Screens blinding

The dust particles can deposit on the surfaces of the screens and the solid particles in the bed and thus reduce the permeability of the screen (" screen blinding ) and the voidage of the packing. This manner of PPR fouling is depicted in Fig. 22. 

For some applications it is important to know the amount of particles that exceed 10 pm. This may be obtained by sieving but practical difficulties due to sieve screen blinding can occur. 

Although many commercial crystallizers operate with some form of selective crystal removal, such devices can be difficult to operate because of fouling of heat exchanger surfaces or blinding of screens. In addition, several investigations identify interactions between classified fines and course product removal as causes of cycling of a crystal size distribution (7). Often such behavior can be rninirnized or even eliminated by increasing the fines removal rate (63,64). 

The screen is typically constructed of a vv edge-bar with an aperture betvv een adjacent bars, which opens up to a larger radius. This prevents solids from blinding the screen as vv ell as reduces conveyance torque. For abrasive materials such as coal, the screens are made of vv ear-resistant materials such as tungsten carbide,... 

Screen-cloth specifications having a relatively large length-to-width ratio are desirable when moisture or sticky material tends to cause blinding with square or short rectangular openings. 

Vibration Amplitude and Frequency Speed and amplitude of vibration should be designed to convey the material properly and to prevent blinding of the cloth. They are somewhat dependent upon the size and weight of the material being handled and are related to the angle of installation and the type of screen surface. The object, of course, is to see that the feed is properly stratified for the most efficient separation. 

The use of rubber screen cloths also solves problems of blinding... 

Blende, /. blend, glance (specif., zinc blend, ZnS) blind, screen, shutter, shield, diaphragm, stop, baffle border. 

A newspaper ad, particularly in a paper with wide cii culation, will no doubt reach the most people. In this or the other written job announcements, the employer should always give name and address along with a brief job description. Sometimes, for one reason or another, a company chooses not to reveal its identity. Such blind ads, however, usually have the effect of discouraging the best qualified applicants. This practice is frowned upon by the American Chemical Society and most newspapers. Listing a phone number, where one can call for an application or further information about the job, will help screen out most unqualified applicants. 

Fedele was silent, staring blindly along the great nave toward the faint candles on the main altar beyond the choir and screen. 

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