Transport Guidance for Steel Cargoes
Cargo humidity and ventilation testing: Example of best practices
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6.9 Cargo humidity and ventilation testing: Example of best practices 6.9.1 During the vessel’s voyage, the crew should obtain regular ventilation reports using the following basic principles to determine if ventilation is required and favorable. Applying the good practice of taking records in a daily log during carriage is an effective measure to help establish that the vessel owner has applied prudent practices to protect the cargo from unnecessary damage. Some examples of best practices are: (1) Temperature readings. Wet-bulb and dry-bulb temperature readings of each hold and the outside air should be taken at least once a watch. When the wet and dry-bulb temperatures are known, the dew point is ascertained from the scale as shown in Table 6.1. It is important that: (i) the outside air control position thermometer should read near the bridge. It should be exposed to the weather in open air, but out of contact with direct sunlight, reflected heat, exhaust ventilators or any other heat source; (ii) the thermometers in the hold should be waved in the air vigorously for a few moments until the temperature of the wet-bulb remains steady. False temperature readings may be observed if this approach is not followed; (iii) it is also good practice to take original temperature readings prior to commencement of the voyage as a benchmark to making further readings during the voyage; and American Club: Transport Guidance for Steel Cargoes 69 (iv) readings of the relative humidity/dew point should be recorded prior to loading when the hold is empty and then again when the cargo hold is full prior to departure. The relative humidity should be kept below 40%. If that is not possible, the relative humidity should be maintained between 40-60%. However, the relative humidity should be no more than 60%, the point where the risks of heavy oxidation and cargo corrosion are more likely to occur. (2) Entry of cargo hold temperature into the Cargo Record Book. Once the temperatures have been measured and the dew point of all cargo holds and the control position has been ascertained, the information should be entered into the vessel’s Humidity- Temperature-Cargo Ventilation Record Book as shown in Table 6.2. (3) Entries into the Humidity-Temperature-Cargo Ventilation Record Book. Under the heading “VENTING”, indicate “Yes” or “No” as the case may be. Under “GENERAL REMARKS”, it is important to indicate events such as any reasons for not ventilating, times of opening and closing of hatches, times of operating mechanical ventilation systems if the vessel is fitted with such equipment, or using portable ventilation equipment. Under “WEATHER CONDITIONS”, brief remarks should be provided on weather conditions over a 24-hour time period particularly if there are periods of rain, fog, heavy seas, water or spray on the deck and/or hatches, etc. 6.9.2 As steel is a non-hygroscopic cargo, the following should be considered when transiting between warmer and colder climates. (1) When transiting from warmer to colder climates. The likelihood of the development of ship sweat is high, therefore ventilation will likely be needed. (2) When transiting from colder to warmer climates. Ventilation will not normally be required. However, cargo sweat could occur if warm air comes into contact with a colder steel cargo. Therefore, cargo holds containing steel cargoes should be sealed at the load port and remain sealed during the course of the voyage until discharge. American Club: Transport Guidance for Steel Cargoes 70 Dry-Bulb Temperatures (°C) tải về 1.97 Mb. Chia sẻ với bạn bè của bạn:
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