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The vacuum system creates an atmospheric pressure difference between the inside of the tank and the surrounding air in order to fill or empty the tank. By creating a vacuum, the slurry can be sucked up. In the spreading phase, the principle is reversed: the tank is pressurised to expel the slurry. This means that there is no slurry flowing through the pump, only air.
Choosing the capacity (air flow) of your vacuum pump is an important step in the configuration of your slurry tanker. In the suction phase, it is interesting that the vacuum takes place within one minute. A pump with a flow rate per minute equal to the total capacity of the tank is therefore logically the first choice. For example, a pump that can suck up 10,000 l of air/minute will not only create a vacuum in your 10,000 l tank in just 1 minute, but will also maintain this vacuum during the entire filling process. If the flow rate was 5,000 l/min, this operation would have taken at least twice the time. In the spreading phase, i.e. the emptying phase, the pump just has to provide enough air inside the tank to empty it evenly. Choosing a too large pump means wasting tractor traction power, with a risk of premature wear. The vacuum level remains the same regardless of the pump chosen.
The 1,000 rpm version (direct connection) is usually more interesting, as it allows, in combination with the tractor P.T.O. rpm selector, to adjust the pump capacity to the required spreading flow. In addition, the pump running at a lower rpm saves engine power, which is beneficial for the tractor traction during spreading.
Cooling the pump is a major challenge for manufacturers. In addition to a traditional air flow, pumps are designed with fins for a conductive cooling. There is a slightly more efficient system, called "Ballast Port", which is also a low-cost solution: a continuous injection of fresh air into the pump body cools it down and allows it to work at 60% vacuum continuously. It is used on most of the models manufactured by “JUROP”.
JOSKIN mainly installs mobile vane pumps driven by an eccentric rotor that always rotates in the same direction: the air flow is directed by a deflector valve to either pump or spread slurry. They all achieve an equivalent vacuum, regardless of the model or capacity. It is therefore the air transfer capacity of the pump that should be taken into account. JOSKIN offers a range from 4,000 to 15,500 l/min. The main models are the MEC from Battioni & Pagani and the PN(E/R) from JUROP. They all have at least one forced drip lubrication that can be adjusted manually or automatically at the factory. The lubrication takes place both during the suction and the discharge phase. The JOSKIN Vacuumoil is specially designed for the pump vanes: a 5 l can is supplied with each slurry tanker equipped with a vacuum pump with vanes.
The 3 JUROP DL vacuum pumps offer large capacities: 17,600, 21,600 and 25,000 l air/min. Coming from the industrial sector, and more specifically from the hydrocleaners, they have two rotors with lobes instead of vanes. The absence of contact between the moving parts allows a lubrication-free operation. It is cooled by air injection. The advantages of this type of pump are its large capacity and small size. Moreover, the JUROP DL is not subject to wear and tear or pollutant emissions. As standard, it is equipped with suction and discharge silencers. JOSKIN also equips its DL pumps with a temperature alarm and filters to prevent foreign bodies from damaging the lobes.
All JOSKIN tankers with a vacuum pump are fitted with a tank overpressure security set at + 1 bar. When the pressure inside the tank exceeds this value, the springs compress, the top lid of the valve lifts and the pressure drops rapidly. Once the pressure is reduced to below + 1 bar, the lid returns to its initial position thanks to the return springs.
Based on a float system, the ball safety device (or overflow valve) prevents the slurry from following the same path as the air. When the tank is filled, the ball blocks the air outlet and prevents the slurry from flowing into the pump.
The self-cleaning syphon (30 or 60 l) serves as an additional safety device between the tank and the pump. It is designed to empty automatically when air is forced back into the tank. For an easy maintenance, self-cleaning syphons are fitted with a cleaning plug.
This ecological and economical system offers 3 advantages: it collects the used oil coming out of the pump, reduces the noise pollution considerably and sucks in the air from above to prevent it from becoming dusty. This accessory considerably increases the lifespan of the pump.
The high-capacity JOSKIN pressure relief valve (Ø 150 mm) allows the air to be quickly evacuated and prevents a premature heating of the pump. It also gives the possibility to adjust the spreading rate by acting on the internal pressure of the tank.
A vacuum pump is equipped with either a mechanical or hydraulic change-over, which allows you to choose between "spreading" and "suction". The hydraulic control is essential when using a filling device such as a JUMBO arm, a dorsal boom, etc. The change-over is operated from the tractor cab to anticipate pumping or spreading.