Plasma-cleaned products for oxygen applications

created by Mr. Nicolas Nitsche |

By purchasing a plasma cleaning system and a special packaging unit, SUCO is now able to offer plasma-cleaned pressure switches and transmitters in the purity levels "free of oil and grease" and "PWIS/LABS free".

What is plasma?

Plasma (Greek: the formed) is a reactive gas consisting of free, energy-rich electrons, ions and neutral particles. The proportion of charged particles, which can be between 1% and 100% (full ionisation), determines the electrical conductivity of the plasma. Since plasma can be generated from the gaseous state by supplying energy, it is also referred to as the fourth state of matter in addition to solid, liquid and gaseous.

Operating principle of the plasma cleaning system

Pressure switches or transmitters of various sizes can be positioned on special workpiece carriers in the spacious process chamber. After the door is hermetically sealed and plasma cleaning is initialized, the process chamber is evacuated by means of a vacuum pump.

At approx. 1 mbar pure oxygen is added as process gas. A high-frequency generator forms an electromagnetic field as an energy source, which ionizes the oxygen and transfers it into the highly reactive plasma. Organic contaminants based on hydrocarbons (CH chains) are completely destroyed in the plasma and removed via the vacuum system.

At the end of the cleaning process, the process chamber is ventilated in a controlled manner. The cleaned products are then removed with gloves and individually sealed in PE bags. In addition to technical data and approvals, the label on the packaging also indicates the respective cleaning process.

Oxygen applications

When handling oxygen (O2), certain safety and accident prevention regulations must be observed. Oxygen as a medium itself is not combustible. However, in conjunction with a flammable substance such as oil or grease, spontaneous ignition may occur due to frictional heat, electrostatic discharge or sparking. Even a slight increase in the oxygen content within an air-gas mixture can accelerate the combustion process (temperature and speed) considerably.

Free of oil and grease

In terms of quality assurance, SUCO pays attention to the provision of oil and grease-free individual parts when selecting its suppliers. Trained personnel and operating instructions, such as the use of silicone- and grease-free media, ensure an oil- and grease-free assembly and calibration of the pressure instruments.  

On the production and process side, it cannot be completely avoided that isolated small quantities of lubricating oil or skin grease stick to a workpiece. Since even the smallest oil or grease residues are sufficient to cause a fire or explosion when handling oxygen, SUCO recommends to use only plasma-cleaned pressure switches and transmitters when handling oxygen or other flammable air-gas mixtures.

Plasma cleaned

The cleaning process by the plasma cleaning system in sealed individual packaging ensures that no more than 20 mg of organic hydrocarbon compounds are detectable per m². The maximum purity level of 20 mg/m² corresponds to level B according to ASTM G93-3:2004 (< 33 mg/m²) and is regularly monitored by Germany's national accredition body (DAkkS).

SUCO recommends the use of EPDM sealings for oxygen applications, which can be used in a temperature range from -30° to +120°C. The burn-out resistance of EPDM gaskets has been certified by the Federal Institute for Materials Testing (BAM) in a test report.

The maximum permissible pressure for oxygen applications varies depending on the housing material from 10 bar (galvanized steel), 35 bar (brass), up to 250 bar (stainless steel).


The acronym PWIS refers to "Paint-Wetting Impairment Substances" such as lubricants, oils, greases or silicones. Within the painting process, PWIS can cause contamination and coating defects - so-called craters - and thus impair the quality and durability of the paint. For this reason, the painting processes of vehicle and engine manufacturers are often subject to strict requirements.   

Due to a longer process duration and the use of PWIS-free gloves and PE bags, SUCO's new plasma cleaning system can also achieve the purity level "plasma cleaned for PWIS/LABS-free surfaces" and thus PWIS/LABS free conformity according to the national standard sheet VDMA 24364.

A further advantage of plasma cleaning is the temporary increase in surface energy. By activating plasma, the surface of the pressure switches and transmitters is chemically modified so that functional groups (OH-groups) can attach themselves, which temporary increase the wetting ability.

Application areas

Production and manufacturing
  • Autogenous welding and flame cutting: Outflowing fuel gas-oxygen mixture is ignited and oxidizes in a kerf on the workpiece.
  • Glass and steel industry: Glass furnace / blast furnace pure oxygen is added to accelerate and optimize the melting process (Oxyfuel process)
  • Textile industry: Highly dosed oxygen as bleaching agent for fibres and cellulose
Chemical, pharmaceutical and food industry
  • Chemical industry: Process engineering oxidation of organic compounds
  • Pharmaceuticals: Distillation and oxidation of sterile water
  • Packaging under modified atmosphere: Fumigation of food with liquid oxygen
Water treatment
  • Wastewater treatment: In the field of biological water treatment, ozone (O3) can oxidize pollutants and persistent substances from wastewater treatment plants
  • Drinking water treatment: By adding oxygen, iron, manganese, ammonium, hydrogen sulphide or methane is removed from drinking water.
  • Ozone production: disinfection of swimming pools and process water
Medical Technology
  • Ventilation and anaesthesia equipment: Medical oxygen for ventilation in emergency medicine and the treatment of chronic lung diseases

SUCO issues a manufacturer's declaration to prove the respective degree of purity - plasma-cleaned for oxygen applications or PWIS/LABS-free.

Should you have any questions regarding the use of pressure switches or transmitters in your application, the respective country representative of our international sales network will be pleased to advise you at any time. Due to decades of experience in the field of pneumatics, hydraulics and fluid technology SUCO has a comprehensive know-how in dealing with demanding, safety-relevant applications of any kind.

More information about plasma cleaning can be found here: