OTM-7.13	Oil Tanker Manual OTM Cargo Heating	Doc No.: OTM 7.13 Revision: 01 Date: 15 Oct 2024 Issued by: DPA Approved by: MD

1. APPLICATION

This document applies to Officers and Watch Keepers onboard fully managed tank vessels.

2. PURPOSE

To specify procedures on cargo heating.

3. RESPONSIBILITIES

• Chief officer - Overall in charge for cargo heating.
• Deck officers - To assist as required during cargo operation.
• Chief Engineer - Overall in charge for supplying deck steam for heating.
• Watch Keepers - Assist chief officer & deck officers.

4. CARGO HEATING GUIDELINES

Heating program during voyage depends on the type of crude oil cargo.

• Aromatic crude oils contain little or no wax. May allow cooling during the voyage if:
  • Cargo heating system can raise the temperature to the required temperature before discharge.
• To avoid phase separation of the wax:
  • Maintain paraffinic crude oils above critical temperature or cloud point.

Follow heating instructions from charterers. Contact operators if in doubt. Excessive heating of cargo will:

• Increase light end vapor losses.
• Reduce the solvency of the crude for crude oil washing.
• Speed up the fall out of sediment and water otherwise suspended in the crude, waste fuel.
• Increase the possibility of vapor lock problems with the cargo pumps during discharge.

5. PRACTICAL GUIDELINES ON CARGO HEATING

For effective heating ensure following:

• Prevent loss of latent heat.
• Prevent live steam return to hot well.
• Check return line drain & ensure hot water flow.
• Control steam pressure.
• Clean steam traps & ensure no blockage.
• Include steam traps under planned maintenance system (PMS).

Hot well in Engine Room receives return hot water from heating system.

Monitor hot well content by:

• Visual checks.
• Install oil content sensor on steam return line.

6. GENERAL CARGO HEATING PROCEDURES

Pre-heating checks:

• Domestic Fresh water consumption.
• Distilled water consumption.

Starting procedure:

• Avoid water hampering, ensure following:
  • Drain water & warm up main steam line.
  • Drain water & warm up steam coils.
• Slowly open steam inlet.
• Maintain constant pressure throughout the steam line.
• Install pressure gauges at three places on main steam line (Forward, Mid-ship & Aft).
• Physically verify pressure at regular intervals.



Coution:

• Check heating coil return water free from oil on main deck prior opening main return line.
• Keep all steam coils open & regulate pressure using tank outlet return line valve.
• To regulate temperature in tanks shut off steam coils as required.
• To adjust tank temperature do not use individual steam coil valves.
• Slowly increase cargo temperature.

Responsible officer to supervise starting of heating.

Daily record following:

• Cargo Temperature.
• Pressure on steam line at all locations.
• Status of return line valve.

Symptoms of leaking coils:

• Oil traces in hot well in engine room.
• Oil traces in return line drain on deck.
• Increased water consumption.

Shut down procedures:

• Reduce heating as the oil level falls in the cargo tanks.
• Shut off heating once heating coils are exposed.
• Open drain to break vacuum once steam inlet is shut.
• Cold climate precautions:
  • To avoid freezing damage, immediately air blow steam coils.
  • To avoid any steam entering the coils, blank steam coil inlets.

7. TESTING OF HEATING COILS

Pressure testing frequency

• Prior loading heated cargo: Integrity test using steam or any liquid medium at a minimum pressure of 5 Kg/cm².
• At least once a year: Hydrostatic test using water or any other liquid medium at 100% of normal working pressure.

Hydrostatic test procedure

• Fill the heating coil with fresh water (or thermal oil in case of Thermal heating system) taking care to eliminate all possible air pockets before raising the pressure.
• Install a pressure gauge near the inlet or outlet of the steam coil.
• Slowly increase the pressure to required value.
• When the maximum pressure is reached, maintain that pressure for 30 minutes.
• Monitor the pressure on the manometer to verify that there is no significant reduction in pressure.
• If the tank is safe for man entry, then visually inspect the coils from inside of the tank to confirm that there are no leaks.

Steam test procedure

• Drain of any previous condensates from the coils.
• Slightly open the inlet valve and fully open return valve so that a steam flow is achieved.
• Slowly open steam inlet to avoid rapid thermal expansion of the heating coil and subsequent risk of damage.
• Open return drains to allow any trapped water to escape on deck and then close when steam appears.
• Slowly increase the pressure to required test pressure.
• If the tank is safe for man entry, then visually inspect the coils from inside of the tank to confirm that there are no leaks.
• If the tank is not safe for entry, then monitor the pressure from deck level using the pressure gauge. Maintain the pressure for 30 minutes in this case.

8. REFERENCED FORMS AND CHECKLISTS

• TNK08 & 08A - Cargo heating record.