What is the Difference Between a Gasket & a Seal?

What is the Difference Between a Gasket & a Seal?

When trying to choose between a gasket and seal, your first impression might be that they are the same thing. After all, they perform essentially the same function, right? In some ways, they are certainly the same, but there are some important differences that you should understand when deciding which one is right for your project. Gaskets seal a connection between two components or flanges that have flat surfaces, while seals are used between engine parts, pumps, and shafts that rotate.

What is a Gasket?

Gaskets seal a connection between two components or flanges that have flat surfaces, while seals are used between engine parts, pumps, and shafts that rotate. Gaskets are used wherever a union or flange is required to prevent leaking. Gaskets are most commonly used as static seals.

What are gaskets made of? 

Gaskets are manufactured using many different materials. Viton, Neoprene, Nitrile, Pure Gum Rubber, EPDM Butyl, and SBR are just a sampling of the most common rubber or elastomeric materials commonly used to manufacture gaskets. Gaskets can be manufactured from many more diverse products including treated fiber (vegetable Fiber), Cork, Cork and Rubber, Non-asbestos (Aramid fiber), Graphite, PTFE, or closed cell sponge when a highly compressible gasket is required.

How often should a gasket be changed? 

 Every time any equipment is taken apart and then reassembled, a new gasket should be used.

What industries use gaskets? 

Gaskets are used in many industries including oil and gas, pulp and paper, electric generation, and transportation.

What is a Seal?

As already mentioned, seals are used between engine parts, pumps, and shafts that rotate rather than those that are static. This type of seal is generally a molded or machined product. Seals tend to be flat and round, while gaskets are often cut into different shapes so that they fit the components. Most seals are made of an outer ring that is metal and nests over an inner surface that is often made of rubber. The inner circle is tilted just a bit, which creates a lip for the seal. The lip is designed as a second barrier against any drops that manage to get past the first edge of the seal. It is essential that seals be installed correctly because, if it’s installed backward, you could end up with a leaky mess on your hands.

What are seals used for? 

Common uses for seals include keeping leaks from occurring at the end of the shaft where it comes out of the cover and sealing hydraulic lines. This type of seal is generally a molded or machined product. Seals are often used in bearings, which is basically just a ball bearing surrounded by a rubber seal, which keeps it from leaking and sometimes reduces the amount of noise that occurs during operation.

How to install a seal? 

When installing the seal, it’s usually fitted into the hole by a press and then tapped further in using a hammer. Lubrication is usually necessary to keep the crankshaft from damaging the seal as it goes through it.

When should a seal be replaced?

When a seal breaks down, the entire bearing must be replaced rather than just the seal.

Let the experts at Blaylock Gasket and Packing help you find the right gasket or seal for your project.

Click here to Contact us today or call us at 800.259.8770

Oil seal basics: how o-rings, seals are designed.

Tip: oil seal Basics

Most of you will already understand these basics of how an oil seal is designed but we wanted to put this tip out for people new to the field.

In an oil seal environment there is a shaft that is rotating inside a housing or bore. Because of friction, there must be some clearance between the shaft and the bore. The function of the oil seal is to stop whatever fluid is inside from leaking out the clearance between the shaft and housing. The seal may also be used to prevent outside materials, such as dirt, from moving in through the clearance.

"Dynamic sealing" is the relationship between the rotating shaft and the seal and is handled by the sealing element. A garter spring may used in the oil seal to increase the radial interference between the seal lip and contact point on the shaft. In order to achieve this interference, the oil seal's ID must be slightly smaller than the diameter of the shaft.

"Static sealing" is the relationship between the housing and the seal. In order to achieve this interference, the oil seal's OD must be slightly larger than the diameter of the housing or bore.

An oil seal normally consists of three basic components: the sealing element, the metal case and the spring. The purpose of the sealing element is to stop the fluid from leaking between the shaft and housing. The metal case will give rigidity and strength to the seal while it is being held in the bore or recessed groove. The spring will help make the sealing element more effective. All materials must be selected depending on the environment in which the oil seal will function.

Differences between Single and Double Face Mechanical Seals

A mechanical seal is a device used to contain the gas within the stationary compressor casing where the rotating shaft passes through. Thus, keeping the gas from escaping into the environment.

If you’re thinking about purchasing a gas compressor from Ro-Flo for your application, you’ve likely noticed that there are two options for the shaft seals: single face mechanical or double bellows. Single face mechanical seals are valued for their simple, robust design that is easily repaired in the field, while double bellows seals offer a second level of protection. Here is an explanation of the differences between single and double bellows mechanical seals and the best applications for each type.

Single Face Mechanical Seals

While the concept of a seal is straightforward, in operation inside a rotary sliding vane compressor, the execution is more complex. Single face mechanical seals utilize a spring to press together two flat surfaces (faces), which slide against each other. Lubricating oil is injected into the seal housing to cool and lubricate the seal’s internals. The lubricating oil forms into a thin film between the sealing faces, creating a barrier between the process gas and the atmosphere.

To keep your single face mechanical seal operating properly, be sure:

The seal is receiving the proper quality and quantity of lubricating oil

There is no debris being introduced to the sealing faces

The sealing faces and/or o-rings aren’t damaged during installation

Double Bellows Mechanical Seals

This type of seal has two sets of contact faces. The two sets of faces are back-to-back, or dual-opposed, separated by a coil spring, thus pushing in opposite directions. The double bellows mechanical seal requires a lube oil support system. The support system is designed to keep the seal parts submerged in oil and to maintain pressure on this oil system that is greater than the pressure inside the compressor. With this pressurized system, if leakage occurs at the outer seal, it will be towards the atmosphere and air will not be drawn into the compressor. If leakage occurs at the inner seal, lube oil will be pushed into the compressor. Either of these leakages will be detected with a pressure sensor on the oil support system, so the compressor can be shut down prior to any gas leaking to the atmosphere. Details of the required lube oil support system can be found in Ro-Flo’s Installation, Operation and Maintenance Manual.

It is important to note that the lube oil support system must be pressurized prior to pressurizing the compressor or gas piping system – whether for pressure testing or compressor operation. If the process gas system is pressurized prior to the support system being pressurized, the seal is likely to fail.

Double bellows mechanical seals are used for any application in which the additional protection is desired. Often, this type of seal is stipulated by safety and environmental regulations. Many users of Ro-Flo compressors are in the oil and gas industry or managing biogas, therefore this type of seal is quite common.

If you’re uncertain which type of seal is the correct one for your application, our engineering team will be happy to discuss the advantages of each.

Get Started With Ro-Flo Compressors

If you’re ready to purchase a gas compressor, trust the experts at Ro-Flo to help you through the process. Our team has years of experience and is trusted by the top 25 largest oil and gas companies in the world. Contact us today to get started.