Abstract: A limit ring for use in a pump arrangement includes a cylindrical body positioned about a central longitudinal axis, a first end and an opposite second end. A central passage is defined through the cylindrical body and is centered about, and extends, along the longitudinal axis between the first end and the second end. The central passage has a circular cross section when viewed along the longitudinal axis. The limit ring further includes a number of channels defined in the cylindrical body radially outward from the central passage, each channel extending between the first end and the second end of the cylindrical body.

Abstract: A limit ring for use in a pump arrangement includes a cylindrical body positioned about a central longitudinal axis, a first end and an opposite second end. A central passage is defined through the cylindrical body and is centered about, and extends, along the longitudinal axis between the first end and the second end. The central passage has a circular cross section when viewed along the longitudinal axis. The limit ring further includes a number of channels defined in the cylindrical body radially outward from the central passage, each channel extending between the first end and the second end of the cylindrical body.

Abstract: A glandless submersible electrical dynamo operative at high temperatures comprising a casing containing a stator and a rotor and a metal alloy filling the space within the casing. The metal alloy is liquid at the operating temperatures of the pump and is an alloy of bismuth, preferably with lead or tin. The bismuth is present in an amount of between 40-60% and the alloy has the property of substantially no volume change upon solidification.