Positive Ventilation Store
C & P Gibson, Weston Hills, Spalding wanted to install a positive ventilation store for the chipping potatoes that they bag and sell to chip shops through the winter until May.
Welvent have built in the past an ambient box store, a grain drying store and a letter box bulk drying store.
Richard Gibson wanted to be able to dry potatoes thoroughly before cooling so a positive suction wall was opted for with a high airflow for drying.
A new building was constructed 24000 long x 18300 wide x 6100 high to store boxes 6 high with each stack (in pairs) having its own ventilation plenum covered with a PVC cover. The store holds 750 tonnes.
A suction plenum was built across the back wall with 4 doors on to ventilate the pairs of boxes and get maximum airflow through the potatoes. The air mixing refrigeration unit is in the centre of the plenum with tubes rising out through the top to blow air across the top of the boxes before being sucked through the sides of the boxes. Two sets of extract louvres and fans, inverter controlled are to each side of the unit giving a drying volume of 70cfm/tonne. The extract fans run the correct speed to match the position the louvres are in. The volume can be reduced to 50cfm/tonne when dry and the cooling beings. The refrigeration unit is 60kw to cool to 2.5°C if required, but this chipping will be stored at 8-9°C.
The store is controlled via a VC4000 controller which has a drying program, ambient and ambient refrigeration program. The compressor is inverter controlled to give a pin point duct temperature, thus being very energy efficient.
Two extra fans are fitted to the top of the duct with 90° bends blowing air over the top of the boxes before being sucked through the sides of the boxes positively. The slave fans stop any CIPC gas going through the refrigeration coil. The fans are speed controlled to put the gas in slowly and positively as recommended by the BPC.
The boxes were specially constructed so air cannot leak through the ends at the forklift points and blocked off with the side boards as they are staggered to stop air short circuiting.
The store was commissioned in September with full instruction on its operation given to Richard Gibson.