Graphite seal makers sound alarm over quality of Eastern imports

Graphite manufactured in the UK and Europe must meet stringent quality tests before being passed fit for sealing duties. In particular, it must contain no more than 2 per cent ash residues. However, according to Econosto and SGL, some imports from China and the Far East `contains on average six to seven times more ash residue'. These residues contain sulphur, which reduce the material's temperature resistances, and fluorides and chlorides, which can promote corrosion of flange surfaces. These impurities can sometimes occur in clumps within the graphite which can burn inside the gasket, say the companies, leaving it with the consistency of Swiss cheese `and about as much use.'

Graphite is an expensive option for sealing, previously only used for critical applications. However. its use is becoming more widespread since the phase-out of asbestos. Low-cost imports are obviously tempting, but Econosto md Tony Seall points out that it could well be a false economy. `The cheaper, low quality graphite products are simply not capable of surviving long-term in such conditions.' One major process company has already reduced its jointing temperature from 450 degrees C to 375 degrees C because of graphite failure and is considering reducing it further, he claims.