Repairing damged hot-deep galvanized pipe 1

[Hwanii]

Hello!!

I'm working as a piping enginner.
For FW aboveground, galvanized pipes are installed. our procedure to install as follows

1. Cutting and welding pipes to fabricate the spools as per ISOs
2. Make them hot-dip galvanized
3. Install them in the field

When the change of the line is inevitable, we should do the same process once again.
It's wasting time because the entire spool should be re-galvanized.

Is there any way to repair the changed welding joint only in galvanizing such as painting??

 

[MikeHalloran]

When the change is inevitable, you could have a complete new spool galvanized and ready to install immediately.

Or you could make friends with a galvanizer. Some processing outfits offer "expedited service" for extra money. Does your preferred galvanizer offer that? Can you justify spending extra money to save time? Is there anything you can do to speed the process, e.g. blast cleaning the modified/recycled modified spools or doing some other prep to make the galvanizer's life easier?

So-called "cold galvanizing compound", which looks and smells and applies like paint, has been available for decades. The people who sell it swear that it's magical. My limited experience says it's not even particularly good paint, much less a substitute for hot dip galvanizing.

Suppose you go ahead and paint the last few welded joints instead of dipping them. If they fail in, say, five years instead of 25 years, does that cost more than does the time lost waiting to get the spools dipped? I.e., maybe you can turn the issue into a business decision.



Mike Halloran
Pembroke Pines, FL, USA

 

[LittleInch]

Why are you galvanising it? Are you next to or in the sea? For any minor changes, why not shot blast the new bits or the weld area and then apply a high build two pack epoxy or PU brush applied coating? There are many coatings which do a similar job as galvanising, at least for new sections. If you get a grey colour, you might not be able to spot the difference....

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[bimr]

There is no way to properly repair galvanized joints, that problem is one of the drawbacks of galvanized piping.

Consider use of Dresser couplings:

http://www.plumbingsupply.com/galvanized-compression-fittings.html

 

[TomDOT]

While I too agree that much of the "cold galv in a spray can" is crap, some is better than others. I should restart my comparison project of the stuff.

However, thermal spray zinc (metallizing) is an excellent repair method.

 

[SJones]

Might I inquire as to whether the pipe is internally galvanised, as it tends to be with firewater, and what you would plan to do with the internal surface? Australian standard AS 2312 outlines a galvanising repair procedure using zinc rich paint.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.