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Anonymous Poster #1

Carbon Steel Pipeline Internal Coating

07/10/2017 5:14 PM

Would someone tell me do they internally coat carbon steel pipelines ? (From the TV, The pipelines look like externally coated, but the pipe internal looks like not being coated and rust.)

If they do internally coated, does the coating around the welding section get burnt or damaged? How do they recoat the welding section internally?

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#1

Re: Carbon steel pipeline internal coating

07/10/2017 7:39 PM

There are all sorts of coatings for all types of applications....heat shrink wrap for field weld joints is most common....

http://www.arguslimited.com/en/pipeline_corrosion_protection

http://www.tenaris.com/en/products/onshorelinepipe/coating/internalcoating.aspx

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#2

Re: Carbon steel pipeline internal coating

07/10/2017 8:10 PM

You are assuming that the carbon steel piping joints are butt welded after coating .... this is not necessarily the only joint construction.

If the piping system is above a certain diameter, spools can be shop fabricated, internally blasted and coated, then assembled using flanged joints in the field. I believe that the minimum diameter size is 4 inches.

Most CS piping installed have an external coating also ..... which brings up another point.

CS piping systems which require both an internal and external coating, as well as additional flanges required for assembly...... end up costing about the same as an all stainless system.

Something to consider .....

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#3

Re: Carbon steel pipeline internal coating

07/11/2017 6:20 AM

Yes they do at customer request. Typically on long seam SAW 24-48" pipe the customer can request internal FBE coating or as an alternate lacquer coating but that is normally applied if the pipe is going to be in a laydown yard for a long period of time. Coating the ID of a pipe takes a different production line and is a more expensive option for the customer.

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#4

Re: Carbon Steel Pipeline Internal Coating

07/11/2017 7:49 AM

I have used these. They come in any length you need and do a very nice job of evenly coating i.d.'s of pipe, etc....

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#5
In reply to #4

Re: Carbon Steel Pipeline Internal Coating

07/11/2017 1:44 PM

How would you do a 40' long pipe section?

Our ID coating is on a center mounted 50' long arm and the pipe is spirally moved under a controlled rate to coat to API standards.

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#6

Re: Carbon Steel Pipeline Internal Coating

07/11/2017 2:04 PM

Silly man, they weld the pipe first, then coat. If the pipe is below a certain size, you may need trained rodents to enter the pipeline for inspection, installation, or repair.

OR you could coat the steel using various treatments after mill scale removal, again it depends on pipe size, what the line will carry, and whether you need a permanent or temporary coating.

If water service, sometimes epoxy linings may be installed (circulating cooling water lines for example) if personnel can get in there and sandblast the interior of pipe, remove all debris, and then coat the pipe, it is a mess, really.

Small diameter pipes may be sleeved with a polymeric lining and epoxied to the clean pipe internal diameter in some cases, only done when conditions limit replacing the pipe, and it has to be coated to prevent buried line failure. Very expensive.

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#27
In reply to #6

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 11:11 AM

Sounds like Chicago Went-A-Weasel. I ran into that outfit in the '70s. They specialized in albino weasels and midget welders. The welders had to be able to work inside a 14" pipe. The weasels were part of a cleaning protocol. They would open up two points on a pipe and run a ferret through wearing a harness and pulling a line. The line was used to pull an aircraft cable that was used with various brushes and swabs to clean the pipe. Then came the weasel. They would shampoo the weasel and put him in weasel pampers (so that he wouldn't leave any wesidue) and then run him through the pipe. When the weasel came out it was inspected under a stereo microscope and if his fur was clean, the system was certified clean.

Pipe crawling robots put them out of business.

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#7

Re: Carbon Steel Pipeline Internal Coating

07/11/2017 2:07 PM

Undefined: <...they...>.

Steel pipelines are cement-lined and joined with couplers. Why on earth would anyone want to weld (rhetorical question - NNTR)?

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#10
In reply to #7

Re: Carbon Steel Pipeline Internal Coating

07/11/2017 2:18 PM

some are, but many are not. define universal set as {U}

define some are as R{U} as the ones that are cement lined, and sub-set R{U}, as the group that are not cement lined.

Clearly, {U} = R{U} - R{U}

The real question: is U is, or is U ain't my constituents?

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#8

Re: Carbon Steel Pipeline Internal Coating

07/11/2017 2:10 PM

Rubber-lined pipework is bolted together at flanges using an intervening joint, usually of PTFE. Why would anyone want to weld (rhetorical question - NNTR)?

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#9

Re: Carbon Steel Pipeline Internal Coating

07/11/2017 2:12 PM

Why not use other piping materials, such as PE, PVC, ABS, PVDF or glass fibre instead (rhetorical question - NNTR)? These can all be welded.

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#11

Re: Carbon Steel Pipeline Internal Coating

07/11/2017 2:22 PM

Weld-fabricated steel anything can be galvanised after welding. Galvanised piping has a zinc coating on the inside. Do not weld after galvanising!

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#12

Re: Carbon Steel Pipeline Internal Coating

07/11/2017 4:21 PM

Really, without information as to the purpose of the pipeline (fluid being transported), there is no telling what might be on the inside of the pipe as laid.

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#13

Re: Carbon Steel Pipeline Internal Coating

07/11/2017 4:33 PM

Thank you for all the answers. Yet my question is understood. I am asking how does the internal coating stand the heat or temperature of welding ? At the joint welding of a pipeline, you still would have a section (ring) do not get coated (due to welding. The metal melt in the joint, 1000+ deg C.).

My question is how this welded ring section being coated internally (if they do)? There are tens of 20', 40' length pipe strings being welded together at the same time during a onshore pipeline construction project.

I am asking about the pipeline, like those 20", 30" diameter Keystone oil pipeline project seen on TV news. They looks green outside (coated), brown inside (more likely not coated).

I actually had worked on crude oil and refined product pipeline projects. We did not coat the pipes internally. Epoxy coating the pipes adds about 20% of the pipe cost, but ~2% of the overall project cost (I forgot the exact figures). One of the argument I got was "How do you coat the internal of the welding section?". (The external welds were grounded, polished and coated.)

I am no longer in the industry. My puzzle did not go away. So I ask again.

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#14
In reply to #13

Re: Carbon Steel Pipeline Internal Coating

07/11/2017 4:50 PM

Basically, like you suspect, anything organic that is coated on the interior wall of the pipe at the end being welded will decompose, vaporize, and also interfere with the welding protocol.

Oil and gas pipelines may not be coated prior to layment for several simple reasons:

  1. The oil/gas has been processed to nominal condition that does not readily support fast corrosion rates.
  2. Sacrificial anodes are responsibly used as legally required on all major and minor pipelines these days. Conditions of cathodic protection are monitored periodically.
  3. Any corrosive agent present may in fact passivate the metal to an acceptable extent if the pipeline is temporary, non-permanent, as long as iron oxides are stable in any anodic areas.
  4. There are interior and exterior spiders (machines) that can spin a wrap coating on these, but I have seen more of this treatment on exterior of pipelines.
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#17
In reply to #13

Re: Carbon Steel Pipeline Internal Coating

07/12/2017 3:31 AM

This is a simple materials compatibility issue that can be solved by using a materials compatibility database appropriately.

  • Welding what materials? All manner of materials can be welded and the forum is still no closer to discovering what the one(s) in question actually is/are!
  • What is the wetting fluid inside the pipe? Steel pipes containing kerosene at ambient temperature do not usually need an internal coating.
  • There must be an end client Piping Specification which defines the compatibility of a number of piping methods with the expected wetting fluid(s); does this not give answers?
  • The cost of installing the wrong pipe and putting things right vastly exceeds any cost of doing it right in the first place. So what has cost got to do with anything?

Confused of Dodman's Lane.

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#15

Re: Carbon Steel Pipeline Internal Coating

07/11/2017 10:41 PM

Many carbon steel fabrications are coated to resist corrosion; it usually depends on the service and desired life.

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#16

Re: Carbon Steel Pipeline Internal Coating

07/12/2017 1:39 AM

Most of carbon steel pipelines in nuclear and conventional power plants are not inside coated. Also, it is known from practice, that a water filled pipeline behave better for corrosion that an empty one; this is applied in district heating where during warm season the distribition pipe networks stay filled with water. It also true that the water in power plants and district heating systems is demineralized and degassed. Today, where coating is required inside of the carbon steel piping (although in most cases exists alternative like PEHD, PVC, etc.), this coating indeed is applied AFTER the pipeline is complete/welded and is done by circulation/treatment of a chemical solution for tens of hours. In nuclear power plants carbons steel pipe may be treated by depositing a protective layer of magnetite.

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#18
In reply to #16

Re: Carbon Steel Pipeline Internal Coating

07/12/2017 9:01 AM

You seem to give or have the impression that all power generation plant water is "pure". That is completely and totally false, unless perhaps any steam portion of the plant utilizes an air-cooled condenser.

Types of water found in a combined cycle power generation plant:

  1. Ultrapure HRSG makeup water.
  2. Ultrapure gas turbine injection water (some models only)
  3. RO purified water (back blended with city or raw water) for evaporative intake cooling.
  4. Softened loop water, often referred to as service cooling water, and used on any heat exchangers that operate with higher skin temperatures than the surface condenser.
  5. Open-cycle cooling water (from cooling tower) to surface condenser, and service water secondary heat exchanger(s). Very high mineral content in most cases.
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#20
In reply to #18

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 2:56 AM

Piping suggestions:

1 and 2 could be stainless steel, which does not need to be coated.

3 could be plastic, which does not need to be coated.

4 and 5 could be steel or iron, uncoated, as the water will have additives to prevent corrosion and bacteriological action.

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#26
In reply to #20

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 9:40 AM

Spot on, old chap.

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#19

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 12:44 AM

Yes. Very probably true. I'm not used with Combined Cycle Stations..

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#25
In reply to #19

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 9:40 AM

That is a good topic for you to study up on then.

By the way, one finds pretty much the same set of water in coal-fired simple cycle steam plants.

Simple cycle Brayton engine (ground-based jet engines) that are engineered for torque output rather than thrust output, generally do not have the same exact water requirements, especially the larger so-called "frame built" units over 100 MW.

Aeroderivative ones from GE do have water injection capabilities that increase output, and reduce NOx (unless configured with the later generation of dry NOx burners.).

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#21

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 4:41 AM

From the TV?????????/

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#22

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 4:52 AM

Good one. Right...."Power Stations". .. thank you.

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#23

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 5:01 AM

If you mean pipe with inner clad:

Very rarely have I encountered this situation, but it is not difficult:

1.- Prepare the bevel leaving two projections (2-3 mm) of clad in the root of both pipes

2.- Weld the two projections of clad with WPS appropriate for the type of clad

3.- VT to the clad welding, if you have access and equipment check with inner borescope

4.- Finish welding with appropriate WPS for pipe material

5.- Rt the weld

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#24

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 8:17 AM

Cement-lined pipes:

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#28
In reply to #24

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 12:58 PM

X pando

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#29

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 1:15 PM

Quite a few types of carbon steel are not coated, but are passivated after the pipeline is constructed. In some cases passivation is a chemical treatment after the pipe is fabbed, but before it is flushed and put in service. In some other cases, the fluid pumped through the line is chemically treated to passivate and maintain a passive coating on the pipe interior. One place this is typical is in sprinkler systems where the water is maintained low oxygen to force corrosion products to form a tight black oxide coating which in the long term protects the pipes. It also explains why the first water out of a sprinkler system is usually black and pretty stinky.

The Flint MI lead in the water crisis was similar in that the system used lead pipes and pH greater than 7 water to form a tight passive coating in the lead pipe. When the water source was switched, the water was not treated to maintain a high pH and the coating was stripped out of the pipes, resulting in high lead content in the water..

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#30
In reply to #29

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 1:38 PM

weasel wesidue. Sounds nasty to me.

I say use a pig and be done with it.

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#31
In reply to #30

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 1:42 PM

I thought you had to start working for a living.

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#32
In reply to #31

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 1:47 PM

Shhh...I still have 12 minutes left on lunch, as lunch did not start til noon.

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#33
In reply to #29

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 1:54 PM

You are speaking for fire protection sprinkler systems, right?

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#34
In reply to #33

Re: Carbon Steel Pipeline Internal Coating

07/13/2017 1:59 PM

Yup

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