7 replies to this topic

[Bill B7]

I found that this has been discussed in past years.  In my case, It appears that the heat transfer coefficients I see (~500 btu/hr sf °F) are for the internal coefficient only.  Shouldn't we also take into account the resistance to heat transfer through the wall and outside of the tank?  The fact that my tanks are indoors (no wind, no rain) are what prompted this thread, since the htc for the outside of the tank will be << the condensation coefficient on the inside.

 

Any thoughts?

[latexman]

When we steam out our atmospheric tanks, we remove the roof manway and lower side manway for relief.  We don't count on the 4" gooseneck vents we have.

 

We have never tried to calculate this.  It happens too quick.  Open up all your manways, is my recommendation.

[breizh]

Hi,

Agree with Latexman.

https://www.cheresou...6717-steam-out/

 

Breizh

[fallah]

When we steam out our atmospheric tanks, we remove the roof manway and lower side manway for relief.  We don't count on the 4" gooseneck vents we have.

 

We have never tried to calculate this.  It happens too quick.  Open up all your manways, is my recommendation.

 

Agreed,

 

The free vent/overflow line and other facilities might not to be able to handle the situation following to a sudden condensation and all manways/gauge hatch should be open up to handle the probable vacuum...

[Bill B7]

All,  I am in agreement with your comments about opening the hatches.  I am trying to confirm that this will provide adequate relief - i.e. are the hatches large enough.  My interest here is in determining whether a more granular estimate of the heat transfer (condensation) rate could be made, compared to using the high htc values I have seen in the past.

 

Thanks for your respoinses.

[fallah]

All,  I am in agreement with your comments about opening the hatches.  I am trying to confirm that this will provide adequate relief - i.e. are the hatches large enough.  My interest here is in determining whether a more granular estimate of the heat transfer (condensation) rate could be made, compared to using the high htc values I have seen in the past.

 

Thanks for your respoinses.

 

Not just the gauge hatch but top and side manways are kept opened too during steam out...

[breizh]

Hi,

Stay on the safe side and open all the manways available. This is based on experience. Have you ever seen a column or a tank collapsing due to misjudgment? This is happening in seconds. Who cares about the transfer coefficient? 

 

Edit:

https://www.linkedin...syed-adil-hasan

https://www.eng-tips....cfm?qid=153233

 

You may find data in Kern Process Heat transfer and Perry's chemical engineers' handbook.

 

Breizh  

[Bill B7]

Thanks.  Breizh, I do care about the transfer coefficient.  I think there is a misunderstanding.  We will be opening the manways and hatches.  I am attempting to determine if that will provide adequate relief.  In order to estimate the in breathing I need to determine condensation rate (from the heat transfer rate), so the overall heat transfer coefficient will be important.

 

Based on the responses, I will use a conservative estimate of 600 btu/hr sf °F and size the manway accordingly.

 

Thanks again.