7 replies to this topic

[Samin]

Dears

 

For heating storage tanks which one is the best choice: steam coils or suction heaters?

what is the criteria for selecting between these choices? (tank dimention, heat duty,...)

how to decide about the number of suction heaters?

 

many thanks,

 

[kiansafaie]

Dear samin
Please explain, what is the suction heater and how dose it worked?
Thank you

[fallah]

Samin,

 

In general, for the tanks with large diameter/height and low pumping rate using suction heater seems to be logical and economical. For small tanks and high pumping rate it's better using steam coil. Anyway, to make final decision for heating method selection all detail info should be available... 

[Zauberberg]

If the minimum ambient temperature is below the minimum acceptable temperature for the storage fluid, the decision is straightforward.

In order to receive proper advice, please provide more information as suggested by Fallah.

[Art Montemayor]

A tank suction heater is a special heat exchanger - usually heated by steam - that is used in pre-heating a stored, viscous or heavy liquid prior to it being pumped out of the tank.  It allows the pump to operate with a positive NPSH by lowering the suction side pressure drop due to the lower, heated liquid viscosity.

 

This device is used where one does not need to maintain the entire tank at an elevated temperature around the clock.  It is especially favored where only intermittent pump-outs are needed, where it is undesirable to insulate the entire tank, or where the availability of heating steam is scarce.

 

Refer to the attached literature for detailed fabrication details.  Note that the term "stream" is in error and should be STEAM.  The unit is welded directly onto the lower side of the tank and only the liquid entering the pump is heated.  It is not an effective device for heating the tank; it serves only for heating the pumped fluid.

 

I have used this type of heater in feeding fuel oil #6 (or Bunker C) to boilers from large storage tanks where I didn't want the additional costs of building and maintaining tank insulation and steam costs.

 Suction Heater - High Viscosity Liquids.pdf   89.61KB   539 downloads

 Tank Suction Heater.pdf   5.51MB   1235 downloads

[Samin]

thank you for all your responses,,,

 

the dimention of storage tank is 9m height and 12m diameter. liquid maintaining temperature is 60 °C.

pump in and pump out flow rates are 400 m3/hr and 600 m3/hr and not continuous but intermittent.

 

is this information is sufficient for taking proper decision? 

 

best regards

[Art Montemayor]

Samin:

 

I believe that I already gave you sufficient information on how to arrive at YOUR decision:

1) This device is used where one does not need to maintain the entire tank at an elevated temperature around the clock.

How important is it to keep your product stored at a high temperature?  If it isn’t required, then why heat it and incur all the capital and operating costs of steam consumption and insulation requirements?

2) It is especially favored where only intermittent pump-outs are needed.

You are storing approximately 1,000 m³ of product.  You don’t tell us the quantity pumped out (you only tell us the rate) intermittently, so it is your decision as to whether this quantity is significant or not.

3) It is especially favored where it is undesirable to insulate the entire tank.

Are you willing to insulate 150 m² of tank insulation just to maintain 60 ^oC?  You will have to install and weld insulation supports and tie-downs on the tank surface - if these are not already present.  You will have to maintain the insulation during its life.  You additionally will have to face the possibility of having tank wall corrosion directly under the insulation.  This will have to be inspected on a routine basis to avoid unseen tank wall failure.  I personally avoid any storage tank insulation whenever I can justify it.  But that is your decision.

4) Is there availability of heating steam and how expensive is the capital and operating incremental cost of heating the total tank versus heating only the pump-out?  You should prepare these calculations and be prepared to defend your logical decision.  This is expected in order to reach a logical engineering decision.

[Samin]

Dear Sir

kind regards for your complete and exact help.

this case was new for me and i didn't have any experience.

many thanks