Delta Primary as well. I just took 3 old westinghouse 10 KVA transformers out of service that powered old equipment out of a 4kv sub station that we took out of service. Were in the Process of eliminating 4 KV and upgrading alot of stuff either to 13.8kv or 23kv.
We use equipment. We have mini cranes on our buckets or we will use a small crane truck to hoist them onto the pole. Some of the transformers weigh a few hundred pounds. The ones I took down were manageable to move on the ground but you couldn't pick them up.
Heat exchangers to cool the oil inside. Hot oil inside is cooled by convection into the pipes and makes it run a little cooler. Bigger units have a set of fins to make the cooling surface bigger. Really big ones have a tank on top to hold the oil as the transformer heats up on load and the oil expands.
All run a little above ambient, but all are limited to running too hot. Most of the time they are only going to go up to 70C at the surface, inside it will be a little hotter, but the unit cannot go too hot as the paper insulation in the transformer will degrade, and the oil will break down faster. Inside the core it can get up to 90C, right inside the winding, but most have a way to circulate the oil inside, by having sectionalised windings and core spacers between winding sections to allow flow. A 1MVA transformer has 2 44 gallon drums of oil in it. Power companies come around every few years and filter the oil and check it, the filter removes suspended water and paper fibres that may be present.
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