What are the Different Varieties of Piston Seals Available

What are the Different Varieties of Piston Seals Available


Step by Step Guide to learn piston seal design, advantages, and working

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What are piston seals?

Piston seals make sure that any fluid or some other type of media will not pass around the piston. Because the pressure of system accelerates the piston downward the cylinder in the process of a pressure cycle.

Piston rings or seals are basically active or dynamic seals. They are usually of two types, like:

  • single-acting piston seals
  • double-acting piston seals.

Furthermore, it totally depends on the requirements of cylinder that, which kind of piston seal will it use.

These seals actually manage contact of sealing between the cylinder bore and the piston.

And this moving piston rod in fact produces extreme pressure on the piston seal. That boost contact forces between the cylinder surface and seal. Because of this, the qualities of surfaces of the sealing surfaces are very crucial for accurate seal performance.

The other name of piston seals is piston rings. Manufacturers use these piston rings in hydraulic cylinders in order to seal the fluids. They are actually inside the cylinder head and seal opposite to the cylinder bore. So, they stop fluid from flowing through the head of the cylinder.

This increases the pressure on one side of the piston, which causes the cylinder to retract or extend.

What are the materials that designers use in piston seals?

When it comes to materials which designers use in piston seals, it totally depends on the selection of seal profile. The use of materials truly depends on essentials qualities and on the profile. In addition, manufacturers make use of many materials in a piston ring. But at the same time, it is also possible that they can use only one material.

On the other hand, most common piston rings can use the following materials,


  • thermoplastic polyurethane (H-PU)
  • Viton
  • nitrile rubber (NBR)
  • acetal
  • polytetrafluorethylene (PTFE)
  • EPDM, etc.

Furthermore, when designers design the piston rings for some special and specific application. Then designers have to consider the expected pressure as well as consider the acceptable friction losses. And also checks whether the head of piston is split or integral.

Hence, it is clear that manufacturers manufacture the piston seals on the basis of usability and function. Moreover, they also classify them according to their needs and requirements.

How do piston seals work?

Piston rings work in such a way that, they contain pressure on one side of the piston and prevent leaking. So, they allow greatest mechanical exertion to apply to move the piston with the cylinder bore. Hence, piston rings have intended to stop or prevent leakage ahead the piston.

And hence these seals have ability to maximize the performance of the system. These piston rings have capability to drive either for both purposes either,


  • pneumatically

Piston seals allow to do this by the help of a proper piston seal which designers design for every application. In order to drive ram, pressure can apply from one or two directions and piston can fix from both. Although piston seals have known as a different kind of hydraulic seals. And these seals are actually a variety of rod seals.

What are most common types of piston seals?

Basically, there are two main types of piston rings according to their basic functions.

And these are:

  • hydraulic piston seals
  • pneumatic piston seals.

Here we are giving the complete information about these two types of piston rings.

Hydraulic piston seals:

hydraulic piston seals are one of the best piston seals. Because they have ability to provide determined protection in very strong and heavy-duty hydraulic applications. And they also make use of these seals for high-temperature and extreme environments.


There is a wide range of these seals which have strategically built and designed to use in hydraulic applications. Moreover, these hydraulic applications have designed to work in the conditions of high pressure and high temperature.

Designers have designed these piston rings to operate in pressure up to 7250 PSI (500 bar). And they also have capability to operate above the described temperature under some special conditions.

pneumatic piston seals

Manufacturers have used pneumatic seals for some basic applications or systems. Designers have designed these piston seals with wisely selected materials which are corrosion resistant. These rings are best for lower operating pressures. These seals also perform properly in rotary along with reciprocating motion. In addition, these seals are perfect for pneumatic cylinders and valves.

What are design considerations for piston steals?

Here are some design considerations of piston rings. So that they can perform properly during high and extreme pressures. Furthermore, they provide best sealing performance as well as maximum durability.

  • Pressure Rating
  • Lip vs. Squeeze Seals
  • Single- or Double-Acting Piston Seals
  • Non-symmetrical Piston Seal Design
  • Seal Lip Geometry.

Pressure Rating:

The maximum ratings of pressure of these seals has highly affected by these factors, like:

  • Wear rings
  • Extrusion gaps, clearances
  • Seal material
  • Temperature
  • Back-up rings

Lip vs. Squeeze Seals:

Primary design of piston steals expressively affects all in all function of the seal. And it happens specially at low pressure. Manufacturers of these seals also provides a complete series of low-friction piston rings for more challenging applications.

These seals are:

  • Lip seals
  • Squeeze seals.

Single- or Double-Acting Piston Seals:

These seals basically contain two types of seals.

For example:

Uni-directional or Single-acting:

These seals have ability of sealing dynamic pressure from just one side.

Bi-directional or Double-acting:


These seals have ability of sealing active and dynamic pressure from two sides.

Non-symmetrical Piston Seal Design:

Here are 3 features and advantages of non-symmetrical piston seal design.

  • The shape of outer diameter lip is different from the lip of inner diameter.
  • These type of piston seals provide sealing contact for low and static pressure sealing.
  • These seals are most stable and also provide best sealing efficiency in comparison to symmetrical seals for example,
  • Polypak type seals
  • U-cups.

Seal Lip Geometry:

Here are 3 types of these piston seals.

These are:

  1. Knife-edge and straight seal lip
  2. Beveled seal lip
  3. Rounded seal lip

What are the benefits of piston seals?

piston seals suppliers and manufacturers

Piston rings have multiple benefits over other types of seals. Furthermore, uses of piston rings have several advantages in industrial applications or systems.

Some benefits are:

  1. These seals are useful in low as well as high pressure system operations.
  2. These are low cost.
  3. These piston rings do not allow dirt or any other impurity to enter the inner mechanical system.
  4. Designers can easily eliminate failure of the incorrect installation.
  5. Manufacturers can order these piston rings in bulk because these are cost-efficient.
  6. Designers have designed these piston seals for very long service lives.
  7. Most important benefit is, there is lack of need for the purpose of tightening.
  8. It is very easy for an engineer to change a piston ring. He can change it in just a few minutes.
  9. Designers use piston rings to reduce eruption on oil plants
  10. These seals have ability to prevent all leakage, hence they can reduce chances of repairing.


Piston rings or seals are most beneficent hydraulic seals. These seals are cost effective and very easy to use. Piston rings also have ability to perform as,

§ Single acting piston seals

§ Double acting piston seals.

Hence, they are effective in both cases for single acting as well as double acting performances.

So, Piston seals have ability to prevent any leakage of fluid and any media. They are very effective in hydraulic seals.