Bulk Cargo Quality Assurance: Coal GAR/NAR, Petcoke & Draft Survey Explained
Coal quality measures (GAR/NAR), petcoke specs, draft survey methods. Learn how quality discrepancies affect landed cost and payment.
Why Bulk Cargo Quality Matters
Bulk commodities (coal, iron ore, grains, metals, crude oil, petcoke) account for ~80% of global seaborne trade by volume. Quality variations directly affect price and payment disputes. If you contract to buy coal at USD 200/MT @ 6,000 kcal/kg and it arrives at 5,800 kcal/kg, you're losing 3% of value (USD 6/MT on 10,000 MT = USD 60,000 dispute).
Quality is measured via independent inspection certificates at load port (pre-shipment inspection), in transit (draft survey for liquids), and at discharge (outturn inspection). These certificates are used to settle quality-based price adjustments or payment holds.
Coal Quality Parameters: GAR vs NAR
Coal quality is measured on two bases: GAR (Gross As Received) and NAR (Net As Received). The difference matters for pricing.
| Basis | Definition | Use Case | Why It Matters |
|---|---|---|---|
| GAR | Gross As Received: coal tested as received at load point (with surface moisture) | Exported coal; payment basis for most international trades | Includes moisture, so GAR values are lower than NAR (same coal) |
| NAR | Net As Received: coal tested after removing surface moisture (air-dried) | Buyer's internal use; used to estimate actual energy content | Removes moisture variation; shows true calorific value |
Example: Same coal shipment might show:
- GAR: 6,000 kcal/kg (includes ~10% surface moisture)
- NAR: 6,700 kcal/kg (same coal after air-drying)
If the contract specifies "6,000 kcal/kg GAR minimum" but you receive coal that tests 5,950 kcal/kg GAR, you're 50 kcal below spec. On 10,000 MT @ USD 200/MT, this is a USD 150k dispute (price adjustment: 50 kcal / 6,000 = 0.83% × USD 2M = ~USD 166k).
Other Key Coal Parameters
| Parameter | Typical Range (Thermal Coal) | Effect on Price | Standard |
|---|---|---|---|
| Ash Content | 8–12% (Air Dried Basis) | Higher ash = lower value; affects boiler efficiency | ASTM D3302 |
| Sulfur Content | 0.5–1.2% | Higher sulfur triggers environmental penalties; lower prices in high-regulation zones | ASTM D3302 |
| Volatile Matter | 25–40% | Differentiates thermal coal from coking coal; affects burning characteristics | ASTM D3302 |
| Total Moisture | 12–18% (As Received) | Excess moisture increases shipping weight; affects energy content | ISO 589 |
Petcoke Quality Specifications
Petcoke (Petroleum Coke): Residual byproduct from crude oil refining. Quality is critical for buyers using petcoke as fuel or for carbon electrode production.
| Parameter | Typical Spec (Green Petcoke) | Why It Matters |
|---|---|---|
| Sulfur Content | 2–5% (variable by crude origin) | High sulfur attracts premium pricing for fuel; restricted in some jurisdictions (environmental) |
| Vanadium Content | 200–600 ppm (parts per million) | High vanadium damages boilers; lower-vanadium petcoke commands premium |
| Nickel Content | 50–300 ppm | Similar concern to vanadium; impacts processing |
| Fixed Carbon | 85–90% | Measure of usable carbon content; higher is better |
| Volatile Matter | 10–15% | Inverse of fixed carbon; affects combustion characteristics |
Iron Ore Quality: Fe% Content & Penalty Grades
Iron ore traders contract on Fe% (iron content) and penalty elements (silica, alumina, phosphorus, sulfur). The base product is typically 62% Fe, and penalties apply for each 0.1% deviation.
| Specification | Typical Range (62% Fe Fines) | Penalty per 0.1% Deviation |
|---|---|---|
| Fe Content | 61.5–62.5% | USD 0.50–1.00 / MT per 0.1% |
| SiO2 (Silica) | 4–5% max | USD 0.20–0.50 per 0.1% over limit |
| Al2O3 (Alumina) | 2–3% max | USD 0.10–0.30 per 0.1% over limit |
| P (Phosphorus) | 0.06–0.10% max | USD 5–10 per 0.01% over limit |
Example: Iron ore contract: "62% Fe fines, SiO2 max 4.5%." Outturn inspection shows 62.0% Fe (on spec) but SiO2 = 4.7% (0.2% over limit). Penalty = 0.2% × USD 0.30 = USD 0.06/MT. On 100,000 MT shipment = USD 6,000 deduction from invoice.
Draft Survey: Volume Measurement for Bulk Liquids & Slurry
For crude oil, refined products, iron ore slurry, and other liquid bulk cargoes, quantity is measured via draft survey (ship displacement method) rather than mass weighing.
Draft Survey Process
- Pre-loading: Measure empty vessel draft (how deep it sits in water)
- After loading: Measure loaded vessel draft + trim (fore/aft tilt) + list (side tilt)
- Displacement calculation: Use hydrostatic curves to convert draft change to volume (m³ or BBL)
- Density conversion: Multiply volume by product density (API gravity for crude; specific gravity for slurry) to get mass (MT or BBL)
Accuracy & Disputes
Draft survey accuracy: ±0.3–0.5% on volume, depending on sea state, vessel condition, surveyor skill. This means on a Suezmax tanker (500,000 BBL), survey variance can be ±1,500–2,500 BBL = ±USD 150k–250k dispute at USD 100/BBL.
ISO 4136 standard: Sets procedures for draft surveys. Most international crude sales incorporate ISO 4136 as the dispute resolution method.
Pre-Shipment Inspection (PSI) & Outturn Inspection
Two key inspection points:
| Inspection Point | Timing | Purpose | Used For |
|---|---|---|---|
| PSI (Pre-Shipment) | Before loading vessel | Verify commodity meets contract spec; proof seller delivered correct quality | Seller's protection; proof of compliance to issuing bank (LC docs) |
| Outturn (Discharge) | At discharge port after voyage | Measure degradation during transit; identify buyer's losses | Buyer's protection; basis for quality claims |
Standard inspectors: SGS (Société Générale de Surveillance), BV (Bureau Veritas), Intertek. These firms are recognized globally for neutrality and accuracy.
Real Example: Coal Quality Dispute & Payment Adjustment
Numerical Example: Coal Quality Dispute: GAR Variance & Price Adjustment
Buyer files claim against seller OR seller's insurer (marine insurance). Seller typically absorbs loss or delays are documented. PSI proved seller met spec; outturn proved degradation in transit (vessel condition, moisture, oxidation during 30-day voyage).
How to Prevent Quality Disputes
In the Sales Contract (SPA):
- Specify exact quality parameters: "Coal 6,000 kcal/kg GAR ±100, ash 10% max (ADB), sulfur 0.8% max (ADB)"
- Define tolerance bands: Allow ±0.5–1% variance to account for natural sampling error
- Specify inspection standard: "Per ASTM D3302 (coal) / ISO 3082 (iron ore)"
- Name inspection authority: "Independent inspection by SGS, BV, or Intertek; results final unless fraud"
- Define degradation risk: "Quality deterioration >1% during transit is seller's loss (covered by insurance)"
In Execution:
- Obtain PSI certificate before B/L is signed (proof of spec at load)
- Include PSI reference in commercial invoice + LC docs (for payment certainty)
- Arrange outturn inspection at discharge + mutually agree on inspector
- Document any visible cargo damage (water ingress, leakage, shifting) on cargo manifest
In Dispute Resolution:
- Compare PSI vs outturn certificates; calculate % degradation
- Use Quality Adjustment tool to model price impact and negotiate settlement
- File insurance claim if degradation exceeds agreed tolerance (~1%)
- Refer to arbitration (GAFTA, FOSFA) if seller disputes; typically arbitrator appoints independent re-sampler
This guide is for commodity trade education. Quality standards, inspection procedures, and price adjustment formulas vary by commodity and market convention. Always incorporate quality clauses in your SPA and obtain pre-shipment inspection before shipping. For disputes >USD 100,000, engage a customs broker or trade finance specialist.
Frequently asked questions
What is GAR and NAR in coal trading?#
GAR (Gross As Received): Coal tested as-received at load point, including surface moisture. NAR (Net As Received): Same coal tested after air-drying (removes moisture). Example: same coal may be 6,000 kcal/kg GAR but 6,700 kcal/kg NAR. If contract specifies 'GAR minimum' and you receive coal below that GAR, you have a claim for price adjustment or replacement.
How does coal quality affect price?#
Coal price is based on calorific value (kcal/kg GAR or NAR). A 1% difference in GAR can mean USD 2–4/MT price difference depending on market. On a 10,000 MT shipment, 1% variance = USD 20–40k dispute. This is why pre-shipment and outturn inspections are critical.
What is a draft survey and why do I need it?#
Draft survey measures the volume of cargo by calculating the vessel's displacement change (before loading vs. after loading). Used for crude oil, products, slurries. Method: measure trim/list, calculate draft difference, convert to volume using hydrostatic curves. Accuracy: ±0.3–0.5%, meaning ±USD 150–250k on a USD 50M crude cargo. ISO 4136 sets the standard.
What's the difference between PSI and outturn inspection?#
PSI (Pre-Shipment Inspection): Independent sampler (SGS/BV/Intertek) tests cargo at load port before loading. Proves seller met contract specs. Outturn: Same independent sampler tests cargo at discharge port. If outturn shows degradation (lower quality than PSI), buyer files claim against seller/insurer for the difference.
Can quality degrade during transit?#
Yes. Coal absorbs moisture; metals oxidize; grains can shift or mold in high humidity. Typical degradation: 0.5–2% over 30-day voyage. Contracts usually allow 0.5–1% tolerance. If degradation exceeds tolerance, buyer claims price adjustment or buyer can reject cargo. Most sellers accept quality degradation risk for commodities.
Who should pay for pre-shipment and outturn inspections?#
Buyer typically pays for both (USD 500–1,500 per inspection). Some contracts split: seller pays PSI, buyer pays outturn. For high-value shipments (>USD 500k), both parties often hire independent inspectors to avoid disputes.
What ISO/ASTM standards apply to bulk cargo quality?#
Coal: ASTM D3302 (sampling & analysis). Iron Ore: ISO 3082 (sampling & testing). Draft Survey: ISO 4136 (standard). Petcoke: API standards. These define sampling procedures, lab methods, and acceptance criteria. Most quality disputes reference one of these standards.
Is there a free quality adjustment calculator?#
Yes. ssltglobal.com Quality Adjustment Tool is free. Enter contract spec, outturn test result, unit price, quantity, and it calculates price adjustment. Example: Coal contract 6,200 kcal/kg @ USD 200/MT; outturn 5,920 kcal/kg = USD 2.67/MT deduction = USD 13,350 on 5,000 MT.