BRANDON Ñ Designing, building and managing an on-farm liquid fertilizer facility is nothing at all like handling granular.
There’s a list of considerations a producer must deal with, Dennis Black of Simplot told a recent Fluid Fertilizer Seminar in Brandon.
“Farmers should take a proactive approach in setting up and maintaining a liquid fertilizer site, rather than waiting and allowing a problem to develop,” he said.
Site preparation
Site selection is the obvious first question. Although liquid fertilizer does not generally pose the same environmental risk or danger to health and safety as other agricultural chemicals and is not as dangerous as anhydrous, Black said it’s still important to consider the impact of a possible tank failure.
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Protection of nearby water sources is the main concern. As a benchmark of contamination levels, soil and water samples should be taken to document previous contamination in the area. Do the tests before the first ounce of liquid fertilizer arrives at the site. The tests could be important in future years if problems occur. They may also be required to meet environmental regulations.
“Metal tanks should never be placed on crushed limestone rock,” Black said. “Limestone reacts with water to form acidic substances which cause corrosion to carbon steel floors. Tanks set on a concrete base should have at least a three-quarter inch (two cent-imetre) felt pad to minimize electrical conductivity between the tank floor and the concrete. Pressure treated lumber can also be used.”
The preferred alloy for valves and fittings is always stainless steel, although carbon steel and cast steel can be used.
“Never use copper or brass fittings or valves,” Black said. “Malleable iron is never recommended.”
Connect all tanks to the plumbing system with flexible rubber pipe to compensate for movement between the tank and the pipes.
For security he advised fencing the site with signs identifying products in the tanks and associated risks.
“Material Safety Data Sheets must be available for each type of fertilizer stored and handled at the facility.”
Secondary containment
Black said industry guidelines recommend a containment system that can accommodate 110 percent of the volume of the largest tank, but added that Simplot recommends 125 percent.
A concrete retaining wall around the liquid fertilizer site is usually considered top of the line for containment systems. Treated lumber, galvanized steel and earth walls can also be used.
An impervious 30-mil poly liner should be used with any wall system to prevent liquid penetration into the soil or through the walls.
Well-designed sites have a raised loading pad for trucks and caddies. An accurate metering system is required for pumping into the tanks and pumping out to the application equipment.
The most common metering systems are the three-inch micro motion meter, the four-inch mass flow type meter and the three-inch Coriolis flow meter. Load cells under the tank legs can also provide accurate measurements.
Flat bottom carbon steel tanks designed specifically for liquid fertilizer are the most popular, but hopper bottoms and new stainless steel and poly tanks are gaining popularity.
Each tank represents a significant financial investment so Black said it’s important to give them proper care.
Tank maintenance
Regardless of what metal is used to build the tank, there are common rules and procedures for annual maintenance, Black said. He emphasized that exterior and interior visual inspections should be done every year.
Anyone with a fluid facility should use the liquid tank inspection report form available from dealers. A form should be completed for each tank and filed.
“A copy of all inspections should be kept, including any copies to follow up on identified action items.”
He recommended a full face gasket on the man way, rather than the flange type gasket. This gasket should be changed during annual inspections.
“Cleaning minimizes corrosion and maximizes your tank life,” he said.
“Annual cleaning and inspection gives you the chance to spot any new corrosion pits and stop them from growing.”
Base materials must be prevented from building up above the floor plate on the outside of the tank to prevent corrosion at the wall base.
“To properly clean the interior, a vacuum truck should be used to clean all liquid and debris to allow proper inspection of the floor,” he said.
“The interior surface should not be washed unless there is a lot of scale on the walls or floor. It is not recommended to use high pressure washing because this will remove the mill scale. The floor should be squeegeed as dry as possible.”
It’s also critical to remove sludge buildup to help with visual inspection. Suspicious areas should be checked with ultrasound.
A pit depth gauge should be used to measure corrosion pits. The location and depth of these pits should be documented for future reference. The welded seam where the floor meets the wall needs special attention because this is the area most likely to experience early corrosion.
Flat blade scraping of the walls and floors should only be done in areas that appear to be in more advanced stages of corrosion. Excessive scraping when it’s not needed only hastens corrosion.
Epoxy-lined tanks have a two-component coating on the inner surfaces. Some of them cover the entire inner surface while others only cover the floor and lower walls. Phillips 625 epoxy is one of the most common products for liquid fertilizer tanks.
The epoxy will not adhere properly if the interior was not thoroughly sandblasted before coating. It’s also important to check that the area around the man way neck and all plumbing fittings are well coated.
When checking epoxy-coated tanks, look for blisters where the epoxy might separate from the steel wall. These blisters will often start along a weld seam.
Black said epoxy paint is potentially lethal. A professional industrial painter should be hired for repairs.
If a tank needs welding, it isn’t as simple as ordinary iron welding. Equipment and training are needed to follow the API 650 weld procedure, using 6010 or 7018 rod. Black said that if the farmer or his welder can’t meet those criteria, it’s essential to hire a welder who can.
Replacement plugs should be stainless steel to prevent corrosion.
Black urged farmers to contact their liquid fertilizer rep with questions about corrosion or blistering inside or outside their tanks or if they’re unsure about repair procedures.
Overwinter liquid
Black said the simplest rule to remember when it comes to overwintering liquid fertilizer is: don’t do it.
“With the breakdown of soluble liquids due to cold temperatures, the salts become crystallized solids,” he said. “The major concern is that the phosphates become a gel-like substance and quite possibly could not be brought back to a soluble liquid form.”
If there is no choice, never store it for more than one winter.
“Before winter arrives, make sure you drain all lines and pumps, including those on the nurse units,” said Black.
The liquid should be circulated in the spring before application to bring those crystals back into the solution.
“Circulate the product in each tank for at least 48 hours. It’s a good idea to push the product through a 45-degree elbow mounted inside the tank in a horizontal position so it pushes the fluid around the tank in a circular motion.”
A 25,000-gallon tank needs two days of circulation, a 35,000-gallon tank needs three days, a 41,000-gallon tank needs four days and a 47,000-gallon tank needs five days.
Emergency response
Black said emergency response planning in the event of major spills and fires is an important environmental and safety initiative. It should be developed with local emergency response officials and a copy should be kept by all those involved in the plan.
Employee training is critical, Black added. Staff working with fertilizer should be trained to conduct all major tasks and functions in accordance with procedures developed for that farm.
“Copies of employee training records should be kept to monitor and maintain training.”
