Sieving Machines

Machine sieving is carried out by stacking the sieves in ascending order of aperture size and placing the powder on the top sieve. A closed pan, a receiver, is placed at the bottom of the stack to collect the fines and a lid is placed at the top to prevent loss of powder. A stack usually consists of five or six sieves in a root two progression of aperture size. The stack of sieves is clamped on to a test sieve shaker that is vibrated for a fixed time and the residual weight of powder on each sieve is determined. Results are usually expressed in the form of a cumulative percentage of the nominal sieve aperture. 

The three essentials required in a test sieve shaker are An effective sieving action in order that an end-point is reached this end-point to be reached in a short time and reproducible results. 

In BS 1796 [14] which applies to the sieving of material from 3350 to 53 pm in size, it is suggested that the sieving operation be carried out in 5 min. stages at the end of which the sieves should be emptied and brushed in order to reduce aperture blockage. This procedure can however lead to excessive powder loss. 

Vorti-siv manufacture gyratory and ultrasonic lab sieves that include a de-blinding kit for sieving powders as small as 5 pm. Units operate at 1,750 or 3,450 rpm and have an 8, 10 or 12 in diameter screen. Options include stainless steel or explosive proof construction and continuous discharge chutes. 

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Particle-SiZe Distribution. Particle-size specifications for sugar are not usually a part of the legislated standards, but they are of concern to commercial users and suppHers and are often specified in contracts. Grain-size distribution is determined by using a series of sieves, either hand-sieved or machine-sieved (13). 

Different sieves, different methods Different sieves, same method Same sieve, same method Machine sieving Hand sieving ... 

With machine sieving, sieve motion should minimize the risk of aperture blockage and preferably include a jolting action to remove particles that are wedged in the sieve mesh. 

The time of sieving is closely related to sieve loading, a reduction in the latter resulting in a reduction of the former. It is usual in routine analyses to machine sieve for 20 min. 

The reproducibility is much better than by hand or machine sieving. Size analyses are performed by removal of particles from the fine end of the size distribution by using single sieves consecutively. 

The sieving process may be carried out on either dry or wet samples, shaking by hand or by machine. Sieving is either carried out for a fixed time or until the sample passes through the sieve at a low but constant rate. This latter approach is not usually adopted for stacked sieves. 

Micromesh Sieving machines (Air jet, sonic wet and dry) Biickbee Mears, Veco, Endecottes Alpine, ATM, Gilson, Gradex, Hosokawa, Retsch, Seishin 5-500 -1- im 1-5... 

The feed must be nonabrasive with a hardness of 1.5 or less. The miU is capable of taking 2-cm ( A-in) feed material, depending on the size of the feed throat, and reducing it to a product substantiaUy aU able to pass a No. 200 sieve. For producing materials in the fine-size range, it may be operated in conjunction with external air classifiers. Such an arrangement is shown in Figs. 20-12 or 20-42. A number of machines have internal air classifiers. 

Passiermaschine, /. sieving or straining machine, liquoring machine meat grinder, passiv, a. passive inactive, inert, passivieren, v.t. passivate, render passive. Passivierung, /. passivation. 

Sortier maschme, /. sorting machine, sorter, sieb, n. sorting sieve, -trommel, /. sorting drum. 

Coffee and tea extracts are therefore foamed by N2 or C02 during cooling and partially freezing (e. g. to -5 °C) in a type of ice-cream machine. This foam must have a desired Density, with the inclusion of certain amount of small ice crystals. The foam is cooled on a conveyor belt not to -18 °C, but to -40 °C or colder, as this product must pass a grinding and sieving system to achieve a desired grain size and density. 

The capital cost of air separation machinery is linked to both the size of the beds (which dictates the cost of piping valves), of course to molecular sieve inventory and to the size of the compressor required to run the process. A low product recovery may have little impact on the bed size factor but it has an enormous effect on the amount of gas required and on the cost of compressing that gas. Thus the recovery and bed size factors have direct links to the cost of capital and operations of air separation machines. 

Dry Method. When Hg fulminate is sifted dry, the operation shall be performed in a location safely removed and/or shielded from other explosives, personnel or material which should be harmed by explosions. The motor of the shaking machine shall be started and stopped by a remote control switch. Assemble a No 100 sieve on a No 200 sieve and fit them on a pan. The sieves must be fitted with rubber gaskets. Place a 5g sample of dry fulminate on ihe upper sieve and shake the sieve for 3 mins on a Tyler Ro-Tap (or equal) machine. Carefully brush the material retained on the upper sieve into a weighing pan and weigh. Calculate the wt as % retained on the No 100 sieve. Brush the material passing thru the... 

Zinc ash sieving at the service provider (having a machine for sieving)... 

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