Natural Gas Distribution Pipeline Pressures

[walderr]

Hi,

Does anyone have any information on the natural gas distribution pressures before letdown in various countries? I'm led to believe that it varies from country to country and I'm particularly interested in any data for Europe/North America. This isn't my field and I know very little about it, so any advice will be appreciated! Thanks,

Richard

 

[ICman]

It varies from house to house.

My company considers pressures over 100 PSIG as transmission, for the most part. Less than 100 PSIG is "Distribution", though we have some "High-Pressure Distribution" lines running around 300 PSIG. Our city gates might be set at 60 PSIG, then downstream regulators will be between that and a few Ounces, but there are lots of exceptions.

The user demand (number of users, required flow and pressure, etc.) determines the upstream pressure, as well as the line size, maximum allowable pressure, quality of gas, etc, etc.

Why do you want to know?

. . . Steve

 

[walderr]

Thanks Steve. I think when I said 'distribution', I should have really used 'transmission' - maybe that will make it easier to answer. I'm at the initial stages of exploring the possibility of marketing some of my company's equipment in pressure letdown applications. We already manufacture similar machinery for use in other industries, but I'd like to look into using it for gas letdown at industrial sites or other large scale users where they may require gas at slightly higher pressure than domestic users. Hence I need to know what upstream pressure ranges are likely so that I can either completely discount the possibility or continue to explore further.

The only figures I've come across say that transmission is generally between 500-1,200psig. If, as you say, it is generally much lower (100-300psig) then it obviously makes quite a difference to my calculations! Would you say the figures you gave are pretty standard worldwide then? Thanks!

 

[ICman]

Gas transmission is my primary area. You're figures pretty much match ours at 500 to 1200 PSIG, with an average somewhere around 700-800 PSIG(?). We have storage capabilities, with pressures approaching 4000 PSIG (most are much lower). Line sizes range from 2" to 36".

We (used to) supply gas for power generation. Typically, pipeline (transmission) pressure would be around 1000 PSIG, dropping it to 100-150 PSIG before entering the plant. Gas travels thru three regulators, taking a "double-cut", with some redundancy.

Pressure is limited by relief valves, or more commonly, monitor regulators in the line. The primary suppliers that we use are Mooney (Dresser) and Fisher. (BTW, a "monitor regulator" is a standard self-contained, pilot-operated regulator designed to take over pressure control should the downstream regulator fail.) We use lots of self-contained regulators and somewhat fewer control valves (typically "V-Ball" style). Our control valves operate on 6-30 PSIG (other industries standardize on 3-15 PSIG) and we add a control panel to make the valve fail in its last position.

If you're trying to get into the natural gas industry, it would probably be best to attend one of the "Gas Courses", such as the International School of Hydrocarbon Measurement in Oklahoma City (Spring) or the American School of Gas Measurement Technology in Houston (Fall).

Most of my career was spent in the process industries, including chemical, food, pharmaceutical, and refining. After concentrating in the gas pipeline industry for the last two years, I found it is a lot more unique than I originally thought. Most users are very particular on what equipment they use, and do not seem to tolerate "newbies" well. Other industries (and perhaps non-U.S.) are more willing to try new things.

Cost is a major factor, since many transmission companies get paid just for moving the gas, not selling it. Equipment must work with natural gas (with possibly some trace H2S, moisture, condensates, and mercaptans), as air is not always (usually) available. I suggest your company do its homework and look at providing either complete solutions or sub-contracting to a company that does.

 

[walderr]

Thanks very much for the advice, I'll pass it on to my colleagues in the States (I'm based in the UK). It's likely that we'd be concentrating more on Europe than the US market anyway, which may be helpful judging by what you've said. I was a bit concerned by the fact that many potential customers would expect complete solutions, as you say, and I think this could eventually be a sticking point but we'll see how it goes. Thanks again.