Nitrogen Delivery

http://www.engineeringtoolbox.com/air-flow-compressed-air-pipe-line-d_1280.html

http://www.chemicalprocessing.com/articles/2005/12.html?page=2

The British Compressed Air Society suggests that a velocity of 20 fps or less prevents carrying moisture and debris past drain legs and into controls. A velocity greater than 30 fps is sufficient to transport any water and debris in the air stream. Thus, the recommended design pipeline velocity for interconnecting piping and main headers is 20 fps or less, and never to exceed 30 fps. Field testing reveals that, under these conditions, air stream turbulence is generally negligible. Line drops, feed lines or branch lines less than 50 ft. long work well at a velocity of 30 fps, but velocity here should not exceed 50 fps.

The equipment manufacturer's instructions will give indication as to the size of pipe needed to connect to it. For example, if the inlet connection were 6"/150mm, then the inlet pipework should also be this figure. Introducing a length of 1"/25mm pipe will seriously affect the flowrate into the machine. If 1"/25mm were the size of the supply, one solution might be to install an intermediate reservoir of some size, and connect the machine to the reservoir using the larger diameter, as it is unlikely that 150m³/h will be needed for the full duration of the machine's cycle.

First, though, one might want to check for a missing decimal point: 150m³/h and not 15.0m³/h, for example?

PW Slack,

Thank you for the reply. Your reservoir idea is a good one. I have already installed a receiver downstream of the main storage tank specifically for this purpose.

The readings off the flowmeter have been checked so they are correct. Your theory on the connection points is correct. The main inlet into the machine from the receiver is 2". However, from the main storage tank to the receiver is 1", as stated in my previous post.

I am concerned whether this 1" feed is causing a bottleneck. It looks like the supply from the storage tank cannot keep up with the demand from the machine. I need to rule out the possibility of the pipe being too small as there are other factors involved.

Farnsy

<...whether this 1" feed is causing a bottleneck...>

If the velocity in the pipe is 80-odd m/s, then almost certainly!

Are there any pressure gauges on each end of it?

You do not give the initial pressure of the nitrogen. This will govern whether your pipe is big enough or not. Try this simple calculator (also suggested by another poster).

If you plug in conservative figures of say 200 meters equivalent pipe and pipe bore of 20 mm then in order to get 5 bar at the machine you would need an initial N2 pressure of around 9 bar.

This velocity, though high, is not unheard of for nitrogen supply (dry clean gas). Though for most gases in the process industry we would not go above 40 m/s mainly for "vibration/flow turbulence" reasons.

I would say no... the delivery pipe is not too small: we supply oxygen gas to a smelter plant about 800 m distance their requirement is 4300 prox m3 / hr @ min pressure of 11 bar ... we have a 6 Inch pipe ...

Thank you for your constructive responses. There is a pressure gauge on the receiver. This reads the same pressure which is on the main Nitrogen storage tank - 9 bar.

They read the same pressure on a permanent basis which leads me to believe there is little or no pressure drop in the system.

The receiver is rated @ 10 bar. However, when the machine is running the pressure drops down to just over 5 bar. The machine is demanding so much Nitrogen that the receiver does not increase in pressure. Which has led me to my conclusion that the supply into the receiver from the main storage tank is where the problem lies.

Thanks again.

Farnsy

dear Gentlemen / Ladies

velocity and pressure are inversely proportional to each other.if you throttle the supply valve pressure will come as per requirement but flow will increase.if you reduced the pipe size to 1/4'' dia in respect to 25 mm NB.then your flow and pressure can maintained.

thanks

rcmandal(india)