Hydraulic Press Information

Hydraulic Presses are simple systems. Understanding the fundamentals will assist you in maintaining the machine and quickly solving any problems.

Components of hydraulic wine press.

1. Piston. The pressing plate is attached to the piston.
2. Pump. The pump is driven by an electric motor.
3. Three-way valve.
4. Sump. This is the reservoir for the hydraulic fluid.
5. Electric Control Box.
6. Pressure Gauge with adjustable shut-off pressure.

Brief description of operation.

When the unit is turned on, the pump continually pumps oil from the sump to the three way valve. When the valve is in the center position, the oil is simply returned to the sump.

When the valve is in the left position, oil is pumped to the top of the piston forcing the piston down. At the same time, oil is returned to the sump from the lower chamber of the piston.

When the valve is in the right position, oil is pumped into the lower chamber of the piston, thus raising the piston. At the same time, oil is returned to the sump from the upper chamber of the piston.

The pressure gauge has an adjustable red marker (80-300 bar). When the pressure reaches the selected value, the power to the motor is automatically shut off.

Figure 1.
1. Pump.
2. Motor.
3. Sump. The sump is the hollow support of the unit. The pump, 3-way valve and electrical box are mounted to the sump.
4. Drain valve of Sump.
5. Pump spring assembly. (There is a ball bearing and spring behind this cap.)
6. Pump Output line. This line goes to the 3-way valve. There is a check valve in this line (visible in photo).

When the motor (2) is running, oil flows from the sump (3) through the pump (1) and out the line (6).

Figure 2
1. Line to Top Chamber of Piston
2. Line to Bottom Chamber of Piston
3. 3-way Valve. In photo, it is in the neutral positon.
4. Air bleed valve (this is located on top of the valve housing and behind the line that attaches the pressure gauge)
5. Input Line. Connects pump to valve.
6. Pressure Gauge. The red marker is adjustable (set at ~80 bar in this photo).

When the motor is running with the valve in the center position (as shown in the photo) the oil enters the valve through line 5 and exits out the back of the valve housing into the sump.

If the valve is turned to the left, the oil enters through line 5, exits through line 2 to the top of the piston. At the same time, oil returns from the bottom of the piston through line 1. The oil from line 1 is returned to the sump through the back of the valve housing.

If the valve is turned to the right, oil enters through line 5, exits through line 1 to the bottom of the piston. At the same time, oil returns from the top of the piston through line 2. The oil from line 2 is returned to the sump through the back of the valve housing.


Figure 3. The Electric Control Box.
Please note there are 2 or 3 versions of this box on the presses we sell. The basic functions are the same.

The emergency shut off is the red button on the left. Push in to shut machine off. It must be twisted and pulled out for the machine to run. The right knob is simply the ON/OFF. This particular box has two fuses near the top.

Figure 4. The Piston.
The piston will move down when oil is pumped into the upper line. The piston moves upward when oil is pumped into the lower line.

Figure 5. Sump Oil Cap.
The Sump Oil Cap (2) is located on top of the sump behind the electric control box (1). Remove this to check the oil level. (Use a long piece of wire or stick or string to check oil level.) The cap has a hole in it for applying air pressure to the sump (see Problems and Solutions).


Problems and Solutions

Problem: The Piston will not go down (or up).
Solution: Apply light air pressure for 10-15 seconds to the sump through the sump fill cap while the machine is running. You can simply apply the pressre by blowing into the cap by mouth (the cap has a small hole in it). Or attach a piece of tubing and blow into that.
Cause of Problem: Air bubble in line, usually between the piston and the 3-way valve.

Problem: Marc is thrown out of the basket through the wooden slats.
Solution: Remove more juice from the must before exerting pressure.
Cause of Problem: Air pockets in the must. This is unavoidable to some extent but you can take simple steps to mitigate the size of the air pockets which will greatly mitigate this. The less juice in the must, the less the problem. Therefore, remove as much juice as possible before pressing [This is easier with fermented reds than with whites]. Also, load the basket in layers and use a punch down tool to squeeze out some of the juice before pressing. On large presses, it may be possible to get into the press with rubber boots and walk on it to squeeze out juice. [We have seen this approach in Italy.] Of course, wrap the basket to minimize the mess. Plastic sheeting and shade cloth (available at garden centers) work well.

Special Attention

Always begin pressing with the lightest possible pressure, about 80 bar. This helps to minimize squirting juice and pulp. After the must has been completely pressed at this low pressure, then you may increase the pressure to get more juice out of the marc.

Set the pressure to the minimum, 80 bar, when retracting the piston. Never leave the pressure high when pulling the piston back up.