Rubber lining of Anion / Cation Vessels

[ashfaqanwer]

From past few years there are frequent failures being observed in the
Rubber Lining of Anion /Cation vessels (Demineralizing Units) which include
Disbonded Lining, Blisters, cracking etc. Can some one share his experience
about the same? Is there any alternative to this Rubber lining?

[Nabeel Ahmed Qureshi]

Ashfaq,
Generally, Rubber lining is practiced as corrosion protection system for these vessels but unfortunately in our country we face serious material quality & workmanship issues which result in early failures. However, since living with it we explored an alternative for Rubber lining which are POLYMERIC Coatings. These are simple paint type coatings applied in vessels inplace of rubber lining. The sensitive part of this alternative coating is surface preperation & inspection. Following steps are involved.
1)- Grit blasting the surface to near white metal (SA-2.5)
2)- Inspection of the blasted surface.
3)- Filling of deeply pitted surfaces with the polymeric product & allow to dry.
4)- Ist coat of Polymeric Coating application on the metallic surface with roller type brush.
5)- 2nd coat before complete dry up of the 1st coat (to develop bonding b/w 2 coats)
6)- Leave for dry out
7)- Inspection of applied & dried coating with Sponge holiday detector.
8)- Repair of the leftover areas.
The above polymeric coatings are supplied by "Belzona" & are very easy to apply. Thickness of the applied coating is determined by the service (temperature,pressure) conditions.
These coatings as per our experience give a life of approximately 5+ years.
Hope this would help.

Regards
NAQ

[ashfaqanwer]

Is there any limitations that where we can use these POLYMERIC coatings?
It would be good if you share any reading material on the same.

[yahoo]

Dear Ashfaq,

Be it rubber lining or Polymeric coating, each has its fate as disbonding. best solution is SS lining with 4mm sheet. Also no maintenance problems. That's my experience . Am not a manufacturer. And I can bet its the best for your remote plant.

[ashfaqanwer]

Dear Yahoo,
I appreciate your value addition.
SS lining is no doubt the best way to go but I am concerned with the cost involved in SS lining.

[arcpro]

Ashfaq,
It depends on the number of failures you see in a certain period of time. Normally, SS justifies its cost as an internal lining.
Decision is yours.

[Nabeel Ahmed Qureshi]

Dear All,

We also faced rubber disbondment /complete failures in these vessels at our site. No doubt, SS lining is the best solution but involves a huge cost. After doing comparison we went for Polymeric coating. Before implementing polymeric coatings, we also visited few power plants which were having these coatings in similar vessels from last 5 years with out complaints. I guess this justifies the success of Polymeric coating with much much low cost numbers as compared to SS lining.
The only thing which is most important for long life of these coatings is proper "Surface Preperation".

[Nabeel Ahmed Qureshi]

Ashfaq,

There is a wide variety of coatings available.You can select the desired one by specifying your temperature, pressure & service conditions. The vendor also suggests coatings based on your requirements.
Regards
NAQ