Maximum actual velocity of 400 psig steam from a 10 inch nozzle in 12 inch pipe

[ChRe007]

I am trying to calculate maximum velocity/ flow rate (choked) of 400 psig steam in a planned 10 inch Nozzle for unit A steam supply from an existing 12 inch 400 psig steam supply line to unit B in Tee connection.

I am using 400 psig inlet/outlet steam pressure in 12 inch steam supply existing pipe with a 10 inch nozzle connection planned for unit A with 400 psig steam supply. Pipe roughness assumed 0.0005, Pipe schedule 40, Straight pipe length 20 ft before/after/branch of nozzle. Flowrate, I am using a 100 mlb/hr as basis and 60% going to unit B and 40% going to unit A. Density and Viscosity are per Hysys saturated steam at 400 psig and 100 mlb/hr.

What are best options/methods to calculate this apart from AFT Arrow?

I would appreciate every help for this. Thank you all. Keep up the good work.

ChRe

 

[racookpe1978]

mentally, I am losing you between the Unit A and Unit B cross-connections. Please draw your proposed P&ID/layout, with distances from each each tee.

Why do you expect choked flow from a 10 inch nozzle if venting a 12 inch line?

 

[Latexman]

A dimensioned sketch with assumptions of your pipe and fitting model for the calculations would be helpful. Also, I'm curious, what will the results be used for?

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

 

[ChRe007]

Thank you for your time.

There is a 12" Schedule 40 piping existing and currently supplying to Unit B (to existing process units) with 400 psig steam. We are planning a new Unit A which is trying to use some of this OSBL (out side battery limit of process units) steam supply. There is a 10 inch nozzle available currently on this 12 inch supply line which we think that we can use for steam supply to Unit A.

My main objective to check the availability of the 400 psig steam for Unit A. For that, I am also looking for updated steam balance so I can find exactly how much steam is produced and how much of that is consumed by each unit (Unit B and other units) and how much will be available for Unit A. The client asked me to find how much maximum actual velocity we can get in this 10 inch nozzle for steam and to find how much maximum flow rate (choked?) we can achieve in this 10 inch nozzle. This was to get an idea if this existing 10 inch nozzle is good enough to use per their steam requirements. At this point, I don't know how much of 400 psig steam they require but at least with this basis I was hoping to estimate how much maximum steam we can supply if we had to use this 10 inch nozzle.

Enclosed please find a quick sketch I made to describe the problem. Since, I have not found any piping isometrics, as a starting point, I assumed pipe lengths as 20 ft for segments AB, BC and BD. This will change when I will find these lengths, I did not know if pipe lengths are even required in the calculation. In the sketch, I am showing existing piping in black and planned piping in red (clouded).

Even though we are assuming few parameters, the method will be useful for me when I find values of the unknowns. Please let me know if you need more information.

Regards,
ChRe

 

[Latexman]

Pressure drops at or near Mach 1 are extremely excessive compared to those of a reasonable near-optimum design of, say, 0.5 to 5 psi/100 ft. I'm not sure how useful an availability based on choked flow will be to you. I think it will be unreasonable high. Erosion-corrosion will be terrible at those velocities! That's only one issue; there would be many other issues at those velocities.

My handy dandy spreadsheet tells me that 100 feet of 10" pipe has 0.5 psi drop at 100,000 lb/hr and 5 psi drop at 300,000 lb/hr for 0.86 lb/ft3 and 0.02 cP steam. Depending on the real lengths of pipe that you find in the steam supply and header system, a reasonable availability is probably somewhere near that ball park.

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

 

[ChRe007]

I appreciate your reply, Latexman.

I just heard about required steam flow rate to Unit A is 90,000 lb/hr. So,
The problem statement we are trying to determine is: we need 90,000 #/hr of 400 psig steam, will it fit through a 10” line, what is the anticipated velocity and will it exceed some velocity limit. Or stated another way: we need 90,000 lb/hr of 400 psig steam, we have a 10” connection available that we can use, is the 10” connection too small, to big, or just right?

 

[Latexman]

From the plant layout, available pipe rack, and the P&ID(s), make a conservative estimate of line length and number and type of fittings. You have the flow. You may want to allow for a reasonable capacity expansion. Look up the physical properties. Now, how much pressure drop can the process tolerate. It's 400 psig at the 10" nozzle. Can you tolerate 395, 390, or 380 psig at the end of the new header? Now, what size line will do that? What's the velocity? Is that excessive?

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.