Tie-in to a Cement Lined Piping System

[uaepiping]

The problem:
Tie-in new 6" cement lined piping to a) 20" cement lined header b) 10" Cement lined header.
Contractor's proposal:
A) With 20":
Existing 20" pipe shall but cut. Cement will be cleared by chisels up to at least 20mm from the edge of the cut. A new pipe (100mm) plus flange (already welded and cement lined except for the last 20mm) shall be welded as pipe on pipe. The cement lining shall be repaired by reaching from 6" flanged outlet.
B) With 10":
Existing line shall be cut to weld a new spool. New spool shall have tee (10"x6") and flange (already cement lined except last few mms on reducing tee). There is valve on existing 10" line nearby. The line shall be out of operation so the valve shall be removed and a cement applicator will apply cement on the welded joint (at tie-in) to repair the cement.
The opposing idea:
There is an other opposite idea that for both above cases, the existing line to be cut and flanges to be welded to both ends of existing 20" and 10" Pipe. Make flanged spool with 20" & 10" pipe, 6" outlet and flange. Cement line this spool and bring to make flanged tie-in. Hence no need of site repair of cement. No fear of the future corrosion due to bad workmanship of the cement repair.
Question to Forum:
Whose opinion is correct, the contractor's or the other opposing idea?
Your valuable help is appreciated!

 

[Dhurjati Sen]

Dear uaepiping,

Guess the service is water. Both ideas are okay, both work fine, only the opposing idea is more expensive than the one put forward by the contractor.

If the owner has enough money to spend, then go for the opposing idea, else the contractor's idea would work fine as it has worked almost everywhere in the world.

Regards.

DHURJATI SEN

 

[uaepiping]

Thanks Mr. Sen,
But no international standard supports the contractor's proposal.
Correct me if I am wrong!

 

[bimr]

AWWA Manual M11 states for field welds of lined and coated steel pipe a short length of pipe must be left bare (linings and coatings must be held back). In addition, AWWA Manual M11 states for specifically pipes smaller than 24 in. (600mm) the linings should be filled/repaired from the outside, using handholes.

 

[Dhurjati Sen]

Dear uaepiping,

Check AWWA C205-95 Sec 4.6 Field Joints.

Cheers.


DHURJATI SEN

 

[mk3223]

IMO, in addition to the project cost, the system down time may be also the factor to be considered for deciding the final proposal of the piping change.
While both options are doable, here are potential issues as follows:

A. if adding the branch, be cautious when cut off the pipe coupon and the cement lining inside the header, so to facilitate the cement lining repair on the gap between the header and the branch.

B. if replacing the section of the header with the flanged spool, be aware of the thermal expansion of the pipe, especially the 20" header, as the room temperature may be different at time of the day when cutting and installing the pipe.

 

[uaepiping]

Shell DEP for Cement lining is at inactive status now.