Process pressure

[adrich91]

Hello colleagues!

Today I'm here again to get some help with some issues I have in my head.

First of all: I hear a lot the expression ‘to clean with water with pressure on something’ and I suppose that it is not really pressure that is being talked about, but a lot of flow, isn't it? Because I understand that it is a lot of flow that makes water come out at high speed and it seems that ‘it has pressure’, right? No sense to talk pressure with fluids...

Second: In many processes, after passing liquid from one tank to another, a nitrogen sweep is made to push the excess liquid in the pipes to the final tank. If I have N2 at a pressure of 7 bar, I understand that it is like making a balance between initial point and final point applying the bernouilli theorem where the initial pressure is the pressure of the N2 and the final pressure is the pressure in the final tank, right? I need to make a calculation depending on the pressure drop, fluid...etc to know what N2 pressure I have to apply to overcome the pressure drop and drag the liquid, right?

Finally, third doubt. I would like to know if there is any program at a visual level that you can draw a pump, pipes, tanks and you can move the fluid and see how it behaves, either at a professional level with real data of head losses to be able to possible preferential paths in a pumping system or even if it is only visual for presentations and basic explanations.

Thank you very much, best regards and sorry for my english

 

[Snickster]

Question 1

The pressure upstream of the nozzle on the order of 1000 psi plus is converted entirely into kinetic energy velocity per the Bernoulli equation, less a little pressure drop across the nozzle. The higher the pressure upstream of the nozzle the higher the velocity exiting the nozzle. The impact of the velocity on the item to be cleaned is what washes it.

Question 2

The N2 pressure must be equal to the static head of the liquid in the final tank you are to push the liquid into plus the pressure of the vapor space in the final tank for equilibrium to exist. At this point there is no flow but just equilibrium between the pressure in the final tank versus the initial tank. Then any pressure increase above this point will push the fluid into the final tank, the higher the differential pressure the higher the flowrate. You want to keep the pressure in the initial tank as low as possible so as not to overpressure the initial tank. You need to find out the design pressure of your tanks and make sure they are not overpressurized and insure this by installation of a relief valve on the N2 supply line, or insure you have adequate existing vents on your tanks.

Question 3

I don't know of any but they probably exist.

 

[pointsman]

Regarding your 3rd question, EPANET is a free and fairly simple program (also used at the professional level) which can perform the functions that you list. It's geared toward civil engineering applications and will help you develop an intuition for how hydraulic systems behave.

 

[pierreick]

Hi,
For point 1 , you are referring to high pressure or very high-pressure cleaning requiring specific equipment to supply at the discharge of the nozzle # 500 to 1000 bars at a very limited flowrate, am I right? Typically, a contractor or third-party work.

For point 2 , let you consider pigging system to clear your lines, more effective.
Regarding the 3rd question, download from Internet PSIM2 ( process simulation tool) with an bunch of examples (library).
Free !

https://fo.pumps.org/Education/Free_Pump_Software.aspx

Very good tool.
Note : You can purchase From Katmar software an excellent tool for hydraulic calculation

Pipe diameter sizing, pressure drop and fluid flow rate calculation software | AioFlo

AioFlo calculates pipe sizes (diameter), fluid flow rates and pressure drops for compressible and incompressible fluids.

www.katmarsoftware.com

Katmar is one of the pillars in this forum .
Pierre

 

[LittleInch]

Agree wit most there.

It's really velocity of the water jet which "cleans" things, but people refer t these as "pressure washers" as you need to generate some high pressures to generate high velocites when its forced through a small orifice.

Second point - Be very careful when doing this as its very easy to overpressure the tank at the other end. Very easy.

SO you really need a proper study into how this works. Note also that as you sweep the liquid out the flow can accelerate as the effective length of the liquid flow reduces over time, but the motive force ( the gas ) doesn't.

Forget Bernoulli for these sorts of calculations.

 

[goutam_freelance]

‘to clean with water with pressure on something’

One needs to be careful about the pressure and distance of the nozzle from the workpiece, as at higher pressures and lower nozzle distances, the process may transition to 'water jet cutting' instead of 'water jet cleaning'.