Wooden Drinking Water Tank, Mount Sinai Medical Center (Miami Beach, FL, USA) - rehab and monolithic immersion lining

Mount Sinai Medical Center & Miami Heart Institute - Miami Beach, FL, USA Potable Water Storage Tank, wood rehabilitation and monolithic lining
October 2005
Epoxytec certified contractors: Engineered Lining Systems

Mount Sinai Medical Center, a historic hospital in South Florida (coastal Miami Beach), sought Engineered Lining Systems and Epoxytec to solve a logistical and rehabilitative challenge. On top of the roof, an old custom built wooden tank has been leaking into a catch containment recirculating draining system. This system came with constant headaches, making tenants nervous because of the frequent overflows and leaks coming through the roof, ultimately through ceilings and into the hospital corridors and rooms.

Unfortunately, access to this area is extremely hindering, and the idea of rebuilding a newer designed tank because of these access limitations and coupled with restrictive budgets makes it nearly impossible. However, a restoring solution was recommended by the Epoxytec team. And when installed successfully, the proposed high build elastomeric liner will last and endure as good as . . . if not, better than replacement, within budget, and without hardly any interruption.

As seen above, this tank was built entirely with wood, and because of all the seams, constant leaking is an everyday consequence. Once the water is removed, the wood will lose its swelling state, and in fact, the seams will open even more as a result.

To combat this, extra steel bands were installed and will be tightened while the wood dries.

Epoxytec proposes an extremely elastomeric (flexible) material to use as a liner. Elastomers do provide elongation greater than most liners can provide; however, often times the materials used for elastomerics, such as polyurethanes or polyurea, can be a bit sensitive to the substrate if not prepared correctly.

For this project, the wood and area needed to be dehumidified, using industrial blowers to evaporate all moisture from the area and within the matrix of the wood.

In addition, the wood needed to be sanded down in order to achieve a good profile and a clean, grainy wood surface.

When completed, a test area was evaluated, and the total bond strength was enough to peel off the actual wood itself at around 400 psi. This resulting adhesive performance was acceptable to continue.

As a fail safe, and for extra measures - Epoxytec suggested introducing a water-borne epoxy primer before coating with the elastomeric liner.

The Epoxytec B2 Primer is great for this kind of application. Because it's water-based, any remaining moisture in the wood will not affect the primer; since it is made from water, it will integrate with any remaining or foreseen moisture in the wood.

Another advantage in this situation is the recoat window. Recoat windows (the time you have to coat on top of a previous coating) when using urethanes (such as the liner utilized for this project) is very important. If an applicator were to coat to prematurely before the primer was ready, the system could experience a total failure and delamination as the primer would have been too wet. On the contrary, if the primer dries too long, it would create a slick and sealed surface, hurting the bond strength of the topcoat urethane liner (missing the recoat window).

The Epoxytec B2 Primer is color-indicating. It's goes on grey, and when it turns clear - it's ready for top coating. This takes out all the guessing, and gives the applicator a true "green light" for spraying the top coat.

When the B2 Primer cures, it will seal out all remaining moisture, providing a totally dry and active ionic exchanging substrate for bonding any top-coating. Typically, another 100 - 300 psi can be added to the total adhesive strength of the top coat when using primer.

Water-borne epoxy primer - Epoxytec B2 Primer - going on grey, and ready for top-coating when it turns clear.

Epoxytec certified applicator is preparing a mix of material to be used for filling all major gaps and seams of the wood.

The mixed wood sealant and filler, is a two-component polyurethane joint sealant - Epoxytec Uroseal 45V. This version of Uroseal stays in a thixotropic gel state for vertical and overhead applications. This urethane thixotrope will provide the contractor the ability to use a spatula or putty knife to simply fill all major seams between the wood boards before coating.

Using a plastic spatula - the 100% solid urethane joint sealant is applied vertically.

Epoxytec Uroseal 45V is an elastomeric filler, and will be a totally compatible system underneath the top coat liner (both polyurethane, elastomeric in nature with similar elongation properties).

Suiting up for the final coat. The application will be applied by spray; therefore, taking proper precautions to avoid the harmful atomized mist and over-spray is required. The use of tyvek suits, protective gloves, head and face protection with forced air is typical.

The liner material will require the use of a plural component spray equipment. This dual component spray gun and rig is typically used when applying rapid cure, high build coatings such as polyureas and quick cure polyurethanes.

The material being sprayed is manufactured by Epoxytec. For an ultra-high build, ultra-elastomeric, seamless/monolithic lining system, as required for this wooden tank project and as required for potable drinking water (conforming to ANSI/NSF-61 standards), Epoxytec recommended its Epoxytec Quick Blue lining system.

Epoxytec Quick Blue has to be sprayed in plural component methods due to its ultra-rapid curing properties. The Quick Blue lining system immediately begins curing in 30 seconds. This allows the material to build on top of itself, as thick as desired. In addition, this also gives the project a speedy return-to-service (delivery). This lining scope of the project was completed in 4 days, and water was returned to the tank in less than a business week.

The ultra-high build, elastomeric qualities of the coating provides the benefit of filling small crevasses, gaps, and seams as the applicator sprays. Keeping the nozzle spraying in the seams provides a "fill-as-you-spray" option to the contractor.

The rapid curing benefits of the material will give the applicator ample time to spray sections of the floor, and soon after walk on top of it within a few minutes.

Considering the material is extremely flexible (300% plus elongation), the spray liner material (Epoxytec Quick Blue) is used to fill and line at the same time. The contractor is slowly spraying all joints of the intersection between the floor and walls, and also filling all gaps surrounding the anchors of the ladder. Spraying slowly with a rapid cure material gives the applicator the ability to build up to any thickness required.

Considering the tank is approximately 20 feet in depth; crew supervisors at the top keep a close eye on the spray application crew below. Following strict confined area entry procedures gives confidence to the applicators below.

Epoxytec Quick Blue provides a long-lasting, chemical resistant, monolithically sealed system. This system will hold all water for storage without any more leaks or compromises.

When completed, and fully cured - the Epoxytec Quick Blue system seals with a rubber-like texture. This cold applied, two-component spray coating is similar to having a thick rubberized liner inside the wooden tank. The material system provided incredible cost savings, preventing replacement with limited downtime and resources.

The final liner was applied at around 125 - 250 mils (1/8" - 1/4"), and in some areas (such as in the seams and joints) up to 500 mils (1/2") dry film thickness (DFT).