Method and arrangement for maintaining fluid flow pressure in a system at a preset, almost constant level

An arrangement for maintaining fluid flow pressure in a system at a preset level comprising:

• a pressure accumulator initially holding a pre-pressurized gas pressure (p0) and comprising a valve disc, in the form of a diaphragm accumulator or a bladder accumulator;
• and
• a nozzle valve comprising:
• a valve body having an outflow channel and the outflow channel having a mouth opposite the accumulator wherein the mouth has a cross-sectional area and a diameter,
• a needle with a conical needle head and a shaft axially oriented inside the valve body, for opening and closing the mouth of the outflow channel wherein, the conical needle head has a conical angle,
• a slide element mounted inside the valve body for guiding the needle shaft,
• one or more channels wherein, a fluid inflow into the valve body can pass the slide element when the fluid flows through the one or more channels to the pressure accumulator wherein, the pressure accumulator is connected to the valve body opposite the outflow channel,
• a pre-tensioned spring exerting a force (Fs) on the needle towards the accumulator wherein, the spring having a first end and a second end is supported at the first end by the valve body and at the second end by the needle shaft, whereby the force (Fs) holds the needle shaft against the valve disc of the pressure accumulator ensuring the needle and the valve disc move together;
• whereby, the needle is moveable along its axis in an opening direction and a closing direction in order to adjust the cross-sectional area of the outflow channel mouth around the conical needle head, and the needle having a length such that the conical needle head does not get stuck in the mouth of the outflow channel, thereby always allowing a small fluid leak,
• wherein, the pre-pressurized gas pressure (p0) in the pressure accumulator exerts a force (Fp0) on the valve disc and a force on the needle in the closing direction, whereby, the valve disc in a lowest position disposes the conical needle head in the mouth of the outflow channel closing the mouth of the outflow channel, and the spring force (Fs) with a force (Fp1) exerted by the fluid inflow on the valve disc move the valve disc and the needle against the force (Fp0) exerted by the pre-pressurized gas pressure (p0) in the accumulator opening the mouth of the outflow channel;
• wherein, when the valve disc moves in the opening direction, the pre-pressurized gas pressure (p0) in the pressure accumulator increases to a second pressure (p2) that corresponds to the movement of the valve disc;
• wherein, the diameter of the outflow channel mouth, the conical angle of the conical needle head and a gas volume in the pressure accumulator are such that the conical needle head adjusts the cross-sectional area of the outflow channel mouth around the conical needle head in a manner that a pressure (p1) of a fluid outflow, and a pressure in the whole system, remain within a range determined from the pre-set pre-pressurized gas pressure (p0) while fluid inflow is sufficient to keep the outflow channel mouth open.