'O' Ring Guide

How to use this guide
How to order
The following information and examples
will help you to order the correct ‘O’ ring
and back-up ring for specific applications.
For critical applications, including those
requiring FEP encapsulated ‘O’ rings, we
recommend that you state the following
details to enable us to ensure suitability:
l Pressures and pressure media.
l Operating temperatures.
l Static, or dynamic operation with
speed.
l Housing type.
l Tolerances.
l Any other important factors.
‘O’ rings
Standard sizes Charts 50, 72 & 17000:
please state the JW number followed
by material reference. If no material or
application conditions are specified, we
will supply our PB80 nitrile grade.
EXAMPLE: JW 50-001 PB80.
Aerospace sizes to BS ISO 3601-1:
please use the following example, where
XXXX denotes Size Code, YYY denotes ID,
and ZZZ denotes cross-section diameter.
EXAMPLE: ‘O’ ring – BS ISO 3601-1A-XXXX
– YYY x ZZZ – S, in FR10/80 to DTD 5612A
Grade 80.
Other sizes: please state ID, cross-section
diameter and material.
EXAMPLE: ID 49.4mm, DS 4.1mm, PB80
Back-up rings
Back-up rings are supplied in spiral form
unless single turn is stated. Also, they are
supplied in PTFE unless otherwise stated.
Back-up ring for Chart 50 inch sizes: for
back-up rings to fit inch size shafts and
cylinders, state the JW number for the ‘O’
ring. Also indicate spiral or single turn, and
material.
EXAMPLE: For a JW 50-433 (0.275”
diameter section) ‘O’ ring on a 5½” OD
shaft or 6” ID cylinder, order JW 50-433
PTFE spiral back-up ring.
Back-up rings for Chart 50 metric sizes:
When ordering back-up rings to match
our suggested Chart 50 metric shaft and
cylinder sizes, please use:
l Prefix 150 for shaft applications.
l Prefix 250 for cylinder applications.
l Also indicate spiral or single turn and
material.
(The reason is that ‘O’ rings can be
stretched or squeezed slightly — see
General design notes on pages 27-28
— but the back-up ring must be
manufactured exactly to suit the shaft or
cylinder.)
EXAMPLE 1: For 140mm OD shaft, order
JW 150-433 PTFE spiral back-up ring.
EXAMPLE: For 155mm ID cylinder, order
JW 250-433 PTFE spiral back-up ring.
Back-up rings for Aerospace Sizes to BS
ISO 3601-1: Please contact our Technical
Support Team for back-up rings to BS ISO
3601-4.
Back-up rings for Chart 72: When
ordering back-up rings (which cover those
to BS 5106) please state the same JW 72
number as the ‘O’ ring. Also indicate spiral
or single turn, and material.
EXAMPLE: JW 72-1393-57 PTFE spiral
back-up ring.
Back-up rings for other sizes: When
ordering back-up rings to match ‘O’ rings
that are not listed in our charts, please
state the following:
1) Spiral or single turn, and material.
2) Back-up ring dimensions, if known, or
3) ‘O’ ring inside diameter B; ‘O’ ring
section diameter A; shaft or cylinder
diameter (C or D); housing width and
depth (E and F) — see page 29.
EXAMPLE: PTFE spiral back-up ring to
use with a 49.4mm ID x 4.1mm DS ‘O’ ring
on a 50mm diameter shaft. Housing width
7.1mm, depth 3.5mm.
Note: Back-up rings are manufactured
to suit housing sizes, rather than 'O' ring
sizes. Therefore back-up rings cannot be
supplied based on ‘O’ ring dimensions
alone.
Subsequent orders
When re-ordering from James Walker,
please state the Re-Order Part Number
(eg, OB03400X) shown on our
documentation that acknowledges your
previous order. This will ensure the
swiftest service.
A
B
‘O’ ring diameter section A and
inside diameter B.
To order or get further details, call your local contact shown on rear cover or listed at www.jameswalker.biz 7