SHIP ICE ACCRETION (SHIP ICE)

LEARNING OBJECTIVES: Interpret SHIP ICE program tabular displays. Identify limitations and assumptions. Explain how ice accretion rates are determined by the SHIP ICE program.

The SHIP ICE program provides estimates of ship ice accretion rates vs. time given the wind speed and the air and sea-surface temperatures at various forecast times. Ice accretion from sea spray upon the ships superstructure can impair the operational capability and safety of the ship.

This program can be used to predict the ice accretion on a ships superstructure due to sea spray. It can assist in planning by considering the icing effects along an

Figure 7-4.-Example output of the EM coverage diagram.

LIMITATIONS AND ASSUMPTIONS

The restrictions as well as for granted in using the SHIP the principles taken ICE program are as follows:

. The methods described here are best applied to smaller ships. Ships characteristics, such as freeboard, waterline length, hull response, and ships course and speed are not considered.

. Information relating to ice accretion thresholds is not available and must be developed independently by each user.

. Air temperature is entered in whole degrees (Celsius). For temperatures <-21C, the SHIP ICE model assumes a constant accretion rate based on -21C. The algorithm considers temperatures from -2C to -21C.

. Sea temperature is entered in whole degrees Celsius. The algorithm considers temperatures from 10C to -2C.

. Wind speed is entered in whole knots. The algorithm considers winds from 22 to 71 kt by the following categories:

. If the air temperature is *2C, then the ice accretion is considered to be 0.

. If the wind is <22 kt (BF 6) and the temperature is <-2C, then the ice accretion is considered to be 1.5 cm per day.

The SHIP ICE program determines the ice accretion rates from look-up tables based on the wind category. For each category, there is an ice accretion matrix with an accretion rate for each combination of air-sea temperature (where the air temperatures are between -2C and -21C, and sea temperatures between 10 and -2C.) Figure 7-5 shows an example of a SHIP ICE ACCRETION program.

Figure 7-5.-Examp1e output of the SHIP ICE program.

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