Pump Station Steel Piping Header - interior corrosion concerns 1

[jimdean]

We are currently working on rehabilitation of a wastewater pumping station by placing 30 years olds pumps and other upgrades. Existing 24" steel piping header, also 30 years old, has a current wall thickness of over 1/2". We would prefer to leave the header and not replace it due to operation shutdown timeframes and overall additional costs but not sure if it would last another 20-30 years if not replaced. We are not sure if the original steel header had any interior lining or just bare steel. Anyone familiar with this or have any recommendation or information on this issue - THANKS!!

Jim

 

[bimr]

You have not given a lot of information to go on. No corrosion info, no water data, no piping design pressure, no operating pressure, etc.

Why don't you just compare the as installed pipe thickness to the existing pipe thickness?

 

[jimdean]

Sorry, the wastewater is typical residential wastewater at 60 degrees with a maximum operating pressure of 40 psi and velocity of 6 ft/sec. We do not have any original pipe design or pipe information. Were older steel piping interior coated as I,m not sure a comparison would work if coating is gone? Please reply. Thanks!

 

[BigInch]

If the coating is gone, I'd say ..... you'll PROBABLY need to replace the header.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[jimdean]

I do not know if there was a interior coating previously installed on the piping. I have talked with several contractors noting the old steel piping was not interiorly coated. I want to confirm with the engineering community along with any other suggestions. Thanks

 

[rconner]

[I also posted this reply on the Corrosion forum where I saw you had also posted this inquiry].

It seems near incredulous to me that a water/wastewater header with steel pipe was installed on or about 1976 with no lining whatsoever (do you by any chance have any way to drain and are there any hatches, blind flanges, air releases, spools etc. that could be quickly removed in a short dowen period to sneak a peek at the interior conditions?); however/regardless, if you have confirmed a consistent steel thickness of 1/2" now in this 24" steel piping after 30 years of service, I'm not sure (even if this is bare piping) that I can come up with a persuasive reason you would not be able to get a few more good years out of same in your rather low pressure/40 psi service!
I believe it has however been some common to line water and domestic wastewater pipes that flow full (and non-acid-producing etc.), for internal corrosion protection and maintenance of flow properties, with cement mortar. It is my understanding this can even be done to steel and other piping in place, e.g. in accordance with ANSI/AWWA standard C602,CEMENT–MORTAR LINING OF WATER PIPELINES IN PLACE— 4 IN. (100 mm) AND LARGER, although I am not sure how practical such operations might be for your operational/waste water header configuration/situation. If you are interested in this you might do a search for experienced in-situ lining contractors in your area, that might help with further evaluation/remediation of any problems.

 

[jimdean]

Thank you rconnor for your post. A great idea to try and visually inspect for any existing lining, my operations may not think though - I will suggest it. I agree with you that the future life of this could be quite long and may be worth it as it will provide an estimate $200k savings on the project.

 

[BigInch]

Can coating and condition be ultrasonically examined?

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[SlideRuleEra]

jimdean - I won't offer advice on what to do, since others have given quality information. However I can suggest one way to help "sell" your management the idea of keeping the existing header.

Consider the question "What wall thickness would you use as a replacement 24" pipe header?"

The "Standard" wall thickness of 24" pipe is 0.375 inches (Schedule 20), even "Extra Heavy" has a wall thickness of 0.500 inches. Since the existing pipe has a 0.5 inch wall thickness, then replacement with much heavier (Schedule 40, or greater) pipe would be required to make any sense. In light of the low pressure, etc. using a pipe with that much "safety factor" seems, IMHO, to be unwarranted - and this is even if a corrosion factor is included.

A couple of pages for references for my "numbers"

http://www.steeltubeinstitute.org/pipe.htm

and

http://www.interpipe.com/Pipe_Dimensions_and_Weights.htm

http://www.SlideRuleEra.net

 

[cvg]

I have designed steel pipe waterlines for both underground and aboveground pump station headers which have been in service for 20 years and they were constructed with cement mortar lined and coated steel pipe (CMLC). These were designed for normal operating pressures of 120 psi. I guess it may depend upon what part of the world your project is in as local customs on typical pipe design may be different.

 

[dicksewerrat]

How long can you shut down the header? How long is the header? Would a Cured in place liner (non-structural) be an option?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[jimdean]

We can shutdown for days but get risky if forecast weather changes. Pumping rate is around 14 MGD. Header is around 50 feet with 4 pump connections. Cured in place liner not an option as it has a couple 90 bends with limited access. Thanks for your post.

 

[bimr]

jimdean:

"We do not have any original pipe design or pipe information."

Most piping that I have seen is marked in some manner. You might want to closely examine the piping. Surely, you must have the original design data as well.

Once you have determined what type of pipe that you actually have, compare the thickness of the original pipe to the corrosion over the the 30 years. That should provide you with an answer.

 

[dicksewerrat]

Is this all welded pipe or flanged joints? If flanged, replace it if you are worried about it. Look at pressure rated HDPE

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[jimdean]

Thank you all for your input. While we believe that the existing welded steel piping may last another 20-30 years we have decided to go with new D.I.P. that should last 40-50 years. Thanks again!