Fixtures, operating practice

Hygienic design and operating practice of vaives. fixtures and fittings... 

Materials and labour enter into the left(debit) side and come out of the right(credit) side as finished goods. Practically energies like power or heat and the loss of tools, furniture, fixtures and structures should be added to the left side, but these are quite small in firework manufacture-The operations which move the left side elements to the right are almost all physical and are seldom chemical. For example, the manufacture of potassium picrate as the material for whistles or the nitration of pitch for black snakes belong to the chemical operation. 

Quartz chambers are essential in the semiconductor industry because of the requirement for extreme cleanliness and particle-free operation. In that industry plasma is used to strip photoresist from wafers and to etch patterns into the layers on the wafers. Quartz chambers may be used in industrial applications, however, their extreme cleanliness is rarely required, and there is always the danger of breakage if metal parts or fixtures are used. The maximum practical size of a quartz reactor is about 30 cm (12 inches) diameter. 

Figure 11-51. The goal should be to avoid undercuts wherever possible, especially in small holes and on projections. With rigid plastics, undercuts usually require complex, more expensive molds and particularly molding operations. However, with flexible types of plastics stripping the mold will permit ease of removal from the mold. This action can be used with rigid plastics when it is practical to remove a part while the plastic is still soft, just prior to when the part should be removed. When certain parts that we removed at an earlier stage, cooling fixtures may be applicable.

As a practical application, say two types of light fixtures are available to install in the subject process unit. One that operates at 200°C (392°F) and costs l,000/each (Case 1), and one that operates at 375°C (707°F) and costs 500/each (Case 2). Let s assume the 200 light fixtures are required for the unit. 

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