Gas piping

Jason_13

When sizing gas piping for a residence would I use the .3 or .5 pressure drop table? Which one and why?

Thanks

Alan R. Mercurio_3

Re:Gas piping

If you contact your local gas utility they can tell you what their drop is for your area.

lchmb

gas type

Is it natural gas or LP?

heatboy

It Depends......

In my area I always use .5" as my number because we have lots of old lines where the utility may only promise 4.5" at the gas valve.  But, if you are in an area where you're sure you can get 7" consistently, why not size for 1" or even 1.5" of drop.  Much smaller piping in some cases.  That's why the IFGC has multiple drops listed in the tables.

Tim McElwain

As Alan stated

your local gas utility will give you what they recommend. In my area it is .3 which will typically get you sized correctly just in some cases a little over sized.



I run a minimum 1" gas line to all heating equipment. Most of the time that is safe for most sized residences. For rooftop equipment minimum 1 1/4" to prevent freeze ups of the gas line. To outdoor pool heaters minimum 1 1/4" also.



No 3/8" piping on any thing natural gas. All drop legs to heating equipment minimum 3/4".

Henry

Gas code

Don't any of you guys ever read your National Gas Code? NFPA54 shows you HOW to calculate your pipe sizing and the handbook has examples with a few tables. Here in Canada, we have included tables for both natural gas and propane. Natural gas tables are from 7 inch water to 20 psi. How can you haphazardly say to use 1 or 1 1/4 inch pipe size for rooftops? What is the total developed lenght? What pressure?



BTW, here in the Great White North, we even use 3/4 inch (depending on pressure and recommended pipe sizing according to the gas code)  piping on roofs with no risk of freezing! No drop legs are permitted outside as they can freeze and break.

Mark Eatherton

Question regarding freezing gas lines...

In all of my years, I have never seen ONE fuel line freeze up.



I have also checked many drip legs, and the only fluid I've ever found in the drip leg is cutting oil.



I realize that the moisture content of gas has to vary by location, but here in the Rocky Mountains, I have never had a freeze up and have never found anything in a drip leg that could possibly freeze solid.



Is this really an issue with anyone else?



Curious minds are wandering :-)



ME

Jean-David Beyer

Freezing gas lines.

I know that air compressors, that may develop pressures up to about 150 psi, tend to have drain valves do let the water out of the tanik. I know railroad locomotives run air pressure up to about 135 psi for the brakes. Their air tanks have automatic drain valves to let the water out every few minutes.



I once was just outside the 12 foot high chain link fence here in New Jersey where a very high pressure gas line went through a pressure regulator like the one on the side of my house, but the diaphragm part of it was over 4 feet in diameter and the gas going through the needle valve was just plain screaming. I would guess the pipes were 8 to 12 inches in diameter. If there was any pressure drop through that valve, and I am sure it was considerable, it would freeze any water immediately. They did not seem to have a heater on it. So my guess is that gas transmission companies go to great lengths to keep it dry.

Tim McElwain

Henry read the posting

I know we Americans are way behind you Canadians as far as code goes but my statements about pipe size stated "minimum" pipe size, this was local code when I was setting rules here in RI for MINIMUM PIPE SIZES. I would hope it would be obvious that in order to get the correct pressure to an appliance the pipe has to be sized correctly. But then again who knows.



As for 1" minimum to inside appliances if you do the calculations most inside equipment 60 to 75 feet from the meter 1" pipe will be more than adequate up to almost 250,000 BTU's. Most runs are much less than that on 90% of the homes here in New England. It just made it easier to carry only 1" pipe when doing residential installs. Granted many times 1" would be over-sized that was not a problem for the gas utility I worked for as we had the authority of an AHJ in those days.



As for gas lines freezing I would hate to start counting all the freeze ups on gas lines I have had to go out and clear back in the day. Here was the typical problem Gas came through the ground and entered a building then went through the gas meter and then back outside again. This change in temperature would cause condensate in the gas line that upon elbowing at the roof top would freeze. Solution was an 18" long drip leg filled with methanol to mix with the gas as it transitioned to the roof top, that along with the MINIMUM 1 1/4" LINE would keep it from freezing.I would venture to say that most of you are dealing with gas mains and services that are pounds pressure (high pressure lines). The low pressure inner city lines at a 1/2 pound pressure or less are much more susceptible to freezing.



If all the piping is outside there is much less chance of freezing.



I have had many issues with LP with moisture that is why in the winter time they use methanol mixed with the LP.

Henry

Freezing

Most of our industrial building have gas that comes in and then is metered at each tenant's address. The meter supplies gas for the tenant's heating in the warehouse or workshop and also a make-up  on the roof for office space. Depending on the capacity of the make-up, most of the piping is 7 inch water or if a large make-up 1/2 pound. We try to make the mains in 2 PSI as it gives us the freedom to use vent-less regulators (indoors ONLY). Over 35 years of working in the gas industry, has shown more than one drip pocket before a make-up that has cracked. That is why we banned them in B149.



BTW, I still find it amazing that most of the posters on this site do NOT use a gas code whether local or national. Professional installers asking why they should have a liner or what size vent while this in NFPA54 and they should know. A licensed installer is not a license to take money. It is to certify that the installer is certified to work on gas appliances and related piping and venting while knowledgeable of the code requirements.

Sorry about the rant,but I just saw two more installs that don't meet code and have to be redone at considerable cost. One is a a 750,000 BTU atmospheric boiler venting into a 30x30 inch brick chimney with a 40,000 gas HWT connected underneath. Does it work, somewhat but not during spring summer or fall!

One more, I just came back from the Cuban Consulate. It got flooded by a 30 inch water main breakage just in front of it. Nice people, gave me 3 Cohiba Splendido too make sure that I gave them the quote this afternoon. It seems that the palace in Havana is quite large. It takes a lot of time for someone to walk from one side to the other side to get authorisation for repairs........sometimes weeks.....

bob_46

Pressure drop

Henry, on what page in the National Fuel Gas Code do they tell you what pressure drop to design for? I can't find it. Thnx, bob

Alan R. Mercurio_3

Gas Piping

Henry,

I do follow NFPA 54, 58, 211 and 31 (31 as it pertains to oil) I also follow 54 at the door and 58 at the gate! I’ll expand on this comment once I’m back in my office.

Alan R. Mercurio_3

Gas Piping

Ok Henry, Now that I’m in my office I can tell you exactly what we use as a guide here in NYS I could not remember last night as with age goes the memory





We have been taught to follow the 2006 edition of the National Fuel Gas Code Handbook

Henry

NFPA54

There is a new version of the National Fuel Code, 2009. There are number of important changes. We are now working on our revised B149 hopefully for 2013.

 PM me with your email address. I will email you a neat Excel spreadsheet to calculate pipe sizing from 1 PSI and up. You plug in the distance and initial pressure. It gives you the capacity for piping from 1/2 inch to 10 inch. I will also include our pipe capacity charts for lower pressures. You won't need a calculator to find your sizing requirements!

I can scan the pipe capacity charts for lower pressures. I am not sure how I can post a PDF file here on the forum.

Alan R. Mercurio_3

Thanks!

Henry, That would be awesome thanks for offering to share that with me. It sounds like something that will make my job easier. If you send me the pdf I'd be happy to upload it to the forum, for you.

you can send e-mails to mercurio@koscocomfort.com

Thanks again!

Tim McElwain

Henry perhaps to help

you understand code is addressed differently here in the US than in Canada. We do not really have a "national code". NFPA 54/ANSIZ223.1 is called National Fuel Gas Code but is really the National Fire Protection Association Code out of Quincy, Mass. Example here in Rhode Island we use the International Fuel Gas Code. Other parts of the USA use other codes. They are all somewhat similar so in the area of pipe sizing for example they are much the same. The codes themselves actually state that other acceptable engineering practices for piping may be followed if acceptable to the Local Authority Having jurisdiction. Some state do not implement the new codes immediately but actually have there own code officials go over the coed first.



Massachusetts for example has CMR 248 which is its own state code, they use NFPA 54 as a base but have not yet caught up with the 2009 code for NFPA 54 or 2011 NFPA 58.



So as you see it is somewhat complicated as compared to Canada, perhaps has to do with our form of government.



As for the original question about allowable loss that is an excellent question from a piping contractor because in most areas here in the USA it is determined by the local gas company. The smaller .3 will always allow for larger piping and as the allowable goes up for smaller piping systems. A lot of it has to do with the pressure delivered to the dwelling.



Hope all this helps to clear up some concerns. I also have pipe sizing calculations which make sizing very simple along with charts and tables I have developed for determining air for combustion, louver sizing etc,.I hesitate to make these available without a classroom education as to how to use them properly. They are however in some of my manuals I sell.



While we are discussing this pipe freezing business I would venture to say in this day and age you would have less condensables in the gas as much of what is sold today would be labeled dry gas. As for drips/sediment traps we have a lot of very old piping here in the northeastern part of the US and still need sediment raps and code still requires them. As I have pulled them from time to time I find very fine rust in them.



When I was doing some teaching down in LA and Texas the gas guys down there tell me they still get a lot of oil in the drip legs from tome to time. I guess it has to do with being close to the gas/oil fields. By the time the gas gets up north all of that has sort of accumulated in the lower 48.

Tim McElwain

Henry perhaps to help

sorry for the double post.

Charlie from wmass

Tim a certain gas company

That supplies the pioneer valley does not use drip legs and installs plugs in the tees they have. They say their gas is so clean they do not need drip legs and the myth is up held by many of the local installers of gas equipment. It really bugs me when power companies think they are above the codes.

Alan R. Mercurio_3

Henry,

Where’d you go my friend?

Henry

Busy!!

Sorry, I was putting out fires! Nice explanation Tim. As for oil in drip legs, it is usually threading oil that accumulates. You can tell by the smell and feel. Most installers do not ream or wipe the pipe! I keep catching some of our lazy fitters, every so often.

Annual CSA gas code committee meetings start May 31 in Ottawa. Just in the Propane Handling & Storage code, we have 10 dockets. It will be a long day............... I will be in Ottawa for the week of meetings.

Henry

Alan R. Mercurio_3

Excel spreadsheet

Henry, Could you please e-mail that spreadsheet you told me about. You have me all excited about it LOL

You can e-mail it to mercurio@koscocomfort.com

Thanks

icesailor

Cutting oil in pipes:

Henry,

Maybe I'm not telling you anything, but I have a way of keeping the oil out of the pipes when I am threading it.

I put a couple od 2X4's on the flat, under the back legs of my power drive. With the drive pitched forward, it keeps the oil at the end of the pipe. And if you always ream the pipe, the oil doesn't get caught up behind the ridge. It just runs out into the oil bucket.

Plumdog_2

Condensate in LP gas lines

Well, I have seen liquid in LP lines form uphill quite some elevation from the storage tanks themselves. This was at "camp" type facilities with "tank farms" and LP Evaporator equipment. I don't know if it ever froze, but I would guess not. This liquid would fill the drip leg (and anyplace the line had a "belly" and then enter the appliance gas control valve, with the end result being no heat and ruined valves.  Blowing out the entire system with compressed air would clear it for a couple years or more, but it would come back. But I never saw much of anything in Natural Gas drip legs.

As a side topic; why does the fuel selection mode on my analyser list both LP gas and Propane? I need to know. 

Henry

Spreadsheet

I sent it out a few minutes ago.

Regards,

Henry

Alan R. Mercurio_3

Thank you!

Special thanks to Henry for sharing the Excel Spreadsheet with me and to our host Dan, that makes connecting to friends and fellow professionals around the world possible!

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