2000 Hook-up Book

Clean Steam

Case in Action: Printing Mill Dryer Roll Drainage

Solution Four non-electric Pressure Powered Pumps ™ were select ed as alternatives to costlier electric pump sets. These were in addition to the 16 float and thermostatic steam traps installed on each dryer roll. Benefits • Installation cost was lower for the Pressure Powered Pumps ™ —no electrical wiring/controls required. • Pressure Powered Pumps ™ purchase price was sub stantially lower. • Pressure Powered Pumps ™ operation is safer than with electric pump/controls. • Without mechanical seals, the Pressure Powered Pumps ™ will operate with lower maintenance cost.

Printing mills frequently mix tolulene and isopropyl acetate with dyes to produce “quick drying” inks. This flammable mixture requires special care to avoid explosions and fire. Larger printing mills typically use steam-heated rolls to dry the printed material. The electric motor-driven condensate pumps that are commonly used, require explosion-proof controls/enclosures to accommodate the flammable atmosphere. During a new project design, the consulting Engineer and Client decided to find a better way to deal with the hazardous environment and costly explosion-proof con densate pumps. The cost was of particular concern considering that the project included 16 dryer rolls on 2 printing machines, requiring 4 condensate pumps.

SYSTEM DESIGN

Clean Steam The term “Clean Steam” can cover a wide range of steam qualities, depending on the pro duction method used and the quality of the raw water. The term “Clean Steam” is something of a misnomer and is commonly used as a blanket description to cover the three basic types - filtered steam, clean steam and pure steam. a) Filtered steam is produced by filtering plant steam using a high efficiency filter. A typical specification would call for

the removal of all particles greater than 2.8 microns, including solids and liquid droplets (Fig. 55). b) Clean steam is raised in a steam generator or taken from an outlet on a multi effect still, and is often produced from deionized or distilled water. A simpliffied generator and distribution system is shown in Fig. 56. c) Pure steam is very similar to clean steam, but is always produced from distilled, deionized or pyrogen-free

water, and is normally defined as “uncondensed water for injection (WFI)”. Often, the generic term “clean steam” is used to describe any of the three different types outlined above. It is therefore very impor tant to know which is being used for any application, as the charac teristics and system requirements for each can differ greatly. Note that in the following text, the expression “clean” steam will be used to denote any or all of the three basic types, where no differ entiation is required.

Pressure Reducing Valve

Filter

Separator

Filtered Steam

Sample Cooler

Figure 55 Filtered Steam: A filtered steam station produces steam to be used for direct injection into food products, culinary steam, or for use in sterilizers and autoclaves.

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