Abstract: A mixer for mixing glass fibres into a thick aqueous cement slurry comprises means for feeding glass fibres on to the surface of a batch of the slurry in an upright cylindrical chamber, an agitator mounted on a coaxial vertical shaft and carrying at its lower end both a plurality of short impeller blades and a long horizontal member with tip blades of opposite sense to the impeller blades, so as to cause vertical as well as horizontal circulation of the slurry, and stationary baffles on the wall of the chamber angled to cause production of standing waves on the surface of the slurry.

Abstract: A foaming crude oil is separated into (i) liquid oil containing not more than 10% by volume of gas and (ii) gas containing not more than 200 parts per million of liquid oil by passing the foaming crude oil into a cyclone separator which has means for controllably adjusting the size of the inlet thereto and in which the ratio of the diameter of the vortex finder to the diameter of the vessel in the region of the inlet is from about 0.40 to 0.80, and which is also provided with a disengaging chamber and means for maintaining a minimum liquid level in said disengaging chamber.