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Refractories

Tackling production issues

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David Parkinson* reviews some of PSR’s initiatives that help glassmakers tackle production issues, and lays to rest some industry myths. Cat scratch cord dispersal - How do we do it?

Forehearth fuel efficiency How do we do it?

Refractory glass corrosion resistance - How do we do it?

You might think that the removal of cat scratch cord by the use of stirrers is a simple process. It isn’t. We are not mixing the inhomogeneous ‘cordy’ material into the glass like a food mixer. We are relocating it within the flow of glass so that it does not appear on the surface of the gob as a defect during the gob forming process. To do that we need to understand where the cordy material is and how it settles out in the furnace, forehearth and distributor. In our system design we need to take into account the channel width and glass depth, type of channel (whether profile or classic) glass temperature and type of cord, position of electrodes (if installed), position of the channel joint and position of any pre-existing drain that might also be installed. Given all these variables we then need to ensure that any pre-existing slot in the forehearth superstructure is in the right position and the correct size. If one doesn’t exist, or is in the wrong place, then we need to provide a new one. Most of our installations use paddle type stirrers although on occasions we may specify screw type stirrers, each one being specified with its own special paddle length or screw diameter to ensure that the cat-scratch is correctly dispersed. This is our know-how and it is why we guarantee every system we supply. http://www.parkinson-spencer.co.uk/ engineered-products/cord-dispersal-systems

Most people think fuel efficiency in the forehearth and distributor is a function of the firing system. They are wrong. The firing system can impact upon fuel efficiency but in the final analysis one supplier’s high pressure firing system is not substantially different to another’s. What really impacts on the fuel efficiency of the forehearth and distributor is (1) close control of the internal forehearth pressure such that cold air is not sucked in through the brickwork and peepholes are thereby cooling the sides of the glass flow and necessitating the firing system to work harder to heat the sides up, and (2) avoiding the use of large open flues to radiate heat from the glass surface such that the products of combustion are allowed to escape straight out of the flues creating a negative pressure inside the forehearth. Only the System 500 forehearth and distributor has the engineering that enables successful automatic control of both the cooling and combustion dampers. Any extra capital costs are quickly recovered and substantial fuel savings repeated year on year during each and every subsequent campaign. http://www.parkinson-spencer.co.uk/ engineered-products/system-5oo

Most people think that higher zirconia content automatically equals increased corrosion resistance. They are wrong. This is misinformation from marketing people. For instance a refractory compound formulated from pure zircon silicate (i.e. with 66% ZrO2) will have relatively poor corrosion resistance to soda lime glass whereas PSR-333 material with only 11.25% ZrO2 has excellent corrosion resistance to soda lime glass. A higher zirconia content can sometimes influence corrosion resistance but only if the constituent oxides are correctly sintered together. Slip cast PSR-333 and PSR-315 are direct bonded refractory compounds and the association that occurs between their oxides at high firing temperatures ensures excellent corrosion resistance. http://www.parkinson-spencer.co.uk/ refractory-products/feeder-expendables

Maintenance free forehearth burners – How do we do it? Conventional stainless steel forehearth burner nozzles will progressively block up as volatile materials in the forehearth atmosphere such as soda vapour condense on the relatively cold surface of the burner nozzle. As the backpressure builds from the reducing burner nozzle diameter, the air/gas mixture becomes weak and the maximum firing capacity Continued>>

48 Glass International February 2018

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Glass International February 2018  

Glass International February 2018