What Is Low Iron Float Tempered Glass?

Low iron float glass also named Ultra-clear glass. It is made by matured technical operation norm. It looks just like colorless crystal with higher transmittance.

Compare to common float glass, it is with outstanding characteristics of the high solar lights transmittance, the low reflectance, the low iron, the high mechanical strength and the high flatness, it is the ideal encapsulation material for thin solar modules and thermal collectors.

Low iron float tempered glass is low iron float glass that has been processed through a tempering oven to increase its strength to resist impact, mechanical loads and thermal stress breakage. It is approximately four times stronger than annealed glass of the same thickness and configuration. When it is broken, tempered glass fractures into small fragments that reduce the probability of serious injury as compared to annealed glass.

What is the Spectral Data of 3.2mm Low Iron Float Tempered glass?

Characteristics

It is of higher energy transmittance about 91%

It is expensive compare to clear float glass.

It is highly smooth without patterned which more suitable for thin film solar modules and thermal collectors.
Where to use it?

Front cover glass of thin film photovoltaic technology, including amorphous silicon (aSi), cadmium telluride (CdTe) and copper indium diselenide (CIS).

Front cover glass of thermal collectors.

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Tempered Glass

Tempered glass is produced by heating glass to near melting point (approx. 650℃ and rapidly cooling the surface uniformly with air. Glass produced by this special process has enhanced strength and is used mainly for the rear and side windows of vehicles. It has the characteristic of fracturing instantly if broken.

 

Tempered glass is manufactured by generating compressive stress on the surface through quenching glass after heated to near melting point. When the glass is broken by tensile force, the force is counteracted by the surface compressive stress. Tempered glass is three to five times stronger than ordinary glass at the same thickness.

 

Tempered glass is strong. But if subjected to an external force that exceeds the limit of the compressive stress, it will fracture. Unlike ordinary glass, however, if broken, it fragments into small pieces. As there are no sharp, knife-like shards, it is unlikely to cause serious injury. That is why tempered glass is recognized as safety glass.

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How to measure the heating time of the glass tempering furnace?

Start and heat the glass tempering furnace to the rated operating temperature.  Monitor and measure the temperature in the furnace using a thermometer, while recording the heating time with a stopwatch. The heating time refers to the time it takes for the average temperature of each temperature controlled area to reach the rated operating temperature after the furnace door is closed. 

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What effects do the ceramic rollers in the furnace have on the flatness of tempered glass?

The repeated use and cleaning of the ceramic rollers over time inevitably lead to wear, especially when sanding is required to remove some tough deposits on the rollers. To heat the glass on the rollers with an uneven surface or out of roundness to the transition temperature will certainly result in deformation.

Although the ceramic rollers used in the glass tempering furnace have superior thermal stability and high resistance to thermal shock, the possible unevenness of its internal structure may also lead to deformation under high temperatures. The thermal deformation of rollers will cause the ceramic roller bed to bend, leading to the deformation of glass conveyed on the roller surface.

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Classification of Vacuum Level

The so-called “vacuum” refers to a gaseous state where the pressure in a given space is less than 101325 Pascal (i.e. a standard atmospheric pressure around 101KPa).

The standard or unit of vacuum measurement is called vacuum level. In the international general standards and China’s current standard in force, the most commonly used unit in vacuum measurements is Pascal ( Pa.). 1 Pa is equal to 1N/㎡. The unit used in technical atmosphere is Bar.1Bar=1kgf/cm2. The unit now used less often is torr. 1Torr is defined as 1/760atm.

International general classification of vacuum levels

The international standard usually divides the vacuum into four levels: low vacuum, medium vacuum, high vacuum, and ultra-high vacuum. In absence of strict criteria, the vacuum levels are roughly divided as follows:

Low Vacuum Level   （< 105~102Pa）  —— The pressure difference obtained by low vacuum is used to clamp, lift and transport materials, as well as to vacuum and filtrate (e.g. vacuum cleaner, vacuum suction cups, etc.)

Medium Vacuum Level （< 102~10-1Pa） —— Medium vacuum is generally used to remove the gas or moisture that is retained and dissolved in the material, as well as for vacuum heat insulation and isolation (e.g. food vacuum freezing, vacuum drying, vacuum packaging, etc.)

High Vacuum Level  （< 10-1~10-5Pa） ——vacuum smelting, vacuum coating, and manufacturing of vacuum devices can be done by using the characteristics of low density of residual gas and weak chemical action of any substance in high vacuum. A typical product is vacuum insulated glass. Vacuum insulated glass refers to the glass consisting of two or more pieces of flat glass with micro supporting spacers inside and edges sealed to create vacuum chamber in between. In principle, the vacuum level inside the vacuum insulated glass is lower than 10-1pa, so that the factors such as heat transfer by gas and sound transmission can be ignored.

Ultra-high Vacuum Level  （< 10-5Pa） —— In the ultra-high vacuum state, there is almost no atoms or molecules. It can be used for simulation of a space environment, as well as researches on surface physics and surface chemistry, etc. 

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Thermal Resistance, Thermal Conduction, Thermal Conductance, Heat Transfer Resistance

Thermal Resistance is a heat property and a measurement of a temperature difference by which an object or material resists a heat flow.

The law of heat transfer can be compared to the “Ohm’s Law” that describes the law related to the electricity transfer in electrical science.  

Ohm’s Law: I=U/R

where I is the electrical current flowing through the circuit; △V is the voltage drop between the two ends of the circuit and the electromotive force that drives the flow of electricity; R is the resistance of the resistor, representing the resistance in electricity transfer. 

A similar formula in the process of plane heat transfer is: Φ=T/R where Φ is the amount of heat flow transferred; T is the temperature difference between the two ends and the force that drives the heat flow; R is the thermal resistance representing the resistance in heat transfer. 

An object with better thermal conductivity generally has lower thermal resistance, measured in ℃/W or K/W.

Thermal Conduction is the reciprocal of thermal resistance, i.e. C=1/R，in W·m-2·K-1. 

Thermal Conductance, also known as heat transfer coefficient, refers to the quantity of heat that passes in unit time through an object of 1㎡ area and 1 m thickness when its opposite surfaces differ in temperature by 1K under steady state conditions. The legal measuring unit in China is W·m-1·K-1.  

Heat Transfer Resistance is the inverse of heat transfer coefficient, measured in W-1·㎡·K. The greater the heat transfer resistance, the better the thermal insulation performance. 

Definition, Harms, and Grading Standard of Noise

By physical definition, noise is the sound that delivers completely irregular oscillations in amplitude and frequency. From the perspective of environmental protection, noise is the unwanted sound. 

The distinctive characteristic of noise is that: there is no visible pollutant; it does not generate energy accumulation; it lasts for limited time and is transmitted in limited distance; noise disappears along with the vibration source and cannot be controlled through centralized systems. Noise could come from transportation, machinery and equipment in factories, construction work as well as the social and family activities of ordinary people. 

Noise can harm human beings in many aspects, including hearing loss, sleep disturbances, physical and psychological disorders. Working in an environment with a noise level of 100 dB could make people feel unpleasant, uncomfortable, and even suffer from temporary hearing loss.Noise louder than 140 dB will cause eyeballs to vibrate, vision blurring， and fluctuation of respiration, pulse, and blood pressure. It may even cause blood vessels to contract throughout your body, reduction in blood supply, and adverse effect on speaking ability.

dB is the standard unit of measurement for noise, called decibel. It is the unit for expressing the ratio of power. 

dB Levels
0-20 dB	Very quiet, hard to hear
20-40 dB	Quiet, whisper
40-60 dB	Normal indoor conversation
60-70 dB	Loud, harmful to nerve
70-90 dB	Very loud, could cause damage to nerve cells
90-100 dB	Intensified noise, hearing impaired
100-120 dB	Unbearable, temporary hearing loss with only one minute of exposure.
Greater than 120 dB	Itching or pain in the ear, extremely or totally deaf
About 300 dB or higher	Permanent hearing loss

The national noise emission standard for social environment are as follows:

Type	Applicable areas	Limitation unit：Leq：[dB(A)]
		Daytime	Nighttime
0	For rehabilitation or other purposes that requires an extremely quiet environment	50	40
1	For residential, health care, cultural and educational, scientific research, and administrative office areas that require a quiet environment.	55	45
2	For commercial, trading, and a hybrid of residential, commercial, and industrial purposes that need to maintain the quiet residential environment.	60	50
3	For industrial, logistics, and storage purposes that need to prevent industrial noises from causing serious impact on the surrounding environment.	65	55
4	For areas within a certain distance on both sides of the main traffic lines that require to prevent traffic noises from causing severe impact on the surrounding environment.	70	55

Hertz is also a unit of frequency in the international system of units. It measures the repetitive times of cyclical variation per second. Its symbol is Hz.  Noise can be divided into low frequency noise, medium frequency noise and high frequency noise according to the sound frequency. 

Low frequency noise refers to sounds with frequencies below 500 Hz.  

There are five main types of low-frequency noise sources in China’s residential communities: elevators, transformers, water pumps in high-rise buildings, central air conditioning systems, and traffic.  

Medium frequency noise refers to sounds with frequencies between 500～1000 Hz. Normal conversation in daily life and the sounds of most musical instruments are in the range of medium frequency.  

High frequency noise refers to sounds with a frequency greater than 1000 Hz.  High-frequency noises come from modern means of transport that we are familiar with, such as cars, trains, motorcycles, tractors, and airplanes, as well as the noises generated by tweeters, construction sites, shopping malls, sports and recreational venues, etc.

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