Keeping up with the grind: Seals for coffee machines

Keeping up with the grind: Seals for coffee machines

Keeping up with the grind: Seals for coffee machines

Trelleborg Sealing Solutions supply a specially modified Stepseal® in Turcon® MF to WMF, the world’s leading manufacturer of professional coffee machines. These meet the customer’s requirements for a piston seal that will stand up to brewing at least 100,000 cups of coffee.

Up to 300 cups of coffee an hour – no ordinary coffee machine

You cannot compare the professional coffee machines manufactured by WMF to those found in the average home. Their machines are engineered to brew up to 300 cups of coffee per hour. That means each component must be of the highest quality and durability. In WMF coffee machines, the standard non-abrasive plastic internal parts of domestic models are replaced with metal and the demands on seals within these are high.

In the WMF bistro range of machines, coffee is freshly ground. A piston presses these grounds into a cylinder, at the bottom of which is a metal sieve. To make the coffee, boiling water is jetted through the cylinder, where the seal is located, with a 70 mm/ 2.7 inch stroke of the piston at a pressure of 16 bar/ 232psi. The sieve then swings down and the piston pushes the used coffee grounds out of the cylinder into a collecting tray. This process is repeated for every single cup of coffee, up to 300 times per hour.

The WMF Bistro coffee machine

Hardwearing seals needed with excellent friction characteristics and media compatibility

Seals in these coffee machines need to have excellent friction characteristics for movement against the equipment’s hard metal counter surfaces along with exceptional wear resistance to withstand abrasion from ground coffee beans. They must be compatible with process media including acids in coffee, fats in milk and the aggressive chemicals in cleaning regimes. In addition, pressures are high as the boiling water is forced through the coffee grounds.

The sealing solution proposed to WMF by Trelleborg Sealing Solutions was a modified Stepseal® design, its unique geometry engineered to endure the specific requirements of this intensely dynamic environment. Turcon® MF, a proprietary PTFE based material was chosen for the seal, a compound specifically formulated for food, beverage, and pharmaceutical processing.

Fitted in the cylinder of the WMF coffee machine is the modified Turcon® Stepseal®

Modified Stepseal® in Turcon® MF extends seal life meeting target of standing up to brewing at least 100,000 cups of coffee

Based on ultra-clean technology, Turcon® MF compounds are manufactured from high-purity PTFE grades and additives. Their smooth finish, with high gloss and low porosity, avoids the risk of contamination buildup and reduces particle shedding. Capable of operating in the high temperatures and process media of the brewing environment, its excellent friction characteristics further enhance the seal’s capabilities in this dynamic situation. It is also compliant to FDA 21 CFR177.1550, 3-A and USP Class VI.

The modified Stepseal® manufactured in Turcon® MF is proving to provide extended life in this harsh processing environment, meeting WMF’s target of a product that will stand up to brewing at least 100,000 cups of coffee.

Turcon® MF features and benefits:

  • Temperature resistance from –253°C to +260°C/ –423°F to 500°F
  • Almost universal chemical compatibility
  • Outstanding low long-term compression set characteristics
  • High wear resistance
  • Minimal creep and permeation
  • Surface finish minimizes contamination risk
  • Materials perform well in a broad range of chemical media including organic and inorganic oxides, acids, alkalis, amines, esters and steam
  • Materials compliant to FDA 21 CFR177.1550, 3-A, USP Class VI and sanitary standards

Read the article on sealing in the WMF coffee machine in our ‘in the groove’ magazine

To find out more about food, beverage and pharmaceutical sealing download our brochure for these segments