| 1867 | | Foundation of the company by Theodor Ohl: Production of pumps and water supply lines |
| 1886 | | establishment of an iron lathe company operated with the aid of a steam machine |
| 1994 | | Establishment of the iron foundry and machine factory "Limburger Eisengiesserei und Maschinenfabrik Theodor Ohl" on the territory Blumenröder Str. 3, in Limburg |
| 1978 | | Foundation of the family joint stock company in Limburg |
| 1995 | | Take-over of PAUL STEHNING GmbH |
| 1997 | | Foundation of PETKING S.A. Romania, PET Post Condensation |
| 1999 | | Foundation of PKR PET Kunststoffrecycling GmbH, Bottle-to-Bottle-Process |
| 2003 | | Take-over of OHL Apparatebau & Verfahrenstechník GmbH by SCHOELLER Group and |
| 2004 | | Foundation of OHL Engineering GmbH – PET Recycling Technologies |
| 2007 | | Expansion of a second line for PET Recycling at PKR to a capacity of 18.000 t/a. |
