A debate often emerges about the best material options for the internal lining of Ion Exchanger Tanks. Two schools of thought address the subject. Some people prefer the long lasting but more expensive semi-hard rubber, while others prefer the less expensive but shorter-lived vinyl ester epoxy. Neither is necessarily wrong; the correct choice simply depends upon your circumstances.
The chart below was compiled from Blair Rubber recommendations and end user history.
| 1/4” Semi-hard Rubber Lining | 20-30 mil Vinyl Ester Epoxy |
| Material & Installation Costs: | |
| “Rubber lining cost 25-50% more”. | |
| Surface Preparation | |
| NACE #1 – White metal blast cleaning is a requirement for every good lining system. The steel cleanliness is directly related to the long-term performance of the lining system. | NACE #1 – White metal blast cleaning is a requirement for every good lining system. The steel cleanliness is directly related to the long-term performance of the lining system. |
| Method of Installation | |
| Lay up of rubber sheets, hand-rolled into place. Lining is adhered to the wall with adhesives while in the uncured state. It is then steam vulcanized; the lining is cured into a monolithic system. | All welds and seams are stripe-coated with a roller. The coating is then generally applied with a large-tipped airless spray pump. |
| Installation Time | |
| Fair – Rubber installation is a labor-intense process that requires a skilled applicator. This can increase the overall cost. | Good – A skilled applicator is required, although spray-on application is quicker than rubber. |
| Post Installation Cure Requirements | |
| Two Types of Cure: Steam Cure: 24-48 hours of steam cure (Boiler Required). Ready for food service post-cure. Chemical Cure: Applied on chemical cure rubber, 7 days before service. ChemCure II is FDA compliant. | Two Stage: 1) 24-72 hours at 75°F. 2) Many lining manufacturers will require an additional 2-6 hours of 180°F + dry heat prior to food service. |
| Flexibility: | |
| Excellent – Rubber is very well known for flexibility. If the internal components of the tank tend to move, stretch, or flex, rubber will typically move and flex as well. | Poor – Vinyl Ester Epoxy systems are very rigid. The thickness required for long-term service will be more rigid than thin film (short life) systems. |
| Impact Resistance | |
| Excellent – Rubber linings perform exceptionally well under most impact. Rubber will compress under impact and return to its original state. | Fair – Vinyl Esters would be more likely to chip on impact. Vinyl Esters are very strong and hard on the surface, but it creates an “unforgiving” surface upon strong impact. |
| Care and Maintenance | |
| Good – Rubber linings are virtually maintenance free, but they should not be left empty and dry for long periods of time. Inspections are recommended every 3-5 years or at planned maintenance intervals. | Fair – Vinyl Ester linings are virtually maintenance free and can be left empty and dry. No damage can occur while “out of service.” Biannual inspections are highly recommended. |
| Repairability | |
| Excellent – There are two different types of repairs that can be made. Chemical cure repairs are the most common. Pre-cured linings are also an option and can often be ready for immediate service. | Good – Repair of Vinyl Esters often perform as well as an original lining. Preparation is critical to ensure proper adhesion to an existing lining. |
| Expected Life (varies with service conditions) | |
| It is important to note the actual mil thickness of epoxy being applied. There are various manufacturers and types of Vinyl Esters. Some can be applied thicker, but they do require some type of reinforcement, such as fiberglass. Be sure to contact the manufacturer or read the product specifications before deciding. As you can see, there are advantages and disadvantages to the product that you choose. However, for only a roughly 20%-30% up front cost, you can get a rubber lining that has the potential to last twice as long (if not more). | |