Can the air compressor tank still be used after 18 years?

Conclusion first

the 18-year-old gas tank has a high probability that it can no longer be used. The recommended service life of gas storage tanks is generally 10 years, and 18 years has nearly doubled. Even if it is used for testing, the probability of passing is very low, and once an accident is the consequence of the explosion level, it is not worth taking this risk. If this jar is always equipped with a water-lubricated air compressor, the corrosion in the jar will be lighter, but 18 years is too long, and metal fatigue and weld aging cannot be avoided. It is recommended to replace it directly.

Why is 10 years a hurdle?

Gas tanks are special equipment. Manufacturers will mark a design service life on the nameplate when leaving the factory. Carbon steel tanks are generally about 10 years. This number of years is not determined by beating one's head, but is based on the fact that steel will slowly become brittle and thinner after repeated stress.

Within 5 years, only need to check the pressure gauge and safety valve. After more than 5 years, a comprehensive test will be carried out, including applying water pressure to the tank to see if there is any leakage, and using ultrasonic wave to measure the wall thickness to see if there is any thinning. For more than 10 years, it has to go to the Quality Supervision Bureau for inspection every year. Only after passing the inspection can it continue to be used. If it fails, it must be scrapped.

For 18-year jars, the wall thickness has probably been thinned by more than 20%. According to regulations, if the wall thickness is reduced by more than 20%, it should be scrapped. Even if not to this extent, the weld after 18 years of alternating pressure, fatigue cracks almost certainly exist, but the naked eye can not see it.

What are the specific dangers of 18-year jars?

The first is the tank body thinning. The steel plate will slowly corrode under long-term pressure and humid environment, and the wall thickness will be thinner year by year. If the wall thickness is not enough, the ability to withstand pressure will decrease. If the pressure is slightly higher one day, the tank may not be able to carry it.

The second is weld cracking. The weld of the gas tank is the most prone to problems. Repeated pressure changes will cause fatigue cracks in the weld. This crack cannot be seen from the outside, but once it has expanded to a certain extent, the can will tear directly.

The third is the safety valve failure. The safety valve has been used for 18 years. The spring may be tired and cannot be jumped when it should be jumped, or when it should not be jumped. The safety valve is the last line of defense. If it is not reliable, the whole system will not be protected.

The fourth is the aging of the support and pipeline interface. If the weld of the support below the tank is seriously rusted, the stability of the whole tank will be a problem. The sealing gasket of the pipeline interface has long been aging. Air leakage is a trivial matter. In case the interface collapses under pressure, it will be troublesome.

If you have been using water to lubricate the air compressor, will the situation be better?

It will be better, but not to the extent that 18-year-old cans can continue to be safe to use.

Water lubricated air compressor with water instead of lubricating oil, compression process will not have oil mixed into the air. The condensed water discharged from the traditional oil-lubricated air compressor contains oil, which will accelerate the aging of the coating on the inner wall of the tank, allowing the steel plate to directly contact the water, and the corrosion rate is much faster. The condensed water discharged from the water lubricated air compressor is basically clear water, and the corrosion of the inner wall of the tank is much lighter.

In addition, the compression chamber of the water-lubricated air compressor does not need an oil circuit system, the whole gas circuit is cleaner, there will be no sludge accumulation in the gas storage tank, and clear water will come out when draining, and the water will not be black and smelly like the oil-lubricated air compressor. The environment inside the tank is clean, and the corrosion is naturally slower.

But the problem is that 18 years is too long. Even if the corrosion is lighter than the oil-lubricated tank, the fatigue aging of the steel itself can not be avoided. Metal in the process of repeated pressure relief, the internal crystal will slowly produce micro cracks, which has nothing to do with what air compressor, is the physical characteristics of the material itself.

What the hell to do

if this 18-year-old jar is still in use, the safest way is to stop using it immediately and find a qualified inspection agency to do a comprehensive test. The inspection contents include wall thickness measurement, weld flaw detection, hydraulic test and safety valve calibration. If the test result is unqualified, it must be scrapped and cannot be lucky.

But to tell the truth, the probability of passing the 18-year jar test is very low, and even if it passes this time, next year, the following year, the risk will be one point for every extra day of use.

When replacing a new jar, if it is used together with a water lubricated air compressor, the later maintenance will be much easier. The condensed water discharged from the water lubricated air compressor is clean, there is no sludge in the tank, the drainage is simple, the corrosion speed of the tank is slow, and the actual service life of the gas storage tank can be longer than that of the oil lubricated air compressor.

In a word, the 18-year-old gas tank is like a pair of steel-toed shoes that have been worn for 18 years. It looks like it can still walk, but the materials of the soles and uppers have long been aging, and stepping on nails may cause major problems. Don't save the money, replace it with a new one.