Issue with heavy naphtha increasing pressure in closed system.

[Newuser34]

Hello all,

I am currently scratching my head at pressure readings from 2 separate transducers that are showing pressure increases in a closed stainless still line. At some points the pressure readings are almost doubling from the normal rest state of 40ish psi to 80. This is only happening when the system is at rest. As soon as flow rate stops there is a steady increase in pressure until demand on the system resumes.

One specific example would be an increase of 49 to 84 psi over a 1 hour period of inactivity. I have no inlets for this kind of pressure as all other inputs to the system as far as pneumatic valve supply and services are 70 psi or below. Furthermore air from the pneumatics getting into the system would get really noticable as soon as demand resumed and the pneumatics are the only input thats over 55 psi. If it weren't for both transducers reading the same thing I would have just replaced them by now.

 

[don1980]

When you say the system is "at rest" do you also mean that it is isolated (valves closed)? If so, the increased pressure could be due to thermal expansion.

Another possible explanation is the difference between static and dynamic pressure. Potential energy (read by pressure gauge) decreases as the fluid is accelerated (potential energy is converted to kinetic energy), and vise versa. Is this a vapor system, with the pressure transmitters located where the velocity is exceptionally high?

 

[horacio Torres]

The logical explanation is thermal expansion by heat going into the isolated system.. With heavy naphtha you also has to see temperature increase.


Check that is not leak in the valves. Pressure could be come from the connecting lines.

Horacio

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