Lean air unit

Technical article on lean air systems in CITplus and Chemmanager

1024 700 Alexander Hanf

CITplus / Chemanager published a paper on lean air systems. The article is also been published on chemanager-online.de.

Since it is only available in German, here a short abstract:

Lean Air

Manufacturers of synthetic resins for coatings and paints use artificially produced „air“ with less oxygen to supply the solvent boiler. For safety reasons, during the production process the product is coated with pure nitrogen for a long time; But some production steps require oxygen to react. This oxygen content in the reaction atmosphere must necessarily remain safely below a defined limit concentration, so that the lower explosion limit is not exceeded. Air (compressed air) or Oxygen is mixed with Nitrogen to produce and use lean air at a safe and constant oxygen concentration.

Not only the product quality but also the safety depends on the compliance with the given oxygen content, because the exceeding of the maximum permissible oxygen concentration can lead to explosions and as a consequence to serious accidents.

The influences quality, safety and availability are significant for process plant operators!

With regard to lean air systems, this means:

  1. Quality: Compliance with the defined oxygen concentration -> consistent product quality
    The gas mixture quality and thus the product quality is influenced by the choice of the system technology. Gas mixture quality can be expressed by the reproducibility: Manually controlled gas mixing plants typically achieve +/- 0.5%, automatically controlled gas mixing plants typically achieve +/- 0.2%.
  2. Safety: Safe prevention of exceeding the specified oxygen concentration -> no danger of explosion and guaranteeing the safety of downstream process plants by maintaining the defined oxygen concentration!
    This safety is ensured by a gas analyzer system, consisting of gas analyser, outlet shut-off valve and blow-off solenoid valve. A Safety Integrity Level (SIL) analysis can further increase functional safety. According to the definitions, suitable assemblies are selected, interconnected and ensured by regular check of the security.
  3. Availability: Failure plan -> ensure availability
    The financial impact of non-availability of lean air systems is often significant. Costs for production downtime and for troubleshooting can be estimated and avoided by a failure plan. For preventive increase of the technical reliability the following concepts are used by default in the industry, usually in dependence of available budgets and the evaluated default risks:
    – bypass
    – Backup
    – redundancy


Through graduated measures, the operator’s requirements for quality, safety and availability are defined individually and a customized lean air system is designed accordingly.

Read the entire article here.

For further questions please contact:

Alexander C. Hanf,
Managing Director LT GASETECHNIK
Tel: +49 231 9610700