simmering

In order to tell the story of the Freudenberg Simmerring we need to go back in the days of the Roman Empire.

That's where Freudenberg begins in its history of these sealing products:

Even in ancient times, water was considered one of the costliest commodities. It was the job of engineers to find ways to transport the valuable liquid from its sources into the cities with minimal loss – often over hundreds of kilometers.

The explosive growth of metropolises would have been inconceivable without a secure supply of water – after all, the daily per capita consumption around 100 A.D. was nearly three times what it is during the 21st century.

Lead pipes in a casing of “Roman concrete” were mostly used in ancient Greek and Roman water lines. The efficient integration of these elements required special care. The sealing of the difficult-to-maintain pressure pipelines therefore required several layers of mortar.

SEALS FOR THE FUNCTIONING OF VITAL SYSTEMS
The Romans developed double-piston pressure pumps more than 2,000 years ago, to bring water from deep wells to the surface, enabling a nearly continuous water flow.

Intake openings, cylinders and parts of the riser pipes were made of oak. The valves of the hand pump were leather flaps. Wooden pistons moved in lead-lined cylinders. Leather piston seals were an ideal way to improve efficiency.

With a displacement ranging between 0.5 and 1.3 liters, the pumps were able to transport water from depths of up to 16 meters – in amounts as high as 95 liters per minute.

Very early on, seals were needed to ensure that complex, vital systems operated reliably. Then as now, the basic task of a seal was to prevent or limit the undesired transfer of material from one space to another.

Still, in a physical sense, there is no absolute impermeability. For example, within a few days, even the hydrogen atoms in a fuel cell vehicle’s carbon fiber tank penetrate its several-millimeter-thick walls. “Technical impermeability” is a question of definition – whether it relates to molecules, moisture, droplets or other criteria.

The mechanical principle of the seal described here involves the compression of the sealing material so that its internal pores and the micro-gap between the seal and the parts or the medium to be sealed become so small that the contained material can no longer penetrate it.

Sealing experts talk about a contact seal. Leather was especially well-suited as a sealing material due to its flexibility and was able to play a key role in seals for centuries.

But there is also the question of whether a material is suited for use in a seal long-term. This issue is primarily settled by the nature of the medium that it is supposed to seal off.

FROM TANNERY TO SEALING SPECIALIST

In 1929, Black Friday on the New York Stock Exchange was a difficult turning point for the Carl Freudenberg leather factory in Weinheim. Exports in particular collapsed; they previously represented 75 percent of its business.

So its staff recalled one of its earlier ideas – making sealing collars out of leather scrap, which had no other use. Up until that time, the collars for their own machines were ordered from America at great expense and in poor quality.

Engineer Walther Simmer – whose job was actually to further develop the tannery’s machines – was assigned to tackle the issue. After numerous attempts, he developed a collar ring made of chrome leather, which was embedded in a metal housing ring and pressed against the machine’s output shaft using a screw tension spring. It proved possible to achieve sufficient tightness and durability with the pressure.

Simmer managed to build up a small production operation that made a profit right from the start. One aspect was crucial to the Simmerrings’ success: The company was able to use its existing contacts with the auto industry and replace the felt seals that were employed to that point.

In short order, the amount of leather scrap was no longer sufficient for the company’s sealing ring production, and leather had to be tanned specifically for the purpose of manufacturing them. With the emerging leather shortage in Germany in 1934, the material was on the brink of being replaced as a seal component.

Starting in 1934, intensive research on synthetic rubber production was undertaken – in part to replace leather as a sealing material. Rubber compounds for seal and vibration control applications were developed at the “main lab” in Weinheim.

An elastomer replaced the leather in Simmerring collars in 1936. The development of the Carl Freudenberg leather factory into a market and technology leader in sealing technology was underway.

More than 80 years later, Gallagher Fluid Seals is proud to work with Freudenberg Sealing Technologies.

If you have questions about how their products can benefit you, don't hesitate to contact Gallagher. We'll be happy to hear from you.