El Gamal Mills Cooling Tank Waterproofing
Cooling tanks at El Gamal Mills were lined with hot-spray polyurea in 2020.
01 · Project overview
What is this project?
A mill runs on water as well as grain. Cooling tanks sit in the middle of that, and a leak from one of them does not stay in the tank room. It finds the working floors. El Gamal Mills lined those tanks with polyurea in 2020.
The tanks have to come back into service on a mill’s clock. A coating that wants a week between coats is asking the mill to stop cooling. That is a poor bargain.
| Place | El Gamal Mills |
|---|---|
| Year | 2020 |
| Scope | Cooling tanks |
| System | Hot-spray pure polyurea |
02 · The challenge
What did this structure ask of the membrane?
Cooling water cycles in temperature, and the concrete moves with it. Nozzles, corners and the floor-to-wall joint are where a thin lining fails. Once the tank is full again, the repair is a shutdown.
03 · The solution
Which Krypton system was trusted here?
Polyurea Rayston is sprayed as a thick elastic film in one pass. Gel time is a few seconds, so the lining can be taken around a pipe entry before the material has a chance to sag. That pace suits a tank that has to go back to work.
04 · Application
How is this system built?
Concrete is prepared before any resin goes down. Polyurea Rayston, Krypton’s hot-spray pure polyurea, wants a support that is flat, compact and cohesive. Pull-off strength should be at least 1.4 N/mm2. Cracks are cut out and filled first. High-pressure sand or abrasion opens the pores, and the dust is vacuumed off. Moisture in the concrete must sit under 4 percent. Concrete temperature belongs between 10 and 40 degrees C, and the air should be under 85 percent relative humidity. If damp is suspected behind the slab, two coats of epoxy primer go on, the second one blinded with quartz sand. Metal is cleaned and primed with a polyurethane primer. That bond is what stops a blister when the structure heats up.
A tank pushes water against its own concrete for years. A pinhole at a corner or around a pipe becomes a leak you only find after the finishes are on. The lining has to be continuous, and it has to be finished fast enough that the cell can be closed in one visit.
Spraying is hot and fast. Both components are brought to about 25 to 30 degrees C before they are loaded. In the machine they run hotter: about 65 degrees C on the resin, 75 degrees C on the isocyanate, and 65 degrees C in the hose. Pressure at the gun is at least 140 bar. The usual build is 1.5 to 2.0 kg/m2, which leaves a film about 1.5 to 2 mm thick. Gel time is about 4 seconds at 25 degrees C. The surface is tack-free in a matter of seconds, not hours. Hardness climbs from roughly 28 Shore A at five minutes to about 88 Shore A after four days. One pass should make the thickness. Where a corner needs a second pass, it should follow within about two hours.
Speed is the practical gift on a crowded site. Upstands, outlets and internal corners can be closed before the next trade arrives. The film itself is elastic. Typical elongation is 324 percent and tensile strength is 16.2 MPa, with tear strength around 69 N/mm. It bridges cracks instead of snapping when concrete moves.
Inside a tank the film is there to live under water, not to be looked at. Water uptake is very low, about 0.002 kg/m2 per square-root hour. Chemical testing puts it in class II against 25 percent salt and class III against hydrogen sulphide and 10 percent sulphuric acid. Drinking-water migration tests and a WRAS material approval are on the same datasheet, which is the right background when a tank feeds people or a process. Sunlight is not the duty inside a closed cell. The product carries CE marking to EN 1504-2 and European Technical Assessment 16/0148. Those figures describe the product, not a test carried out in this tank.
Polyurea Rayston technical data sheet
After the spray, the tank is a box you are about to close. Pipe entries have to be sprayed into the same film, not sleeved with a mastic joint. Walls need the same thickness as the floor, because water does not prefer the easy face. Light contact is a matter of hours. Filling waits until hardness has climbed, which for this polyurea is days, not weeks. A buried or covered lining does not need a colour coat. It needs the details finished before the valves open.
05 · Results
What does a job like this ask us to stand behind?
Cooling water stays in the tank, and the floors stay out of it. The lining has to hold that line from the day the valves open.
06 · Products
Which products carry this duty?
Polyurea Rayston
Hot-spray pure polyurea. Typical build 1.5 to 2 mm. Elongation 324 percent. Root resistance tested to CEN/TS 14416.
07 · FAQ
Frequently asked questions
How fast does the polyurea set?
Polyurea Rayston gels in about 4 seconds at 25 degrees C and is tack-free in seconds. Full hardness still takes days.
Will it bridge a crack?
Typical elongation is 324 percent and tensile strength is 16.2 MPa. The film is meant to stretch with the concrete, or with a metal panel, instead of tearing at the movement.
Can the lining hold water people use?
Migration testing and a WRAS material approval are on the Polyurea Rayston datasheet. Pipe entries still have to be sprayed into the same film.
Does sunlight damage it?
Colour can shift because the resin is aromatic. Strength stays. An aliphatic topcoat is added where the film remains in the sun.
What moisture can the concrete have?
Support moisture should be under 4 percent, with concrete between 10 and 40 degrees C. Wetter concrete gets an epoxy primer blinded with quartz.