A leading international supplier to the biopharmaceutical industry, Sartorius Stedim Biotech, wanted to scale up their disposable bags used in single-use bioreactors to a total volume exceeding 2,000 liters.
This posed a challenge for the new stir ring assembly:
  • On this scale, a huge amount of torque would be applied to the stirrer inside the reactor
  • The stirrer should rotate inside the sealed bioreactor bag, eliminating the risk of contamination
  • The drive coupling had to withstand a much higher force than normal


Trelleborg Sealing Solutions recommended an entirely new self -contained unit, designed according to client specifications. Stuttgart contacted Trelleborg Sealing Solutions in Broomfield, USA, who are specialized in plastic bearings. The idea was for a radial magnetic coupling using an assembly of special Duroball® and a housing of Zurcon® polyethylene welded to the bag. The development project involved three countries on both sides of the Atlantic. Broomfield responsible for R&D of the radial magnetic coupling, the engineering was carried out in Stuttgart, and the manufacturing of the bag took place at Sartorius in Aubagne, France. The first coupling design was shipped after only 12 months, and the evaluation prototypes two years later. Following two years of successful trials at a major pharmaceuticals manufacturer, the Biostat STR 2000L got launched in May 2014.
Martina Weingärtner Laboratory Technologist


Throughout this partnership, it was only thanks to the constant updates and frequent visits from Trelleborg that we were able to realize this project so efficiently.

Gerhard Greller, R&D Director Upstream Technology at Sartorius Stedim Biotech GmbH

Customer benefits

  • Close cooperation between the various companies and sites accelerated the R&D process
  • Broomfield site added expertise in integrating engineered plastic parts in Trelleborg’s hardware
  • Trelleborg Sealing Solutions worked closely with the client to successfully test a brand-new, customer-specific assembly