Examples of deterioration and failure under storage conditions in a constant temperature and humidity chamber
Most manufacturers will have more than 80% of the tests that they can guarantee that they can withstand the test before they decide to do the test. Therefore, before purchasing the constant temperature and humidity test chamber, if the product is in the experimental or research stage, it may need to be tested. The box test is followed by a look at the results, and the test box is a finished example of the storage function, a typical example of the type of mechanism and effectiveness that may result from the storage:
1. Oxidation or diffusion between the substrate and the coating can reduce the solderability of the component leads and the printed circuit board. The thermal energy accelerates these processes, resulting in greatly reduced solderability of the surface and reduced wet corrosion. Weldability, atmospheric pollutants may accelerate this corrosion.
2. Other examples of failure caused by temperature changes:
A. The long-term effects of extremely low temperatures, even at lower temperatures, can make plastics quite dry. The electrical and mechanical properties of these plastics may be reduced, resulting in damage or failure during storage operations.
B. Due to the lack of natural effects, the high humidity during storage is more extensive than the high humidity during operation. Long-term storage under conditions of relative humidity above 80% can adversely affect the functional characteristics and reliability of stored products.
C. The humidity of the sealed constant temperature and humidity test chamber is repeated under the condition of high relative humidity with high peak value, or under the condition of periodic humidity change and moderate high humidity, the internal humidity will gradually increase. Therefore, after long-term storage, As the temperature suddenly drops within a certain limit, condensation will form inside the test chamber.
D. Products under high temperature and high humidity conditions, especially in the presence of organic materials, will be affected by mold growth. High temperature and high humidity will also accelerate the chemical effects caused by salt spray and industrial gases.
3. Examples of other failure mechanisms: long-term exposure to high temperature environments can cause drying of electrolytic capacitors and batteries, loss of rigidity of thermoplastics, softening and creep of protective compounds and impregnating waxes. Generally, under such conditions, materials The aging will be more accelerated. Long-term exposure to low temperature will make rubber, plastic and even metal parts brittle and crack, and some seals will be damaged by shrinkage and cracking, high temperature oxidation or wet corrosion caused by mechanical parts. The functional parameters may drift beyond the specified limits and an open or short circuit may occur.
Peristaltic pump
There are a few plaster sprayers that have a peristaltic pump (a tube squeezed by rollers) which also requires compressed air to produce a spray. These types of plaster sprayer can also spray textured coatings with particle sizes up to about 3mm diameter, providing that they are not solvent based.
Piston pump
Newer types of plaster sprayer have a piston pump, which has sufficient pressure to spray smooth (untextured) plaster without compressed air. Full airless pumps are sometimes used to spray smooth plaster, although they are not ideal as the flow rate is too low for volume projects; however, they can be used to spray solvent-based plasters.
Air operated piston type supply pumps can put out as much as 27 gpm. Like the Graco Bulldog 10:1 at about 9 gpm and the Lincoln Pile driver 5:1 at about 27 gpm. These flow-rates are calculated at a maximum of 120 cfm air supply. Material supply hoses are medium pressure at about 600 psi. These pumps are material supply pumps only and additional air is required at the spray gun to propel the material to the surface. These guns are usually an internal mixture type guns where the material and air exits the gun together.
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