Picture of Amnon Ram

Amnon Ram


Along with his wife Ofra, Amnon has been a manager at K&R and a mechanical sealing expert for nearly 30 years.

The importance of adjusting the structural materials of mechanical seals in pumps

In pumps with a mechanical seal, when the pump works and does not leak, we tend to forget the existence of the mechanical seal in it, even though the mechanical seal is the heart of the pump. The performance of the pump depends on the correctness of the mechanical seal and its suitability to the working conditions (fluid, temperature, pressure and speed of the shaft rotation given its diameter).

Advantages and disadvantages of the various materials

When do we remember the mechanical gutter? When the pump is running out. If the pump is running out after a short period of time, the question arises: Why does the mechanical seal fail?

This is the original seal of the pump manufacturer. Right! But the pump manufacturer does not always know where it will be installed and accordingly to take care of suitable building materials. In this article, I will refer to the various structural materials of the rings (permanent and rotating) and elastomers (Seals Elastomer).

It is important to check that the structural material of the mechanical seal fits the working conditions of the pump.

Knitting rings: Proper selection of the materials of the grinding rings (which work against each other), the compatibility between them, the advantages and disadvantages of the various materials they are made of can prevent unnecessary failures. The following are examples of various materials made of erosion rings, detailing advantages or disadvantages.

Stainless steel 316

Its advantages are non-rusting, non-breaking, suitable for food and medicine, good heat conductivity, high temperature resistance and thermal market (resulting from rapid temperature changes). Its drawbacks are that it does not have good lubrication, low friction coefficient, and can work well only against graphite-carbon which has high self lubrication.

White ceramics - Alumina Oxide

Medium self-lubricating, hard but brittle. Works well against graphite-carbon. Tends to get cracks due to rapid temperature changes (thermal market). Good for all types of liquids, though severely attacked.


Self-lubricating. Sealing with salt water like seawater. Suitable for oily liquids such as fuel oil and oil. Suitable for work with graphite-carbon or against steel tempered with greasy liquid.

Cast iron

Good self-lubricating but rusting in water and not resistant to chemicals. Very suitable for work with greasy liquid or oil. Tempered steel: hard but with low self-smoothness. Works well against graphite-carbon and oil versus bronze.


Strong and high hardness. Can not be machined. Smoothness and good self. Under oily conditions works against ceramics. Works great against graphite-carbon. In harsh conditions of abrasive or sewage powders work well when the two erosion rings are from tungsten carbide. Disadvantages: Heavy, expensive, disintegrates over time in contact with liquid, tends to crack from blow or thermal market.


Weak and fragile. We will play with powders, sand, rust and solids. It has excellent self lubrication and therefore can work against all types of materials. There are many types of graphite-carbonate. Some on the basis of resin and between them, which are suitable for food and medicine. There are those with a metallic base suitable for fuels. Resistant to chemistry. Can be machined. Resistant to high temperatures.

Graphite-carbon is a necessary partner in a dry-working gasket because of its high self-lubricating capacity.


Has good self lubrication. Works well against graphite. Working against himself. Resistant in acids and bases and abrasives. Hard. Can not be processed oils. Resistant to high temperatures. Light weight.

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