Current Developments in Piping Technology: Bending and Passivation

GMP facilities in pharmaceutical and biotech production still consist to a large extent of pipes. The costs for construction - but also for reconstructions - vary considerably. Tenders for such projects also often vary considerably.
Currently, there are two interesting developments in this area:

  • The increased use of bending machines (instead of purchased pipe bends)
  • The waiving of chemical passivation

Both developments were discussed with the participants at various pharmaceutical technology seminars. The discussions and survey results of the German and English webinar held on 26 May 2020 with more than 70 participants are presented below.

Bending machines and pipe bends

Many specifications and tenders still exclude bending machines today. Bad experiences with sanitary craft technology may often play a role here. However, the picture is changing:

The survey on bending has shown that although the majority still purchases and welds bends, about 30% of projects also use bending machines.

What kind of bend production do you use in your Pharma / Biotech - GMP piping construction projects?

Bows are always bought and welded in 42%
Bends are usually made using a bending machine directly on the construction site or in the prefabrication assembly department 14%
Small nominal pipe diameters up to DN50 are produced by using a bending machine directly at the construction site, only larger nominal pipe diameters are welded in as purchased bends 21%
None of the 3 mentioned / not specified 23%

The advantages are obvious: You save two welding joints and can create any angle. In narrow spaces (e.g. for shaft threading) this opens up new possibilities for compact planning and construction. Examination of purchased bends - and the comparison with bends produced by compact mandrel bending machines directly on the construction site - had already shown 10 years ago at a well-known pharmaceutical company in Basel that both are equally good. Modern semi-automatic bending machines - with computer control and PTFE mandrel, in which the high-quality material is not contaminated with oil or grease - play an important role.

There are still many arguments against the use of bending machines - mostly quality concerns or economic reasons for e.g. components manufacturers.

Chemical passivation

A further change in views can be observed in the topic of passivation. 20 years ago, almost every 1.4404/1.4435 pipe construction project in the biotech and pharmaceutical sector was completed with passivation. Mostly as a circular rinsing process for 30 minutes to four hours with warm, diluted citric acid or 5% nitric acid. In the meantime, there are numerous publications that question this procedure - at least for clean construction sites where the material is not soiled by greasy fingers. The survey on passivation with the questions below has shown that this point is no longer considered dogmatically.

Which type of passivation do you use in your Pharma / Biotech - GMP pipeline construction projects?

 It is always passivated with diluted acid, even if only 2 welding seams are renewed in one system 24%
 New plants are passivated with diluted acid, small extensions or modifications are not treated in this way from time to time but go into operation directly without chemical passivation 28%
It is no longer chemically passivated, the natural formation of a passive layer by oxygen-containing media is sufficient. 18%
None of the 3 mentioned / not specified 30%

The survey confirms that the majority of GMP projects also avoid extra passivation on a case by case basis. In almost one fifth of the projects, chemicals are no longer used for passivation.  Especially for systems like compressed air or pure steam, this can save enormous costs. Finally, the thickness of the passivation layer before and after passivation is usually not determined.


The state of the art is evolving and it is important to keep up to date on a regular basis.

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