For over 50 years we have been designing and manufacturing customized seals along with our standard product line.
The seals shown and described on this site have been designed, tested and carefully selected as our standard line of metal seals. Using the standard metal seals will satisfy the vast majority of applications and sealing requirements.
There are however, applications which have unique demands and we are pleased to offer our sealing expertise in developing sealing solutions for your specialized applications. Our extensive manufacturing capabilities allow us to quickly produce prototype seals which can be tested in our laboratories to verify leak rate, compressive load and springback.
For over 50 years we have been designing and manufacturing customized seals along with our standard product line. Below is a brief overview of the wide range of unique seals we can offer.
We appreciate your interest in Metal Seals from Parker Composite Sealing Solutions Division. Want to know more about our solutions and how they can fit with your application? Please click the appropriate link below, fill out the requested information and a Parker representative will be in touch.
HOW DO I CHOOSE THE RIGHT METAL SEAL?
Selecting the most appropriate seal for your application can save a lot of money by eliminating the tremendous costs associated with machine downtime, unscheduled service, and spill remediation. We offer a wide variety of metal seals designed to meet the challenges of high temperatures or cryogenics, high pressures, vacuum, corrosive chemicals and even intense levels of radiation. Unlike rubber, composite, asbestos, and other organic gaskets, metal seals do not deteriorate over time due to compacting, outgassing or blowouts. In addition, because the seating loads for metal seals can be significantly less than those required for crush-type gaskets, the strength and mass of the flanges can be reduced. This is particularly important to designers concerned with reducing size and weight.
C-ring – provides a good combination of leak tightness and springback. It is one of the most popular designs.
E-ring – offers the greatest amount of springback of all metal seals. Metal O-ring – used for over 50 years and remains an economical choice for high-load, high pressure sealing.
Spring energized C-ring – is similar to the standard C-ring, but it has an internal spring that produces much greater load for sealing against rough surfaces or when extreme leak tightness is required.
Wire ring – is a low cost, high load, crush type seal used with smooth mating surfaces and minimum relative movement.
Face seal / axial seal – keep in mind that metal face seals, which are ideal for static applications, are compressed by approximately 10% to 20% of their original free height to produce preferred sealing loads for optimized performance. Axial seals can be used in either static or semi-dynamic applications to seal against shafts and bores. Due to the relative rigidity of metal seals in comparison to elastomeric and polymeric seals, the axial seals must be produced to tighter tolerances than face seal grooves. Face seals are generally preferred instead of axial seals due to their relative ease of gland manufacture, installation and seal performance.
High Load vs High Elasticity – high load metal seals are designed for extreme leak tightness. High elasticity seals provide resiliency or springback needed to maintain effective sealing during mating surface separation, such as with thermal cycling.
This is one of the most common questions asked by our customers. Generally, metal seals are not considered to be reusable and are replaced after each use. However, after considering a few important issues, the customer must ultimately be the one who answers the question for themselves.
Issues to consider:
1) What type of seal is it?
An E-ring provides nearly full elastic recovery after the compressive force is removed. E-rings usually are left unplated meaning there is no ductile outer surface which can be deformed into the hardened mating surface by compression. As a result, unplated E-rings and other low load seals are more suited for reuse than other metal seals. O-rings and C-rings undergo mostly plastic deformation and therefore are usually discarded after one use.
2) What is the surface roughness of the mating hardware?
A rough surface will mean an equally rough impression into the soft plated surface of the seal. Reinstalling the seal will result in a mismatch of the plated surfaces and mating hardware surfaces. The surface roughness impression made in the plating upon initial installation may act as leak paths upon subsequent installations. Smooth surfaces will minimize this effect and improve the chances for seal reuse.
3) How flat are the surfaces of the mating hardware?
When a seal is compressed it conforms to the waviness of the mating surfaces. When the seal is reinstalled it is likely that the waviness of the flange will not match with the waviness of the seal. This waviness mismatch may result in leak paths and non-uniform sealing forces on the circumference of the seal. Flat surfaces will increase the possibility for seal reuse.
4) What if the seal leaks upon reuse?
In some applications the time, effort and cost of assembling the equipment or machinery is very high. The money saved by reusing the seal is minimal compared to the cost for disassembly and reassembly if the seal needs to be replaced. Most customers are not willing to risk the cost of the labor replacing the seal to save on the price of a seal. However, if the consequences of a leaking seal are small then the customer will likely be willing to reuse the seal. After considering these issues the customer can decide whether or not to reuse the seal. Most customers will conclude that the seal should be replaced after each use.
Sulfide stress cracking (SSC) is a special corrosion type, a form of stress corrosion cracking commonly found in oil field applications where hydrogen sulfide (H2S) may be present. Susceptible alloys, especially steels, react with hydrogen sulfide, forming metal sulfides and elementary atomic hydrogen. The atomic hydrogen diffuses into the metal matrix.
Stress corrosion cracking requires three simultaneous factors – surface tensile stress, alloy and environment. The alteration or elimination of any one of them can prevent this attack. Where possible, the alteration of the environment or the choice of a different alloy is the best solution. Elimination of stress is usually attempted through heat treatment.
Choosing materials with a high nickel content can greatly improve the resistance to sulfide stress cracking. Heat treating a high nickel content material such as Alloy 718 to reduce the tensile stress to meet the requirements of NACE MR0175 can greatly reduce sulfide stress cracking corrosion.
NACE standard MR0175 does not give a recipe for heat treatment. But it does state that a material such as Alloy 718 should not have a hardness greater then 40HRC. Our -8 heat treatment removes the tensile stress enough to meet the requirement, but still give some strength. The -8 heat treatment will have a reduced seating load of about 30% over our standard -6 solution anneal and age hardened heat treatment.
WHAT IS LEAKAGE?
Leakage describes the unwanted loss, or leak of matter as it escapes its proper location. The matter may be liquid, gas or even solid in the form of powder for example.
It is a fact that every single seal on the planet has a measurable leakage rate. The leakage rate may be zero for some materials, such as liquid water or petroleum hydrocarbons with a relatively large molecular size, but will be more than zero for very small molecules such helium or hydrogen gas. It is possible to manufacture a seal that has a leakage rate of 1x10-11 cc/sec/mm of helium. This is equivalent to the loss of a cubic centimeter of helium every 3000 years. It’s an extremely low number but it is not the same as zero. Leakage is more properly thought of as a continuous spectrum of rates.
There are two primary types of seal tooling including roll form tooling and die form tooling.
Roll form tooling uses a series of rolls to make a particular cross section in any diameter needed. For example a 1/8" cross section C-ring roll form tooling can make a part that is 9.500" in diameter or 40.525" in diameter.
There is virtually no limitation on how large of a diameter can be roll formed. There are practical guidelines however from a handling point of view, too small of a cross section with too large of a diameter may be difficult to handle without bending. The diameter of the roll form also limits the lower end of the diameter. It is not possible to roll form a part with a smaller diameter than the diameter of the roll form.
Die form tooling makes one size diameter and one cross section. C-ring tooling that makes Internal pressure C-rings with a cross section of 1/8" and a diameter of 1.500" cannot be used to make any other diameter.
C-seal (face seals - ECI, ECE, ESI and ESE)
C-rings under six inches are primarily die formed, although tooling may have to be made for certain diameters. C-rings larger than six inches are primarily roll formed. All the standard cross section sizes have roll form tooling already made. Contact Parker with any questions.
C-seal (axial seals – ECA and ESA)
Axial C-rings require very tight tolerances. All axial C-rings are made using die form tooling. If the required seal size is not listed then tooling will
have be manufactured.
E-seal (face seals - EEI and EEE)
E-seals are manufactured using a series of roll forms. The number of roll stages depends on the number of the convolutions and the complexity of the cross section. This number can range from four to as many as 25 roll stages. Parker has designed over 60 different cross sections. E-seal applications tend to be unique and challenging, requiring careful selection to fit the appropriate cross section.
U-seals (face seals – EUI and EUE)
U-seals are manufactured using a series of roll forms. They are simpler in nature than E-seals.
O-rings (face seals EOI, EON, EOP, EOE, EOM and EOR)
O-rings are manufactured by winding tubing around an arbor. Parker has all of the tooling necessary to make any size.
Wire rings (face seals – EWI and EWE)
Wire rings are manufactured by winding wire around an arbor. Parker has all of the tooling necessary to make any size.
It must be understood that a seal is only one component of the hardware necessary to contain the medium leaking. Seals are placed against flanges or shafts /bores and that hardware is just as important to prevent the loss of medium as the seal. The seal must be properly matched with appropriate hardware. Together they function as a team, and an issue with either part may cause the customer to experience more leakage than desired.
If a customer is experiencing an issue with leakage then there are several questions that must be addressed.
1) What is the expectation for leakage?
As written above this might be zero for some applications, but it also may be a specific number for others. A customer may not want to see a pool of oil under machinery and the expectation may be zero leakage of oil. If, however, the customer is trying to contain air from leaking from one part of a jet engine to another part, there may be a measured amount that is allowed.
2) Has the seal type been properly selected for the application?
Different types of seals have different abilities. Some applications require a seal with a low load and high amounts of springback. Some seals have very high seating load and it may not be possible to bolt the hardware down. Some types of seals do not have enough springback for certain applications.
3) Has the seal been properly sized for the application?
Metal seals are less forgiving of sizing error than polymer seals. The seal needs to be correctly sized by taking into account:
a. Cavity depth
b. Cavity dimension tolerances
c. The amount of flange separation that the application may experience
4) Has the correct seal material been chosen for the application?
Proper material selection is critical. Materials must be selected for stress relaxation at temperature. Some materials are more appropriate than others for corrosion resistance, fatigue strength and chemical compatibility.
5) Has the customer hardware been examined?
a. Is the surface finish appropriate for the level of leakage desired? For example, is the customer using a circular lay face seal groove?
b. Is the hardware tolerance understood and accounted for?
c. Is there enough seating load for the seal? For example, are there enough bolts to compress the seal and are they the right size and grade?
d. Do the customer flanges have the correct hardness? For example, seals with a seating load of 200 lbf/inch requires mating surface hardness of at least 35 Rc.
e. Are there radial scratches or digs in the flange sealing surface?
6) Has the seal been examined?
a. Does the seal show signs of abuse or mishandling?
b. Are radial scratches visible on the sealing surface?
c. Has the seal been compressed to the proper cavity depth? Seals such as C-rings operate in the plastic region of the material and will take a set. When measured the seal should show that it has been compressed and the amount of springback should be taken into account.
d. Is there a visible footprint where the seal made contact with the flange hardware? Is this footprint continuous? Does the footprint look the same on all parts of the seal that come into contact with the hardware?
e. Was the seal properly sized? Has the seal diameter been measured?