Ammonium metatungstate spray dryer wall sticking solutions include improve the structure and texture of drying tower, use the proper atomizer, proper installation of atomizer, proper operation process, etc.

1.Improve the structure and texture of drying tower. If the design of diameter of dry tower is smaller than the atomizer cone, it will cause a mass amount of wall sticking. In order to prevent wall sticking, the diameter of dry tower should be larger, thus the liquid material will fall down directly without making contact with wall of tower. But the diameter can not be too large because it will increase cost of equipment and occupied area., also affect flow speed of hot air in the tower and drying quality.

2.Use the proper atomizer. Atomizer is also called nozzle, it is the key part of spray dryer. Its different structure affect the distribution of misty liquid, also diameter and property of micro grains.

3.Installation of atomizer. If there is only one atomizer in the dry tower, the axis of atomizer should be on the center line of tower. If there are more than one atomizers, then the nozzle of atomizers should not be face to face.


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2. Inappropriate control of tungsten blanks granular can affect the quality of tungsten contacts

Since the mixing ratio of particle size of tungsten powder is inappropriate or uneven, resulting in coarse grain, fine grain, boxes of different crystal polymorphs exist in the sintered tungsten bar, in which fine grain may be too burning, which will affect tungsten workability of the ultimately affect the performance of tungsten contacts.


 

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⁵⁷Fe Mössbauer spectra of xNa₂O · (99 − x)WO₃ · ⁵⁷Fe₂O₃ glasses (30 ≤ x ≤ 42) comprised of a doublet due to octahedral iron, Fe³⁺(O_h), and a weak doublet due to Fe²⁺(O_h); a large Debye temperature of 580 K was obtained at low temperatures. Fourier transform infrared spectra of the sodium tungstate glasses showed a gradual increase in the fraction of WO₄tetrahedra (T_d) when Na₂O content was increased. Mössbauer spectra of the tungstate glasses irradiated with ⁶⁰Co γ-rays showed an increase in the fraction of Fe²⁺, due to electron transfer (scattering) from WO and FeO bonds to Fe³⁺, as the electron spin resonance spectra of iron-free sodium tungstate glass indicated a simultaneous formation of W⁵⁺ and the ‘hole’ trapped on the oxygen atom. From the linear relationship between glass transition temperature, T_g, and quadrupole splitting, Δ, of Fe³⁺ (‘T_g − Δ rule’), the slope of the straight line was estimated to be 260°C/(mm s⁻¹). Mössbauer spectra of heat-treated tungstate glasses showed a gradual change from Fe³⁺(O_h) to Fe³⁺(T_d), along with the precipitation of the Na₂W₂O₇ phase composed of W⁶⁺(O_h) and W⁶⁺(T_d). These results indicate that  iron occupies W⁶⁺(O_h) sites in glasses, while it occupies W⁶⁺(T_d) sites in glass-ceramics.

 

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The quality inspection department of manufacturer should check tungsten contacts and fill quality certificate to ensure that products conform to relevant standards.
According to the provisions of GB / T 2828, checking weld strength, size, appearance and roughness of contact surface of tungsten contacts.

Clients can inspect received tungsten contacts, if the result is not consistent with the mark, they can pose this problem to the manufacturer within three months, if these products still not satisfy the standard made by the two sides after mutual identification, and the products fail.

Every passel of product sample should be inspected in accordance with the following regulations:
The purity, hardness and the quantity of crystals of tungsten: Clients can spot-check a batch of products from the tungsten rods and make a sample at its ¼. Or make the sample for tungsten contacts’ inspection directly; if the results fail, then retest. If one of them is still a failure, then this batch of products fail.
Specific inspection rules can negotiate by clients and manufacturers.


 

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Mark
Identify and mark every pack of tungsten contacts with the following items:
Quality;
Specification;
Batch number;
Production Date;
Type and standard;
With the mark of manufacturers and related inspection department;

Package
Using plastic bags to pack tungsten contacts and then putting them in metal or plastic boxes.
Casing tungsten contacts which having the same type, size and batch number on the same box.

Transport
You need to reinforce the boxes which are used to hold tungsten contacts and in which place the moisture-proof paper.
In transportation, you should keep tungsten contacts from violent corrosion, impact, snow and acid rain.

Storage
The location of tungsten contacts storage must be dry and far from alkali, acid, other corrosive gases and so on.


 

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Sodium tungstate is a novel agent in the treatment of obesity. In diet-induced obese rats, it is able to reduce body weight gain by increasing energy expenditure. This study evaluated the role of leptin, a key regulator of energy homeostasis, in the tungstate antiobesity effect. Leptin receptor-deficient Zucker fa/fa rats and leptin-deficient ob/ob mice were treated with tungstate. In lean animals, tungstate administration reduced body weight gain and food intake and increased energy expenditure. However, in animals with deficiencies in the leptin system, treatment did not modify these parameters. In ob/ob mice in which leptin deficiency was restored through adipose tissue transplantation, treatment restored the tungstate-induced body weight gain and food intake reduction as well as energy expenditure increase. Furthermore, in animals in which tungstate administration increased energy expenditure, changes in the expression of key genes involved in brown adipose tissue thermogenesis were detected. Finally, the gene expression of the hypothalamic neuropeptides, Npy, Agrp, and Cart, involved in the leptin regulation of energy homeostasis, was also modified by tungstate in a leptin-dependent manner. In summary, the results indicate that the effectiveness of tungstate in reducing body weight gain is completely dependent on a functional leptin system.

 

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1. Metallurgical defects of tungsten blanks can affect the quality of tungsten contacts

Metallurgical defects of tungsten blanks mainly refer to: in the smelting process, tungsten blanks inside form inclusions, porosity and other defects. Moreover, some of these defects, there is no way to exclude even in stamping process, for example, Ni, Fe and other impurities or compounds distribute in the grain boundary. Because the presence of these pores, impurities and other defects undermine the combination of grain surface, so the metal base is not continuous, which will lead to tungsten blanks in the process generate cracks or tears, may also lead to the final product --- tungsten contacts produce splitting and brittle fracture.


 

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Test methods of tungsten points in interrupter:
Using universal measuring tool to check and measure tungsten points.
According to the provisions in JB / T 9864.2 ------ 1999, weld strength is measurable.
By visual inspection or checking with a magnifying glass, tungsten points’ appearance and weld is known.
According to GB / T 4197 requirements, the number of sections of crystals is counted.
With a surface roughness measuring instrument, the roughness of point surface of tungsten points can be measured.
Purity of tungsten sheet is available according to GB / T 4324.1-4324.30 standards.
Hardness measurements can be in accordance with GB / T 230 rules: If you adopt Vickers hardness measurement test method, the load is 4.904N and should be consistent with GB / T 4340 requirements. Refer to relevant tables, measured values can be conversed and the measurement results should coincide with the provisions of HRA.


 

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Appearance and size requirements of tungsten points in interrupter:

The appearance requirements of tungsten points:
Smooth appearance. There are no rust, burr, discoloration, cold solder joint and other defects in their surface; Furthermore, its electrodeposition is without peeling, de-plating, leak plating layer and other problems.

Uniform welds. The thickness of the weld ≤¼ the thickness of tungsten sheet.
Point surface of tungsten points do not exist depressions or remaining machining marks, its roughness Ra is less than 0.4μm.

The size requirements of tungsten points:
According to drawings or specifications supplied by customer, or on the basis of the negotiation agreed by customer and supplier.


 

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