Caution: Raci 150W cracked by cold water or by cold weather!

[Tech_Marco]

I just received a report that the 150W (A8) tube received cracked after a moment it fired (in Germany). What a big waste!

I explained to the customer that there were couple ways could lead to the crack toward to the tube.

1) When power up a laser, make sure water is flowing and filled up the tube without bubbles before firing. If not, turn off the power immedaite.

2)Even without water flowing during firing up, the tube won't be damaged much if power it off in seconds. However, do NOT water it immediate as the tube is very hot. You need to wait till it cooled down before filled up with water. Otherwise, cold water will crack the tube. Good thing for better timing.

3)During cold weather, room temperatuer usually lower than 20'C especially in factory. Then you need to be very careful to handle the tube in this area. For a small power tube, the condition wont' be as crtical as a high power tube. Like Bart said, laser tube is a device with low efficiency. It only output 10% of the the total power it consume. So, for a 150W tube, it's taking about 1500W power and wasted the energy as heat. Imagine how hot it would be even with seconds power on! Do not feed water below 20'C as a laser tube should be kept in 25~30'C or prefectly at 28'C. Or, you may want to warm up the tube by powering it with less power say 5%. Until the tube is getting warmed or until water is up to 20'C then you can start use it in full power

Now the customer seems not beliveing but there is not much I can do. I checked the weather there and it's 40'F (5'C)!! He said that he filled it up with water but he seems not seeing the problem, 5'C water is cold enough to cause the kill. I can only offer a discount for him to purchase a new tube. Even Raci would tell him the same story I mentioned above. I'm not trying to shift the responsiblity but the true is that I have nothing to do with the crack. The tube we sent was tested by the manufactuer before packing per our request. The tube either cracked from a shipment (customer recieved it in perfect condition) but it won't be possible it cracked itself if saftey concern was taken into account

A lot of people under estimate the 'cold effect' but only focusing on the heat issue or the how to cooli the tube but ignore the weather effect. It's wrong, they should consider how to 'warm up' a tube as well.


See the pictures he sent below.

Regards
Marco

[Ruud Hogenberg]

Marco,

Have reading the story and will leave the true about this in the middle, but i really challenge you on number 3.
For my professional laser the manual says that in case a tube will be cooler then 5c degrees you need to add fluid so it cannot be frozen and damaging by that.
Nothing about starting up from that temperature.
Also they say that the temperature should not go beyond 30c degrees, and good working temperature between 22 and 25.
Further my factory temperature is at night at 10 and during working time 17. I mean 20 is really to warm to work in it and think there will be no factory in Europe with higher temperature. (unless specifiations of your products needs it or at hot summer.)
So your point 1 and 2, agree on this.
But I also should have doubts at point 3.
By google the internet i saw lasermachine operating temperature between 0 and 45C degree.
Even i have seen a reply from you that some of your tube came damaged and stuck at arrival.
I think more about that the tube didnt arrive in good condition, one very small damage in tube does this. It could had not-visible damage.
But ok i am not the expert only to challenge you..

Ruud

[Tech_Marco]

Ruud:

You don't need to challeng as I'm not an expert. All this info I posted here was based the info I was told by a major tube manufaturer in China who ship 300 tubes monthly. I just brough it up for the public in case you have high power tube. Normally people operate 40W to 100W laser and the condition require less than a higher power one (I guess).

FYI, each tube must going through hours testing before they're allowed to get out from the manufactuer. Even a small shop (operate in a small town that I visited in 2006) did run test for all tubes they manufactued. It's very odd to have a defective tube, usually either cracked during shipment or operating it improperly that lead to the problem. If a laser is craced from the manfuacturer, the tube coldn't be possible to pass a test as CO2 leaking and high voltage Arc could be possible generated. Then water could get into the tube and make the crack even worst.

(I have a 60W tube here and I can see the plasma running around due to leaking somewhere)

I'm going to ask my friend to make some test with some old 80W and 100W tube he had on hand for testing. I'll ask him to inject cold water like 5'C and fire it up at room temp say 22'C see if he can duplicate a problem there.

Last, prevention is what I'd to emphasis here. An on ramp with speed limit to 30/Hr doesnt mean that your car will lose control if you're driving at 40/Hr or 50/Hr. It all depends who drive it and what car is it.

Marco

[Ruud Hogenberg]

Marco,

Thank you, that you have requested someone to test this and how to see if it can replicated.

Great
Ruud