UAN 32% Storage — High-Density Liquid N Tank Specification

Five Feature Facts That Define UAN 32 Service

UAN 32 sits in a specific spot in the liquid-fertilizer family:

1. Highest N density among liquid fertilizers in common field use. At 32% N and 11.06 lb/gal, UAN 32 delivers 3.54 lb N per gallon - more than any other field-applicable N liquid. Anhydrous ammonia has higher N density but is a gas at normal conditions.
2. Salt-out at 32°F (0°C). This is the hard engineering constraint. Every night below freezing is a potential salt-out event unless the tank is heat-managed.
3. Neutral to mildly acidic pH. Solution pH is 7.0-8.0 - benign for polyethylene but needs EPDM not Viton gaskets.
4. Negligible vapor pressure at ambient. Unlike anhydrous ammonia, UAN 32 stores and ships at atmospheric pressure in vented tanks.
5. Hydroscopic but not deliquescent. Open-top tank storage picks up humidity but doesn't absorb enough to alter N concentration significantly within a season.

These five facts drive the entire tank-system design. High SG means heavier-wall tank; salt-out at 32°F means winter-management infrastructure; neutral pH means standard fertilizer gasketing; low vapor pressure means standard atmospheric venting; hygroscopic character means fill-point hygiene matters during extended storage.

MOC Stack - High-Density N Fertilizer

The UAN 32 tank system differs from UAN 28 only in tank SG and winter-management infrastructure:

• Resin: HDLPE or XLPE at 1.4-1.5 ASTM specific gravity. Because UAN 32 ships at SG 1.32, tank rated at 1.4 ASTM is adequate; 1.5 ASTM is preferred for tall verticals. Consult manufacturer chart for the specific tank diameter and sidewall height.
• Specific Gravity: 1.4-1.5 ASTM; never 1.2 or lower.
• Fittings: Polypropylene or PVC. Glass-filled nylon threaded fittings fail under UAN salt-out thermal cycling.
• Gaskets: EPDM. Same rationale as UAN 28 - Viton swells under urea service.
• Bolts: 316SS.
• Vent: atmospheric, screened, sized per rapid fill rate (4-inch on 10,000+ gal tanks).

The Snyder urea-solution chart provides the closest direct OEM guidance; the Enduraplas ammonium-nitrate Satisfactory rating confirms the AN fraction. Consult manufacturer chart for tank-farm site-specific requirements before final purchase.

Texas and Oklahoma Panhandle - Why UAN 32 Dominates Here

The Texas Panhandle and Oklahoma Panhandle - from Amarillo through Dumas, Guymon, Goodwell, and up into southwestern Kansas - run heavily on UAN 32. The agronomic rationale:

• Winter lows rarely challenge the 32°F salt-out threshold. Amarillo averages 13 nights per winter below 20°F in a typical year; most years fewer than 5 nights below 0°F.
• Continuous corn and corn-sorghum rotations drive 180-220 lb N per acre demand.
• Ogallala aquifer center-pivot irrigation enables fertigation as the lowest-cost N delivery mode during the pivot-run season.
• Pipeline and rail terminal access from Borger (Koch Fertilizer), Enid OK (Koch), and Donaldsonville LA (CF Industries) keeps UAN 32 supply economical.

A typical retail co-op in the Panhandle maintains 150,000-400,000 gallons of UAN 32 capacity plus 50,000-100,000 gallons of UAN 28 for January-February draw when the longer-range forecast calls for cold snaps.

Y-Drop, Coulter Injection, and Stream-Bar Applicators

UAN 32 is applied via the same three in-season application tools as UAN 28, just at different pump settings to deliver equivalent N per acre:

• Y-drop hoses: dual-hose per row, trail behind a self-propelled sprayer, deposit UAN between corn rows at V4-V10 growth stages. Y-drop technology from 360 Yield Center and similar manufacturers is the dominant side-dress tool on corn today.
• Coulter injection: toolbar-mounted coulters cut a 2-3 inch slit into the soil and a drop tube deposits UAN in the slot at 2-4 inches depth. Lower volatilization loss than surface-applied Y-drop.
• Stream-bar applicators: flat-fan nozzles mounted on the boom discharge UAN as fluid streams rather than a mist, reducing drift and foliar contact. Used when Y-drop hoses are impractical (solid-seeded small grains, narrow-row sorghum).

Metering accuracy matters - a 1-2% miscalibration on UAN 32 at $350/ton fertilizer cost translates to significant per-acre error across 5,000 acres. Retail applicator services verify meter calibration annually; owner-operators check before each major application window.

Fertigation Math - Why UAN 32 Wins the Pivot Season

During the center-pivot irrigation season (typically May through August in the Plains), fertigation is the cheapest N delivery mode per pound. The math:

• UAN 32 at 3.54 lb N per gallon, injected at 10-30 gallons per acre per pass, delivers 35-100 lb N per acre per pass.
• Pivot fuel and labor are sunk costs - irrigation runs regardless.
• Injection pump cost amortizes over 500-2000 acres per year.
• Compared to side-dress applicator cost ($15-25 per acre custom rate), fertigation saves $10-20 per acre per pass.

The design constraint: chemigation-compliant injection system with dual check valves, vacuum breaker between pivot well and injection point, and an electrical interlock that stops fertilizer injection if the pivot drive stops. Nebraska, Kansas, Texas, Oklahoma, and Colorado all require chemigation permits for any fertilizer injection on a well that serves domestic water. Permit cost runs $30-100 per year; annual inspection is required.

Secondary Containment, Fire Code, and Fertilizer Licensing

UAN 32 is a state-regulated liquid fertilizer, not a federally-regulated hazardous material. Compliance stack:

• State fertilizer license: every state with meaningful fertilizer commerce requires retail and wholesale licenses. Fees $100-500 per year; renewal typically annual.
• Secondary containment: 110-150% of largest tank volume, depending on state. Iowa requires 125% minimum for liquid fertilizer over 1,500 gal; Texas requires 110% plus a perimeter curb at any pumping area.
• Emergency response plan: written, site-specific, filed with state regulator. Include contact info, spill kit location, and evacuation procedures.
• Fire code: UAN is not classified as flammable or combustible liquid under NFPA 30. Local fire-code officials may require tank-farm labeling and access-road hydrant requirements under general industrial rules.

For tank farms crossing state lines (a multi-branch retail co-op), build compliance to the strictest applicable state - usually Iowa or Nebraska for liquid fertilizer rules, Texas for commerce-licensing frequency.

The February 2021 Texas Cold Snap - Lessons from a Salt-Out Event

When Winter Storm Uri dropped Amarillo to -13°F and Dumas to -9°F over four days in February 2021, UAN 32 tanks across the Panhandle salted out. Post-event analysis from the Texas AgriLife Extension and the Plains Cotton Growers Association identified three failure patterns:

• Under-sized tank-blanket heaters - 500W panels designed for mild winters couldn't keep up with -13°F wind chill. Minimum for Panhandle operation should be 1000W per 5000 gal tank with full insulation jacket.
• Un-insulated suction piping - bottom-drain lines and pump suctions froze solid, trapping partially-thawed UAN in the tank. Remediation cost $500-2000 per affected tank.
• Vent freeze-plugs - some operations reported vent pipes with trapped moisture freezing shut, creating vacuum conditions during draw that damaged tank sidewalls. Heated or self-regulating-traced vent pipes prevent this.

The Texas Panhandle Feedyards Association, Plains Cotton Growers, and Texas AgriLife published post-event guidance recommending heated, insulated, and redundantly-heat-traced UAN 32 tank systems as the new normal for any tank that might see sub-zero air temperatures. Many co-ops upgraded over the 2021-2022 off-season.

System-of-Construction Table (Snyder Industries)

This is the exact specification Snyder Industries publishes for this chemistry. Every column is required — changing any of them voids the service rating.

Concentration-Band Compatibility (Enduraplas / Equistar Data)

Polyethylene chemical resistance by concentration and service temperature. Satisfactory (S) = long-term service. Limited (O) = occasional only. Unsatisfactory (U) = do not use.

Frequently Asked Questions

Is UAN 32 the same chemistry as UAN 28 just more concentrated?

Same chemistry, different blend ratios. Both are water solutions of ammonium nitrate (AN) plus urea, but UAN 32 carries a higher AN-to-water ratio, which drives both the higher N density and the higher salt-out temperature. UAN 28 typically ships at 40% AN, 30% urea, 30% water by weight; UAN 32 at 44% AN, 35% urea, 21% water. The 4-point N density difference costs you 31°F of cold-weather operating margin.

Can a UAN 28 tank be repurposed for UAN 32 service?

Yes if the tank is rated at 1.4 ASTM SG or higher. UAN 32 ships at SG 1.32 versus UAN 28 at 1.28, so a 1.35 ASTM tank is marginal and a 1.4+ ASTM tank is preferred. Verify the rating plate on the tank before switching services. Gaskets, bolts, fittings, and venting are identical across the two services.

Why does UAN 32 cost less per pound of N than UAN 28 even though it's more concentrated?

Freight economics. Retailers pay per gallon for truck and rail shipment from the terminal. UAN 32 delivers 3.54 lb N per gallon versus UAN 28 at 2.98 lb N per gallon - so the per-pound freight cost drops roughly 19% when moving UAN 32. That freight savings shows up at the retail counter as a 5-15% per-pound-N discount relative to UAN 28 in most markets.

Does UAN 32 need specialty stainless or exotic alloy bolting?

No. 316SS is adequate and is the Snyder-published recommendation for urea-solution bolt hardware. Hastelloy and titanium are not needed for UAN service; specifying them would be over-engineering. Use 316SS at every wetted joint including manway, bulkhead flanges, and pump flanges.

What's a reasonable tank-blanket heater size for a 10,000 gallon UAN 32 vertical in the Panhandle?

1000-1500W thermostat-controlled panel paired with a full-sidewall insulation jacket is the Panhandle standard after the 2021 cold event. Target maintenance temperature 45°F (10°F safety margin above salt-out). Add self-regulating heat tape to the bottom drain, suction piping, and vent stack at 5-10 W/ft. Total electrical load under a -10°F event runs 2-4 kW per tank - plan service panel capacity accordingly.

Is UAN 32 regulated as an explosive precursor?

No. Solid ammonium nitrate and concentrated AN solutions above certain thresholds trigger DHS Chemical Facility Anti-Terrorism Standards (CFATS) and ATF reporting. UAN 32 at 32% total N is well below the CFATS threshold concentration and is not classified as an explosive precursor in its liquid form. Handling rules for solid AN at feed-mills and retail explosive-grade AN (ANFO precursor for mining) are entirely separate from liquid UAN rules.

Source Citations

• Snyder Industries — Chemical Resistance Recommendations (current edition)
• Enduraplas / Equistar Technical Tip — Chemical Resistance of Polyethylene (12-page reference)

Field Operations Addendum — UAN-32 (Urea Ammonium Nitrate 32%)

Expanded Compatibility Matrix. Urea-ammonium-nitrate 32% solution (UAN-32, CAS mixture including 57-13-6 urea and 6484-52-2 ammonium nitrate) is the highest-nitrogen liquid fertilizer in commerce at 32% N by weight, blending urea, ammonium nitrate, and water in roughly equal thirds. HDPE and XLPE are A-rated at all concentrations and at ambient-to-warm temperatures; polymer tanks are industry standard for agricultural UAN bulk storage. Polypropylene is A-rated. FRP vinyl ester and isophthalic polyester are A-rated with appropriate veil. 316L stainless steel is A-rated. Carbon steel is B-rated with inhibitor package (UAN inhibitor packages containing sodium metasilicate or equivalent extend carbon-steel tank service to 20+ years in Midwest fertilizer-dealer practice). Aluminum is NR because the ammonia hydrolysis pathway plus nitrate chemistry attacks aluminum rapidly. Copper, brass, and bronze are NR for the same ammonia-attack reason. Galvanized steel is NR. Gaskets: EPDM, Viton, and PTFE are A-rated; nitrile is B-rated.

Hazard Communication Refresh. UAN-32 solution is classified under GHS as Category 2 Eye Irritation and Category 4 Acute Oral Toxicity. NFPA 704 placard is Health 2, Flammability 0, Instability 1. DOT hazard class is NA1760 Fertilizer Solution or UN2426 Ammonium Nitrate Liquid depending on formulation; Packing Group III. The ammonium-nitrate fraction drives EPCRA and OSHA PSM threshold quantity calculations: UAN-32 at 32% total N contains roughly 45% ammonium nitrate by weight, which triggers EPA Risk Management Plan (40 CFR 68) reporting at aggregate quantities above 10,000 lb. State-level EPCRA Tier II reporting thresholds are typically 500 lb for ammonium-nitrate component. The 2013 West Fertilizer Company Texas disaster drove nationwide regulatory tightening on ammonium-nitrate-containing fertilizer storage, and UAN bulk storage at dealer-scale inventory now requires fire-marshal permitting in most jurisdictions.

Storage Protocol Specifics. Panhandle and Midwest application season (March through May corn-planting and July side-dress) drives UAN dealer inventory turnover; typical farm-dealer bulk storage is 10,000–100,000 gallons per facility with seasonal peak inventory and near-empty post-season. Freeze management is the dominant operational discipline: UAN-32 freezes at 15°F and crystallizes (salt-out) before freezing at temperatures between 15°F and 25°F. Outdoor unheated tanks in USDA Zone 5 and colder (most of the Corn Belt) will crystallize and freeze every winter; recovery requires slow thaw with recirculation. Agricultural-dealer best practice is to store UAN-28 (28% N, freeze point 0°F) in the northern Corn Belt and UAN-32 in warmer southern markets. Vent is standard atmospheric with 20-mesh screen. Containment berms are fire-code mandated at 110% of largest tank volume with impervious liner. Segregate storage from combustibles (hay, seed, chemistry totes of flammable liquids) per NFPA 400 oxidizer-fire-code rules. Segregate from strong acids (exothermic neutralization) and from metals other than carbon-steel-with-inhibitor or stainless. Pump wetted parts: 316L SS or PVDF; transfer hose is EPDM-lined with SS fittings. Recirculation during warm weather prevents stratification and biuret formation at tank bottom. Inventory rotation within 12 months from manufacture.

Three Additional FAQs.

Why is UAN-28 preferred over UAN-32 for northern Corn Belt storage? UAN-28 has a 0°F freeze/salt-out point versus 15°F for UAN-32. Outdoor tank storage in Iowa, Minnesota, Wisconsin, and the Dakotas avoids recurring winter crystallization events that require recovery labor each spring.

Can I store UAN and anhydrous ammonia at the same agricultural dealer facility? Yes, with significant separation distance per NFPA 55 and NFPA 400 for pressurized-ammonia service versus atmospheric-tank UAN service. Dealers with both products typically site ammonia farms 100+ ft from UAN tanks with intervening earthen berms or reinforced fire walls.

What triggered the nationwide fire-marshal tightening on UAN dealer storage? The April 2013 West Fertilizer Company explosion in West, Texas, which killed 15 and destroyed the adjacent town. The facility stored 240+ tons of ammonium nitrate solid with inadequate fire protection. Post-incident regulation imposed NFPA 400 sprinkler requirements, fire-marshal permitting for larger inventory, and FEMA/EPA coordination on emergency response planning at all ammonium-nitrate-containing fertilizer facilities.

Related Chemistries in the Agricultural Nitrogen Cluster

Related chemistries in the agricultural-nitrogen cluster (urea + ammonium + UAN + phosphate-nitrogen fertilizer):

• UAN-28 — Lower-concentration variant
• Ammonium Nitrate (AN) — Nitrate-N fertilizer
• Urea Solution — Urea-only liquid fertilizer

Related Hub Pillars

For broader chemistry context, see the OneSource Plastics high-traffic chemical-compatibility hub pillars:

• Sulfuric Acid (H₂SO₄)
• Sodium Hydroxide (NaOH / caustic soda)
• Ferric Chloride (FeCl₃)