2. Explosion-proof electric motor fitted to pumps
3. Gear pump (Cf. Beigbeder Atienza)
4. variable displacement pump, compensated pressure

1. Los discos van atornillados al conjunto del malacate en los agujeros de las bridas.
"The discs are screwed into the winch assembly, through [or "by means of"] the holes in the flanges."
Note: ["flange" is only the most common equivalent of "brida." Other options include "clamp" and
"dog" (in the mechanical-engineering sense).]

2. Motor electrico a prueba de explosion acopiado a las bombas.
"Explosion-proof electric motor connected to the pumps."

3. Bomba de engranes ["engrane" is the standard spelling (i.e., "gear," in the singular)]
"Geared pump"

4. Una bomba de desplazamiento variable, presion compansada [should be "compensada"]...
"Pressure-compensated variable-displacement pump…" (see the web sites below)