Article by Oliver Bellina<\/strong><\/p>

The Batch stones<\/strong> are a sort of defect and they have to be recognized as soon as possible; in fact they are a very important indicator of the\u00a0\u201chealth\u201d of the melting and fining process<\/strong>, or in other words, of the back side of the glass furnace.<\/span><\/p>

Typical batch stones essentially consist of unmelted SiO2 sand grains<\/strong> that, due to their lower density, float over the melt and \u201crun fast\u201d to the throat. Consequently the presence of these inclusions in the final product, could generate a high level of rejection<\/strong> associated with decrease of process yield (pack to pull) and increase of scrap.<\/p>

The Batch stone appears as a deep, white matt conglomerate<\/strong>, although it can sometimes be glossy, other times porous. Thus, observation is insufficient as a means to distinguish it from other types of inclusions resulting from cracked refractory material (SiO2 or high mullite construction materials).<\/p>

To obtain a clear identification of a stone’s nature it is necessary to perform an EDS analysis by SEM<\/strong>, but frequently the timing of identification is a key point to take into consideration in order to speed up the problem solving process and obtain an effective Non-Quality cost saving.<\/p>

With experience, it is possible to reliably recognise this sort of stone through a quick defect observation with a petrographic microscope<\/strong> (microscope in polarized light).<\/p>

The reasonable identification of batch stones can be performed keeping in mind:<\/p>

• The stone appears as a deep white matt inclusion<\/strong> of various dimensions.<\/li>
• Batch stone inclusions are always surrounded by a high number of bubbles<\/strong>, a result of the melting process due to degradation of raw materials (mostly carbonates and water evaporation).<\/li>
• The stone is included in Silica enriched glass pockets that generate a \u201ccompression stress\u201d<\/strong> visible in polarized light: pockets could be stretched by the production process (as in tubular glass) becoming cords.<\/li>
• The Batch Stone inclusions are often associated with an increase of rough knots and chemical cords that show a compressive stress in polarized light<\/strong>.<\/li><\/ul>

  When those defects are correctly identified, the problem resolution could be reached by managing a series of set points including thermal profile, bubble rates and other parameters<\/strong>.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

  \n\t\t\t\t\t\t

  \n\t\t\t\t\t

  \n\t\t\t

  \n\t\t\t\t\t\t

  \n\t\t\t\t

  \n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<\/div>","protected":false},"excerpt":{"rendered":"

  Article by Oliver Bellina The Batch stones are a sort of defect and they have to be recognized as soon as possible; in fact they are a very important indicator of the\u00a0\u201chealth\u201d of the melting and fining process, or in other words, of the back side of the glass furnace. Typical batch stones essentially consist […]<\/p>\n","protected":false},"author":4,"featured_media":4089,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[45],"tags":[],"class_list":["post-4113","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-tutorial","entry","has-media"],"yoast_head":"\n