In various industries, thousands of gas and steam turbines are equipped with insulation systems containing calcium. What is often concealed in the process:
The calcium-containing insulations tend to form the carcinogenic and environmentally harmful chromium (VI) compound calcium chromate. Although this thermochemical reaction is well known, turbine manufacturers and insulation companies have so far tacitly accepted the problem.
But now the truth is being revealed and the chromate scandal is moving into the public eye.
Thus, the German "Hessische Ländermessstelle für Gefahrstoffe" which belongs to the German state of Hesse published the following document on its website on 13.04.2023 (the whole document can be downloaded below by link-clicking):
"In power plants, chromium (VI) compounds (chromates) have been detected on plant components in connection with insulation and assembly pastes containing alkali/alkaline earth metals."
The formation of carcinogenic chromates is described in great detail, i.e. the thermochemical reaction of e.g. calcium oxide as a component of high-temperature insulation such as the mineral wool found everywhere in power plants, but also other alkaline or alkaline earth-containing insulation materials with chromium-containing alloys of stainless steel hot parts, which are also frequently found.
The reference to "power plants" (e.g. gas or steam turbines (editor's note), "generators", "large engines" (as we know them from CHP or cogeneration technology (editor's note)), "process plants of the chemical industry" and "generally everywhere where the four starting conditions
chromium steel
Insulating materials or assembly pastes containing alkali/alkaline earth metals
thermal stress
Oxygen of the ambient air
permanently come together over long periods of operation, the undesirable formation of chromates must be expected," it continues.
Extensive protective measures required; uninvolved work groups also indirectly affected; risk of contaminants spreading to other areas of the company possible
In the section
"Affected workers and exposure situations" it continues:
"Stripping and dismantling work, which can lead to chromate exposure, is often carried out in power plants by employees of industrial service providers, i.e. external companies. Since the removal of thermally aged mineral wool is likely to release chromate-contaminated fibre dusts into the air we breathe, it is suspected that industrial insulators in particular may be exposed. After stripping, other workers, such as employees of technical testing organisations, may be exposed by working on components with chromate-contaminated surfaces. If chromate-contaminated fibres and dusts remain in the work area or are carried into other work areas, the permanent staff of the plant operator may also be exposed after completion of the actual maintenance and repair measures."
It goes without saying that old insulation contaminated with chromates must be disposed of properly and labelled as hazardous waste, also the stripping work must be carried out with the latest knowledge under special conditions, such as enclosing the contaminated areas and wearing full protective equipment at all times.
On the subject of substitution, the Centre of Expertise for Product Safety and Hazardous Substances writes:
"Of the above four initial conditions plus the contact time, there is only an influence on the choice of insulating materials and assembly pastes used."
The insulation industry with its associated insulation companies and associated service providers is therefore facing a paradigm shift and a Herculean task associated with it.
On the one hand, every inspection of a turbine in a power plant or the service of CHP motors in biogas plants and other technical plants will become a costly special construction site and it can be assumed that the interest in calcium-free insulation materials and insulation systems will now increase by leaps and bounds because the operators logically do not want to repeat the cleaning and inspection work that is now due a second time.
Information letter from the Hessian State Office for Hazardous Substances
Chromate exposures in power plants
Formation of carcinogenic chromium(VI) compounds on surfaces of thermally stressed chromium-containing steels through contact with alkali/alkaline earth metal-containing insulating materials and assembly pastes
Here is the promised link to download the document "Chromate exposures in power plants" (click on the symbol)
This blog post was originally intended to report on the first calcium-free insulation projects in Germany and further calcium-free insulation projects in the UK; however, due to new developments, the editorial team has decided to publish the
We will report shortly on substitutions of calcium-containing insulations with alkali-free and alkaline earth-free insulating materials and systems (see picture) that have already been tested in practice:
