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The Importance of Choosing The Right O-ring for Fluid Sealing Applications

January 3rd, 2019 by

O-rings are the most common tools used for fluid sealing applications. They prevent leakages in pumps, valves, connectors and cylinders. The economic and compact components of o-rings are capable of carrying out dynamic and static operations in hydraulic and pneumatic applications.

 

Selecting the right o-ring is important to ensure a flawless sealing solution. The smallest mistake while choosing an o-ring can not only cost the business a loss of capital but also a loss of the clients’ trust. Every little feature of the o-ring makes a significant contribution in the end sealing results.

 

Several criteria are applied in order to determine the right size of o-ring after the nominal groove dimensions have been finalized. The following basic principles are extremely important in order to maintain the integrity of the seal along with a longer durability:

 

 

1) Compression

 

An o-ring must have a bigger cross-section than the radial gap of the groove. This consumes its elastomeric properties to provide a basic sealing force. The compression applied depends on the type of application which can be dynamic, static or many more.

 

2) Stretch

 

Since o-rings are used in various kinds of applications, they comprise negative or positive tolerances. Hence, a minor permanent stretch is applied in general, whereas in rod applications a minor permanent interface is applied over the outer diameter. This helps in a snap fit that assists with the assembly.

 

3) Gland fill

 

Even though early compression applied offers a low-pressure sealing, to maintain a high-temperature sealing, an energized pressure is needed. The groove width needs to be sufficient to allocate the pressure in the groove. This ensures that the centre of the pressure energizes the seal. To allow different rates of thermal swelling and expansion of o-rings as the media goes into the solution inside the elastomer, the standard gland fills are below 85 per cent.

 

These principles can be applied to numerous scenarios wherever o-rings can be used. These can be pistons, rods, face seal grooves and other such applications. A variety of standards have been evolved to support in specifying sealing solutions for standard metalwork dimensions.

 

In the o-ring industry, the term ‘size reference’ is also known as ‘dash size’. These terms denote the size and tolerance applied to the o-ring. A basic understanding of the different sizes of the o-rings can help the engineer identify the seal that minimizes the machine requirements. This, in turn, will help minimize the costs of the entire process. Consider the designing of a hydraulic actuator along with a common system pressure and a minimum force required. Based on these basic criteria, the operative area according to the piston’s requirement can be determined. Also, the minimum cylinder bore diameter can be calculated with this.

 

 

Different Standards of O-rings

The British standards comprise of BS 1806 and BS 4518, which are related to the metric and nominal o-ring size. These standards provide engineers with the liberty to apply their tolerances to grooves. However, the BS 1806 applies low levels of pressure to smaller cross-section o-rings and does not offer a good quality sealing solution for rod seals and pistons. These standards work well for face seal groves.

 

The Society of Automotive Engineers, USA has AS 5857 and AS 4716 as the two standards for dynamic and static sealing solutions used for rod seals and pistons. These are the most widely used standards of all and they provide comprehensive tough hardware specifications when matched with the AS 568 o-rings.

 

According to theInternational Standard Organization, the standard ISO 3601 defines grooves in a comprehensive manner. Providentially, the AS 568, BS 1806 and ISO 3601 dash sizes for o-rings correlate together. If an engineer states a -224 o-ring, he will know that the component dimensions will be 1.734 X 0.139 inches used for a two-inch cylinder bore application.

 

Engineers need to obtain assistance from experienced o-ring designers or use an easily available selection software package for the application. An improper calculation of the o-ring size will result in leakages.

Cost Against Quality

 

The standard rubber formula includes a polymer which can vary. To cut down production costs, the manufacturers replace a certain amount of carbon black or simply force mineral fillers with cheap fillers like talc and kaolin. These materials offer the rubber the same amount of hardness but a lower price as compared to rubber formulated with expensive mineral filler or carbon black. Apart from the hardness factor, there are many other factors as well. Therefore it is important to choose a reputed manufacturer that meets tensile strength, hardness, chemical compatibility and other such factors.

 

O-ring, a common tool that helps in keeping equipment running, may not initially seem important. Using the right o-ring for your application requires a small investment which is extremely essential. This results in quality work and guaranteed profits in the long run.

   

The Significance Of O-Rings For Sealing Solutions

September 28th, 2018 by

Since the first one was registered in 1896, it won’t be wrong to say that o-rings were one of the oldest inventions! This ring-like designed loop helps in the prevention of gases or liquids. It is known to be one of the easiest precision mechanism objects ever manufactured and they continue to be the most widely used products for sealing solutions.

 

The production of o-rings requires carious manufacturing techniques like compression moulding, transfer moulding, extrusion, injection moulding or machining. As per the application requirements they can be made using different rubber materials. While designing o-rings a number of factors need to be kept in mind like the cost, quality, quantity, sealing pressure, application temperature, movement, chemical compatibility, lubrication, action and much more.

 

In some scenarios, o-rings are required to be exposed to tremendous heat or toxic chemicals. This is why different materials are used to make o-rings to fit the requirements depending on the application. Similarly, the o-ring sizes may vary according to the usage requirements.

 

O-rings are basically used to place into a groove for it to hold the air or fluid in place and then squeeze it between the two surfaces. When this action is performed, the pathway where the air or fluid is escaped from is blocked. The speciality of a rubber o-ring is its muscle-memory, which means it goes back to the original shape. This feature is what helps o-rings function with sealing under low or no pressure. When pressure is applied, the o-ring is squeezed in opposition to the wall of the groove which forces it to expand in the opposite direction. This technique helps o-rings perform the sealing function against the ends of the groove.

 

There are a number of industries that extensively use o-rings. Some of these are listed below:

 

1) Aerospace:

 

The aerospace industry is highly dependent on o-rings. They need to use o-rings with the design and material which provide flexibility to fulfil their demands. Extreme temperatures and radical fluctuations in temperatures are a few concerning conditions in the aerospace industry. The utilization of o-rings is done for hydraulic systems, landing gear systems, gas turbine engines, braking and many such purposes.

 

2) Automation:

 

The various automobile products are of different natures. They consist of gas and liquid, refrigerant gases and liquids and lubricant oils of various nature. Adding to these is the difference in temperatures. To these, we must add the dissimilarities in the different temperatures that the fluids are put to work in along with the speed that can vary the exercise conditions. O-rings are of great use for the braking circuits, lubricant circuits and the air-conditioning systems.

 

3) Oil & Gas:

 

he oil and gas industry portray extreme conditions which need the o-rings to operate in these conditions accordingly. The mechanical, fluid phase and thermo-chemical conditions need to be accommodated in order to maintain the required integrity of the o-rings. They are required to be resistant to sour gas, explosive decompression, aggressive chemicals and extreme temperatures.

 

4) Chemical Processing:

 

The applications in chemical processing industries are often critical. Besides the wide chemical resistance in o-rings, the resistance to the difference in changing temperature also holds great importance. They requisite to have the ability to eliminate cold flow and drift and are able to pass over the portholes without any damage.

 

5) Food & Beverage:

 

The food and beverage industries require o-rings to be able to withstand the thermal and chemical environments that are present in the equipment. They also need to hold back any unknown or unwanted contaminants in the process. Since they may come into contact with consumption items, these o-rings need to be capable of remaining hygienic and receive an effective bacterial treatment while they still maintain their physical properties.

 

Sealing solutions among all kinds of industries require o-rings in various forms for different applications as per their custom requirements. We manufacture o-rings that are capable to resist high temperatures and pressures that do not bulge and are flexible and suitable for all kinds of environments.