Why is there a tempered sight glass explode rate?

Why is there a tempered sight glass explode rate?
A tempered sight glass explode and the classification of 1, classification of tempered sight glass tempered sight glass explode birth, accompanied by self ask. Tempered sight glass explode can be expressed as a tempered sight glass without external directly under the action of automatic broken phenomenon. Can occur in the tempered sight glass explode in tempering processing, storage and transportation, installation and use of the process. Self detonation can be divided into two different causes: one is self detonating caused by visible defects in sight glass, such as stones, sand particles, bubbles, inclusions, gaps, scratches, bloding and so on; two is the self explosion of tempered sight glass caused by NIS impurities and heterogeneous particles in the sight glass. 2, the controllable characteristics of tempered sight glass tempered sight glass explode reason unclear explosion problem, the responsibility is difficult to understand. The time of self explosion is not definite, it may be just out of the furnace, it may be 1~2 months after the factory and 1~2 years from the factory. The time of more self explosion of the tempered sight glass may be 4~5 years after the product is finished. According to incomplete understanding, the probability of most manufacturers' products is about 3 per cent, and the probability of individual manufacturers' products may be even higher. The fundamental reason for self ignition of tempered sight glass is that sight glass contains nickel sulfide and heterogeneous particle impurities. It has not been fundamentally found out how the sight glass is mixed with nickel, the greatest possible source of all kinds of nickel - containing alloy components used on the equipment and various heat-resistant alloys used on the kiln. For oil fired furnaces, nickel rich condensate has been reported in a small furnace. Sulfur is no doubt derived from sulfur compounds in the batch and fuel. When the temperature is over 1000 degrees, nickel sulfide exists in molten sight glass in droplet form, and the curing temperature of these droplets is 797 degrees. 1 grams of nickel sulfide can generate about 1000 small stones with a diameter of 0.15mm. Nickel sulfide can occur at any time after production, so it can not be completely eliminated now, so far it has not been effectively prevented from being called "cancer of sight glass curtain wall". The "cancer of the sight glass wall" came from the mouth of the famous architect Forster: that year, the London City Hall, designed by the firm, broke the sight glass from the floor to the ceiling. The town hall near the Tower Bridge of London, all made of sight glass cladding, the contractor will have to check all the internal sight glass. A spokesman for the City Council of London said, according to the preliminary investigation, the problem was that the sight glass contained nickel sulphides, that is, the sight glass was contaminated with nickel during the construction, and the sulfide in the nickel and sight glass was chemically reacted to cause rupture. It is difficult to replace nickel sulfide after self explosion, and the treatment cost is high. At the same time, it will be accompanied by large quality complaints and economic losses, resulting in the dissatisfaction of the owners and even more serious other consequences. It is called "cancer of the sight glass curtain wall". Two, the self ignition rate and self explosion reason of tempered sight glass are 1 and the self detonating rate is not consistent with domestic manufacturers, ranging from 3% to 0.3%. The average explosion rate is calculated according to the number of pieces, without considering the size of the single sight glass and the thickness of sight glass, so it is not accurate enough and can not be more scientifically compared. For calculation of the explosive rate, must determine the unified hypothesis. The uniform conditions are determined: every 5~8 tons of sight glass contains a nickel sulfide enough to cause self detonation; the average area of each toughened sight glass is 1.8mm, and the nickel sulfide is evenly distributed. The calculated 6mm thick tempered sight glass explode calculation rate is 0.64% ~ 0.54%, 6mm toughened sight glass of the explosive rate is about 3 per thousand to 5 per thousand. This is basically consistent with the actual value of high level processing enterprises in China. Even completely according to the standard production, can not completely avoid the tempered sight glass explode. It is easy to use hundreds of tons of sight glass in large buildings, which means that the rate of nickel sulphide and heterostructure impurities in the sight glass is very high, so the tempered sight glass is still unavoidable, although it is heated by hot dipping. 2. The cause of uncontrolled self detonation of tempered sight glass - the source of uncontrolled self detonation of nickel sulfide (NiS) and heterogeneous particle toughened sight glass is not only the NIS particles in the traditional understanding, but also many other heterogeneous particles. The initiation and expansion of cracks in sight glass is mainly due to residual stresses near the particles.  This kind of stress can be divided into two categories, one is phase transformation stress during phase transformation expansion, the other is residual stress caused by mismatch of thermal expansion coefficient. Nickel sulfide (NIS) and heterophase particles. The interior of the sight glass contains nickel sulfide, which is in small crystal state and will not cause sight glass breakage in general, but the phase state of the nickel sulfide impurity is changed due to the reheating of the tempered sight glass. The high temperature alpha state of the nickel sulfide is frozen when the sight glass is quenched. They may take a year to recover to the beta state, because the nickel sulfide impurities in the low temperature beta state will increase in volume. The local stress concentration in the internal sight glass, tempered sight glass explode when will happen. However, only larger impurities will cause self detonation, and only when impurities are at the core part of tensile stress, can self toughening of tempered sight glass happen. NIS is a kind of crystal. There are two crystalline phases: high temperature phase alpha -nis and low temperature phase beta -nis. The phase transition temperature is 379. When the sight glass is heated in the tempered furnace, the heating temperature is much higher than the phase transition temperature, and the NIS is all transformed into alpha phase. However, during the subsequent quenching process, the alpha -nis is too late to turn into beta -nis, so it is frozen in toughened sight glass. At room temperature, alpha -nis is unstable and has a tendency to gradually turn to beta -nis. This transition is accompanied by about 2 to 4% of the volume expansion of the sight glass transition under tensile stress is huge, as a result of suicide.

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Why is there a tempered sight glass explode rate

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