Working Of Thermic Fluid Heater Deaerator-Cum-Expansion Tank - ASKPOWERPLANT

Working Of Thermic Fluid Heater Deaerator-Cum-Expansion Tank

working of thermic fluid heater deaerator-cum-expansion tank

How To Work Thermic Fluid Heater Deaerator-Cum-Expansion Tank.

Heii all my Askpowerplant family members hope all is well during this COVID-19 pandemic situation. So please proper take care of you as well as your family. And also followed the COVID-19 guidelines. Today we discussed a very important topic related to the thermic fluid heater that’s topic is “working of thermic fluid heater expansion tank “in this article we discussed every part of the expansion tank and their working principles in a detailed way. So please read this article up to the end if you don’t know how to work a thermic fluid expansion tank.


According to the name of this equipment, we clearly understood that for what proposes this tank used. Yes, this tank is used for holding the volume of working fluid when it heated to ambient temperature to working temperature. Its density decreases with an increase in the temperature of the fluid.

So this tank is generally installed in a process to help to handle the extra volume of working fluid which is increases due to increases in the fluid temperature. From ambient to operating temperature the thermal fluid in the system will typically expend in the range of 30%.

For example every 100 0C rise in the fluid temperature, the volume of working fluid increases by 7% so in that condition expansion tank to be installed to take care of extra volume generated when the working fluid expands with the help of giving heat.


Generally, we know about the thermic fluid heater expansion tank is that it is also called the deaerator- cum-expansion tank because in the main parts of expansion tank deaerator section also play a very important role its take part for improving the working of the thermic fluid heater as well it’s operating efficiency. We know the working of the deaerator section in a detailed way in this section but first of we clearly understood that what are the main parts of the thermic fluid expansion tank. Main parts of the thermic fluid heater expansion take are the following:

  1. Expansion tank
  2. Liquid level switch
  3. Deaerator section
  4. Thermal Buffer Section
  5. Buffer Section Drain
  6. Expansion Tank Volume Area
  7. Vent for Piping to safe catchment
Deaerator-cum-expansion tank of the thermic fluid heater
Deaerator-cum-expansion tank of the thermic fluid heater

Brief Explanation Of Deaerator-Cum-Expansion Tank


Deaerator cum expansion tank is provided in the return line. the thermic fluid in the complete circuit expend in the volume is 7% per 100 0C rise in temperature of thermic fluid hence the section of the size of expansion tank capacity should be minimum 20% of the total volume of oil to be filled up in the system. The deaeration vessel capacity depends upon the flow rate. Its size can be roughly decided considering 2.5 to 3 m/s fluid velocity at its inlet nozzle.


The standard de-aeration cum expansion tanks supplied are suitable for most of the standard processes. In case the volumetric expansion of the thermic fluid of the system is more than the capacity of the expansion tank provided, a separate extra expansion tank needs to be incorporated. The thermic fluid also contained some higher fractions which flash off at elevated temperature while commissioning. These are to be driven out of the system to have proper functioning of the equipment.

The combined expansion and deaerator tank is so designed as to take care of the expansion of the thermic fluid and also to drive away from the gases or entrapped air. This tank should be installed at least 1 meter (3 feet) above the highest point in the thermic fluid pipeline. it is also necessary to confirm that the NPSH ( Net Positive Suction Head ) at available at pump suction is more by at least 0.5 m, than the NPSH required for your pump supports are welded to the tank, with the help of which the tank can be fixed and bolted to the structure.


The liquid level switch is a very important device when we operate the thermic fluid. During the operation time whenever fluid level goes down up to the safe working limit at that time this switch plays their role, it senses the level and given the signal to the panel and at that time a buzzer will come. So panel operator get alert and check the working fluid level in the expansion tank. If he found it’s below the safe working limit he doing the top up the fluid.

3.Deaerator section:

Deaerator tank is combined with the expansion tank as shown in the attached picture and it is generally used to vent out air from the fluid which acts as a resistance in transferring heat to the fluid.

It removes all volatile matter from the system to avoided pump cavitation. The deaerator section also allows oxygen to be vented from the system on a continuous basis during the operation to avoid oxidation of the thermal fluid and removes other volatile particles generated by the fluid itself during system operation.

4.Thermal Buffer section:

Buffer section prevents the movement of any oil that has not cooled sufficiently into the expansion section. This avoids contact of very high thermal fluid temperature with oxygen contained in the atmosphere which causes fluid to break down. Do not insulate this section.

5. Buffer section drain

Buffer section drain is used for the flush out the volatile matters which collect into the bottom of the buffer tank.

6.Expansion tank volume area

in the expansion tank above the liquid level which area present which is used for the expansion of thermal fluid that’s area is called expansion tank volume area or the area inside the expansion tank from the liquid level switch to the normal working level of the fluid that’s called the expansion tank volume area.

7. Vent for Piping to safe catchment

in the above section of expansion tank a vent is given to safe catchment of fluid whenever overtop and also during the operation time due to some operation abnormalities expansion tank could be overflowed so protecting of wastage of fluid this vent arrangement is given to every expansion tank of the thermic fluid heater. This overflow fluid goes to drain tank or we can say storage tank of the thermic fluid of heater.


This tank generally put on the ground floor to which drain and overflow from the combined expansion and deaerator tank are connected, has to be of capacity at least equal to the capacity of the combined expansion and deaerator tank. the overflow pipe should be taken till the bottom of this tank and should be provided with sparger arrangement to avoid hot oil coming in contact with air to prevent it from degradation.

While installing the thermic fluid circulation pump, arrangements should be made to install a small pump of 1000 liters/hr. At about 30-40 MLC of pumping head. The pump is connected to the suction head of the TF circulation pump, for charging the system with thermic fluid when required. It is necessary to have such an arrangement because it is not advisable to use the thermic fluid circulation pump for charging thermic fluid in the system. This will also help in filling the system from the bottom driving out all the entrapped air.

Facebook Comments

I have faced problem in our thermic fluid expansion tank, we have the expansion tank temperature is to high as normally, around 200 temperature rises, and expansion tank is hammering, please suggest me what is the reason of over heating in expansion tank

Hello sir,

We are facing issue of frequent temperature shoot up in expansion tank nearly above 90 deg cel.Hence our Thermic fluid heater is getting tripped frequently as set point is given 90 deg celsius. We have dearator cum expansion tank design.I want to know whats the set point in this type of design and what should be the safe normal temperature of expansion tank during thermic fluid heater in such type of design


Leave a Reply

Your email address will not be published. Required fields are marked *

Translate »