CAN FREEZER STORE MOBILES BE ADAPTED TO STORE FRUIT PALLETS?

After receiving several such inquiries recently,  some implications are listed below. 

Most freezer mobiles were designed to carry loads equal to or more than what is required to store fruit pallets.  At 2450 mms high fruit pallets require 12m clear to get 4 pallets in the height and not many existing freezer rooms are more than 11M.

For pome or deciduous fruit, gross pallet weights should be standardized at about 1300/1350 kgs especially if storing pears is a possibility. The current standard for citrus is 1450/1500kgs, possibly due to the higher initial lemon box weights.

The beam heights more than 9000 mms should have spacings in between pallets and frames of approximately 100 mms.

3 pallet Bay pitch measurements for older freezer mobiles are normally 3400mms.  Bay pitch is the measurement center of upright to center of upright.

With a 100mm frame/ lug combination, this allows 4 gaps of 75mms which is workable below 9000mms as fruit pallets have corner guards that keep the load relatively straight.

Any lean resulting from incoming transport should be rectified before storage in the mobiles using an inverter.

If in-rack sprinklers are required for the fruit configuration, hopefully not, check the nominal pallet back-to-back gap in the center of the mobiles as this should be 150mms rather than the standard  100mms in freezer stores.  If the nominal gap is under 150mms and problematic then an alternative is to consider adjusting the closing distance of the mobile bases so that a nominal 150mms is achieved.  Sufficient space at the rear of the mobiles for flexible hoses is also important but generally, existing gaps can be made to work.

Check with suppliers regarding row spacer positions and designs. While the mobile bases are generally adaptable to fruit pallets, the racking superstructure is more problematic. Existing load beams standard designs to fit a 3400mm bay pitch are generally 155mms deep.  Steel thickness is 1.6mms for 3000kgs UDL  i.e. 1000kgs gross per pallet and 1.9mms for 3600kgs UDL or 1200kgs per pallet. It is almost impossible to tell the difference and requires either a thickness tester or access to the original rack drawings. 

As apples are about the only product that can be considered for a  1.9mm thickness beam, as a general rule existing load beams must be changed.  Unless the mobile base beams are of the old 80mm by 120mm square tube design they must be changed too.   In this instance new base beams should have 25mm by 25mm angles welded to their outer faces, especially with shorter pallets, see below,  to ensure that the pallet blocks are supported.    

Frames also require attention. Just because the total weight per bay for fruit is equal to or less than that for frozen goods does not necessarily mean that the frames will work.  The vertical pitch is important. In freezer stores, it was generally 1752.6mms to suit a 1.5m high pallet.  Fruit pallets generally need a vertical pitch of 2743.2mms which changes the frame loading properties, especially as the first beam level is moved up. “Raising bottom beam levels by 20% can result in frame strength going down by 50 % “(as stated by a local certified structural engineer, Jock Pretorius – JMP Struct)

Currently checked existing upright profiles for 2 levels of fruit pallets, with the bottom level either on the mobile base or floor have shown that existing local rack frames cannot take a fruit pallet configuration.  The width of the new uprights is important as an upright/lug combination of more than 100 mms will decrease the gaps between pallets and pallet upright frames.  Some locally sourced upright frame replacements are of a composite construction which changes the frame base fixing hole positions. The new hole centers must be accurately placed on the mobile bases before drilling and tapping.  

Fruit pallet sizes especially on the front-to-back measurement may not be 1200mms as slightly shorter wooden pallets allow for different and more efficient container stowing patterns.  As standard frame widths on most existing mobile bases are 1100mms pallet overlap, nominally 50mms on both sides, becomes less. It’s important to make sure that the pallet blocks are on the beams as their disposable nature means that the bottom bearers may not take the load. The general answer to this is to use pallet support bars, which come in two types either full or partial support.  Some clients require 2 pallet supports per pallet and others one.

If you need input on your particular mobile system, give us a call to Barri Malherbe, our SEMA approved rack inspector who will be able to assist.

Barri-Leon Malherbe