Fluid discharge apparatus and method of use

A fluid discharge apparatus for cleaning and/or jetting the interior of a fluid conduit, the fluid discharge apparatus comprising:

• a body, the body comprising an inlet configured to receive fluid from a fluid source, and one or more fluid discharge ports;
• and
• a valve arrangement disposed in the body and passively operable to be cycled to provide an interrupted flow of fluid through the body by moving between a first condition and a second condition via a partially open condition to provide said interrupted flow of fluid through the body, wherein in the first condition fluid entering the body from the inlet is prevented from passing through the apparatus, wherein in the second condition a flow path having a maximum flow area through the apparatus is defined and fluid is discharged through the one or more fluid discharge ports, and wherein in the partially open condition the flow path through the apparatus is defined and has a flow area less than the maximum flow area;
• wherein the valve arrangement comprises a piston disposed in an axial bore in the body, the piston operable to move axially in the body between the first condition and the second condition, via the partially open condition,
• wherein the valve arrangement comprises a stem disposed in a bore of the piston, and the piston is arranged to move axially with respect to the stem,
• the stem comprises one or more flow apertures, which are radially oriented in the stem and/or the apparatus,
• wherein the piston comprises a first active piston area formed on a face on an interior profile of the piston, whereby a pressure acting on the first active piston area moves the piston in a first direction relative to the body, and whereby said pressure acting on the first active piston area in the first condition moves the piston from the first condition to the partially open condition when the pressure acting on the first active piston area in the first condition exceeds a predetermined opening pressure,
• and wherein the piston comprises a second active piston area larger than the first active piston area and formed on a face on an exterior profile of the piston, whereby a pressure acting on the second active piston area moves the piston in said same first direction relative to the body, and whereby in the partially open condition the second active piston area becomes active so that pressure acting on the first and second active piston areas in the partially open condition is operable to move the piston from the partially open condition to the second condition of the apparatus when the pressure acting on the first and second active piston areas in the partially open condition exceeds the predetermined opening pressure.