O Ring

 Original Creation : 08-2014

O Ring

O Rings are SEALING Devices made from Rubber Material. They have a ROUND Cross- Section.

O rings are generally used to provide sealing of Fluid between two :- 

Static Components – i)Like between Filter casing and Filter Cover  ii)Crankcase Door and Crankcase etc  OR 

Between one STATIC and  another Slow Moving RECIPROCATING DYNAMIC Component —

i)Like a slow moving Piston inside a static  Hydraulic Jack cylinder

 ii) Dynamic Spool and in a Static Direction Control valve Block. Etc.

 If you observe machineries carefully , you will realize the following types of NON O Ring sealing are used:

Between –

Static and Rotary components – LIP SEAL—

i) Rotating shaft and Static Pump Body —

ii)Rotating Shaft and Static Stern Tube -- etc               

 For sealing between Static and Fast moving Reciprocating Component— we use PISTON Rings , BUCKET Rings etc

Example - Between Diesel Engine Cylinder Liner  and Piston 

The MATERIAL of the O Rings VARY depending on the sealing Environment 

 O Rings may require to Seal a variety of Fluids ranging from ..i) Sea water ii) Fresh water  iii) HOT fresh water iv) Chemicals v) OIL ..both Hot and Cold vii) Hot and Cold  Gas or AIR at various PRESSURES etc etc.

Subsequently the Materials vary from simple Rubber to Neoprene to Viton and other variants or Specials Synthetic materials.

 

Fitment and Correct Use

  

Fundamental to be remembered is that ACTUALLY an O RING DOES NOT GET COMPRESSED Volumetrically It only Changes Shape. When Compressed in X Axis—it will expand in Y Axis. 

You can see Above that

·         In Figure 1 The O ring was installed between two flanges and NONE of the Flanges have a Groove to Receive the O ring. This arrangement will Fail . O rings ALWAYS Need a GROOVE for Fitment

·         In Fig 2 –Observe that after Compression of O ring there is still space in the Groove.This is a successful sealing.The O ring just protrudes out from the flange BEFORE Installation and  During Horizontal Compression there is ENOUGH SPACE in the groove to ALLOW the O Ring to Expand Vertically

·         Fig 3—a Case of OVERSIZE O Ring .—There is No SAPCE for the O Ring to expand inside the groove and subsequently this O ring remains protruded in the Gap between the Two Flanges and eventually may fail at higher pressureds. The UNDERSIZE O ring will FAIL for Obvious Reasons.

 WorkAbouts--- 

O Rings of different sizes are available in the Open Market as Assorted O Rings. O ring Cords are also available for various sizes.

O rings can be made from O Ring Cords by using a SUPER GLUE. And these work Just as fine  in most of the NON –Presicion Places and Low Pressure applications.

However in Precision Equipment’s like PURIFIERS , ME Pneumatic Control Valves etc these tend to FAIL. These equipments usually use NON STANDARD size O rings –say 3.35mm dia etc. A standard O Ring of 3.5 mm dia from the Assorted O Ring kit will appear to fit in Fine, to the USER but after FITMENT, will leave one with enormous problems. Ofcourse there is always a Commercial Motive of the Makers who would like to make some profit on selling O rings as Spare Parts.

 It should also be Borne in Mind that It does not make sense to use Non Maker O Rings In CRITICAL Places like  ME , AE Liner sealings etc here the consequences of Failure  and resulting disruptions in Operations are UNACCEPTABLE. USED O Rings which are UNSUITABLE  for Further USE will appear to be HARD. But Renewal is Recommended in Critical Places during O Haul.