Standard Size Nitrogen Purge Connection

you need to purge fast enough that you can get plug flow. I suggest you speak to some tanker people, they will tell you what pipes they use and what you need to connect to.

Logically, the connection needs to be the same size as the tanker pipe, ideally.

• If it is smaller, then it will restrict the flow.
• If it is the same size then the tanker pipe will restrict the flow, which is unavoidable, and therefore acceptable.
• If it is larger then the tanker pipe will still restrict the flow, and a smaller one could have been used instead.

Hi Muke,

Welcome and enjoy this site, it is great!

Can you tell me why you are purging and what the pipe being purged usually has in it, and the diameter of the pipe please?

Can you also say if you are purging a gaseous substance or a semi-solid?

Are you doing a pressure test?

Are you going to use road going tankers to purge? Or will it be a larger vessel such as a ship that delivers the Nitrogen?

Take care

Hi

This line is Gas injection line(To injection Well), having Sour Gas. After depressurization of line from 488 barg to 2-3 bar g. AFor any maintainance purpose operation team has to purge line with Nitrogen, its not a testing its the part of shutdown and maintanance. Line size is 6" (3.2 Km). Some part is undergound(Off plot) small portion is onplot. In Design review we got action to choose standard purge connection and time require to purge the line.

For natural gas.

2" Thread-O-ring (Purge and equalization fitting rated at 3600psi) manufacturer is T.D.Williamson, use with a TDW tapping machine and valve for a No-blow environment. use multiple fittings if required. Always use a purge stack (pipe threaded into valve) and follow proper grounding procedures. use a verification instrument to determine completion of purge.

verify all components used are designed for the use and pressure of the application.

Metallurgical and mechanical properties (welding), SMYS, MAOP, MOP, Temperature and/or chemical compatibility of gaskets, o-rings, lubricants, oil's etc...

Hi Guest,

Good suggestions here!

But I would have thought the pipe should have a purge connection between each stop-cock rather than an afterthought? Plan for what is known will have to be completed and all goes smoothly.

Take care

It all depends on the size and length of pipe you need to purge. If the pipe is 3/4" then a 3/4" connection would work. If the pipe is 2" then the 3/4" fitting will restrict the flow and the time it takes to purge. There is no standard size since each application is different. Size your purge connection to the same size as you pipe. Take into account the pipe volume and make sure your purge connection can handle the pressure that will be generated during the purge process.

Bear in mind the pressure differential. If you bring in a 3/4" pipe at 2000 PSI it can expand to purge a lot of pipe at 15 PSI.

Usually nitrogen purges are a little above 15 PSI, unless they are also a pressure test.

Jamesw,

If pipeline size is 6" then purge connection shall be 6" only? I think this is not conservative and practical.

It all depends on multiple factors. How long is the pipe, pipe diameter, any time constrants etc. If you have a 6" diameter pipe the is 100' long on you have no time issues then you can use what ever connector you might have available. I have used 1" connectors to purge vessels the size of a two story house. Since it din't matter how long this took the 1" connector I had worked just fine. There have also been times where the time I had available to purge was limited. In those cases I got the biggest connector I could get. 20+ years of pressure/vacuum testing has taught me that the fastest way to purge something is to go as big as practial. If time is not an issue then it really doesn't matter what the size of the connector is. There are calculations that can be used based on volume of the pipe, flow rate of the connector, and desired time where you can calculate the right size fitting to use to purge or fill a vessel.

Hi jamesw,

I fully agree with what you say.

I have not seen any 6" input/output 'nipple', but an inch or two is usual, (25/50 mm).

As has been said and as I hinted in an earlier post the pipe size, and time restraints and the availability of any specific pressured supply to purge the required pipe also comes into the equation.

Really depends how long the 6" (15 cm) pipe is. Is there any breaks or stop cocks in the pipe that can be utililised to cut the amount of purging necessary?

In which case the purged length may be just a few feet or metres?

Take care