What Does a Seal Do?

What does a Seal Do?

Posted on 2017/02/28 | Cliff | Seals

Seals are everywhere around us in our modern world but often hidden. Even at home, there are quite a few examples – from the kitchen to the garden to the car. In simple terms… seals either keep good stuff in, bad stuff out, or provide a separation barrier between things.

Some everyday examples

  • In the kitchen: your oven has a rubber seal around the door to keep the heat in while allowing you to get things in and out for cooking, and then you ‘seal in the goodness’ of the food with an air-tight container (with a sealing lid)
  • In the garden: your water spray gun connects to your hose fitting with a rubber seal to hold the water pressure and stop leaking, so you can control the watering of your garden.
  • In your car: the doors all have a moulded rubber seal around them to keep the rain out, while allowing you to get in and out.

In the industrial world

A mechanical seal interfaces between two systems or mechanisms to prevent leakage or contamination flowing between them, especially for liquids or gases under pressure. A seal is typically made of soft flexible material and presses between two hard surfaces which are not perfectly smooth.

Seals often allow freedom of movement while stopping substances intruding where they’re not wanted. One application is where a mechanical component goes into and out of a container of gas or fluid and a seal prevents leakage of the gas or fluid.

The common application of a piston and cylinder

A piston and cylinder can be used in two ways – either a high-pressure fluid or gas pushes the piston (for engines) or the reverse where the piston pushes the fluid or gas (for pumps).

In the case of pumps, a piston ejects a fluid or gas out of a cylinder. With no seal, the imperfect contact between the piston and cylinder would allow the fluid or gas to leak through the gap, ooze out in the wrong place, and be lost.

One example is a car brake system: putting your foot on the brake pedal pushes a piston which pushes brake fluid down a tube to push another piston which pushes a shoe against a wheel drum to slow the rotation. Without good seals, the brake fluid would leak out at both ends until the brakes no longer worked.

With compressors, a piston squeezes air or another gas into a smaller volume, to be released somewhere else – and the seal stops it leaking.

Endless applications

Seals have become crucial components in a huge range of technologies to keep them functioning properly, in a wide range of sectors including automotive, pharmaceutical, electronics, food & beverage productionenergy/power, plus aircraft and spacecraft. Eclipse manufactures and supplies reliable high quality seals for all these industries.