Valves for oxygen service go through a complex process

Industrial valves and oxygen applications: ‘from standard to special’

Valves for oxygen service go through a complex process in order to be properly prepared for the special requirements. One can only guess from the end result how much work actually goes into these valves.
 
^ Valves for oxygen service go through a complex process

Selected by David Sear
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Siekmann Econosto GmbH & Co KG, located in Dortmund, develops and produces industrial valves for a wide range of industries, including oxygen applications. For oxygen service, Siekmann dismantles standard valves obtained from various manufacturers into their individual parts and subjects them to an elaborate procedure in a specially developed production area. In this sensitive process it is important to achieve the highest degree of purity. The valves are used among other things in air separation plants (LZA/ASU) for the production of industrial gases.

The company has defined the target for surface cleanliness on the basis of customer and regulatory requirements and has developed and established a corresponding cleaning process. The processes take place in a delimited area within the company premises. Specially trained employees only enter the premises in prescribed protective clothing such as disposable overalls, overshoes and gloves. The socalled clean area and the clean rooms are free of particles and oil as far as possible. Special equipment includes modified equipment such as test benches, which are not operated with compressed air but with pure nitrogen. A contamination of the individual components or groups of components after cleaning is thus excluded. Like the valves themselves, the workplaces, all tools and machines are subject to regular inspections in order to maintain consistently high cleanliness levels.

Preparation for use in oxygen service

In the first step, the respective industrial valve is completely dismantled. All individual parts are given unique numbers to facilitate subsequent reassembly. In this context, the valve accompanying document is issued (manufacturer, materials, nominal sizes, etc.).

This is followed by mechanical treatment to remove sharp edges and burrs. This improvement is subject to a first visual inspection. The clean area is then the scene of the cleaning process, where larger parts are first cleaned with high-pressure cleaners and smaller parts are pre-cleaned in a cleaning system. The components are then cleaned in an ultrasonic bath with special cleaning agents and solvents and various rinsing processes with final nitrogen drying. This ensures the removal of cleaning agent residues, oils and greases (<125 mg/m2) as well as foreign particles (>0.5 mm / maximum 50 mg/m2). The result is components that are free of burrs, loose chips, scale, rust, weld spatter and tarnish. Afterwards all components are brought into the clean room. Under black and white light, Siekmann Econosto specialists search for reflections that reveal impurities such as oil residues. Any component deemed non-acceptable is returned to the cleaning process - otherwise it is assembled in the clean room.

When reassembling non-metallic materials, the main focus is on lubricants, packings and seals which have been verified by the Federal Institute for Materials Testing (BAM). This means that they have been tested in terms of pressure and temperature limits in accordance with the operating conditions in oxygen service and withstand the most critical safety aspects in the liquid oxygen range. The new visual inspection with white and UV light, function tests and leak test of the special valve complete the tuning, because of course a perfect functionality must be given beside a contamination-free surface before the presentation to the customer acceptance can take place.

Before packing, labels with stainless steel wire are attached to the fittings, which mark them as “free of oil and grease for oxygen”. Desiccant bags are added to the packaging in PE tubular film, which absorb condensing moisture through ambient air enclosed in the sleeve. The customer receives the final documentation, which is required for both internal and external purposes, with detailed information on the entire process. The valve can be stored until commissioning, whereby the protective cover must remain unopened until then in order not to falsify the result of the complex “upgrade”.
 

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