Reasons for failure of mapping study of a cold room

Mapping study is the procedure or process of recording and mapping the temperature and humidity in various assets such as Warehouse, cold room, vehicle, Freezer etc. The temperature and humidity will not be same everywhere in the asset. There will be a different temperature and humidity in the corners and different in the center of the space being unused.

In a cold room, the area which is near to a cooling fan will be having coldest temperature and near to the door may have the hottest temperature.

The Basis of temperature & Humidity mapping of the various assets is to assure that all storage areas should maintain the required temperature and humidity. The result of the mapping study is a temperature distribution map defining the cold spot and hot spot of the storage area.

Mapping study will be carried out with a sufficient number of Data Loggers. We distribute these data loggers within the 3-dimensional space or the storage area of the asset to map temperature and humidity. We place these loggers in a horizontally, vertically and depth plain. We locate the data loggers in locations that are likely to have temperature variations or humidity variations.

The temperature mapping study includes four stages:

1. Preparing the SOP, protocol or procedure for temperature mapping study.
2. Carrying out different tests of  mapping study as per the protocol.
3. Preparing the Report for mapping study after data collection.
4. Giving the recommendation for remedial actions after analyzing the mapping report.

The mapping study in the cold room includes various different tests.

The test will be carried out in Empty and Loaded conditions. There will be a power failure test and a door opening test followed by Temperature Recovery Test in both empty and loaded conditions. As per the dimension & layout diagram of the cold room, we place the data loggers. One data logger will be outside of the cold room for recording the ambient temperature and humidity.

There will be acceptance criterion for the mapping study. All the data Loggers located inside the cold room should maintain the temperature between the defined low limit and high limit. Depending upon the type of asset, the lower limit, and the higher limit will be changed. For a cold room, usually the low limit is 2°C and high limit is 8°C. There will be a specific limit for humidity also such as between 45% to 65%. After the execution of different tests, there is a chance of failure in the mapping study in a cold room.

Hot & cold points inside cold room

The reason for the failure of the cold room in a recent case study was due to Low temperature at a certain point and high temperature at certain other areas. During the period of mapping study, when the temperature goes above the high limit or below the lower limit, it will lead to failure in the mapping study.

In such case, the customer has to take corrective actions to close the deviations. Reasons for failure of Humidity distribution study in another case study was very high humidity in the cold room.

Common reasons for failure of a cold room

We are listing below common reasons which cause failure of mapping study fo a cold room.

1. Air curtains may be required at the doors of the cold room to maintain the temperature and humidity inside the cold room.
2. The temperature displayed in the temperature controller, which is kept outside the cold room may not be correct.
3. The temperature controller and corresponding sensors are not properly calibrated. You will be setting a certain temperature on the controller. However since the controller is not properly calibrated, it will be sending wrong signals to the cooling units.
4. The location of the sensor of the cooling unit may not be at a correct location.
5. The humidity may be higher than permitted levels.
6. The uniform distribution of temperature will be affected if the location of the cooling units is not positioned correctly.
7. The defrost cycle of the cooling units may not be correctly timed. If there are more than one cooling unit, the defrost cycle has to be properly adjusted so that both the units do not go off together.
8. High racks in front of the cooling units may block proper airflow inside the room.

Recommendations for corrective actions against failure of mapping study

The mapping study report will include the remedies or recommendations for the failure of the mapping study. They include:

1. Calibration and checking of the controller of the cooling unit.
2. Adjust the high and low cut-off limits of the controller. eg. for a cold room you may program the upper and lower limits as 6°C and 4°C respectively. This will help you to achieve a constant temperature between 2° C to 8°C.
3. If corrective actions are not effective, the customer has to isolate the hot or cold areas. They should not store products in these areas.
4. Installing a continuous temperature monitoring system inside the cold room for real time monitoring.
5. The work practices such as keeping the door opened or closed need to change.
6. The racking or shelving needs to be repositioned to improve air circulation.
7. Relocating the heating devices if applicable.
8. Adding cooling units if required.
9. Installing a humidifier or dehumidifier in the cold room to maintain the desired humidity.

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