THE IMPORTANT FEATURES AND ROLES OF A ROLLING DIAPHRAGM

Diaphragm seals are found in industries that need maximum execution in severe environments, such as the automobile, aviation, pharmaceutical, and food and water-processing industries. Mechanical systems usually use hydraulic actuators which is one of the major factors in the applications. Rolling diaphragms are ductile fluid control tools that are used to secure a perfect seal in any system, involving a piston and cylinder. Made from a combination of elastomer and fabric, they are found inevery shape and size.

 

The bellofram rolling diaphragm is a pliable and durable seal that has a unique layout which allows proportionately long piston strokes while avoiding the sliding friction, throughout. Coming in the shape of a cone that has been cut, or top hat, the diaphragm is folded within itself when positioned so that, during the mechanism, it rolls and rotates repeatedly on the piston skirt and cylinder wall.

 

The rolling action is easy and trouble-free, completely omitting any sliding contact and diverging friction. The exterior flange is clamped to the cylinder in the middle, connected to the top of the piston, this shapes a faultless blockade, averting pressure loss and massive leakage. It all comes down on the substance and outline that has been chosen to function thoroughly with an applied pressure of 3000 pounds. The temperatures range from –120ºF to +600ºF. There are diaphragms that are accessible, with a high tolerance to oil, acids, alkalies, steam and other corrosive fluids.

 

Features of a Rolling Diaphragm

A couple of advantages of rolling diaphragms include precise, repeatable positioning, long stroke lengths, without a spring rate, that refers to pressure made by rubber trying to return to its moulded area.

 

– It is completely friction free.

– There is no breakaway friction or evasion to start the motion all over again, even after being in one position for a long time.

– The spring rate is constant and there is stability in the resistance that is applied for pressure throughout the stroke .

– Because of its high sensitivity, the diaphragm is easily responsiviations in pressure.

– There won’t be any leaks.

– It is so versatile that it can be equipped for a variety of pressures, temperatures, and liquids.

– The position is consistent along with pressures that are similar, despite the direction of the stroke.

 

Role of Diaphragms in Automotive

Air cylinders have piston and rod seal friction which can encounter a jerk at low speeds or pressures. These seals have low durability, which makes it harder to maintain a course without drift. These can be avoided by replacing them with rolling-diaphragm air cylinders, which don’t have dynamic seals that result in wear and tear, friction or leakage. Furthermore, a top-notch seal is attached around the piston that is held back from the sliding motion and in turn, gives a better seal that doesn’t leak and drain the actuator.

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

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.

What Makes Cryogenic Deflashing Method a Cut Above The Rest?

Before the final inspection and packing, moulded rubber parts must undergo a finishing process to remove excess flashes. “FLASH” is an excess amount of rubber that oozes out between the two halves of a mould during the moulding of rubber parts.

 

The flash occurs in areas where different sections of the mould join together and are called the ‘parting line flash’. The remaining part of the mould flash traces around where the different sections of the mould join together.

 

Flashes cannot be avoided no matter what technique has been used to manufacture these rubber products. While manufacturing high-performance materials for growing markets like electronics and automotive, intricate finishes, consistency and strict tolerance must be met.

 

Importance of Cryogenic Deflashing

 

 

This is the only method that makes it possible to eradicate complex flash at the inner dimensions. Parts with a thin flash can be removed through cryogenic deflashing quickly. The traditional deflashing methods generally deliver a poor deflashing effect as it is done manually with the help of blades, scissors or knives. The manual trimming method has a high variability in quality and the production rate due to the geometry of the parts. Since the finish quality is not up to the mark, it leads to high rejection rates. Unevenly deflashed products when used can affect and damage the machine it is used in.

 

The Process of Cryogenic Deflashing

 

 

Cryogenic Deflashing is a combination of rapid rotation, nitrogen and plastic blast media is used to get rid of the flash in an extremely precise and economical way. The rubber parts are arranged in a perforated container which is then inserted in a blast enclosure.

 

The containers rotate and evenly expose all sides towards the blast media. The enclosure is insulated with firm polyurethane foam for stable temperatures. The liquid nitrogen decreases the temperature inside and freezes the flashing to make it fragile.

 

With the use of pure nitrogen with zero moisture the requirement of a dryer is eliminated. A fast-moving impeller shoots the polycarbonate pellets in the container. These high-speed pellets trim the inner as well as the outer diameter flashing neatly in a single operation. The effective lubricity and hardness lessens the impeller’s wear and increases its durability.

 

Parting- line flash thickness determines the capability of the system to finish the moulded part in concurrence with the cycle time and LIN consumption. A thicker flash is more difficult to get rid of and requires lengthier deflash cycle time which results in higher LIN consumption. The optimum parting-line flash thickness is 0.001” to 0.005”. Optimum finish quality and LIN consumption are based on the mould design and condition.

 

 

Advantages of Cryogenic Deflashing

 

 

Cryogenic deflashing offers numerous advantages over other traditional or manual deflashing methods:

 

● This process maintains an element of integrity and precision and ensures greater productivity.

● Due to this using a batch process, the cost of per piece is lesser as the number of parts processed in a specific time increases. This makes the manufacturing process economical and cost-efficient.

● Repairing or replacing a mould rises up the expenses bracket. In this method, the moulds can bede-flashed which extends their durability.

● It delivers consistent results in every lot.

● This technique is completely non-abrasive.

● The entire procedure is highly automated which eliminates the need of a human operator.

● This method eradicates the use of any toxic chemicals and is enclosed to a minimum sound which proves it to be environmental-friendly.

 

Harkesh Rubber uses cryogenic deflashing which is the most advanced deflashing process, unlike most of the other OEM’s. This method polishes the parts (typically O-Rings) and minimizes any sign of the flash or parting line delivering an efficient and precise product.

 

With this process, we ensure precision and fulfill our commitment of delivering a quality product. This technique not only improves the performance of the product but also saves the time and effort invested which eventually reduces the cost of production as well.

Case Study – Special EPDM Compound Diaphragm for Aircraft Engine Application

ABOUT THE CLIENT

The Client is an established Control Valve Manufacturer from America.

 

BUSINESS PROBLEM

 

The vendor who provided the rubber seals for the client for almost 5 decades was acquired by the competition. Since the vendor had to comply to military secrecy, they stopped sharing the information with the client regarding the base polymer, physical properties required, and other necessary details.

 

This put the client in a fix as they did not have the required details about the parts supplied by the vendor. They also needed to manufacture a special diaphragm to support a huge military account in the USA.

 

OUR SOLUTION

 

Harkesh Rubber came in contact with the valve manufacturer. Since we had the experience to meet their moulding requirement, we soon figured out the need to develop a suitable compound formulation for this application.

 

Once we took the feedback from the customer regarding the application and approval tests required, we determined that the compound needed to work in Aviation Turbine Fuel. After that, we selected the EPDM material for the application. We also reviewed the old material test certificates of the previous vendor and deciphered the special needs the compound would require, like the use of silicone oil and very high elongation.

 

RESULTS

 

With our analysis and research, we developed a special EPDM compound that was suitable for work in Aviation Turbine Fuel at high temperatures and with a work cycle in excess of 10,000 hours. We created diaphragm samples from the compound and supplied them to the client. They assembled the components and delivered them to the leading Aircraft Engine Manufacturer. Once the trials were conducted over a year, the diaphragm and the compound were approved.

 

BENEFITS

 

The client was able to retain their account with the leading Aircraft Engine Manufacturer.

 

Since 1982, we have built a reliable reputation in the rubber industry on our unique solution based approach that has made us the preferred partner for critical sealing solutions. We provide high precision, cost-effective sealing solutions for technically demanding applications.

The Significance Of O-Rings For Sealing Solutions

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.

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