Hydraulic Seal Catalog

Seal

Style

T-Seals Piston, Rod, Intermediate Base, Wide Base
Loaded Lip U-Cups / Polypaks® Standard Lip, B lip, Deep Base
U-Cups AN, B, Symmetrical
Vee Packings (Sets) AN, DBH, FBF, FBH, CRF, CRH
Rod Wipers AN, K, H, D
WV Packings (Sets) AN, DBH, FBF, FBH, CRF, CRH
Piston Cups Standard, Miller, Wabco, Custom Bolt Holes

T-seals

Piston & Rod T-seals

Product Description

Mikron T-seals come in both Piston (MPT) and Rod (MRT) styles. The T-seal is designed as a double acting seal and fit a standard O-ring groove (intermediate and wide base glands are also available). The t-seal design prevents extrusion and spiraling up to 5,000 PSI. Mikron’s standard T-seals are made with a 70 durometer Nitrile (MB170) sealing element and two (2) split Nylon (Nylon 6) back-up rings. We offer a variety of sealing element and back-up rings materials to solve OEM and service repair requirements.

The Mikron T-seal eliminates rolling or spiralling, even under long-stroke or dry-rod conditions. When piston or rod movement does occur, even under very low pressures, the design allows the back-up rings to lock the sealing element in place all while retaining the space-saving attributes of the O-Ring design.

Detailed Information

Because the Mikron T-seal has a back-up ring on both sides of the sealing area, it functions very well in double-acting applications. Mikron T-seals also adapt to wider gaps and immediately respond to pressure surges and shocks.

The Mikron T-seal is compressed to eliminate low pressure leakage. The back-up rings float between the T-seals’ flanges and the rod or bore, minimizing friction and wear. When pressure is applied, a bridge is formed before extrusion can occur. The T-seal’s back-up utilizes hydraulic pressure to keep it in contact with the rod or cylinder wall, which prevents extrusion from occurring.

Material Science

The T-seal is available in low temperature Nitrile (MB470), a 60, 80 & 90 durometer Nitrile (MB160, MB380, and MB390), a Carboxilated Nitrile (MB190), Fluoroelastomers (Viton®) (MF190) and many other standard materials. Also our chemists can assist with custom materials as well.

Pricebooks

Piston T-Seal MSRP

Rod T-Seal MSRP

Documents and Downloads

T-Seal Brochure & Sizes

T-Seal Part Number Definitions

Loaded Lip U-CUPS (PolyPaks ®)

Types of Loaded Lip U-Cups (PolyPaks ®)

Standard Style Loaded Lip U-Cup "B" Style Loaded Lip U-Cup
"DB" Deep Base Style Loaded Lip U-Cup  

Product Description

The Loaded Lip U-Cup is a very versatile seal because it can be used as a rod seal or piston seal. The energizer ensures constant pressure on the sealing lips. It is considered a multi-purpose seal and is designed for significantly improved performance.

Mikron offers three styles of the Loaded Lip U-Cup: Standard, Deep Base, and “B” Style. In addition, Mikron will supply Loaded Lip U-Cups in various types of elastomers to meet your specific requirements. Please refer to Figure 1 on the right column of this page which shows these various styles.

The Standard design is usually symmetrical in cross section in which the height of the U-Cup is the same as the cross section. The Deep Base (DB) U-Cup is the same basic design as the standard style except that the height is taller. The “B” Style has a back beveled lip and is generally the same height as the deep base, but functions with more lip interference. This design helps to ensure optimum sealing function. This style is particularly useful in high pressure conditions. In addition, design of the “B” style Loaded Lip U-Cup combines ease of installation with rugged construction for a highly effective seal in heavy duty applications. This series of sealants can be designed into the original equipment for significantly longer life than some of the other types of seals.

Detailed Information

The chamfered lip design of the “B” Style Loaded Lip U-Cup Series proves to be an excellent sealing device for most conditions. The Deep Base U-Cup is capable of being stacked in order to replace Vee packings. In the event that these packings are stacked, be careful that the packing does not lose lubrication. It is important that the leading seal does not create the other to go dry in the process. There is a possibility that these seals can get overheated from the friction, causing premature failure as a direct result of this heat build-up. In addition, as stacked sets, Deep Base rings are functional single lip seals. The design eliminates all voids between seals under vacuum or pressure. Gland pressure is not required except in split-ring applications. Continuous ring Deep Base packings are very efficient seals. Another feature of the Loaded Lip U-Cup design is that this series of packings is interchangeable with Vee packings and U-Cups

It is important to remember that when installing Loaded Lip U-Cups through or over threaded or other sharp projections to provide adequate clearance between the diameter of packing and projection (approximately 10% free cross section of seal). The cylinder bore or rod should have a 25° maximum chamfer at its entrance to facilitate installation and to eliminate the possibility of damage to the seal. It is best for the seal to be entered on the chamfer, in its free state, before being forced into position Finally Loaded Lip U-Cups should be lubricated prior to installation with a suitable lubricant.

Design and function

The pressure range for this packing is from vacuum to 10,000 psi, based on machine parts being within J.I.C. Standard tolerance and the type of elastomer from which the seal is made. Also the temperate range is dependent upon the type of elastomer from which the seal is made. The energizer keeps the lips of the seal pressed against the sealing surfaces thus allowing the Loaded Lip U-Cup to seal under low pressure.

A Loaded-lip U-Cup groove axial length is a few thousandths of an inch more than the height of the Loaded Lip U-Cup. This allows the seal to float and helps it seal under slight side loads. Loaded Lip U-Cups give longer wear life because of a larger lip contact area than the live contact area of other conventional packings.

Although the Loaded Lip U-Cups have exceptional resistance to abrasion, no seal should be expected to give long service when operating on poorly finished or pitted surfaces, scored cylinders or rods. The finish on both the rod and cylinder should be 10 rms to 16 rms. This finish not only is smooth enough to keep the packing from tearing, it allows seepage and thus lubricates the seal.

Additionally, there are other considerations when designing Loaded Lip U-Cups. Following are some cases. In the back-to-back piston application as in a double acting piston, there is a need for the energizer to be removed to prevent pressure forming in between the seals. For these situations, it is recommended that the “B” style Loaded Lip U-Cup be used.

Seals are not designed to function as bearings, therefore, they must not be included in calculations of bearing areas of Piston or Rod. For any additional information on specification, design or installation of these Loaded Lip U-Cups, please contact Mikron directly. Please feel free to contact us regarding any questions or concerns on any of the other products referred to.

Operating Environments

Temperature is of primary important since the pressure medium is always in contact with the packing. At high temperatures, the pressure medium may sometimes vaporize, thus causing it to be particularly penetrating. Packings must be specially treated to resist such conditions. It is imperative that maximum operating temperatures be considered when packings are selected.

The chemical composition of all pressure mediums is of primary importance. Mediums used by many manufacturers are by-products of the processes for which the hydraulic or pneumatic machinery is employed. Often, the result is that the chemically active liquids are the pressure media against which packings have to act. Use of a by-product is sound enough practice, provided the chemical composition of the pressure medium is considered when packings are selected.

Material Science

Depending on the specific application, Loaded Lip U-Cups are usually made of either Carboxylated Nitrile, Urethane, E.P.D.M. or Fluorestomer (Viton ®) compounds. Again, the difference in material depends upon various application factors and operating environments. It is best to contact Mikron directly with your particular specifications to ensure that your Loaded Lip U-Cups are manufactured of the proper elastomer to meet your requirements.

Available in standard materials. or other custom formulations.

Documents and Downloads

"Standard" Style - Size Chart

"B" Style - Back Beveled Size Chart

"DB" Style - Deep Base Size Chart

Standard U-CUPS

Types of U-Cups

Standard Style U-Cup AN6226 Design "B" Style U-Cup
Symmetrical Style U-Cup  

Product Description

Mikron U-cups are available in various shapes, size ranges and in homogenous or fabric reinforced compounds. U-cups are most often used for sealing rams or rods. The U-cup is a very popular seal due to the small gland space required. Because U-cups are a single lip design, there are important factors that must be considered when installing or designing a U-cup.

The standard series of U-cups are available in a wide variety of homogenous and fabric reinforced compounds to suit various pressures and environments. The selection of fabric or homogeneous compounds should be made on the basis of operating pressure, temperature, and the type of air or fluid medium with which the packing must function.Mikron offers different types of lip configurations. In addition to the standard lip style, Mikron also supplies back bevel lip and loaded lip U-cups.

Detailed Information

The U-cup derives its name from its shape and is self sealing on both the inside diameter and outside diameter. U-cups are classified among single lip packings, and they’re a combination of cup and flange design. They are among the most versatile and compact of all seals. U-cup selections should be based on the I.D. and O.D. sealing requirements, operating pressures, temperature, and the media in which the cups must function. It is not recommended that U-cups or any other single lip seal be used in any application where there is excessive side loading. The shape of the U-cup is the reason that it is such a successful seal. As the gases or fluids push into the U shape, it forces the lips out against the surface to be sealed as shown below.

Design and Function

Homogeneous U-cups are primarily pressure packings, being used for pressure of less than 1,000 psi. They are not recommended for pressure above 2,000 psi. They basically contain low frictional qualities and are completely automatic in action. For higher pressures, fabric reinforced U-cups are needed. As pressures increase, with fabric reinforced U-cups, heel is brought into contact with back-up ring and presses against it. There is always line contact between tip of lip and cylinder, but with increased fluid pressure, more and more of lip comes into contact with wall. Pressure at which this happens naturally depends on the hardness of cup material and on its design which can be controlled.

Due to the geometric shape of the U-cup configuration, it acts as an automatic pressure compensating seal and provides the needed radial force on a limited contact area. Under zero or very low pressure, the U-cup sealing characteristic is primarily determined by the low radial load caused by the initial installation interference. It is important for the pressure distribution of this load to have a sharp peak so that the packing is an effective sealant.

U-cups are pressure driven not only against the moving face, but also against the supporting walls of its recess. Therefore, only positioning pedestal is needed instead of mechanical retention by bolts or retaining plates. The internal pressure to be sealed acts equally in all directions over the entire inner surface. Therefore, packing is statically balanced and secure because pressure cannot escape.

The primary advantage of this packing is in the flexible lips, which allow the interference built into the packing to be great, without increasing initial stress or friction. Under the no-load conditions, the friction is very low because there is generally enough clearance between the heel of U-cup and the cylinder.

Detailed Design and installation

All U-cup installations should be designed to allow the U-cup to have necessary clearance if going over or through threaded surfaces or other sharp projections. The surface finish for a static seal surface should be 32 RMS maximum. The dynamic surface finished should be in the range of 8 to 16 RMS. Finishes rougher than 16 RMS could cause premature lip wear and finishes finer than 8 RMS can result in failure of the seal due to loss of lubrication.

As mentioned earlier, the U-cup is a floating seal, there is a recommended packing space for different seal depths. This added gland space allows the pressure to equalize on both lips, thus keeping the U-cup from rolling. A special internal lube can be added to homogeneous U-cups when there is a lack of lubrication, such as a dry air application. This lubricating ingredient leaches to the surface of the seal and will continue to do so for the life of the seal. Contact Mikron for further information on the internal lube material.

The MU6226 (AN6226) U-cups are symmetrical. The height of the U-cup is the same as the cross section. When designing the MU6226 U-cup into your equipment, remember the standard material for this type of U-cup is homogeneous. If the pressure media you are using is water or water and glycol, you should inform Mikron of the application. Water will cause the cotton duck in fabric U-cups to wick, and then swell, causing delamination of the fabic and early seal failure. There are numerous gases and fluids that require sealing. Mikron will be able to give the best recommendation when you supply complete information on your specific design or application.

Operating Environments

Temperature is of primary important since the pressure medium is always in contact with the packing. At high temperatures, the pressure medium may sometimes vaporize, thus causing it to be particularly penetrating. Packings must be specially treated to resist such conditions. It is imperative that maximum and minimum operating temperatures be considered when packings are selected.

The chemical composition of all pressure mediums is of primary importance. Mediums used by many manufacturers are by-products of the processes for which the hydraulic or pneumatic machinery is employed. Often, the result is that the chemically active liquids and gases harmful to the packings material are the pressure media against which packings have to act. Use of a by-product is sound enough practice, provided the chemical composition of the pressure medium is considered when packings are selected.

Material Science

Under high pressure and with an excessive gap between rod and cylinder, the U-cup will attempt to extrude into the gap. Maintained a close tolerance between the rod and cylinder will extend the life of the Y-cup. For older and worn equipment, a special non-extruding material (MBF-110) can be molded to the heel of a fabric U-cup. This must be done during the manufacturing of the U-cup. For further information, contact Mikron.

Available in standard materials. or other custom formulations.

Documents and Downloads

Homogeneous U-Cup Size Chart

Fabric U-Cup Size Chart

"AN" Style U-Cup Size Chart

Vee Packings

Vee Packing Styles

"AN" Style DBH Deep Base Homogeneous
FBF Flat Bottom Fabric CRF Center Ring Fabric
CRH Center Ring Homogenous  

Product Description

Mikron offers a large selection of Vee packings that any other manufacturer. They are available in various sizes, stack heights and compounds to meet a wide range of applications. Our Vee packings are multiple-lip (chevron) seals comprised of a group of endless rings. They are popular for sealing rods and pistons.

The standard series Vee packings are available in a wide variety of homogeneous and fabric reinforced compounds to suit various pressures and environments. The selection of fabric or homogeneous compounds should be made on the basis of operating pressure, temperature, and the type of air or fluid medium with which the packing must function. All Mikron Vee packings are manufactured as endless rings, but may be special ordered with the rings split. In addition to the standard Vee packings, Mikron can supply sets of customer specified height and diameters, cut from spiral coil. Also offered are metric and military AN-6225 sizes.

Detailed Information

The most commonly used of all lip type packings is the Vee packing. The Vee packing installation can be used for either low or high pressure applications and with either single acting or double acting cylinders. Fabric Vees are for high pressure while Homogeneous Vees are for low pressure. The term pressure medium or operation medium is applied to any gas, liquid, or semi-liquid, such as air, water or grease, which exerts pressure against a packing or which is retained by a packing.

Vee packings (that are properly installed) will generally outperform other lip type seals, particularly at pressures over 25,000 psi. They are always installed in sets. Each set contains a number of Vee rings (based upon the pressure) and male and female adapters. The number of Vee rings in each set is referred to as pressure rings. Refer to the Table to determine the number of rings per set based on solid rings. This Table applies to the majority of installations. There will be exceptions, of course, depending upon special operating conditions, where the table guidelines do not apply. In these cases, you may contact Mikron for more specific information

Recommended Number of Packings per Set Based on Solid Rings

 

Pressure P.S.I

Number of Rings

0 to 500 3
500 to 1,500 4
1,500 to 3,000 4
3,000 to 5,000 5
5,000 to 10,000 6
10,000 and over ---

Standard Vee packings use a 90° included angle (commonly referred to as 45°) measured on one side only. Some, however, use a 30° (or 60° included) angle for special applications.

Design and Function

To maintain proper support, the female adapter (which supports the entire set) should be made with dimensions of .010” over nominal I.D. and .010” under nominal of O.D. In conjunction, the male adapter should be made of same dimensions as the female adapter.

Because the female adapter is the support in the set of the Vee packing, it is of great important. It also takes the wear and determines the overall quality of the Vee packing set. It can change the wear pattern of the packings and is capable of increasing or decreasing the service life. The adapters are made from various fabric and elastomer combinations as well as synthetic materials. When ordering synthetic packings, the need for specific information as to the exact conditions under which the packings are to be used is most important.

In essence, the female adapter should be of a material that is hard enough to withstand extrusion and yet able to breathe and compress under high pressure, without distortion. The male adapter, on the other hand, can be made from any of the materials indicated in the table. The male adapter does not need to be especially heavy because it does not affect the wear pattern, life or leakage.

Vee packing sets are often split on an angle for ease of installation. Each ring in the set is staggered to the top of the Vee packing set at 90°. In addition, endless (solid) rings are highly recommended due to their excellent sealing qualities and longer life. Installing endless rings is certainly worthwhile. When installing, it is necessary for the gland nut to be snug; and then turn the gland nut ¼ turn past that point. This is when it is important to check for leakage. As, over-tightening of Vee packing will lead to early failure. Therefore, sets of Vee packings should never be tightened excessively and should always be allowed to function as mechanical packings. They are also sensitive to pressure changes.

Operating Environments

Temperature is of primary important since the pressure medium is always in contact with the packing. At high temperatures, the pressure medium may sometimes vaporize, thus causing it to be particularly penetrating. Packings must be specially treated to resist such conditions. It is imperative that maximum and minimum operating temperatures be considered when packings are selected.

The chemical composition of all pressure mediums is of primary importance. Mediums used by many manufacturers are by-products or direct products of the processes for which the hydraulic or pneumatic machinery is employed. Often, the result is that chemically active liquids and gases harmful to packings materials are the pressure media against which packings have to act. Use of a by-product is sound enough practice, provided the chemical composition of the pressure medium is considered when packings are selected.

Although Vee packings have exceptional resistance to abrasion, no packing should be expected to give long service when operating on poorly finished or pitted surfaces, scored cylinders or rods. The finish on both the rod and cylinder should be 10 rms to 16 rms. This finish not only is smooth enough to keep the packing from tearing, it allows seepage and this lubricates all the rings in the Vee set.

The stack height of each Vee ring has a tolerance of plus or minus .010”. This tolerance also applies to adapters. However, sets of Vee packings should not be allowed to function loosely in the gland.

Material Science

Pricebooks

Fabric Vee Packing (MBF-100) MSRP

Documents and Downloads

Decimal Size Chart

Metric Size Chart

"AN" Style Size Chart

Rod Wipers

Rod Wiper Styles

RWH "H" Style Rod Wiper RWD "D" Style Rod Wiper
RWK "K" Style Rod Wiper RWAN "AN" Style Rod Wiper

Product Description

The Rod Wiper’s main function is to keep the rod and cylinder clean and free from foreign matter, thus preventing premature failure. The Rod Wiper is not a pressure sealing element, yet it avoids possible abrasive effects which may result if contaminants were to reach the sealing and rod bearing elements. Various styles, sizes and compounds are available within the four categories of Rod Wipers illustrated above.

Design and Function

There are various types of Rod Wipers available. The selection depends upon the function and operating environments. You may consult with Mikron directly to determine the best usage for your application.

The RWH Rod Wipers are capable of providing both sealing and wiping functions in one component in low pressure systems. While the outside lip scrapes foreign matter from the rod, the other lips serve as pressure seals in low pressure pneumatic applications or as secondary seals trapping slight leakage in high pressure hydraulic systems.

The RWD Rod Wipers are the one piece snap-in type rod wipers/scrapers. This type is ideal for heavy-duty applications. The toughness and resistance to wear minimize seal deterioration under very severe action of abrasive materials contacted during the wiping action. These Rod Wipers are able to adjust with wear and side motion providing a very effective wiping action over the extended lifespan.

A third type of Rod Wiper is the RWK style. These homogeneous double lip seal wipers are designed to be used with homogeneous rubber or fabric reinforced U-cups. They can be used with other types of conventional packings in light to medium duty applications where operating conditions require positive wiping action but where deposits of foreign matter are not present.

RWAN/AN Rod Wipers are the one-piece rod wiper scrapers. These are designed for applications which require toughness and high wear resistance which minimize seal destruction under the severe action of abrasives contacted during the wiping action. These Rod Wipers adjust with wear and side motion to provide effective wiping action over their entire lifespan. They are also compatible to A/N specifications. For more information, contact Mikron directly.

Operating Environments

Temperature is of primary importance since the pressure medium is always in contact with the Rod Wiper. At high temperatures, the pressure medium may sometimes vaporize, thus causing it to be particularly penetrating. Rod Wipers must be specially treated to resist such conditions. It is imperative that maximum operating temperatures be considered when Rod Wipers are selected.

The chemical composition of all pressure mediums is of primary importance. Mediums used by many manufacturers are by-products of the processes for which the hydraulic or pneumatic machinery is employed. Often, the result is that the chemically active liquids and gases harmful to the Rod Wipers material have to act. Use of a by-product is sound enough practice, provided the chemical composition of the pressure medium is considered when wipers are selected.

Material Science

The standard elastomer used in the manufacture of Mikron Rod Wipers is Carboxilated Nitrile or (XNBR). XNBR provides harder, tougher vulcanizates with higher abrasion resistance, modulus tensile and tear strength than that of conventional Nitriles. In addition, this elastomer offers superior resistance to fluids, high temperatures and compression set. In order to function most effectively in wiping the rod, it is important that the material it is made of be elastic in nature.

Mikron Rod Wipers are able to provide long lasting and efficient wiping action. The Carboxilated Nitrile material is hardly affected by exposure to sun, weather or ozone; and it is unaffected by low level radiation. This Carboxilated Nitrile material is outstanding when used with most petroleum base hydraulic fluids and oils, acetic and alkaline solutions under 10% concentration, salts, aliphatic alcohols and hydrocarbons, and mixtures containing less than 80% arometics. On the other hand, it is not recommended for use with automatic brake fluid, esters, ketones, pure aromatic compounds, strong concentrated acids or bases, or very strong oxidizing agents. The Carboxilated Nitrile of the Rod Wipers will perform over a temperature to 300°F constant.

Available in standard materials. or other custom formulations.

Documents and Downloads

'AN' Style XNBR Rod Wipers

'H' Style XNBR Rod Wipers

'D' Style XNBR Rod Wipers

'K' Style XNBR Rod Wipers

'AN' Style FKM Rod Wipers

'H' Style FKM Rod Wipers

'D' Style FKM Rod Wipers

'K' Style FKM Rod Wipers

WV-Packings

WV-Packing Styles

"AN" Style DBH Deep Base Homogeneous
FBF Flat Bottom Fabric CRF Center Ring Fabric
CRH Center Ring Homogenous  

Product Description

The WV was so names by Mikron because the outline of the seal resembles the letter “W” and also because it seals in many ways as does the “V” packing. While similar to Vee packings, the WV style provides sealing properties that are largely independent of stack packing pressure. The standard series WV packings are available in a wide variety of homogeneous and fabric reinforced compounds to suit various pressures and environments. The selection of fabric or homogeneous compound should be made on the basis of operating pressure, temperature, and the type of air or fluid medium with which the packing must function.

In addition, Mikron WV packings are available with center rings (abbreviated “CR”), flat bottoms (abbreviated “FB”), or deep base (abbreviated “DB”). Deep Base style packings provide extra strength and stability for single element rod or piston applications; DB versions are available only in homogeneous compounds, whereas center ring and flat bottom are available in homogeneous or fabric compounds.

Detailed Information

The WV packing is designed so that it will provide multiple lip seal in a fixed gland depth which is usually shorter than the gland depth required for standard Vee packing. Because of the design of the WV packing, the lips of each ring are free to flex when in a nested stack so each lip automatically reacts to fluid or air pressure, providing a better seal in a given packing space. There is no compression adjustment required during the seal life.

Since the WV packing is a multiple lip seal, it is recommended over a single lip seal for applications where side loading is a factor. The multiple lip also provides extra stability, in the case on seal fails, there will be another seal to serve as back-up. There is interference built into both the I.D. lips and the O.D. lips so that there will be sealing capabilities at low pressure.

Installation

Since the rings are designed to be free floating, it is not recommended that the rings be installed in a compressed state. There should be between .014” and .060” of area in the gland depth so that the rings are allowed to float. The amount of this free floating is determined by the rings cross section and the number of rings being installed. Some air applications use only one DBH style ring as a rod seal. Again, make sure the gland depth allows the seal to float.

Due to the lip interference of WV packings made of fabric material, they (at times) may be difficult to install. A blunt or rounded end instrument should be used to push the lips into the gland. It is not advisable to use a sharp object, such as a screw driver or tire iron to install a WV packing due to the damage it can do to the sealing lip. WV packings should not be forced over sharp or threaded areas. The flat bottom (FB) ring or in some cases the Deep Base (DBH) ring act as a female ring as in a Vee set and should always be the ring farthest away from the pressure force. The lips of each ring should always be toward the pressure force.

Design and Function

If your design is of medium to high pressure, it is recommended that you utilize fabric reinforced rings. The following is a guide to pressure rating of multiple rings, including flat bottom rings.

Pressure P.S.I

Number of Rings

250-500 3
500-2,000 4
2,000 - 5,000 5
5,000 - 8,000 6

A homogeneous ring may be also used for sealing at low pressure. Do not include the homogeneous ring in calculating pressure rating. Due to the different materials used as homogenous, it would be difficult to rate this type of ring. If you wish to use all rings made of homogeneous material, it is recommended that tests be conducted. The surface finish for a static seal surface should be 32 RMS maximum. The dynamic surface finishes should be in the range of 8 to 16 RMS. Finishes rougher than 16 RMS could cause permanent lip wear and finished finer than 8 RMS can result in failure of the seal due to loss of lubrication.

Operating Environments

Temperature is of primary important since the pressure medium is always in contact with the packing. At high temperatures, the pressure medium may sometimes vaporize, thus causing it to be particularly penetrating. Packings must be specially treated to resist such conditions. It is imperative that maximum operating temperatures be considered when packings are selected.

The chemical composition of all pressure mediums is of primary importance. Mediums used by many manufacturers are by-products of the processes for which the hydraulic or pneumatic machinery is employed. Often, the result is that chemically active liquids are the pressure media against which packings have to act. Use of a by-product is sound enough practice, provided the chemical composition of the pressure medium is considered when packings are selected.

Material Science

Documents and Downloads

WV Packing Size Chart

Piston Cups

Piston Cup Styles

K - Piston Cup KMFP - OEM Piston Cup

Product Description

As with other packings manufactured by Mikron, the Piston Cups are made of various elastomers and function in various temperature ranges and pressure ranges.

It is important to select the pressure range, temperature range and the type of air or fluid medium in which the Piston Cup will function. It is a commonly used packing. The Piston Cup’s primary application is on a piston head, plunger or ram in either hydraulic or pneumatic service. Its mechanical sealing surface is at its periphery.

The Piston Cups are utilized so often due to: economical cost, excellent service life, efficient assembly, universal acceptance, and simple accessories.

Detailed Information

Major characteristics

  • No matching of recess required
  • Installed against piston head or backing plate
  • Follower plate is inside
  • Compression-sealed on bottom
  • Performs satisfactorily under low or high pressures
  • Excellent service life
  • Relatively simple installation

The standard homogeneous Piston Cups are recommended to handle low pressures (under 150 pounds/square inch) in air, water, hydraulic fluids, and lubricating oils. The homogeneous series is manufactured in Buna-N, EPR, Viton®, Silicone, and most other homogeneous materials. These cups can also be manufactured of the aforementioned material with internal lubricant added for dry applications.

Fabric reinforced version of Piston Cups prevents extrusion in medium pressure installations (up to 1000 p.s.i.) or where the diametrical clearances are greater. This line of Piston Cups is typically manufactured of stiff but flexible Buna-N and cotton duck fabric. Piston Cups are also available in softer compounds for low pressure applications where reinforcement is required.

Unlike symmetrical seals, non-symmetrical types employ different cross-sectional shapes to seal the static and dynamic surfaces. Piston Cups may be technically described as non-symmetrical seals since their dynamic and static sealing lines are quite different in shape. Until exposed to excessive pressure, these seals are extremely stable since they are installed by clamping into the piston or gland structure.

Single-acting cylinders, as in the case of hydraulic rams, must rely on mechanical means to retract (or, in some cases, extend) the rod. A typical pneumatic design uses an internal spring to extend the rod, and air pressure to retract. Obviously, the spring and pressure port arrangement could be reversed to provide power extension and spring retract. The piston seal referenced above is a seal whose performance is characteristic of the lip-type seals. These cups provide very flexible seals able to tolerate large clearances at the low pressures typical of pneumatic service. They are helpful in controlling the cost manufacture. They are also quite flexible in poor surface finished which are sometimes deliberately utilized because of their ability to trap injected lubricants and save them in small surface reservoirs.

A gland extension provides protection against crushing the Piston Cup when the rod is fully extended, and may also serve to prevent blocking the air inlet by overtravel of the cup lip. A similar extension provided by the piston nut prevents crushing the return spring.

Material Science

Documents and Downloads

Homogeneous Size Chart



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