Between inspection intervals, it is common to move the roof legs on floating roofs, up into the “low legs” position. This is to reduce the possibility of landing the legs on the floor while drawing down on the tank contents. As this cycle is often 10 years or more, it is also common for corrosion to build up between the roof leg and the sleeve attached to the roof deck. The corrosion buildup can cause the leg to seize in the sleeve and require considerable effort/cost to move the legs to the “high leg” position prior to tank turnaround.
Zerust® has developed Zerust® Axanol Z-Maxx a a proprietary heavy grease product with Zerust corrosion inhibitors. This treatment method cost effectively reduces corrosion rates in this area using existing and proven corrosion inhibitor products.
Trials of the Roof Leg Saver system have provided excellent results. An example of these tests are shown using 50 roof legs, below. A “Control” and 3 protective options were installed. In each of the 4 configurations, coupons were inserted between the roof leg and the sleeve. The “Control” and “Z-Maxx” options were exposed to the atmosphere and the others were enclosed in a Zerust VCI treated polyethylene “Sock”. Additional VCI chemistry was added to the 4th test option, but it was determined that it did not provide any additional protection to the Z-Maxx + Sock configuration.
The picture above shows an external floating roof with the roof legs in the “High” position, in this position, there is typically about 6’ of space between the floor and roof. The roof leg is pinned through the sleeve in this position prior to landing the roof to do maintenance inside the tank.
In the picture above the legs have been pulled up and pinned in the “Low” legs position. This reduces the space between the floor and roof to approximately 3’, allowing for more product to be emptied from the tank without “Landing” the legs on the floor. Some of the legs have been protected with the Zerust Leg Socks while others are left exposed to the environment.
Zerust® Axanol Z-Maxx containing volatile corrosion inhibitors (VCI), which protect metal from corrosion
To avoid application failure:
- These installation instructions must be followed.
- Do not install or open pails with Z-Maxx in wet condition.
- Remove build-up corrosion from the leg surface.
Before beginning installation:
- Identify all parts of the Installation kit shown to the right.
- Gather all materials and tools.
Coupon results have been taken approximately every 60 days for almost one year (since mid-2014) and are consistently showing the following pre-cleaning results. Contaminants on the coupon surface or in the Z-Maxx grease can be seen in the first two sets of coupons (Control & Blue). The Z-Maxx grease where “Socks” were used to create an enclosure, were contaminant free.
After cleaning, the protected coupons were completely corrosion free. Based on the visible contaminants present in the Z-Maxx grease of the “Blue” configuration, it is recommended that the Sock protective barrier will substantially extend the effective life of the Z-Maxx product.
ZERUST® AXANOL Z-MAXX INSTALLATION STEPS
Remove the pin and pull the leg up until the oil level is visible on the leg surface.
Apply a thick layer of the Z-Maxx over the entire leg assembly.
Install thicker portion of the grease where the leg is sliding inside the sleeve.
Lower the leg and re-install the pin. Apply the grease over the entire leg assembly.