Thermocouples keep building block production going

A Hawco product story

Edited by the Engineeringtalk editorial team Mar 8, 2000

Conax Buffalo "soft seal" compression glands and thermocouple probes are playing a vital quality maintenance role within the building materials production industry.

Conax Buffalo "soft seal" compression glands and thermocouple probes are playing a vital quality maintenance role within the building materials production industry and particularly so for Celcon, which produces autoclaved aerated concrete, 'aircrete' foundation, Standard and Solar type building blocks.

The company is committed to the most stringent quality standards imposed by the British Board of Agrement and ISO 9002 Certification within its production plants at Westbury in Wiltshire, Borough Green in Kent and at Pollington, Humberside so a processing monitoring programme is essential.

The Celcon blocks are manufactured within a fully automated continuous process from a mix of sand, lime, cement and PFA.

A proportion of powdered aluminium is also added.

The aluminium reacts with the other constituents to produce hydrogen gas, which bubbles through the mixture and thus aerates the resultant 'cake' to produce a light cellular structure.

The bulk expanded cake is wire cut to produce individual 'blocks' which are palleted and cured within a battery of 50 metre long autoclaves at a steam pressure of 175 psi.

The autoclave cycle is critical to the integrity of the cured blocks and it is, therefore, important to Celcon that the process conditions are constant throughout the many hundreds of blocks within the autoclave both, along the length of the pallet trains and from top to bottom of the stacks.

Conax K-type sensor probes are inserted at intervals along the length of a batch attached to travelling leads which exit from the autoclave body via a cluster of Conax MHM glands supplied by UK temperature and pressure specialist distributor Hawco.

Unlike many conventional compression glands, Conax Buffalo pressure and vacuum sealing assemblies are able, as with Celcon's installation, to carry wires, probes, thermowells or multiple elements through a pressure or environmental boundary and maintain a total integrity of the seal at the point of penetration.

The success of the Conax Buffalo sealing methods is attributable to the development of soft sealant technology and complete knowledge of the performance characteristics of specific materials, their sealant properties and reactions to compression.

Standard sealant materials employed include Lava (natural magnesium silicate), Teflon, Neoprene, Viton and Grafoil.

The experience gained through many safety-critical applications within the process control, aerospace, and nuclear power industries indicates that Conax Buffalo technology is preferred to alternative and virtually permanent installations, such as welding, or where a mechanical mounting device could deform or damage the inserted element.

Routine maintenance or replacement of components under these circumstances is found to be both costly and time consuming.

By comparison, Conax Buffalo sealing glands reduce the overall cost of ownership through reductions in installation time, downtime and the cost of replacement parts, particularly where inserted elements require removal and replacement for calibration, cleaning, sterilisation or positional adjustment.