Propylene Oxide Total Landed Cost Calculator: From FOB to Your Tank is a procurement modeling framework that converts an FOB purchase price into a delivered cost at the receiving tank flange through a sequence of logistics, customs, storage, and volume-correction adjustments. Propylene oxide (PO), CAS 75-56-9, is a liquefied flammable epoxide with a normal boiling point of 34 °C at 101.3 kPa, a vapor pressure of approximately 59 kPa at 20 °C, and a closed-cup flash point below -37 °C. Commercial PO is shipped under a nitrogen pad as UN 1280, Class 3, Packing Group I under the IMDG Code. The calculator separates the landing process into eleven fields: FOB benchmark, ocean freight, cargo insurance, import duty, discharge port charges, tank usage, nitrogen and vapor handling, inland freight, loss allowance, in-transit inventory carrying cost, and customs clearance fees. The output is a cost per metric ton at the receiving tank, not at the vessel discharge manifold.

The arithmetic basis is TLC = FOB + O/F + I + D + T + F + L + IC, where O/F is ocean freight, I is cargo insurance, D is import duty, T is terminal and tank charges, F is inland freight, L is loss allowance, and IC is in-transit inventory carrying cost. The model treats domestic taxes as a separate layer because the destination country may apply a value-added tax to the duty-inclusive CIF value. The sequence matters: ocean freight is added to FOB to create CIF; insurance is calculated on CIF; import duty is calculated on CIF; and domestic taxes are calculated on the duty-inclusive CIF if the receiving entity is not exempt. The calculator records each field as a USD/t value so that the resulting tank-arrival cost is immediately comparable across FOB ports.

Commercial propylene oxide consumed in polyether polyol and propylene glycol manufacture is typically specified at a purity of ≥99.9% by gas chromatography, water content ≤0.02 wt% by Karl Fischer titration (ASTM E203), aldehyde content ≤0.01 wt% as acetaldehyde, and acidity ≤0.01 wt% as acetic acid. The strained epoxide ring reacts exothermically with acids, bases, amines, and metal chlorides. The calculator therefore flags receiving tanks that also store or transfer amine-containing intermediates, alkali-catalyzed starters, or chlorinated solvents. If the previous cargo is incompatible, the model adds a dedicated cleaning and verification cost: water wash, pigging where piping permits, nitrogen drying to a dew point below -20 °C, and atmospheric oxygen checks before transfer. These operations are not included in standard terminal tariffs and therefore appear as separate inputs.

FOB price benchmarks for PO are influenced by upstream propylene value and co-product credits. In the chlorohydrin process, chlorine and lime are consumed and propylene dichloride and brine effluent add cost; in the propylene oxide/styrene monomer process, ethylbenzene input and styrene co-product credit affect the net cost; in the propylene oxide/tertiary butyl alcohol process, isobutane and tertiary butyl alcohol or methyl tertiary butyl ether credits affect the net cost; in the hydrogen peroxide-to-propylene oxide process, hydrogen peroxide cost and catalyst selectivity dominate. The calculator does not attempt to reproduce these process economics; it accepts FOB as an input because the landed cost differential is calculated downstream of the seller’s tank. However, FOB values should be entered from the same production-route benchmark when comparing origins because PO from different routes can have different specification profiles, especially trace methanol or tertiary butyl alcohol content.

The FOB input is not necessarily a plant-gate price. Under Incoterms 2020 FOB, the seller delivers the cargo on board the nominated vessel at the load port. Loading terminal charges, barge-to-ship transfer, and ship readiness costs before FOB delivery may be included in the FOB price or charged separately depending on the contract. The calculator accepts FOB as the total amount paid to the seller, including any FOB-port terminal lift fee. If the contract is CFR or CIF, the model reverses the freight or insurance component to avoid double counting. FOB, CFR, and CIF are handled with separate arithmetic paths so the ocean freight and insurance fields are not entered twice.

Why Is the FOB Price Never Equivalent to the Tank-Arrival Price?

The gap between an FOB benchmark and the receiving tank cost arises from ocean freight, cargo insurance, customs valuation, terminal charges, inland logistics, and quantity adjustments. In this calculator, the FOB input is entered as a USD/t value for a defined parcel size, usually 1,000 t, 2,000 t, or a coaster/barge lot. Ocean freight is configured separately because chemical parcel tanker freight is not published as a single tariff. The rate depends on route, vessel class, bunker adjustment factor, port restrictions, and cargo inerting or cooling requirements. A 2,000 t to 10,000 t parcel of PO on a Type 2 chemical tanker will require a vapor return line and possibly cooling or pressure control, which can raise the carrier’s minimum freight rate compared with a less hazardous organic solvent.

Insurance is applied as a percentage of the CIF value. For bulk liquid chemical cargo under Institute Cargo Clauses (A) with war risk and strikes extensions, the premium commonly ranges from 0.1% to 0.5% of CIF, but PO flammability and route-specific risk can push the premium toward the upper end of the range. The model does not calculate the premium from a fixed table; it accepts the underwriter’s quote. Import duty is applied to the CIF value using the destination tariff for propylene oxide under harmonized system subheading 2910.20. Actual duty rates vary by origin, trade agreement, and destination customs schedule. The calculator treats duty as a user input rather than a fixed constant because an assumed rate can understate or overstate the landed cost by a material margin.

The calculator adds a loss allowance independently of cargo insurance. Propylene oxide cargoes can show apparent volume loss during discharge because of vapor displacement, line clearing, nitrogen purging, and vessel-to-shore measurement differences. Unless the bill of lading and outturn quantities are corrected to the same temperature and density basis, the difference is partly a measurement correction rather than physical loss. The model applies volume correction using the density and temperature relationship from the certificate of quality. Where terminal volume correction factor tables are not available, a method consistent with ASTM D1250-08 or an equivalent API MPMS Chapter 11 procedure is used. The shore tank level is converted with the tank strapping table, and the vessel quantity is corrected using the vessel calibration table and the cargo temperature at the time of measurement.

The customs value is determined under the destination country’s implementation of the WTO valuation agreement. In most imports, the CIF value is the FOB value plus ocean freight and insurance. Import duty is then applied to the CIF value. Where the buyer and seller are related parties, customs valuation may not simply use the invoice CIF value; the destination authority may apply a deductive or computed value method. The calculator includes a customs value override field for this reason. A 0.1% apparent loss on a parcel equates to 1.00 USD/t for every 1,000 USD/t of CIF, but the actual monetary impact may be higher if duty and tax are assessed on the bill of lading quantity rather than outturn. The model therefore permits a customs quantity override separate from the physical loss allowance.

If the Receiving Asset Is a Pressurized Sphere Rather Than an Atmospheric Cone-Roof Tank

The receiving tank design changes the transfer pump head, vapor balancing arrangement, and utility consumption. Propylene oxide can be stored in low-pressure refrigerated tanks designed to API 620 or in pressure spheres designed to ASME Section VIII, Division 1. A cone-roof atmospheric tank is generally unsuitable for PO because the liquid boils at 34 °C at 101.3 kPa, and even with a nitrogen pad the standing losses and flammable vapor concentration in the vent path require additional control. In the calculator, receiving tank type controls shore-side backpressure and pad gas consumption. Pressure spheres operated at 200 kPa to 350 kPa gauge may use 1.3 to 1.5 tank-volume changes of nitrogen per transfer cycle for inerting and line clearing. Refrigerated storage near -5 °C to 5 °C lowers vapor pressure but adds refrigeration energy and can require low-temperature materials for pump seals and instrument connections. The calculator includes a utility input for nitrogen in normal cubic metres and for refrigeration energy in kWh/t discharged.

Terminal transfer charges are not a single fixed item. A 2,000 t parcel discharged through a 200 mm marine loading arm into a shore tank can incur dockage, wharfage, receiver service, temporary storage, nitrogen, and tank heel management. The calculator separates terminal charges into a port fee component and a tank usage component. The port fee is a lump sum per vessel call or a tariff per metric ton. Tank usage is charged per tank day. A PO parcel held in temporary storage for more than the terminal free allowance, often 7 to 14 days depending on the terminal contract, accrues daily charges and increases inventory carrying cost. The model therefore includes a demurrage input for days between cargo receipt and final local dispatch. If the local dispatch is by ISO tank or road tanker, the terminal may also charge a loading fee, hot work permit review, and vapor recovery fee; these are entered as separate local logistics costs.

Transit Loss Allowance, Customs Duty, and Local Delivery Input Fields

Customs value is determined under the destination country’s implementation of the WTO valuation agreement. In most imports, the CIF value is the FOB value plus ocean freight and insurance. Import duty is then applied to the CIF value. Propylene oxide is classified under HS 2910.20; the actual duty rate must be taken from the destination customs schedule because preferential origin declarations and free-trade agreements can reduce the rate. Domestic value-added tax is calculated on the duty-inclusive CIF value and is shown separately because recovery may depend on the receiving entity’s tax registration.

The equipment interface between the vessel manifold and the receiving tank is a frequent source of unplanned cost drift. A 200 mm vapor-balanced hard arm or composite hose must be compatible with propylene oxide; EPDM or PTFE-lined stainless steel is preferred for gasket and seal contact, while carbon steel piping may be used where moisture is controlled. Transfer pumps are typically sealless canned motor or magnetic drive designs to reduce emissions and seal leak risk. During discharge, the shore system maintains a liquid velocity in stainless steel piping between 1.0 m/s and 3.0 m/s to limit static accumulation. The receiving tank is inerted before transfer begins, and the vapor return line is connected so that displaced nitrogen is sent back to the vessel or to a controlled vent with flame arresters. A low-level cutout on the shore tank and an independent high-level alarm form part of the receiving facility’s protection layer. The calculator adds a repair and downtime contingency for these interface items only when the terminal tariff excludes them.

PO reactivity introduces a process conflict that must be handled by the model. Propylene oxide reacts with iron chloride and other Lewis acids; any receiving system that has handled chlorinated solvents or acidic intermediates without neutralization must be checked for residual acidity. The calculator flags a cleaning cost if the previous cargo is incompatible with PO under the terminal’s last-cargo list. Published data for this specific configuration is limited; the model therefore applies a conservative cleaning allowance that is replaced by an actual pigging, water wash, and dryness check at the terminal. Water contamination above the 0.02 wt% specification can initiate slow ring-opening in the presence of low levels of acetic acid and heat. The loss allowance field is intended to capture such off-spec or partial polymerization events only when they are within the contractual tolerance and are not recoverable under cargo insurance.

For local delivery, the calculator accepts ISO tank, road tanker, rail tank car, or dedicated pipeline options. An ISO tank is typically a 24 000 L to 26 000 L stainless steel tank meeting the IMDG Code portable tank requirements for UN 1280, protected by pressure relief valves and inerted with nitrogen. A road tanker may be a 30 000 L to 40 000 L insulated vessel with top or bottom loading and vapor return. A rail tank car may be a pressure-capable vessel appropriate to the route regulation, with bottom outlet control and grounding provisions. The inland freight field is entered as USD/t and does not default to a fixed rate because local carrier tariffs and return-empty charges differ widely. If the receiving plant is connected by a dedicated pipeline, the model adds a pipeline transfer loss allowance and a nitrogen batch separator adjustment. Pipeline transfer is often lower in variable cost but requires a scheduling and buffer tank that matches the plant’s PO consumption rate.

The final output of the calculator is a delivered cost per metric ton at the receiving tank flange, with the total displayed both as a single USD/t value and as a cash-flow timing array by cost block. The model also stores the input values in a versioned audit log so that a later increase in demurrage or a change in duty rate can be traced without losing the original assumption. For a receiving site that dispatches PO to multiple tanks or production units, the total landed cost can be allocated by volume or by transfer batch, but the allocation rule is held as a separate field because it affects internal product costing rather than the purchase cost itself.