85% propane versus 95% propane in HVOF

[pulaunias]

Dear members,

I am a starter in HVOF (I worked on plasma spray before; but HVOF seems to be very different), and this forum has been an important source of learning. I will appreicate it if any one can adivse me on requirement of propane gas in HVOF.

As I mentioned in another post, I am struggling to get quality (meaning 95%) propane for our DJ 2700 HVOF. Today I confirmed with a supplier that they sell 85% propane (propane% between 85% and 90%). I intend to use one as a last resort, if I cannnot get the dear 95% proapne that I dream of.

My question is: does anyone know if 85% propane makes any difference in flame temperature or other important aspects for the gun (I guess butane makes slightly higher pressure during combustion as the molecular size is bigger so contains more C and H atoms). Or make it short, can/may this work?

Wikipedia (under the item: gas burner) seems to suggest that propane, butane, and butane-propane mix make flames of the same temperature. But I think I'd better be more cautious.

I hope I can get 95% propane from another supplier next week. I may try both and let you guys know a rough comparison when I get the results.

Thanks very much!


PS: I know butane has a lower vapor pressure so it does not evaporate well compared with propane; this should not be a major problem for our case, as we will draw the liquid out and feed it to a vaporizer, which will warm the liquid and turn it into a gas.

[Met.Eng.]

Dear pulaunias,

Firstly i dont use propane gas with my Hvof system but my manufacter always recomend high purity gas. 99,90 H2, 99 Ar, 99,98 O2 ect. I think Calorific power of the flame is not affected much.Calorific power can be seen next to an unstable flame,

.

[pulaunias]

Thanks Metallurgy_eng.

I am always afraid of H2 combustion, no idea why. What is your system? DJ 2***? My DJ consumes a large volume of H2, if I use H2; so I must manifild a lot of H2 cylinders to allow the sytem to run continuous.

[Met.Eng.]

I'm sorry but I will give a general answer.
You should use the recommended gas for your system. I think the system is not safe to modify. Our siztem a little different than yours." is not the property of Metco"
Also a good idea to consult with other members. However, I think the gas purity should influence the quality . But do not forget the price of gas also increases with increasing purity.

[pulaunias]

You are right, Metallurgy_eng. Thanks. Our supplier adivses us to use >95% propane. Hopefully will get it this week. Not an easy job here; we are far away from major petrochemical plants.

[loriolo]

Hi Palaunias
That's a good choise, but 98,5 would be better, the purity of gas is important for HVOF, because the pressure inside the gun are very high, and there is the risk of deformation of the combustion chamber, and the gun will be seriusly damaged, do not use other kind of gas, for DJ 2700 you can use only Pure propane, Mapp gas or Flamal, Natural gas, if you need to use H2, you must update your system with DJ 2600 version.
Regards

[Stephen Booth]

You are right, Metallurgy_eng. Thanks. Our supplier adivses us to use >95% propane. Hopefully will get it this week. Not an easy job here; we are far away from major petrochemical plants.

Hi Pulaunias,

I had experience for many years trying to run a DJ 2700 and Top Gun using 60 40 Propane Butane mixture. As that was the only available gas mixture. In my opinion, even this mixture works fine, it is mainly the input pressure of 9 bars that needs to be strictly adhered to ... meaning if you drop below 9 bar input, then the system does not operate correctly.

If you can use the vaporizor to achieve this, then you should be fine. However, make sure the propane butane mixture is consistent from one batch to the next batch, otherwise your coating parameters will be invalid.

[pulaunias]

Hey Stephen and Loriolo,

Thanks so much for your valuable information. I got >95% propane after hard struggles, at a higher price than 85% propane.

Theoretically we can run DJ 2700 with the 85% propane, but this is kind of approaching the limite of the vaporizer (also violating service provider's recommendation), which specified that the propane content should not be below 85%. I decided to seek a higher safety margin.

Thanks guys!

[pulaunias]

if you drop below 9 bar input, then the system does not operate correctly
_____________________________________________________________________________
Here my DJ 2700 specifes the propane pressure requiremtn as 6.2 bar and 88 normal liter/min.

I guess what you meant is that the vapor pressure in the propane tank should be 9 bar, which will be reduced to 6.2 bar by a regulator. The 9 bar is required to ensure enough vaporizing speed to supply the DJ without falling below the threshold 6.2 bar when vapor is drawn out.

Is my understanding correct? In out operation we just open the tank vale full (I remember it could reach almost 10 bar when tank is full; it drops during use; eventually no way to run) and let the regulator maintain the 6.2 bar.

[Stephen Booth]

if you drop below 9 bar input, then the system does not operate correctly
Yes, indeed you are correct, I checked the parameters, 6.2 bars at the controller, but typically at the bottle, or propane tank much higher.

With LPG we only got about 5 bar, but with 95Propane we achieved 9 bars on a full bottle, or a warm bottle using heaters.


_____________________________________________________________________________
Here my DJ 2700 specifes the propane pressure requiremtn as 6.2 bar and 88 normal liter/min.

I guess what you meant is that the vapor pressure in the propane tank should be 9 bar, which will be reduced to 6.2 bar by a regulator. The 9 bar is required to ensure enough vaporizing speed to supply the DJ without falling below the threshold 6.2 bar when vapor is drawn out.

Is my understanding correct? In out operation we just open the tank vale full (I remember it could reach almost 10 bar when tank is full; it drops during use; eventually no way to run) and let the regulator maintain the 6.2 bar.

[Yod]

Thanks Metallurgy_eng.

I am always afraid of H2 combustion, no idea why. What is your system? DJ 2***? My DJ consumes a large volume of H2, if I use H2; so I must manifild a lot of H2 cylinders to allow the sytem to run continuous.

Did you use 2700 on hydrogen without changing the design?

[Stephen Booth]

Thanks Metallurgy_eng.

I am always afraid of H2 combustion, no idea why. What is your system? DJ 2***? My DJ consumes a large volume of H2, if I use H2; so I must manifild a lot of H2 cylinders to allow the sytem to run continuous.

Did you use 2700 on hydrogen without changing the design?

you need to change some parts inside the DJ 2700 to use at DJ2600

[Yod]

Thanks Metallurgy_eng.

I am always afraid of H2 combustion, no idea why. What is your system? DJ 2***? My DJ consumes a large volume of H2, if I use H2; so I must manifild a lot of H2 cylinders to allow the sytem to run continuous.

Did you use 2700 on hydrogen without changing the design?

you need to change some parts inside the DJ 2700 to use at DJ2600

what is the difference? nozzle geometry? mixer geometry?