Hoppers, sampling from

Food Blended food mixed with pelletized diatomaceous earth. Added mixture to extraction column. Extracted with SC-C02. Eluted nonfat samples from Florisil trap with acetone. GC/ECD No data 82-99 Hopper and King 1991... 

Take 7 samples from each additional location to further assess each significant event, such as filling or emptying of hoppers and IBCs, start and end of the compression or filling process, and equipment shutdown. This may be accomplished by using process development batches, validation batches, or routine manufacturing batches for approved products. 

The first option, from a falling stream, is usually used at a transfer point between conveyor belts, from under a discharging hopper or from the end of a pneumatic conveying system. Open ended scoops or shovels are unsuitable for manual sampling... 

Sampling from deep hoppers and open stockpiles is the most difficult and inaccurate of all sampling operations and it should be avoided whenever possible. 

Thickened cake discharge can simply be into a hopper which is emptied by a pump actuated by level probes in the hopper. However, modern technology often requires the discharge to be monitored for solids content, if not rate. For this a small stirred buffer tank is used. A sample from this tank is pumped and recycled continuously to provide a continuous sample. The stirred buffer tank is sized to smooth out major fluctuations which can occur in the decanter discharge, due to hold-up in the casing. 

Ter Borg reports about experiences from wall friction experiments with more than 500 bulk solid samples from the chemical industry [7], The results of a statistical analysis of the best combinations of bulk solid and wall material are shown in Fig. 15. For the case of axisymmetric flow (vertical cylinder with conical hopper) the percentage of silos showing... 

Hopper ML, Griffitt KR. 1987. Evaluation of an automated gel permeation cleanup and evaporation systems from determining pesticide residues in fatty samples. J Assoc Off Anal Chem 70 724-726. 

When the entire sample has been delivered, each collector will contain powder exactly representative of the initial batch. Each collector will also contain a size gradient from top to bottom. Therefore, if the quantity required for analysis is less than the amount in any single collector, the process must be repeated. This is achieved by placing the contents of one collector back into the hopper and reriffling. The Micro Riffler, Fig. 13.2, can riffle samples less than 1 g to accommodate the need for small final samples. 

The mechanical and electrostatic ash samples were obtained by emptying the specified vacuum-operated hoppers just prior to the start of the run. When the test was completed, a cap plug was unscrewed from the bottom of the hopper permitting the hot ash to flow out. A 10-gal sample of each of these ashes was collected and split, maintaining a 16-oz sample of each ash. With the amount of ash involved, it was impossible to obtain a representative sample of the total amount of ash collected in the hopper during the test period. 

The data from the mercury in ash determinations are presented in Table V. Four types of ash samples were analyzed and reported bottom, initial mechanical, final mechanical (multicones), and electrostatic ash. Because of the inability to empty an initial mechanical, a final mechanical, and an electrostatic ash hopper simultaneously prior to the start of a test, normally only three ash samples were collected during any one test. 

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