15 replies to this topic

[Faisal Ghafoor]

I am interested in knowing how much maximum flow is allowed through 6'' nozzle of 25000 Ton ammonia tank. For piping normal velocity in CS is 3 m/s, and NORSOK standard even allows 6 m/s.

Will it be okay if I select velocity of 4.5 m/s for intermittent service. The head loss is around 0.03 bar, calculated for 0.5 v2/2g.

 

Pls guid is this right apporach or some other considerations are more critical, considering intermittent service.

 

[fallah]

Faisal Ghafoor,

 

Please consider rho*v² value (in kg*m*s^-2) and type of inlet device; max 1500 if no inlet device, max 3000 if half pipe or baffle inlet device, max 6000 if schoepentoeter or other vane pack inlet device is being used...then nozzle size will be specified...

[curious_cat]

Faisal Ghafoor,

 

Please consider rho*v² value (in kg*m*s^-2) and type of inlet device; max 1500 if no inlet device, max 3000 if half pipe or baffle inlet device, max 6000 if schoepentoeter or other vane pack inlet device is being used...then nozzle size will be specified...

 

 

kg m^-1 s^-2 ? 

[fallah]

 

kg m^-1 s^-2 ? 

 

 

Yes...kg m^-1 s^-2 is correct... 

[Bobby Strain]

If this is a refrigerated, atmospheric storage tank, size the nozzle (inlet) using normal pipe sizing criteria. The tank vendor normally sizes the nozzle for you. It is typically on top of the tank, and extends into a downcomer. The criteria given above is for two/three-phase separators, one phase being vapor.

 

Bobby

[fallah]

Yes, if it is a storage tank, nozzle sizes could be same as corresponding lines sizes; but the nozzle sizes should be specified by tank designer might or might not to be tank vendor. Indeed, the above mentioned criteria can also be applied for sizing of nozzles in incoming lines of vessels and columns containing single phase  fluid...

[Chemitofreak]

@ Fallah,

 

Are you sure that the Rho-V(Square) criteria is used for sizing liquid inlet/outlet nozzles ?

 

As far as my knowledge goes it is only applicable for two phase and gas phase inlet/outlet nozzle sizing.

 

Liquid inlet/outlet nozzles are generally sized based on the liquid inlet/outlet velocity or as per vendor recommendation the size is defined. 

 

Correct me if I am wrong.

 

Thanks in advance.

[fallah]

Chemitofreak,

 

Yes, the Rho-V (Square) criteria is mostly used for two phase and gas phase inlet/outlet nozzle sizing; meanwhile in some cases it is to be used in liquid inlet nozzle sizing but with different limitations values. For example TEMA has Rho-V (Square) limitations for impingement plate requirement for gas/liquid/two phase inlet nozzle at incoming line to the shell in shell and tube heat exchangers...

[shahid780812]

For storage tanks, usually nozzle size is same as line sizes howerever it is essential to also ensure that, inlet nozzle velocity shall be maintained as less than or equal to 1 m/sec untill there is a liquid cover of 1 meter in the tank. This is to avoid build up of static charge.

[shahid780812]

For storage tanks, usually nozzle size is same as line sizes howerever it is essential to also ensure that, inlet nozzle velocity shall be maintained as less than or equal to 1 m/sec untill there is a liquid cover of 1 meter in the tank. This is to avoid build up of static charge.

[Chemitofreak]

@ Shahid,

 

Thanks for the information about maintaining the liquid velocity during initial tank filling. 

[Mathi]

For storage tanks, usually nozzle size is same as line sizes howerever it is essential to also ensure that, inlet nozzle velocity shall be maintained as less than or equal to 1 m/sec untill there is a liquid cover of 1 meter in the tank. This is to avoid build up of static charge.

 

Storage tanks are usually protected with Earthing. In that case, there can't be any build up of static charge. Besides, the inventories are being pumped at a discharge velocity between 2-3 m/s. In this case, the possibilities of limiting the velocity is nil.

[Chemitofreak]

 

For storage tanks, usually nozzle size is same as line sizes howerever it is essential to also ensure that, inlet nozzle velocity shall be maintained as less than or equal to 1 m/sec untill there is a liquid cover of 1 meter in the tank. This is to avoid build up of static charge.

 

Storage tanks are usually protected with Earthing. In that case, there can't be any build up of static charge. Besides, the inventories are being pumped at a discharge velocity between 2-3 m/s. In this case, the possibilities of limiting the velocity is nil.

 

 

It might be a precautionary measure/good engineering practice.

 

Although the tanks are earthed, a dip pipe is always provided or the inlet nozzle is located below LLLL for avoiding generation of static charge.

[curious_cat]

 

For storage tanks, usually nozzle size is same as line sizes howerever it is essential to also ensure that, inlet nozzle velocity shall be maintained as less than or equal to 1 m/sec untill there is a liquid cover of 1 meter in the tank. This is to avoid build up of static charge.

 

Storage tanks are usually protected with Earthing. In that case, there can't be any build up of static charge.

 

Wishful thinking I think. In practice, there's many static related incidents on storage tanks I think. 

 

Due to various design or maintenance related issues I think. e.g. A float type gauge having some small unearthed part etc. 

[curious_cat]

 

Besides, the inventories are being pumped at a discharge velocity between 2-3 m/s. In this case, the possibilities of limiting the velocity is nil.

 

 

 

The flow rate is the conserved quantity not the velocity itself. 

[fallah]

 

Storage tanks are usually protected with Earthing. In that case, there can't be any build up of static charge. Besides, the inventories are being pumped at a discharge velocity between 2-3 m/s. In this case, the possibilities of limiting the velocity is nil.

 

 

Mathi,

 

Please note that tank earthing (or grounding) will only prevent discharge from the tank to earth; but it will not prevent a discharge from the liquid inside the tank, where the static charge built-up, to the tank itself...