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Cattle deaths

lyledunn
Some 10 prize bullocks died in quick succession whilst housed over winter in a cattle shed. The government vet was unable to reach a conclusion on cause but apparently does not discount electric shock as an indirect cause. 

The shed comprises steel columns and trusses with corrugated iron sheeting over. The floor comprises re-Inforced concrete slats over the slurry tank. The pens have steel barriers supported by steel posts all of which are heavily corroded but still making contact with other albeit fortuitously.

The earthing system is TT with the shed steelwork on its own providing a substantially low impedance of 5 ohms using a loop tester. A 100mA RCD protects the rather ropey lighting circuits.defccf32df3c757507a0db6ad0a35f87-huge-a5af3537-8eae-4a3c-9126-68fa60b61ac7.jpg

whilst the floor could be wet, I can’t conceive how a voltage difference could be established even if the steelwork was at 230v

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    The shed roof is deliberately not continuous and with relatively open sides to both gable ends it must be a dreadful place in the middle of a cold wet winter!



    Actually for the cattle, this is well designed. Humidity and stale air which leads to respiratory diseases is more serious than cold and wet. When the building is filled with cattle, a lot of moist warm air is produced which rises and goes out through the spaces between the roof sheets. This is replaced by fresh air coming in through the open gable ends. It is surprising how this airflow prevents most rainfall coming through the roof but not all.

    What is less well designed is the metal work which will be corroded and may be bolted together so  may be electrically continuous sometimes and have high resistance joints at others. The bonding required by section 705 may never have been present and even it it was, is unlikely to have been maintained.

    There may be electrical fittings which are dirty and dusty which are no a problem when dry but conduct a lethal current after rain.

    The concrete slats will have re-bar in them which combined with a coating of cattle slurry will make a fairly effective path to earth.

    I'm inclined to agree with Andy B. You may never find the cause so instead replace what is there. Use class 2 fittings if possible.


    Dave
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  • 0

    The shed roof is deliberately not continuous and with relatively open sides to both gable ends it must be a dreadful place in the middle of a cold wet winter!



    Actually for the cattle, this is well designed. Humidity and stale air which leads to respiratory diseases is more serious than cold and wet. When the building is filled with cattle, a lot of moist warm air is produced which rises and goes out through the spaces between the roof sheets. This is replaced by fresh air coming in through the open gable ends. It is surprising how this airflow prevents most rainfall coming through the roof but not all.

    What is less well designed is the metal work which will be corroded and may be bolted together so  may be electrically continuous sometimes and have high resistance joints at others. The bonding required by section 705 may never have been present and even it it was, is unlikely to have been maintained.

    There may be electrical fittings which are dirty and dusty which are no a problem when dry but conduct a lethal current after rain.

    The concrete slats will have re-bar in them which combined with a coating of cattle slurry will make a fairly effective path to earth.

    I'm inclined to agree with Andy B. You may never find the cause so instead replace what is there. Use class 2 fittings if possible.


    Dave
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