CTM 9.10 A2	Chemical Tanker Manual CTM Carriage and handling of propylene oxide	Doc No.: CTM 9.10 A2 Revision: 01 Date: 15 Oct 2024 Issued by: DPA Approved by: MD

1. PROPYLENE OXIDE

Propylene oxide is a colourless, low-boiling, high vapour pressure, highly volatile liquid with a sweet, ether-like smell. It is highly flammable and reactive. Propylene Oxide must be handled after giving due consideration to the information given in IBC Code (section 15.8), ship specific P&A and PO manuals, MSDS, or any other equivalent document.

Property	Value
Product name	Propylene oxide
Shipping name	Propylene oxide
Chemical family	Alkaline oxides
Density	830 kg/m³ @ 20°C
Specific gravity	0.824 @ 3.89°C
Dynamic viscosity	0.58 (mPa) @ 20°C
Vapour pressure	57.7 (kPa) @ 20°C
Vapour density	2
Boiling point	34.2°C
Melting point	-111.9°C
Flash point	-37°C
Flammable limits	2.3% to 37%
MARPOL annex	II
IMO ship type	2
IMO pollution category	Y
Oil Like	No
High Viscosity	No
Solidifying	No
Appearance	Colourless liquid
Odour	Ether-like odour

Propylene oxide may be carried in independent pressure tanks (design pressure above 0.7 bar gauge) or also in independent or integral gravity tanks (design pressure equal to or less than 0.7 bar gauge). When carrying Propylene Oxide in tanks with design pressure less than 0.6 bar gauge, a cooling system may be required (dependent on voyage time/route etc.). When required, such cooling systems should consist of at least two cooling plants, each with sufficient capacity to maintain the liquid below boiling temperature at the containment pressure. Cooling medium should be compatible with propylene oxide.

2. PERSONAL PROTECTIVE EQUIPMENT (PPE)

When PO is being handled, the crew member shall wear chemical goggles, suitable boiler suit, chemical boots, and gloves. While working on deck around an area having high risk vapour exposure, they should wear a personal gas detector suitable for detecting PO vapours. In case vapour concentration exceeds 1 ppm (50% of TLV-TWA), they should wear level 2 PPE with BA on pressure mode. Details of these requirements are mentioned in Office Management System.

3. TANK AND CARGO LINE ACCEPTANCE REQUIREMENTS

In the case of Propylene oxide or Ethylene oxide/Propylene oxide mixtures, all cargo transfer lines, spool pieces, and jump lines are subject to the same restriction for prior products as are cargo tanks.

Unless cargo tanks are properly cleaned, these products shall not be carried in tanks which have contained as one of the three previous cargoes any products known to catalyse polymerization, such as:

• Mineral acids (e.g. Sulphuric, Hydrochloric, Nitric)
• Carboxylic acids and anhydrides (e.g. Formic, Acetic)
• Halogenated carboxylic acids (e.g. Chloroacetic)
• Sulphonic acids (e.g. Benzene Sulphonic)
• Caustic alkalis (e.g. sodium hydroxide, potassium hydroxide)
• Ammonia and Ammonia solutions
• Amines and amine solutions
• Oxidizing substances.

Subject to charterers' requirements, the following may be considered banned last cargo before carriage of propylene oxide. This needs to be confirmed with the charterer once the voyage has been fixed:

• Nitric acid
• Ammonia and Ammonia solutions
• Amines and Amine solutions
• Caustic/Alkalies

All shore and ship cargo lines and tanks are to be presented clean (residual free), dry, odour free, and rust free, with pressure tested heating coils. Heating coils should be blown clear with nitrogen and blanked on both sides. Some customers, e.g., Shell, require wall wash standard subject to previous cargo:

• Chlorides < 1ppm
• All priors Hydrocarbons < 125 ppm
• All priors Permanganate (PFT) > 40 mins
• Inhibitors Non-Volatiles (NVM)

5. PLANNING AND STOWAGE

• Stowage planning is to be carried out by calculating max volume as per the ship specific maximum allowable tank filling limits diagram that is available on the ship. Maximum volume of cargo should not exceed 98% at reference temperature. IBC 15.8.26.1.
• On ships with 600 mb PV, it means a reference temperature of about 45.8°C, at which cargo shall not exceed 98%. This corresponds to about 94.3% at 20°C (approx. temp of PO at load port).
• Vessel to use Odfjell stowage planning system and commodity booklet. This has a user friendly interface and helps officer to plan stowage taking care of adjacent cargoes, compatibilities, heat adjacency issues. It gives information on cargo specifications and customer requirements for various customers. Requirements mentioned in the ship specific PO manual must be complied.

5.1 Loading preparation

• Prepare the tank(s) according to regulatory requirements and to customer standard. If previous cargo was an acid/caustic or an amine, or if acid/caustic was used in cleaning ensure all residues have been removed. The lines/system should be tested by checking the PH of the cleaning water during the final cleaning.
• Customer requirements should be checked and tanks prepared accordingly.
• Ballast and void spaces should be maintained as per ship’s PO manual requirement.
• When conditions allow, inerting of double bottoms can efficiently be done when de-ballasting the same spaces.
• Each ballast space must be fitted with a P/V valve, nitrogen filling lines and be gastight.
• All packings and gaskets in the cargo containment system to be checked and replaced as necessary.
• The cargo pump cofferdam to be purged with nitrogen to check for leaks.
• Heating coils to be pressure tested for leaks, purged with N2 and sealed off both sides.
• Closed level gauging devices to be tested and ensure operational. To prevent incorrect readings from pressure sensor based systems, correct function and zero setting must be carried out according to manufacturers' instructions.
• Nitrogen filling connections and equipment for maintenance of N2 blanket to be checked.
• Before arrival all PO tanks valves and associated piping scheduled to load Propylene Oxide are to be pressure tested to ensure tightness. Any leaks must be repaired. For pressure testing refer to the Office procedures.
• Besides preparation of general fire-fighting equipment, the deck sprinkler system for cooling should be checked and tested. A charged hose should be kept near the manifold, provided atmospheric temperature permits.
• Closed sampling device to be checked ready for correct sampling.
• Use only stainless steel or any other compatible material hoses marked: "FOR ALKYLENE OXIDE TRANSFER ONLY."
• Test and calibrate Oxygen meters. (GMI 500 or Teledyne or equivalent)
• Check vapor return hoses and connections. Vapor return hoses must be clean, resistant to Propylene Oxides, and approved as vapor return hoses. (USCG).

5.2 Before and during the loading

• Some charters may have a requirement for the PO tanks to be prepared to wall wash standards. The requirement for each voyage shall be verified as per the voyage orders. Very often pre-inspection of tank cleanliness/suitability will be arranged in order to start Nitrogen purging prior to arrival at the load berth / port.
• Purging of ballast and void spaces will also normally take place prior to arrival at the load berth/port.
• Upon reaching required oxygen level, tank to be pressurized to 200 mb and carefully checked for leaks. Expect 5-10% pressure drop in first 10 minutes, thereafter the pressure should hold more or less steady for the next 20 minutes. If pressure drop exceeds, then fix the leak and redo the test. Loading should not commence until compliance with pressure test is achieved.
• All hatches and any other openings must be kept closed and tight after such purging and not be opened before final purging at the load berth. The vessel to maintain above 100 mb pressure in the cargo tank till commencing the cargo loading. Keep a 12 hours log of pressure and oxygen content.
• In all cases, empty or partially filled double bottom, and void spaces, adjacent to the Propylene Oxide tanks must be purged down to an Oxygen level of less than 2% prior to commencement of loading. The vessel to maintain positive pressure and maintain a 12 hours log of oxygen content and verification of positive pressure.
• Adjacent cargo tanks must either be inerted to less than 2% oxygen if empty or loaded with compatible cargo or ballasted.
• The vessel to maintain positive pressure in the cargo tank. Keep a 12 hours log of pressure and oxygen content.
• Under no circumstances should loading be started before completion of purging all adjacent empty spaces.
• Connecting the cargo hose must be supervised by a senior deck officer, either the Master or the Chief Officer must be present.
• Prior to loading, the manifold and the affected tank area to be marked off and unauthorized personnel not allowed in this area. Post proper warning signs.
• Pre-loading inspection to be carried out as per Office preloading checklist. The pre-loading inspection should include; High level and overflow control functional check, tank tightness, remote temperature accuracy check, tank pressure gauge, closed ullage device and safety equipment preparedness check. Some items may need checking prior purging to ensure any issues they have, are addressed. Final recheck shall be done prior loading.
• Cargo tanks for Propylene Oxide will be purged down to less than 2% Oxygen or as per customer requirements (Shell requirement is 0.5% oxygen).
• Before commencement of loading the piping system to be pressurized and tested for leaks, using Nitrogen.
• Under no circumstances must the tank be opened for ullaging or sampling. Always use closed level gauging and sampling devices.

5.3 Immediately after loading

• Use 99.9% nitrogen for line clearing.
• Cargo lines must not be allowed to be drained into the drip tray.
• Disconnecting the cargo hose must be supervised by a senior deck officer.
• Upon completion of loading and prior hose disconnection, ensure tank pressure is minimum 100 mbar and pressure not reducing for next 30 minutes. In case there is a drop in pressure, advise senior deck officer, investigate and rectify followed by a new tightness check.

5.4 Cargo monitoring during voyage

• Positive pressure minimum 100 mbar must be maintained in the cargo tanks throughout the voyage.
• Observe and record cargo temperature and pressure of PO loaded tanks every 4 hours. Check and record Oxygen content once every day. Pad using 99.9% nitrogen as required.
• Daily measure and record the Oxygen content in ballast tanks, void spaces and adjacent cargo tanks surrounding the P.O. tanks. Maintain a positive pressure in these spaces.
• Abnormalities (Temperature, pressure or Oxygen Content) to be highlighted immediately to:
• Office
• Odfjell
• Charterers (as required)

6. TANK INTEGRITY AND EMERGENCY PROCEDURES

6.1 Rise in temperature or pressure

Any abnormal significant increase of temperature or pressure might indicate that the cargo may be reacting.

6.2 Internal reaction (Polymerization)

• The Propylene Oxide is normally of sufficient purity to preclude a concern for abnormal reactivity at ambient or slightly elevated temperatures.
• A slow increase in temperature that cannot be explained by changes in conditions external to the tank, such as increased ambient temperatures or solar exposures, should be monitored closely and increased cooling and rinsing the deck with seawater should be considered.
• Contact Office Operations team if the cargo temperature continues to rise. A sudden unexplained increase in temperature is highly unlikely, but in case that happens, advise charterers and Office both. Abandonment of the cargo could be necessary in such cases.

6.3 Loss of pressure in tank

• Immediately investigate the cause of the leak.
• Maintain positive pressure.
• Rectify the source of leak.
• Top up with Nitrogen after rectifying leak to increase the pressure in the tank to 100 mb.

7. DISCHARGING OPERATION

7.1 Preparations prior to discharge

• Purge the pump(s) cofferdam by N2 before commencement of pumping. Test the water sprinkler system.
• Use only stainless-steel hoses marked: "FOR ALKYLENE OXIDE TRANSFER ONLY".
• Prior to discharging, the manifold and the affected tank area to be marked and unauthorized personnel should not be allowed in this area. Post proper warning signs.
• Under no circumstances the tank(s) should be opened to the atmosphere for ullaging and sampling. Use only closed devices.
• The Oxygen level in the cargo tank(s) might be checked by the cargo surveyor prior to discharging.

7.2 During discharge operation

The tank atmospheric pressure to be closely monitored and kept around 70-150 mbar or any other value as agreed with the terminal during the discharging, with Nitrogen supply of 99.9%.

8. TANK CLEANING AND SLOP DISPOSAL

8.1 Tank washing

• All cleaning and slop disposal must be done in accordance with IBC, P & A and Propylene oxide manual, and records should be maintained.
• After discharge, keep the tank(s) inerted until cleaned. Ensure at least 100 mb pressure is maintained.
• Cargo pump cofferdams to be purged with Nitrogen immediately after completion of discharging.
• Without opening any tank hatches, fill about 2 to 5 cubic meters (subject to the size of tank) of fresh water into the tank through the cargo line. Leave the water in the tank for minimum 2 hours. Pump this water overboard if at sea, or alternatively, into a slop tank (inerted to below 2% Oxygen).
• Clean the tanks using cleaning machines (in case of sudden decrease of pressure in the tank, immediately stop tank cleaning and open the gas freeing vents).
• Blow the heating coils using Nitrogen.
• Ventilate the tank using fixed ventilator fan with outlets through gas free vents.
• During the cleaning/ventilation operation, all precautions must be taken to avoid any sources of ignition at or near the tank. Crew members should be kept away from the area. Refer to the procedures in the Ships P&A Manual and PO Manual.
• Cargo pump cofferdams to be purged with Nitrogen.
• Prior entering the tank after ventilation, tank atmosphere must be verified that it is safe for enclosed space entry.

8.2 Safety consideration during tank cleaning

• Propylene oxide vapours are heavier than air, and in certain weather conditions, Propylene oxide vapour may concentrate above deck-level and travel a considerable distance along deck or enter into any other tank or spaces that may be left open or it may accumulate between frames on the main deck.
• Propylene Oxide vapors are highly soluble in water, such that a water spray (Butterworth) into a tank containing Propylene Oxide vapor may result in a rapid reduction of the interior pressure. Such a sudden pressure drop could result in outside air entering the tank creating a combustible atmosphere or could result in structural damage of the tank. Therefore, it is crucial to fill 2-5 m3 of FW in the tank before commencing tank cleaning. Nevertheless, formation of vacuum in the tank is likely to take place during the initial stage of the tank cleaning. Hence, the pressure in the cargo tank should be monitored closely.

8.3 Slop disposal and arrangements

The slop is to be disposed of according to regulations of MARPOL Annex II. For slop arrangements that require disposal to shore reception facilities, the ship must report its estimated slop quantity. When the ship requires slop disposal to shore and before mixing it with other compatible slop residues it must be discussed with the local agent.

9. FIRE AND EXPLOSION HAZARD

• Flammable liquid
• An extremely reactive, flammable liquid with a wide explosive range.
• Flashback along vapour trail may occur.
• Fire or contamination may cause violent rupture of the tank
• Alcohol resistant foam or multi-purpose foam and water spray is to be used as fire extinguishing medium.
• Use water for dilution and heat removal. Massive water spray can extinguish small Propylene Oxide fires.
• Use water spray to "knock down" vapour.
• Explosion hazard requires approaching a burning tank with caution. Cool tanks with water spray.

10. HEALTH HAZARD

• Vapours are moderately irritating to eyes, nose and throat. Personnel will not usually tolerate moderate or high vapour concentrations.
• If vapour inhaled, it will cause headache, nausea vomiting or loss of consciousness.
• Liquid will burn skin and eyes. Contact with uncovered skin produces frostbite.
• Ingestion will cause serious illness or death.
• TLV-TWA is 2 ppm.

11. PERSONAL EMERGENCY PROCEDURES

• Vapour inhalation: Remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, oxygen should be administered by qualified personnel. Call a physician or transport to medical facilities for immediate medical advice. Inhalation of vapours from cargo tank will also have to be considered as inhalation of Nitrogen.
• Ingestion: If swallowed, rinse mouth and go immediately to hospital. Inducement of vomiting to be indicated by a doctor only.
• Eye contact: Immediately wash eyes with clean water for at least 15 minutes while periodically lifting the lower and upper eyelids to enhance flushing. Remove contact lenses after the first 5 minutes and continue washing. Seek medical attention immediately.
• Skin contact with liquid: In case of contact, immediately flush skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Seek medical attention if irritation of skin persists. Thoroughly rinse the contaminated clothing on deck before bringing it inside accommodation. Destroy contaminated shoes or any other material that could absorb the cargo.
• Medical management: Refer to the IMDG supplement Medical First Aid Guide (MFAG) and charterer’s MSDS.

12. REACTIVITY INFORMATION

• Stability: Polymerize violently on distillation or in the presence of catalysts such as non-oxidizing mineral acids, sulfuric acid, nitric acid, organic acids, caustics, ammonia, aliphatic amines, alkanol amines and certain salts.
• Material compatibility: No copper or copper-containing alloys or other Acetylide forming metals should be in contact with liquid or gaseous Propylene Oxide. Stainless Steel, Mild Steel, Zinc Silicate Coatings are materials resistant to Propylene Oxide.
• USCG compatibility chart: Group 16

13. SPILL OR LEAK PROCEDURE

• Personnel protection: Wear chemical resistant protective clothing and respiratory protective device (Minimum Office PPE Level 2).
• Avoid contact with liquid.
• Contingency plan: Follow contingency plan given in Office Emergency and Contingency Manual.
• Leak combat: If leak on cargo transfer system, stop the transfer and empty the line system. Wash contaminated area with amounts of water. Secure ignition sources. Flush contaminated area with large amounts of water.