205 to SNA 218 may also be supplied with felt seals but they comprise loose felt strips that are fitted directly in the grooves, i.e. they have no metal backing.

SNA plummer blocks with felt seals are given the suffix TO, for sample SNA 505 TO.

iii. Labyrinth seals

The labyrinth seal type TS shown below, is recommended in cases where SKF standard seals cannot be used for one reason or another, for instance if they do not match the diameter of the shaft.

Depending on the radial space available for the collar, the (a) or (b) design should be chosen (refer to table below for dimensions) :-

Design 'A'

Design 'B'

Type 'TS'- Narrow Collar

Type 'TS' - Wider Collar

Table showing dimensions for sealing collars for 'special' seals type 'A' and 'B'.

Housing Sealing collar Rubber cord
Design Dimensions 4mm dia.
655° IRH
dd de df A10 A11 A12 A13 A14 Length
(approx.)
H9 h13 h13   h13 JS13   h13  
Designation -- mm mm
SNA 505 a Max.21 30,5 37,5 6,5 18 10 4,5 3 75
b 21 - 27 30,5 37,5 12 23 15,5 10 3 95
SNA 506-605 a Max.26 35,5 42,5 6,5 18 10 4,5 3 95
b 26 - 32 35,5 42,5 12 23 15,5 10 3 115
SNA 507-606 a Max.36 45,5 52,5 6,5 18 10 4,5 3 125
b 36 - 41,5 45,5 52,5 12 23 15,5 10 3 140
SNA 508-607 a Max.41 50,5 57,5 6,5 18 11 4,5 3 140
b 41 - 46,5 50,5 57,5 12 23 16,5 10 3 155
SNA 509 a Max.46 55,5 62,5 6,5 19 11 4,5 3 155
b 46 - 51,5 55,5 62,5 12 24 16,5 10 3 175
SNA 510-608 a Max.51 61 68,5 6,5 19 11 4,5 3 175
b 51 - 57 61 68,5 12 24 16,5 10 3 195
SNA 511-609 a Max.56 66 73,5 6,5 19 11 4,5 3 185
b 56 - 62 66 73,5 12 24 16,5 10 3 205
SNA 512-610 a Max.61 71 78,5 6,5 19 11 4,5 3 205
b 61 - 67 71 78,5 12 24 16,5 10 3 225
SNA 513-611 a Max.66 76 83,5 6,5 19 11 4,5 3 225
b 66 - 72 76 83,5 12 24 16,5 10 3 245
SNA 515-612 a Max.75 85,5 93 6,5 19 11 4,5 3 245
b 75 - 81,5 85,5 93 12 24 16,5 10 3 270
SNA 516-613 a Max.80 91 98,5 7,5 22 14 5 3 260
b 80 - 87 91 98,5 12,5 27 19 10 3 290
SNA 517 a Max.85 96 103,5 7,5 22 14 5 3 280
b 85 - 92 96 103,5 12,5 27 19 10 3 305
SNA 518-615 a Max.90 101 108,5 7,5 23 14 5 3 305
b 90 - 97 101 108,5 12,5 28 19 10 3 320
SNA 529-616 a Max.118 129,5 138,5 7,5 24 14 5 4 375
SNA 520-617 a Max.125 136 145 7,5 24 14 5 4 405
SNA 522-619 a Max.135 146 155 7,5 24 14 5 4 440
SNA 524-620 a Max.145 156 165 7,5 24 14 5 4 460
SNA 526 a Max.155 166 175 8 26 16 5,5 4 500
SNA 528 a Max.165 176 185 8 26 16 5,5 4 530
SNA 530 a Max.180 191 200 8 27 16,5 5,5 4 590
SNA 532 a Max.190 201 210 8 27 16,5 5,5 4 620

iv. Special seals for plummer blocks of type SNA

The following is an extract from the SKF catalogue, edited for this Handbook.

Essential manufacturing data

In TSP 6020 "Plummer blocks of type SNA", some types of special seal are shown below and the related application dimensions of the housings are given in the table.

This table gives the dimensions required for the manufacture of the seals, which are easily made from tubular material.

Illustrated here are two seals for extremely severe operating conditions, a labyrinth seal and a combined 'V'-ring and gap seal equipped with a nipple for lubricating the 'V'-ring.

Click on thumbnails for larger image.

The table below gives the dimensions necessary to ensure that the seals fit the housings.

Other dimensions may be varied however, in view of the manufacturing tolerances, the bearing internal clearance and the inevitable misalignment, sufficient radial clearance in the labyrinth must be ensured.

Table showing machining dimensions for 'special' seals

Housing Sealing collar dimensions O ring
db dc A7 A8 A9 655° IRH
h11 h11 h13 h13    
Designation mm mm
SNA 505 31,5 37 8,5 4,8 3 34,2 x 3
SNA 506-605 36,5 42 8,5 4,8 3 39,2 x 3
SNA 507-606 46,5 52 8,5 4,8 3 49,5 x 3
SNA 508-607 51,5 57 8,5 4,8 3 54,5 x 3
SNA 509 56,5 62 9,5 4,8 3 59,5 x 3
SNA 510-608 62 68 9,5 4,8 3 64,5 x 3
SNA 511-609 67 73 9,5 4,8 3 69,5 x 3
SNA 512-610 72 78 9,5 4,8 3 74,5 x 3
SNA 513-611 77 83 9,5 4,8 3 79,5 x 3
SNA 515-612 87 93 9,5 4,8 3 89,5 x 3
SNA 516-613 92,5 98,5 12 4,8 3 94,5 x 3
SNA 517 97,5 103,5 12 4,8 3 99,5 x 3
SNA 518-615 102,5 108,5 12 4,8 3 104,5 x 3
SNA 529-616 131 137,5 13 5,8 4 134 x 4
SNA 520-617 137,5 143,5 13 5,8 4 140 x 4
SNA 522-619 147,5 153,5 13 5,8 4 150 x 4
SNA 524-620 157,5 163,5 13 5,8 4 160 x 4
SNA 526 167,5 173,5 14,5 5,8 4 170 x 4
SNA 528 177,5 183,5 14,5 5,8 4 180 x 4
SNA 530 192,5 198,5 15 5,8 4 192 x 4
SNA 532 202,5 208,5 15 5,8 4 205 x 4

- Protective collars

The following is an extract from the SKF catalogue, edited for this Handbook.

Where operating conditions are severe, the 'V'-ring and felt seals of plummer blocks SNA 505 to SNA 518 and SNA 605 to SNA 615 may be supplemented by a light alloy collar, a standard component available from SKF.

The collar protects the seals against damage and also improves the sealing effect. The bore diameter tolerance is H10.

The protective collars are designated TSNA (000) B, for example TSNA 505 B.

Table showing SKF collar dimensions.


COLLAR d1
Shaft Dia.		 D W A
TSNA 509 B 40 92 30 20
TSNA 511 B 50 111 30 22
TSNA 513 B 60 115 30 20
TSNA 515 B 65 122 22 16
TSNA 516 B 70 130 30 20
TSNA 517 B 75 135 30 22
TSNA 518 B 80 145 34 26
TSNA 520 B 90 185 45 30
TSNA 522 B 100 190 27 20
TSNA 524 B 110 210 40 30
TSNA 526 B 115 220 40 30
TSNA 528 B 125 235 40 30
TSNA 532 B 140 250 40 30

- End covers

The following is an extract from the SKF catalogue, edited for this Handbook.

If the bearing is mounted at the end of a shaft i.e. not a through-shaft, the bore at the outer side of the housing should be closed by means of a cover.

These end covers, which are supplied separately in packages, are designated ASNA followed by the number of the housing, for example ASNA 506-605.

Plummer blocks of the series most frequently used, SNA 5 and SNA 6, are available with a seal set comprising one end cover and one 'V'-ring seal and are then given the suffix ATA, for example SNA 505 ATA.

- Locating rings

The following is an extract from the SKF catalogue, edited for this Handbook.

The bearing seating in the housings is sufficiently wide to allow axial freedom for any bearing. A bearing which is to locate the shaft should therefore be fixed in position by means of one or more locating rings. Floating bearings are generally not fitted with locating rings.

If this bearing is mounted on an adapter sleeve, the locating rings should be placed as follows to suit the application :-

 

i. 1 ring on the same side as the sleeve nut.

ii. 2 rings - one on each side of the bearing.

iii. 3 rings - two on the same side as the sleeve nut.

iv. 4 rings - two on each side of the bearing.

c) Plummer Block Reference and Designations

The following details apply to SKF's standard plummer blocks, covers, sealing arrangements, etc. and are provided here to assist with the correct designations for the various components.

Brg.
Shaft Dia.		 V-Ring
Seal & Washers		 Felt Seal V-Ring
Cover Plate		 Poly-Urethane Collar Locating Ring Labyrinth
Seal O-Ring		 End Cover
50 TA TC ATA TSNA511 FRB9,5/100 TS11 ASNA511
75 TA TC ATA TSNA517 FRB12,5/150 TS17 ASNA517
90 TA TC ATA TSNA520 FRB12/180 TS20 ASNA520
100 TA TC ATA TSNA522 FRB13,5/200 TS22 ASNA522
110 TA TC ATA TSNA524 FRB14/215 TS24 ASNA524
125 TA TC ATA TSNA528 FRB15/250 TS28 ASNA528
140 TA TC ATA TSNA532 FRB17/290 TS32 ASNA532
160         FRB10/300 TS36 716150/36
180         FRB10/340 TS40 716150/40
200         FRB10/370 TS44 716150/44
220         FRB10/400 TS48 716150/48
240         FRB10/440 TS52 716150/52
260         FRB10/460 TS56 716150/56
280         FRB10/500 TS60 716150/60
300         FRB10/540 TS64 716150/64
320         /580 TS68 716150/68
340         /600 TS72 716150/72
360         /620 TS76 716150/76
380         /650 TS80 716150/80
400         /700 TS84 716150/84
410         /720 TS88 716150/88
430         /760 TS92 716150/92
450         /790 TS96 716150/96
500         /870 TS106 716150/106

Suffix TA to housing e.g. SNA 520 TA, indicates supplied with two V-ring seals and washers.
Suffix TC to housing e.g. SNA 520 TC, indicates supplied with two felt seals and light alloy rings. 
Suffix ATA e.g. SNA 520 ATA, indicates supplied with one V-ring seal and washer and one end cover. 

For polyurethane protective collars see standard No. CM/0900/PB1B. When calling up these parts the material must be stated since SKF also supply light alloy collars with corresponding part numbers.

Locating ring designation indicates width and o/dia e.g. 10/370 = 10 wide x 370 o/dia. 

References for this section :-

SKF - General Catalogue 3000 IIE/GB666 11 - July 1978. 
SKF - SNA Plummer Blocks Ref. No. TSP 6020. 
SKF - Special Seals for SNA Plummer Blocks Ref. No. TSP 6021 
SKF - Drawing No. 2156428. 

d) Layout

Bearings are usually mounted onto pulley shafts at pre-defined spacings, which is the norm followed in the industry.

Factors which affect the bearing centers include the width of the conveyor belt and hence pulley shell, the width of the (discharge) chute work, the design of the pulley support structure and whether or not the pulley is a take-up pulley, tail pulley or drive pulley.

The standard bearing spacing followed is as per the table below :-

Belt width Face width Chute plates I/S Bearing centres Clearances for wide centres
See legend below
Wide Narrow
W F A B C D E G
450 550 650 1000 760 225 50 50
500 600 700 1050 810 225 50 50
600 700 800 1150 1020 225 50 50
750 900 1000 1350 1170 225 75 50
900 1050 1150 1550 1370 250 75 50
1050 1200 1300 1700 1520 250 75 50
1200 1350 1450 1850 1680 250 75 50
1350 1500 1600 2050 1830 275 75 50
1500 1700 1850 2300 1980 300 100 75
1650 1850 2000 2450 2130 300 100 75
1800 2000 2150 2600 2280 300 100 75
2100 2300 2450 2900 2580 300 100 75
2400 2600 2750 3200 2880 300 100 75

Legend :- 

D = Pulley face to centre-line bearing housing.
E = Pulley face to belt edge.
G = Pulley face to inside chute plate.