Glass faults

The quality of the glass to be fed into the mould had to be improved for the manufacturing of the 8 m mirror substrates. In the spin casting technique, there is no longer the possibility to avoid glass faults such as bubbles, solid inclusions, crystals, and striae in the final machining, as there is with the conventional technique. 

The maximum acceptance limit is around 2%, with higher values giving rise to increased risk of glass faults (13). 

Any piece of equipment under pressure is a potential hazard and must be properly shielded. Shields of clear plastic, properly anchored, will often suffice. Vacuum has its problems too. More than one glass flask with an almost imperceptible fault has imploded under vacuum, with an effect much the same as an explosion. Here, too, shielding is recommended. 

The most usual fault in making a rounded end is to leave a lens of thicker glass at the point where the spindle was drawn off. This may be because either insufficient glass was drawn away with the spindle— if this is the case more can be pulled off with a piece of rod-—or else... 

Anon., CISHC Chem. Safety Summ., 1984, 55(218), 34-35 Diethylamine fumes from a reactor were usually absorbed in a glass scrubber through which sulfuric acid was circulated, but an unresolved fault in the level sensor caused the acid circulation pump to operate intermittently. While the pump was not running, amine fumes condensed in the dip pipe, forming a sohd crust (of the sulfate) which allowed a quantity of condensed amine to accumulate out of contact with the acid. When the pump was restarted, the neutralisation exotherm was sufficient to shatter the scrubber and distort the mesh guard around it. 

Faults in the Glass.—Notwithstanding a]l the precautions that may he taken, air-bubbles frequently remain, and generally exist in great number when the fining process has been obstructed by too great difficulty of fusion in the glass. They aro technically termed seed, blibe, or blister. 

Waves and strive are faults of too common occurrence, arising from a want of homogeneity in the vitreous maBS. The latter of these terms is applied to the effect produced when the density of the glass, in consequence of imperfect fusion, Is not uniform throughout,... 

The nature of the complaint dictates the appropriate response, which could range from a conciliatory letter ( I am sorry you do not like our product... ) to a full public recall of product and cessation of production until a fault is resolved (for example a major incident of fermentation in a glass bottled product). In all cases the cycle of events must be to understand the problem, to identify the cause, to decide the response and then to take appropriate action. 

Do not distress yourself with such thoughts I said. Very few people were drinking retsina. He would have known if he had accidentally taken some other person s drink—would have known by the smell before his first sip. His death was not your fault and it was not an accident. Either his glass was deliberately poisoned or it was switched with one that had been. ... 

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