Tempered sight glass explode mechanism
Nickel sulfide toughened sight glass internal expansion is the main cause of the tempered sight glass explode. After the toughened sight glass, the surface layer forms compressive stress. The inner core layer is tensile stress, and the compressive stress and tensile stress constitute a balance body.
Sight glass itself is a brittle material, withstanding pressure but not withstanding, so most of the broken sight glass is caused by Zhang Yingli. When the nickel sulfide crystals in the tempered sight glass phase change, the volume expansion, the expansion of the nickel sulfide in the sight glass plate core stress layer causes a greater Zhang Yingli in the tempered sight glass, and when the tensile stress exceeds the limit of the sight glass itself, it will lead to the self explosion of the tempered sight glass.
Foreign studies have proved that:
The main material of sight glass is quartz sand or sandstone, which is brought into the nickel. Fuel and excipients are brought into the sulfur, burning and melting at 1400 to 1500 degrees, and forming nickel sulfide.
When the temperature is over 1000 degrees, nickel sulfide is distributed randomly in molten sight glass. When the temperature drops to 797 degrees, these small droplets are crystallized and solidified, and nickel sulfide is in the high temperature state of the alpha -NiS crystal (six square crystal). When the temperature continues to fall down
At 379? C, the crystalline phase is transformed into a beta -NiS (three square system) at low temperature, accompanied by 2.38% volume expansion. The speed of the transformation depends on the percentage content of the different components in the nickel sulfide particles (including Ni7S6, NiS, NiS1.01), but also on the temperature around them.
If the nickel sulfide phase transition is not completely converted, the process will continue even in natural storage and normal temperature conditions, but only at a very low speed.
When the toughened sight glass is heated, the temperature of the inner core of the sight glass is about 620.
At the temperature, all nickel sulfide is in the high temperature state of the alpha -NiS phase. Subsequently, the sight glass enters the cooling grid and the nickel sulfide in the sight glass is cooled.
Phase transition at 379 C. Unlike the float annealing furnace, the toughening time is very short, so it is too late to turn into low temperature beta -NiS.
The high temperature nickel sulfide phase is frozen in sight glass. Rapid quenching makes the sight glass tempered and forms a stress balance body with external pressure and internal tension.
In the tempered sight glass, nickel sulfide phase changes at low speed, and the volume expands and expands, and the force on the surrounding sight glass increases. The toughened sight glass core itself is a tensile stress layer. The volume expansion of nickel sulfide in the tensile stress layer also forms a tensile stress. These two tensile stresses are superimposed, which is enough to cause the rupture of the tempered sight glass, that is, self explosion.
Further experiments show that for the surface compressive stress 100MPa
The toughened sight glass inside Zhang Yingli is about 45MPa. At this time, any diameter in the tensile stress layer is greater than 0.06mm
The nickel sulfide can lead to self destruct. In addition, according to the statistical analysis of self explosion, more than 95% of the self ignition is caused by nickel sulfide with particle size between 0.04mm and 0.65mm. According to the fracture mechanics of materials, the average particle size of nickel sulfide initiated by nickel sulfide is calculated to be 0.2mm.. Therefore, the main reason for the self explosion of tempered sight glass is that nickel sulfide is recognized by the sight glass processing industry at home and abroad.
There are some other factors of tempered sight glass explode:
The sight glass slotting and drilling are not reasonable, the quality of the raw sight glass is poor, the thickness is not uniform, such as the embossed sight glass, the uneven distribution of stress, such as the curved steel sight glass and the regional tempered sight glass.

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Tempered sight glass explode mechanism

Tempered sight glass explode mechanism	Tempered sight glass	Tempered glass	Tempered glass plate	Tempered glass disc
Tempered sight glass explode mechanism	Tempered sight glass	Tempered glass	Tempered glass plate	Tempered glass disc
Tempered sight glass explode mechanism	Tempered sight glass	Tempered glass	Tempered glass plate	Tempered glass disc