Steam Jacket Viscosity Reduction Calculations 1

[19omalley90]

Hi everyone,

I'm looking to determine the time it takes for the viscosity of the pumpage to reduce to a suitable level to allow the pump to operate freely. The pump in question is a CP13 PP26 (API674 Direct Acting Recip.) The pump end has been fitted with steam jackets. I have limited information as follows:

pumpage - heavy hydrocarbon (tar)
steam temp. in jackets - 215C
thickness between steam jacket cavity and pump body - 0.4375"
material - cast steel
pumping temp. - 120C (min) to 242C (max)
Discharge pressure - 17.5 kg/cm^2
Suction pressure - 3.6 kg/cm^2

I realise that this in not alot to go on but I would be very grateful to hear your thoughts/recommendations to give me a better idea of how long it will take to reduce the viscosity to allow the pump to work.

If you would like further info just let me know.

Thanks for your attention!

 

[BigInch]

It depends on how many BTUs are delivered to the tar. Do a heat transfer calculation from heated surfaces into the tar. Once you know how many BTU's/sec can be transferred to the tar, you can find the time it takes to raise the inlet temperature to the outlet temperature.

From "BigInch's Extremely simple theory of everything."

 

[19omalley90]

Thanks for your prompt and helpful reply!

I now have a value for BTU's/sec but I'm not sure what to do with it to find the time it takes to raise the temperature of the tar to a suitable level.

Any suggestions?

 

[BigInch]

I always have suggestions.

Sorry I didn't notice the SI units, but we'll continue with these BTUs for now, so I won't make a mistake. Maybe we'll try SI later.

We need the heat capacity of the tar.
The heat capacities of liquid hydrocarbons are about equal to their specific gravities, SG x 1 BTU/Lb-F[°]

Its SG is probably close to water, so let's just say it is 1 BTU/lb-F[°]

... divide the heat capacity of the tar by the BTU/sec and multiply by the mass (pounds) of tar in the cylinder and multiply again by the F degrees that you want to raise the temperature,
[Δ]T_F[°] say from 25[°]C to 200[°]C is 175C[°] so multiply that by 9/5 to get F[°] for [Δ]T_F[°]

SG_tar * 1 BTU/lb-F * M_lbs_tar / H_BTU/sec * [Δ]T_F[°]

That's the number of seconds you'll have to apply the heat to reach your target temperature, assuming that the heat is uniformly being applied to the surface of the tar. Then just check your tar's viscosity at that target temperature to see if it is suitable to pump.





From "BigInch's Extremely simple theory of everything."

 

[19omalley90]

Brilliant, I now have a final answer for my question.

Thanks very much for your help!