2 replies to this topic

[rajarani87]

Dear all;

I am going to redesign the plant nitrogen piping, bcoz based on current requirement our PRV stations are not able to provide the requirred flow and also i have seen some under size piping in the plant.

1) Can anybody provide some guidelines how to do line sizing of the gas piping?

2) I know consumption and peakload of N2 so how data can be used?

3) How to evaluate whether the existing 50NB line size from utility to PRV station will serve the purpose or i need to increase the line size to give proper flow?

4) guidelines on gas piping network analysis?

Regards,
VVV

[Art Montemayor]

This is a basic, straight-forward, fun project. It is a lot of fun because you have a bounty of basic data at your hands:

• You know the consumptions and the peak flow rates;
• You know the trajectory of the pipes, since they already exist;
• You therefore know the accurate count of the line lengths and all fittings and valves;
• You are transporting a very pure and clean fluid; therefore your friction factor is accurately known and will remain basically a constant throughout the life of the pipe because the fluid in an inert gas that produces no oxides or internal roughness.
• You know all the properties of the gas and you also know that the flow will be essentially isothermal.
• You know the supply pressure and you should also know the required pressure at the end of the piping run.

You set up the fluid flow equations on a spread sheet to calculate the pipe diameter required to achieve the maximum allowable pressure drop that you can tolerate. Because the gas is inert and clean, you can tolerate a reasonably higher-than-usual velocity (10 to 15 ft/sec). The item that sets the required diameter is the max. allowable pressure drop. With the calculated diameter, you check to see if you are within a reasonable, acceptable velocity range.

[rajarani87]

hi Art Montemayor, thanks for the reply...

1) Are u telling me to take pressure drop for every length of pipe. Means first to collect data of total length, number bend, valve on line, etc., all that data then start the pressure drop calculation???
2) How to do it for whole plant as we are having lot of tapping of n2 to reactor or vac catch pots?? Because it is tidious to make a layout drawing of N2 network. As we don't have isometric drawing of the N2 piping
3) DoYou have some examples for pressure drop calculations??

Regards,
VVV

Edited by rajarani87, 20 June 2012 - 06:27 AM.