Why we have to clean the inside of the gas cylinder?

Söröshordók

1. There are cases at official gas cylinder inspection when gas cylinders cannot pass on the tests without proper inner cleaning The inner part of the gas cylinder cannot check. The inspector cannot see the wall of the cylinder bacuse it is dirty. The inspector cannot judge if the gas cylinder is safe or not.  If there is no proper cleaning, then the gas cylinder is a scrap!
   

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2. At scuba diving, at firemen breathing protection the gas will contact our body directly. We breath the gas from the gas cylinder.  The inner contamination could damage our health. It could also cause direct emergency cases. Nobady should be in a situation when underwater the used scuba gas cylinder’s valve blocked because of an inner contamination! I have a personal friend from gas cylinder refurbishment, who says that she will just make a dive with the gas cylinder what was cleaned by her!
3. The biggest gas factories like Linde, Messer, SOL will make it obligatory to clean the inner part of the gas cylinders on certain fields. This kind fields are  food industry (food grade CO2, food grade Nitrogen) medical (medical oxygen, medical dinox). The Luxfer Gas Cylinders made a succesful beverage campaign in the UK, when they advertise the inner cleaniness of the aluminium gas cylinder. You won’t feel the tase of rust in your beer!
4. The inner cleaniness of the gas cylinders is very important on the high purity gas and gas mixture filling! It is doesn’t matter if  a high priced gas – sometimes more expensive than the gas cylinders itself – could be used for 6 month or could be used for 2 month. If the gas will lost its stability because of the dirty gas cylinders then you have to trash it before you could consume the complete contains of the gas cylinder.

The above mentioned examples show you some cases when you could save your money only with gas cylinder inner cleaning. The gas cylinder will reaim in service. The usage of the gas cylinder is healthy and safe. The laboratories and calibration stations could be sure they could use the gas for longer period.

What and how will contaminate the inside of the gas cylinder?

At the steel gas cylinders the biggest problem is the inner rust. The moister could get into the cylinder in many ways. I have seen and I have refurbished gas cylinders what had a drastical ice jam on the bottom. They were store outside without any protection with an open thread. We had examples where the ice not damaged the cylinder because there were 1-2 liter oil inside. The biggest problem is the not proper storage and the not proper usage of the gas cylinders. I list some example:

1. Not proper drying after pressure test. The gas cylinders removed from the water pressure test ramp could contains 0,5-1 liter  water. It stucked on the bottom of the gas cylinder or on the wall of the gas cylinders
2. At temperature drop down the high humidity will condensate on the wall of the gas cylinder.
3. At low temperature the empty gas cylinder with a not closed valves could receive moister through the open valve. An applied plastic plug cannot protect the gas cylinders if we store them outside.
4. If the applied valve is not an RPV  (Residual Pressure Valve), the user could consume all gas from the cylinders! In this case with a bad technology beer or soda water or cola could get inside of the cylinder. Old filling technology could pump not small amount of oil into nitrogen gas cylinder.

Gázpalack belső sörétezése

Mechanical tilting and rotating with abrasive materials

The technology is outdated. The essence of the technology is that we put an abrasive material into the gas cylinder (rod, shoot, metal pieces…) and for minimum 1 hours (or more) we rotate, and tilt the gas cylinders. The mechanical movements and gravity will do the job. Because of the small force hittings the inside of the gas cylinder will be cleaned. Slow, difficult, not give enough energy! Murphy laws will say the cylinder wall will be cleaned where it is not necessary and the most problematic contamination will remain. There is a version when we introduce a metal rod with a chain into the cylinder and we start to rotate. The rotating chain will clean the surface.

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ICS1850 gázpalack belső tisztító gép gázpalack fordító és mozgató egységgel

Sand blasting

I worked with this technology first.  The advantage of this method against the previous methode is the higher impact. It will remove the agressive contamination. The difficult handling of the dust is the biggest disadvantage of the sand blasting.  The operator regularly must wear a heavy protection clothes (like a spacesuit) They are working in a separated blasting chamber with heavy protection without any comfort. It is difficult to solve the dust protection. Remaining dust will be in the gas cylinder after blasting.  It will stick to the bottom and the wall.  We could apply several bar air blowing but still difficult to remove. The washing would damage the metal clean surface.

Gas cylinder inside shot blasting

The impact is the highest here. It comes from the weight of one metal piece. It generates less dust. The volume of the dust could be handled easier.  Generally the gas cylinder is in upside down position. During a cleaning cycle the shot pieces flow out from the gas cylinders. The automatization of the gas cylinder inner cleaning is easier. The work of the operator is light. The multi-holes on the lance of the shot blasting guarantee the cleaning of the bottom and the neck part of the gas cylinder. They orientation of the holes are in different angles. The multi-bouncing movement of the shot pieces make the neck and bottom cleaning more effective. The rust patches and other contamination are dissapear. Disadvantage of this technology – like at the sand blasting – is that it is sensitve for wet. Basically the technology is prepared to clean dry contamination. The metal pieces during usage become smaller and smaller at wearing or breaks. The not effective parts are filtered from the process in automatical way.

From 3 above mentioned solution the most expensive is the shot blasting. Although if we calculate the automatic cycle, high automatization, less labor cost, high quality it could bring back the money in short time. Definitely I suggest the 3rd solution as a superior solution for gas cylinder inside cleaning.

Lajos SZABÓ

Hungary, Csongrád ,09th of June 2017