Essential difference between screw press and hydraulic press

Hydraulic oil press is a kind of oil press equipment, which uses liquid as pressure transfer medium and presses the oil according to the principle of hydrostatic pressure transfer. It is a closed loop system composed of two parts, hydraulic system and oil press body. They are mainly composed of hydraulic pump station, control valve, motor, electric appliance cabinet, oil cylinder, barrel, frame and so on. The spiral oil press is a kind of oil pressing process which produces the high temperature and high pressure from the rotation and extrusion between the squeezing ring and the press ring. The utility model is mainly composed of a frame, a control cabinet, a spiral shaft, a pressing ring, a cake outlet and the like.

1.Oil extraction method

Hydraulic oil press
Hydraulic oil press is a kind of oil press equipment, which uses liquid as pressure transfer medium and presses the oil according to the principle of hydrostatic pressure transfer. It is a closed loop system composed of two parts, hydraulic system and oil press body. They are mainly composed of hydraulic pump station, control valve, motor, electric appliance cabinet, oil cylinder, barrel, frame and so on. According to the driving power of the oil pump, there are two kinds of power source: manual and electric. The pressure can be divided into vertical and horizontal.
The hydraulic press is a static press method, and the technological process is fried-crushed-steamed-pressed, because the pressing process is not high and not more than 60 degrees, it is a typical cold pressing process, the largest vegetable oil and protein nutrient retention, oil from primary color and fragrance flavor, without filtering can be eaten directly. General high-grade oil, such as tea oil, olive oil, flax oil, due to high nutritional value and high price, generally require the use of hydraulic press, now a lot of peanut, soybean and rapeseed with hydraulic press, squeeze the oil taste better. 

 
hydraulic oil press
Screw oil press
The screw pressing is a method of dynamic pressing, which is forced by the spiral shaft to feed the material, and produces high temperature and high pressure under the rotation and extrusion between the squeezing ring and the pressing ring, thereby enabling the oil to be crushed from the oil and extruded into the oil to produce the oil out of the cake. The utility model is mainly composed of a frame, a control cabinet, a spiral shaft, a pressing ring, a cake outlet, etc. According to the way of work can be divided into round and row machines. As the press process is accompanied by friction, the high temperature inside the chamber, often exceeding 200 degrees, is a typical hot pressing process. The temperature is too high, resulting in protein structure damaged severely to produce phosphoric acid material, color black, squeeze the oil filter, sometimes need to add salt water to remove acid.
Most of the rapeseed oil is from screw press now, the screw press is characterized by large output and simple process.
In addition, the hydraulic pressed cake is round cake, because the static pressing process without overheating phenomenon, cake protein fully retained, high nutritional value, can be used as feed for pigs or senior fish bait fishing; The spiral pressed cake is sheet cake, due to the crushing process at high temperature, the loss of nutritional value of protein depleted, can only be used as fertilizer or leaching of raw materials.

hydraulic oil press

2.Oil quality
Squeezing method of hydraulic oil press oil is a pure physical method, no temperature in oil extraction process, the organic component does not destroy the oil, linseed oil, oil well, free of impurities, a lot of places now used to crush sesame, walnut and other high-grade oil. In the process of oil extraction, the screw mill produces high temperature due to mechanical friction and destroys the organic composition of the oil, in the process of rotational friction, some oil with high oil content will produce oil sludge and squeeze out from the ring. The oil content will be a little more. Because of higher oil temperature from oil, nutrients damage, but also the need for pressing after cooling treatment.

 
hydraulic oil press
             

3.Output
Hydraulic oil extraction machine is relatively low, single machine can be small, oil in the press before the order of work, need to be broken, steamed, fried and cake, more equipment, and covers an area of large, cumbersome work, high production costs, equipment investment, production is small. So it's usually used to crush premium oils.
The screw press has small investment and high processing capacity. A device can be processed soybeans, rapeseed, peanut, cottonseed oil, tea seed granule, the machine structure is compact, durable, high yield and oil yield, convenient operation and maintenance, low investment cost, suitable for sporadic pressing, cold pressing and hot pressing, is a kind of ideal oil equipment.

hydraulic oil press


4.Oil recovery, utilization
In the process of pressing, the hydraulic press does not destroy the organic composition of the oil, and the cake has two high value and wide application range,
like some food processing enterprises do walnut powder, almond, peanuts, a part of the oil can be done after the reduction treatment or processed into other products, so it has certain requirements for oil yield, hydraulic press machine to adjust to different pressure can control the oil rate, these enterprises will be more suitable; It is impossible to achieve in the screw press machine, screw press in the oil extraction process by mechanical friction to produce high temperature, oil extraction process of oil in the water will drain, it also caused some losses for direct sale of cake (moisture content with hydraulic press cake in about 10% moisture content by screw press oil cake is only 2-3%).

5.Power distribution
Small and medium-sized hydraulic press machine, matching power is generally in 1.5-3KW, and a small screw press machine, equipped with power is also above 5KW!

6.Failure rate and price of damaged parts
Hydraulic press machine is driven by the oil pump and some control valve work, the fault mainly in the pipeline and sealing plunger, maintenance mainly to replace some seal or can be solved, easy maintenance and cheap parts. Screw press by mechanical rotation, resulting in a large number of friction in the oil extraction process, the screw shaft wear and squeezed between the ring rather quickly, if the workload is generally six months to be replaced once, folded parts trouble, the price is higher;
The vertical structure of hydraulic press machine, button type centralized control, small occupied area, convenient operation.

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