SEAL DESIGN INDEX
PAGE 1: General Seal Design Applications		PAGE 10: Rubber Design
PAGE 2: Preliminary Gland Design		PAGE 11: Materials
PAGES 3 - 9 Gland Design Specific
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Basic O-ring and Gland Design

An o-ring is a simple and versatile ring shaped packing or sealing device. Having a circular cross section that functions as a seal, in both static and dynamic applications, by being compressed between the mating surfaces comprising the walls of the gland, in which it is installed. Although o-rings can be made from a variety of materials, they are most commonly molded in one piece from an elastomeric material.

Reasons for O-ring Failure
Failures are usually due to a number of causes and typically
include environmental issues. For example, excess friction
causes heat, which in return causes the o-ring to swell, therefore
exposing the o-ring to a possible harsher chemical or environmental
attack.	Successful O-ring
Such effects may be compounded due to human error in overlooking
critical elements of gland design; including but not limited to
preliminary testing, proper o-ring compound use, poor installation,
lack of proper maintenance or lubrication. Some of the more common
reasons for o-ring failure are as follows:
			Failed O-ring
-incorrect o-ring size			"Non-Fill
-incorrect installation
-poor maintenance or lack of lubrication
-incompatibility of the elastomer and the environment subjected too
These problem causing attributes can be difficult to evaluate, so it is	Failed O-ring
strongly recommended that adequate testing be performed in actual	"Extrusion and Nibbling"
environmental settings.
			Failed O-ring
			"Breaking or Cracking"

Cross Section and Inside Diameter "I.D." Calculation
Dynamic Cross Section		Static Cross Section
- The following refers to a dynamic application, see gland		- The following refers to a static application, see gland design
design section for listings		section for listings
1. List the bore diameter		1. List the gland depth and multiply by the minimum and
2. List the piston groove diameter		maximum squeeze requirements ( see the gland design
3. Subtract the groove diameter from the bore diameter,		section for listings).
and divide the difference by two.
4. Refer to corresponding table (see gland design section		Static I.D. Calculation
for listings) to establish minimum and maximum squeeze		List the diameter of the part that the o-ring that will be
requirements.		stretched over during installation and reduce this figure by 1%
5. Multiply the figure from step three, by the minimum		to 5% therefore reducing the o-rings I.D. to allow for stretch,
and maximum squeeze requirements obtained in step		similar to the dynamic I.D. calculation. Then look up the o-ring
four. The two figures obtained represent the minimum		in the gland design section by I.D. and corresponding
and maximum o-ring cross section diameters, for the		cross section.
particular application.
Dynamic I. D. Calculation
The inside surface of the o-ring will be resting on the
bottom of the piston groove. To have a complete seal the
o-rings I. d. must be smaller than the piston groove diameter
(see above). The o-rings I. d. therefore will be slightly
stretched in the application. The stretch should be a minimum
of 1-2% but not exceeded 5%. The following formula
calculates the o-ring I. d.
O-Ring I. d. = Groove Diameter / % of stretch desired (1% - 5%)

Types Of Squeeze
As shown, o-ring squeeze may occur in two possible ways.
1. Axial Squeeze "A": Where the squeeze
occurs on both the top and bottom surfaces of
the o-ring.
2. Radial Squeeze "B": Where the squeeze
occurs on the inner and outer surfaces of the
o-ring.
Basic Applications
Two basic o-ring applications.
1. -Static Applications "A": O-ring is contained
within two non-moving parts.
2. -Dynamic Applications "B": O-ring is contained
within moving gland walls.

Basic O-ring Design

How O-rings Seal

An o-ring acts as a seal by blocking any potential leaching path, of a liquid or gas, between two closely matted surfaces. An o-ring is installed in a machined grooved gland (see gland design for examples) in one of the two surfaces to be sealed. As the two surfaces are brought together the o-rings cross section becomes deformed producing a tight seal, see image. The greater the squeeze the greater the deformation . The reason an o-ring acts as such a good seal is because of the elastomer material in which it is made from. An elastomer typically a highly viscous material having the tendency to remember its original shape for a long time, allowing it to be compressed and recompressed without losing its original shape and therefore its sealing ability. It is important to choose the right elastomer for each intended application. Each elastomer has different thresholds for heat, cold water, gas etc. For examples of different elastomers and there unique characteristics please visit Columbia's elastomer section.

Preliminary O-ring Design Considerations
1. What will be the function of the part	2. What type of Environment will the product be subjected to
- Seal a fluid	- Any water, chemicals, or solvents that could cause deformation to the part
- Transmit a fluid	- Oxygen or Ozone
- Transmit Energy	- Sunlight
- Absorb Energy	- Wet or Dry Environment
- Provide Structural Support	- Continuous or cycled pressure
	- Dynamic or Static stress
3. What is the desired product life	4. What are the desired properties
- Elongation Strength	- Compression Set Resistance
- Resistance to Deformation	- Resilience (Rebound)
- Compression Sets	- Tear Strength
- Resistance to Embrittlement	- Heat Aging Resistance
	- Etc. (see materials for more properties)