7 replies to this topic

[hianbotech]

We are designing a cooling water system for a petrochemical plant. As part of the design of the cooling tower, vent lines were added in the risers or the cooling tower. Hydrocarbons detection have been provided in these vents. However I would like to know how to size these vents. In some go-bys, we found that the vent lines have the same size of the risers.

 

As additionally information, our cooling water system is a closed loop and some heat exchangers has hydrocarbons at high pressure in the tube side. Relief valves for tube rupture have been provided for this  heat exchangers.

 

I would like to know some guidelines to design the size of the vent lines to be added in the return line.

 

Best Regards and thanks

 

[Atttyub194]

I will give you reply on weekend

 

regards

[Atttyub194]

Dear hianbotech

 

Good day!

 

It is general practice to provide vents of same size as that of riser if the system is supplying hydrogen or similar gases in order to avoid pressurization of the system. This is done in addition to providing rupture disk on the cooling water side of exchangers

 

Recommendations  may be searched in AiChe papers on incidents of cooling towers

 

However,  if intend to optimize the size then please do consider the slug flow through riser. However, when I have done a very extensive exercise then this only resulted in reduction is vent size from 16" to 12" and with practically no economical gain with such a huge transient flow analysis

[hianbotech]

Thanks for your answer.

 

As you said we kept the same size of the riser. We checked other projects and they followed the same criteria.

 

Best regards and thanks again

[arvind]

Hi Hianbotech,

 

Reason of providing vent line on cooling water riser is to escape any noncondensable gases (like air, lightend HC etc.) from the cooling water circuit.

The elevation of this high point depends on the pressure drop across cooling tower inlet distributor.

for eg. if cooling tower inlet distributor have pressure drop of 0.1 bar then vent line from the riser should be atleast 1 meter higher elevation from the top of riser.

 

Regards,

Arvind

 

[iplan]

Regarding the sizing of vents in cooling tower risers, I am required to size vents in our cooling tower risers. I understand generally the vent size is kept same as the riser size. I would like to have any reference technical/fire protection literature on this.

 

Kindly help.

 

Thanks in advance,

iplan  

[iplan]

In continuation to my above post,  I am trying to size the vent based on exchanger tube failure case , considering two tube areas.  Also, no allowance is being provided to the availability of pressure safety device at the exchanger cooling water outlet.

 

Looking forward to the learned members' inputs please.

 

Thanks

iplan

[Atttyub194]

Dear all

 

Good day

 

Due to heavy work load i am unable to answers the queries . I will reply soon probaby after october 2013

 

Sorry for any inconveniuence

 

Best regards and God Bless you