minimum slopes for water transmission lines
minimum slopes for water transmission lines
(OP)
What is the minimum acceptable slopes for large water transmission lines(dia. 60 inch),can we use 1 per thousand ?
Is there any standard which give the minimum slope?
Is there any standard which give the minimum slope?





RE: minimum slopes for water transmission lines
RE: minimum slopes for water transmission lines
RE: minimum slopes for water transmission lines
A number of Air valve manufactures give recommendations
RE: minimum slopes for water transmission lines
RE: minimum slopes for water transmission lines
Why is a critical gradient for air travel necessary?
Remember: The Chinese ideogram for “crisis” is comprised of the characters for “danger” and “opportunity.”
-Steve
RE: minimum slopes for water transmission lines
RE: minimum slopes for water transmission lines
RE: minimum slopes for water transmission lines
On the other hand, I have also heard that once water pipelines are placed in service, there may also be some significant abilities of ensuing flow, at least under some conditions, to "scavenge" at least some quantities of accumulated air from some high points, so same does not cause any practical problem even if there is no air valve (or air valve "working") there.
I think there have been a few technical papers written on air effects and removal from pipelines, including some from folks who market air valves; however, I have also heard that some air valves can malfunction and/or be concerns as future contamination points.
I guess exactly where all these lines should be drawn so to speak, with all issues considered, is the province of responsible engineers.
RE: minimum slopes for water transmission lines
RE: minimum slopes for water transmission lines
I noticed in "Section 9. Information from practical experience, Section 9.2 Pipeline Profile" on pg 67 of the literature research, that slight "minimum slopes" (to and from air valves etc.) similar to what others have provided in response to this inquiry are mentioned in this paragraph, but the paragraph also ends with the statement, "Some designers however are using flatter slopes in some cases and avoiding the requirement for installation of air valves, particularly in areas where maintenance and access are difficult."
I assume this requires some knowledge and/or experience of the designer with the specific conditions involved with that application condition that allow this to be done (in other words it appears they assume/know the air may be acceptably moved, with all parameters considered, along the pipeline in at least in these instances.)
This issue appears to be a very complicated subject with many available references, and I will add one I have seen but didn't happen to notice on the Wallingford list that also may be of interest to some -- "Air Binding in Pipelines", by Mr. Richard T. Richards published in the June 1962 AWWA Journal). Air is of course in most pipelines for many reasons and can have many effects (some of which can be deleterious in at least some circumstances when they occur, as explained in many references on the subject).
RE: minimum slopes for water transmission lines
I assume the latter requires some knowledge and/or experience of the designer with the specific conditions involved with those pipeline application conditions that allow this to be done (in other words it appears they assume/know the air may be acceptably moved, with all parameters considered, along the pipeline in at least in these instances?)
This appears to be a potentially very complicated subject (depending on the actual pipeline conditions) and with many available references, and I will add one more reference I am aware of but didn't happen to see on the Wallingford list that also may be of interest to some (as it discusses a great many different types of pipelines and air removal scenarios/methods, at least that were known at the time) -- "Air Binding in Pipelines" (by Mr. Richard T. Richards and I think published in the June 1962 AWWA Journal).
RE: minimum slopes for water transmission lines
Always placed air releases/hydrants at the high points. NEVER had a line fail a pressure test.
Sure, you might spend the first 30 minutes actually pushing the air out of the line, but after that, they all held the required pressure and time durations.
Minimum gradient = debunked
RE: minimum slopes for water transmission lines
I have never worked in the US but I have worked in many other countries of the world and standard good practice is to lay water transmission pipelines to a minimum gradient. Yes you can place air valves/hydrants at close spacing and keep flushing through to remove the air but is that a good substitute for proper design ?.
With a 50 mile long 60 inch pipe you will spend a lot more than 30 minutes and use an awful lot of water trying to purge the air. I recently commissioned a 800 km long 4.0m diameter transmission pipeline and we would not have got very far if we had not designed to a minimum gradient.
As a designer you have to decide when it is appropriate and when it is not necessary to design to a minimum gradient.
Minimum gradient = debunked=Professional indemnity insurance =debunked
RE: minimum slopes for water transmission lines
RE: minimum slopes for water transmission lines
RE: minimum slopes for water transmission lines
RE: minimum slopes for water transmission lines
We recently designed 150 km of 1.2 m diameter transmission line in Kuwait. The maximum difference in ground level over the length of the pipeline was less than 8.0m. There were practically no service crossings along the length. We adopted a minimum slope and prepared a typical saw tooth profile. Granted that this is more expensive than designing a flat pipeline but I am sure a flat pipeline would have provided the Client with persistent problems. Air in pipelines can have serious consequences in respect to surge as well as difficulties in testing. I have never seen a hydrant on a transmission pipeline.
Air valves should be provided at changes in slope where the slope changes from less steep to steeper than the hydraulic gradient.
RE: minimum slopes for water transmission lines
Manual M51, "Air-Release, Air/Vacuum, and Combination Air Valves"- Selection, installation, and maintenance of air valves in potable water systems.
From www.awwa.org.
RE: minimum slopes for water transmission lines
Do other product pipelines have minimum slopes?