Welcome - You need to look at the other answers given when you posed this question as a Guest.

I repeat:

You have a centrifugal pump. The viscosity change of any decent Thermal oil between 95 and 120 deg C is relatively small as these are usually high viscosity index oils so this should not affect the pump or the system too much. (Not enough to explain a 6.4 bar pressure difference anyway).

I would strongly suggest that your system is contaminated with water and that you are having problems pumping steam. Increase the temperature to around 110 deg C while continuously venting the system and see if you get any vapour coming out. Keep venting until all moisture is removed from your system.

Dear Sir,

Appraise for your respond. the Lab Analysis were asf:

1. Viscosity, cst @ 40 C = 50.68

2. Water COntent % = 0.1

3. TAN (mgKOH/gr) = 0.37.

Appreciate If you have standard requirement for thermal oil used and share to me.

Kind regards

What oil are you using?

1. Viscosity, cst @ 40 C = 50.68 (Shell Thermia for example has a viscosity of 25 cSt at 40 degC.) TAN number is only useful if you know what the original oils TAN number was.

0.1% water is way too high for a thermal oil system. Dry out the system as suggested above.

Very simply off the top of my head (so shoot down the example if I have the numbers wrong), if you had a 1000 litres of oil with 0.1% of water you have 1 litre (1 kg) of water. When that turns into steam with a specific volume somewhere around 1.5 m³/kg you end up with roughly 1.5 m³ of steam for every 0.9 m³ of oil.

These numbers are not correct as there are all kinds of pressures etc coming into play, they are merely to illustrate that you need oil with zero water content in a closed thermal system.

How much noise is the pump making at 95degC, 120degC and 160degC?

An increase in noise means that the pump is cavitating, i.e. the process fluid, or a component of it, is boiling before it passes through the pump. The noise is the collapse of that component's vapour within and downstream of the pump, and will wreck it in short order.

Is the pwer consumed same under all these conditions?

Dear Sirs,

Appraise for your comments and idea. Original THermal OIl Viscosity is 32cst @ 40* C.

we had heated up to 124*C today and pressure drop to 3.0 bar from 8.0 bar in Cold Condition. It seem that the steam / water vapour was there.

If I heated up to 124* C for 48 hours and kept vent it out, is it possible to reduce or release the water content?

what is the best way to renew the Oil? by fill up the system from Expansion tank or fill the new oil to drain tank than pump it into the system by filling pump which is meaning fill up from the bottom line.

Your advise are really appreciated and honoured

Regards