No Place Like Dome
Published by Nicholas Woodroof,
Since fertilizer will corrode exposed steel in storage, figuring out creative solutions to this problem is key to cutting down on regular maintenance and replacement costs.
A fertilizer company in Carlsbad, New Mexico, US, needed new storage after a microburst damaged its A-frame storing fertilizer. The company selected six steel-reinforced concrete domes from Dome Technology based partly on corrosion prevention. Steel reinforcing gives the domes their strength, but since the entire dome interior is made of concrete, the storage structure will not corrode.
Concrete will have hairline cracks that can be penetrated by fine fertilizer dust. This was not a concern expressed by this potash customer; however, urea customers have had these concerns, which were mitigated by spraying a polyurea coating on the interior surface of the dome. A corrosive-resistant powder can also be mixed into the concrete when pouring the floor.
Water wreaks havoc with fertilizer and, since most fertilizers are hygroscopic, they attract moisture that dissolves the product and corrodes it too, producing weak acids which break down steel and damage concrete. It is therefore advisable to allot a portion of a budget to corrosive-resistant rebar and/or additional concrete over rebar.
To protect product from humidity, a dehumidifier is also highly recommended. By housing one on top of the dome, humidity in the headspace can be controlled and the ideal interior climate can be maintained. Humidity monitors can also be installed, allowing site managers to survey and adjust interior conditions.
Figure 1. A dome provides protection from rust and moisture on the storage side and protects other components from corrosion too.
Protection from rust and moisture on the storage side is one thing, but there are ways to extend a facility’s lifespan by protecting other components from corrosion too. While many fertilizer storage companies use front end loaders, those that select integrated reclaim systems can protect metal components from rust in multiple ways. Stainless steel is always an option, especially in the case of food- or pharm-grade fertilizer products, but can be cost-prohibitive. Another route is to paint the metal so corrosion is not an issue; it is vital to perform regular maintenance so chips and scratches in the surface do not allow an access point for moisture.
Alongside rust prevention, there are other ways domes ensure a longer lifespan than traditional methods of fertilizer storage.
A continuous single-ply PVC waterproofing membrane ensures complete waterproof protection for the reinforced concrete shell and consequently the material stored within. A mould-resistant UV-protective resin coats both sides of the membrane, providing long-term protection from these two common sources of degradation. The exterior requires little superficial maintenance.
Rivets, fasteners or other mechanical connections found in other storage are not used, thus removing potential sources for leaks and rust. This waterproofing provides long-lasting protection for the stored product and the structure itself.
To read the rest of this article, download World Fertilizer's May/June issue for free: https://bit.ly/2ZSj4XN
Read the article online at: https://www.worldfertilizer.com/special-reports/11062020/no-place-like-dome/
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