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D6470-99 – Standard Test Method Technical Guide
📐 Scope and Applicability
This test method, designated D6470-99 (Reapproved 2020), covers the determination of salt in crude oils, expressed as % (m/m) NaCl. It covers the range from 0.0005% to 0.15% (m/m) with a detection limit of 0.0002% (m/m). The test method is applicable to nearly all heavier petroleum products, including crude oils, residues, and fuel oils. It may also be applied to used turbine oil and marine diesel fuel to estimate seawater contamination.
| 🟦 Parameter | 📏 Specification |
|---|---|
| Range (as NaCl) | 0.0005% to 0.15% (m/m) |
| Detection Limit | 0.0002% (m/m) |
| Applicable Materials | Crude oils, residues, fuel oils, turbine oil, marine diesel fuel |
⚙️ Test Procedure and Apparatus
The test method involves homogenizing the crude oil, dissolving a weighed aliquot in xylene at 65 °C, and extracting with specified volumes of alcohol, acetone, and water in an electrically heated extraction apparatus. A portion of the aqueous extract is analyzed for total halides by potentiometric titration. The apparatus is made of borosilicate glass and includes a 500 mL boiling flask, a Hopkins reflux condenser with a vapor outlet to a vent or hood, a thistle tube of approximately 70 mL capacity, a heating tube with a chimney, and a 250 W Nichrome heating coil regulated by a rheostat.
| 🛠️ Component | 📐 Specification |
|---|---|
| Boiling Flask | 500 mL capacity |
| Hopkins Reflux Condenser | With vapor outlet to vent/hood |
| Thistle Tube | Approximately 70 mL capacity |
| Heating Coil | 250 W, Nichrome wire |
| Rheostat | Suitable resistance and capacity |
📊 Significance and Measured Properties
Knowledge of water extractable inorganic halides in oil is critical for assessing the need for desalting. Excessive halide, particularly in crude oil, frequently leads to higher corrosion rates in refining units. This test method provides a reliable measure of salt content expressed as sodium chloride. Water extractable salts originating from additives in oils are codetermined. The values stated in SI units are regarded as standard.
💡 Tip: Ensure thorough homogenization of the crude oil sample to achieve representative results. Adhere to the sampling practices outlined in standards D4057 and D4177.
⚡ Warning: Xylene and other solvents used are flammable. Perform all extraction steps in a well-ventilated area or under a fume hood. Follow appropriate safety and environmental practices as indicated in Section 1.5.
❓ Frequently Asked Questions
🔍 What is the detection limit of this test method?
The detection limit for salt as NaCl is 0.0002% (m/m).
💡 Why is potentiometric titration specified for analysis?
Potentiometric titration provides accurate and precise quantification of total halides in the aqueous extract, essential for reliable salt determination.
⚡ Is this method suitable for all crude oil types?
It is applicable to nearly all heavier petroleum products, including crude oils, residues, and fuel oils. It may also be applied to used turbine oil and marine diesel fuel to estimate seawater contamination.
📌 What range of salt content does this method cover?
The test method covers salt content from 0.0005% to 0.15% (m/m) as NaCl.