8/12/2019 Tools of the Trade: A-frame gantry hoist

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Tools of thetrade:

A-frame gantry hoist

Chiz Harward

lthough not often seen much outside ofdeep urban sites, the A-frame gantryAhoist is a great bit of kit and can be the

best way of getting spoil out of a deepexcavation and is far preferable to using

So, how are you going to get your spoil out?buckets and a bit of rope!

These hoists are ideal for sites where theObviously this system depends entirely on theexcavation will proceed to some depth and aintegrity of the barrow, a worrying thought givensteady supply of spoil needs to be removed

the state of some barrows.80l is handily thefrom the excavation area, but it is notsame volume as a full barrow. The hoist canpracticable to use a machine to muck-out. Theyalso be used to carry tools, finds andhave been successfully used on shafts of overpaperwork into and out of the excavation -you8m depth.definitely shouldnt be carrying tools up anddown ladders.The hoist is erected on site and should take

about half an hour to assemble -assuming allYou will need to write site-specific methodthe bolts are there. The frame is boltedstatements for the installation and use of thetogether and carried to its intended position,hoist, and have a clear system of safe working -counterweights are placed in bins attached toespecially making sure that the skip is not putthe back of the hoist and it is often best to

back into the trench whilst people are workingattach the hoist to any edge protection system there -accidents have happened. Everythingsuch as scaffolding. The motor unit is then liftedneeds to be recorded and all staff need trainingonto the gantry beam: this is the hardest bit ofin all the procedures you have put in place. Theassembly as the beams can get warped andhoist and all related equipment should bethe motor unit is very heavy, lifting planchecked before each shift, and a record kept, itrequired! Once the motor unit is in place stop-is wise to use a permit to work system forbolts prevent the unit running off the back of theexcavations that use a hoist.gantry. The hoists run on 110V power, usually

at 32A as the power can drop if using longBear in mind that your excavation may beextension leads and you may need a separateconsidered a confined space and you maytransformer for each hoist.

need a written escape plan and means ofemergency access/egress plus a designatedTo lift the spoil a steel 80 litre skip is far betterTopman, gas monitors, harnesses and possiblythan a barrow hoist -where chains are attachedbreathing apparatus sets.to the barrow and lift the entire barrow.

Photograph

MoLA

IfA Diggers Forum newsletter 7: Autumn 2011

8/12/2019 Tools of the Trade: A-frame gantry hoist

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If it is deemed suitable by a properly competent indeed. In addition if you are going to beperson then the hoist might be able to be used working in a deep excavation then having a

as a means of rescue if a worker needs hoist will usually be a cheaper option than aevacuation from the excavation -so they will dedicated 360 digger for spoil muck-away, Ifneed to wear a body harness so they can be he or she is a fellow archaeologist then thewinched out. You will need to indicate on the hoist operator can help with taking levels, fillingrescue plan if you intend to use the hoist as a out context sheets, bagging finds and takingmeans of rescue, and of course train everyone photos.in its use, and of course, record this.

Small tracked cranes can also be used,As we have seen, there is a fair amount of combining the benefits of mobility with thepaperwork involved with using these hoists -but ability to lift vertically.much of this would be required anyway given

that you are likely to be working at depth. The Conveyor belts have been used successfully tobenefits of safely getting tools in and spoil out get spoil out of deep excavations, althoughfar outweigh the paperwork and a hoist or some they seem to frequently break down, and theresimilar mechanised method should always be is a danger of spoil falling off the side. Theyused instead of buckets up ladders. also require a lot of room as they cannot be at

a steep angle.It is possible to muck out an excavation using askip attached to chains on the arm of a 360 Whatever particular system is best for your sitedigger, or to shovel into the bucket of the will depend on your specific circumstances: themachine, however this requires far more care A-frame hoist is certainly tried and tested forthan using a hoist, plus small 360s dont have archaeological works and has been

a particularly deep reach and are very awkward successfully used for many years.to operate safely in a confined trench. Theconsequences of a machine strike on theshoring or on a person in the trench are grave

C

otswoldArchaeology

IfA Diggers Forum newsletter 7: Autumn 2011