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FAQ

Brand O-Rings Size Chart

Scubapro to AS568 standard O-Ring sizes

EPDM: Ethylene Propylene Diene Monomer rubber

NBR: Nitrile Rubber

FKM: Fluoro Rubber / Viton

PU: Polyurethane Elastomer   

  

Scubapro Part №
AS568
SHORE A
MATERIAL
01-050-108
-00390NBR
01-050-110
-00370FKM
01-050-117
-00685EPDM
01-050-421
-00690PU
01-050-120
-00770NBR
01-050-126
-00885EPDM
01-050-422
-00885PU
01-050-394
-01090FKM
01-050-132
-01070NBR
01-050-136
-01085EPDM
01-050-137
-01085PU
01-050-138
-01185EPDM
01-050-143
-01190FKM
01-050-424
-01185PU
01-050-145
-01285EPDM
01-050-403
-01290FKM
01-050-425
-01285PU
01-050-147
-01385EPDM
01-050-347
-01485EPDM
01-050-420
-01485PU
01-050-158
-01585EPDM
01-050-396
-01590FKM
01-050-427
-01585PU
01-050-160
-01670NBR
01-050-161
-01770EPDM
01-050-162
-01770NBR
01-050-395
-01770FKM
01-050-177
-02280EPDM
01-050-407
-02270FKM
01-050-179
-02270PU
01-050-164
-02770NBR
01-050-385
-10970NBR
01-050-193
-11185EPDM
01-050-428
-11185PU
01-050-195
-11180FKM
01-050-363
2,2x1 mm70NBR
01-050-323
-12550NBR
01-050-360-17970NBR


Download Our Scubapro O-Rings Size Chart

Apeks to AS568 standard O-Ring sizes

EPDM: Ethylene Propylene Diene Monomer rubber

NBR: Nitrile Rubber

FKM: Fluoro Rubber / Viton

     

 Apeks Part №
AS568
SHORE A
MATERIAL
AP6403
-00490NBR
AP1299
-00685EPDM
AP1282-00770NBR
AP1154
-01075FKM
AP1409
-01170EPDM
AP1445
-01270EPDM
AP1410
-01370EPDM
AP1159
-01475FKM
AP1267
-01575FKM
AP1298-01770NBR
AP4089-01870NBR
AP1438
-01970EPDM
AP1420
-02470NBR
AP2013-02770NBR
AP1166
-11175FKM
AP1405-11370NBR
AP1505-11470NBR
AP1277-11970NBR
AP1278-21370NBR
AP7502-61070NBR
AP2041
1,7 x 1 mm70EPDM
AP5711
2,5 x 1 mm75FKM
AP130015 x 1,5 mm70NBR


Mares to AS568 standard O-Ring sizes

EPDM: Ethylene Propylene Diene Monomer rubber

NBR: Nitrile Rubber

FKM: Fluoro Rubber / Viton

     

 Mares Part №
AS568
SHORE A
MATERIAL
46110101
-00670EPDM
46110205
-01070EPDM
46110107
-01170EPDM
46110108 
-01270EPDM
46110215
-01370EPDM
46110211
-01490NBR
46110225
-01770EPDM
46110247
-11175FKM
46200559
15 x 4 mm70EPDM
46110106
-61070NBR



Sherwood to AS568 standard O-Ring sizes

EPDM: Ethylene Propylene Diene Monomer rubber

NBR: Nitrile Rubber

FKM: Fluoro Rubber / Viton

     

 Sherwood Part №
AS568
SHORE A
MATERIAL
6121-122
-00470NBR
5121-101
-00670EPDM
G007A
-00770NBR
6110-129
-00870EPDM

6121-135 

6400-113

-00970NBR

5121-104 

6110-119 

6161-101 

6121-137

-01070NBR
5121-104
-01170EPDM
6400-115
-01370EPDM
5121-105
-01470EPDM
5121-106
-01570EPDM
6400-125
-01670NBR
6400-102
-02070NBR
5110-107
-02270EPDM

6110-131

6400-107

-02370NBR
6110-125
-02470NBR
5110-109-02570NBR
5121-102
-10670NBR
6121-129
-10770NBR
6400-138
-11170FKM
6500-112
1,95 x 1 mm70NBR

6121-141

6110-123

-90370NBR
6400-135
-90570NBR

6110-115 

6121-104

-90670NBR


Scuba Diving O-Rings

Black is the normal color to be used and in fact, offers the optimum performance. Viton Black is stronger, more stable, and more elastic, even after continuous exposure to extreme conditions associated with the scuba diving sport (i.e. salt water, UV light, high temperature etc.). We recommend that you use a black Viton for your diving gear.
Green is the color of choice in Europe for color-coding Viton, whereas brown is the color in the US.  






Characteristics of Viton® O-Rings, Seals & Gaskets

Temperature range: -20°F to 400°F (-29°C to 204°C)

Standard hardness: 70-75 Shore A

Hardness range: 50-95

Standard colors: black, brown

The hardness of o-rings is measured by the Shore A durometer the higher the durometer, the harder the compound. 70 Shore A is softer than 90. The soft O-Rings are appropriate for dynamic applications where the o-ring is providing a seal with a constantly moving part, such as inside regulators. O-Rings commonly used in scuba diving equipment, that come in different hardness ranging from 70 to 90. Usually, HP and tank necks use 90, and LP uses 70. 
The hardness of the o-rings must be consistent with the technical requirements of manufacturers of diving equipment.

The materials commonly used in SCUBA applications


Abbreviations
Elastomer
Trade names
Description
NBR, Nitrile
Acrylonitrile-butadiene rubber
Perbunan
Most O-rings used in SCUBA are made from Nitrile, a hydrocarbon-based synthetic rubber. Nitrile offers excellent resistance to many oils and acids and has good physical properties. However, Nitrile is not a very oxygen resistant material and is not considered oxygen compatible. Nitrile is also often referred to as Buna-N.
FKM
Fluoro rubber
Viton®
O-rings made of FKM Viton® have been the preferred choice for oxygen and nitrox compatibility in SCUBA diving applications. FKM Viton® is an elastomer with excellent oil and oxygen resistance at high and low temperatures, very good chemical resistance. Even for use with ordinary air, most experts agree that FKM Viton® O-rings outperform common Nitrile O-rings.
PUR
Polyurethane
Adiprene® Millathane®

O-ring is made of Polyurethane. Polyurethane is very abrasion-resistant, but it is sensitive to UV light (sunlight). Good hydraulic oil and gasoline resistance. Resistant to pure aliphatic hydrocarbons (propane, butane, fuel).Resistance to mineral and silicone oils and greases.Resistant to water, oxygen, ozone, and aging. Excellent tear and abrasion resistance

EPDM
Ethylene propylene diene rubber
Nordel®
EPDM materials generally have a high resistance to hot water, steam, aging, and chemicals, and are suitable for a wide range of temperature applications. EPDM has good resistance to hot water and steam, detergents, caustic potash solutions, sodium hydroxide solutions, silicone oil and greases, many polar solvents, many diluted acids, and chemicals. Special qualities are recommended for glycol-based brake fluids. EPDM materials are totally unsuitable for use with all mineral oil products (lubricants, fuels). They can be used between –45°C and +130°C (peroxide-cured –50°C to +150°C).

The Difference between FKM and Viton®?

  • FKM is the short form for the fluoroelastomer category according to the American standard ASTM.
  • Viton® is the registered trademark of DuPont Performance Elastomers.

Viton o-rings are commonly available in 75 & 90 Shore Hardness. These compounds are normally stocked in Black although other colors can be manufactured in Brown / Green / White

Black FKM VITON ® better properties over brown or green material.

Viton and Buna are two of the most commonly used elastomers for o-rings in scuba diving applications.
Viton is far superior to Buna for high-temperature applications. Viton seals provide an indefinite seal for temperatures up to 400°F, and for temperatures up to 600°F they offer an excellent seal for more than 48 hours. Buna, on the other hand, is only effective up to 250°F. However, Buna seals provide a low-temperature sealing option with effective sealing down to temperatures of –22°F, while temperatures below 5°F render Viton seals ineffective as they become quite hard and inflexible.
Buna is much less universally resistant than its Viton counterpart which suffers degradation from weather and ozone exposure. 
Both of these sealing options offer an extensive list of dive applications, and they both serve well in scuba gear.

Five Common Reasons why Scuba O-Ring Fail

  Explosive Decompression

  O-Ring Failure Description: The seal exhibits blisters, pits, or pocks on its surface. 

  Absorption of gas at high pressure and the subsequent rapid decrease in pressure. 

  The absorbed gas blisters and ruptures the elastomer surface as the pressure is rapidly removed.

  Contributing Factors: Rapid pressure changes. Low-modulus/hardness elastomer.



   Installation Damage

  O-Ring Failure Description: The seal or parts of the seal may exhibit small cuts, nicks, or gashes.

  Contributing Factors: Sharp edges on glands or components. Improper sizing of elastomer. 

  Low-modulus/hardness elastomer.  Elastomer surface contamination.




  Spiral Twisting Failure

  O-Ring Failure Description: The seal exhibits cuts or marks which spiral around its circumference.

  Contributing Factors: Difficult or tight installation (static). Slow reciprocating speed.

  Low-modulus/hardness elastomer. Irregular O-ring surface finish (including excessive parting line). 

  Excessive gland width. Irregular or rough gland surface finish. Inadequate lubrication.



  Abrasion - Friction

  O-Ring Failure Description: The seal or parts of the seal exhibit a flat surface parallel to the direction

  or motion. Loose particles and scrapes may be found on the sealing surface.

  Contributing Factors: Rough sealing surfaces. Excessive temperature. Process environment containing 

  abrasive particles. Dynamic motion. Poor elastomer surface finish.



  Compression Set

  O-Ring Failure Description: The seal exhibits a flat-sided cross-section, 

  the flat sides corresponding to the mating seal surfaces.

  Contributing Factors: Excessive compression. Excessive temperature. Incompletely cured elastomer. 

  Elastomer with a high compression set. Excessive volume swells in chemicals.


The information has been gained from manufacturing partners.

Have no worries, fatal o-ring problems are very rare if you are well informed and know how to use them correctly. 
O-ring leaks, however, are common and can ruin a dive or an anticipated dive vacation. Luckily, knowing how to deal with o-rings is simple and will reduce inconveniences a lot. You can replace most of the o-rings safely on the spot and with minimum skills. Many of them are includes in most Save-A-Dive kits.

Silicone Grease

Lightly applying to the housing rubber seals should help to stop them drying out and cracking. This should at least help the seals to last longer. As to improving the actual seal, 
I would guess that keeping the seals lubricated may have a positive effect overall. Used the silicon grease for GoPros, Underwater Camera Case, Dive Torches
Yes It is ideal for applications with plastic and rubber.
This is silicone grease approved for use with incidental contact with drinking water. Its food-grade. 
It is NSF 61 approved and meets or exceeds the requirements of FDA regulation 21

Yes, this grease is totally safe for any application. It’s designed for seals and o-rings for waterproof watches and diving computers.

Yes, it’s 100% pure silicone. Non-flammable, non-toxic formula.

No, silicone grease is commonly used for lubricating and preserving rubber parts, such as O-rings. Additionally, silicone grease does not swell or soften the rubber, which can be a problem with hydrocarbon-based greases.

No, we do not recommend putting silicone grease on latex as it can cause degradation in the material of the seals.