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The current situation and development trend of screw oil press

September 16, 2021

screw oil press

The application of screw oil press has a history of more than 100 years. During this period, people in the industry have continuously improved its various aspects of performance. Until today, the research topic of screw oil press is still one of the research hotspots in the oil machinery industry. 


At present, the screw oil press can be divided into two types according to the screw form: single screw and double screw oil press. The double-screw oil press is developed on the basis of the single-screw oil press, which uses mechanical external force to extract oil from the oil. The pressing structure is basically the same, and they are all composed of snails, slivers, and cake heads. my country's oil supply is complex and diverse, and the pressing characteristics of different types of oils are quite different, so diversified requirements are put forward for the design of the pressing structure. How to design and manufacture a good pressing effect according to the characteristics of one or a type of oil The oil press is a problem that needs to be solved urgently.


Since Anderson in the United States invented the first continuous screw oil press in 1900, the screw oil press has been more widely used as the main equipment for extracting fat from oil. Screw oil press has its unique advantages: simple principle and structure, low manufacturing cost, and can be used for continuous pressing of different types of oils, basically realizing the needs of different pressing processes. However, as people’s requirements for the quality and output of oils are increasing, traditional oil presses are no longer able to handle the mechanical structure, wear resistance of main components, quality and output of oil, and adaptability to oils. Adapt to new needs. Therefore, a large number of new screw oil presses have been developed, and large-scale and automation will be the future development direction of oil presses.


The slurry enters the slurry inlet of the screw press dewatering machine at the required concentration, and the slurry is pushed axially in the filter drum by the rotation of the screw shaft, and the volume of the spiral groove gradually decreases, so that the slurry is subjected to radial and axial Gradually dehydrated and concentrated by mechanical squeezing. The back pressure device installed at the pulp outlet can adjust the squeezing force and pulp concentration. The high-concentration slurry is discharged from the slurry outlet, and the filtrate passes through the filter drum on the filter drum and is collected to the filtrate outlet for discharge.


The screw shaft works under various resistances and friction forces of the slurry, and its main failure mode is wear or damage due to insufficient strength. When designing the screw shaft, it is necessary to select the material and structure according to the production capacity and working conditions of the screw press dehydrator, determine the structural parameters such as the diameter of the screw shaft, compression ratio, and pitch, and then carry out the force analysis and strength check.


In addition to meeting the requirements of strength and rigidity, the material of the screw shaft should also have good wear resistance. From the structure, the screw shaft can be divided into a cast structure and a welded structure. The casting structure is to cast the spiral blade and the shaft as a whole. Generally, nodular cast iron and cast steel are used as materials. Cast steel has higher strength and better plasticity, good casting performance and cutting performance, and the design of large-scale screw press dehydrator should adopt cast steel. In order to accelerate its wear resistance, the working surface of the spiral should be spray welded with wear-resistant cemented carbide with a thickness of 2 to 3 mm. The welding structure is to process the spiral blade and the shaft separately and then weld them together. It is characterized by convenient addition and low cost, but the thickness of the spiral blade generally does not change. The spiral blade at the back of the compression section wears faster, which will affect the use of the spiral shaft. life. The materials generally use No. 45 steel and 40Cr steel. The cutting performance of No. 45 steel is better, the cost is lower, and the wear resistance and corrosion resistance are lower. The strength of 40Cr steel is higher than that of No. 45 steel. It can be surface quenched after processing, and the surface hardness can be further accelerated.


There are three main manufacturers of screw presses in the world: Anderson and French companies in the United States and Simon in the United Kingdom. They are introduced separately below.

(1) Anderson oil press

In the Anderson oil press, it is characterized by two vertical and horizontal pressing shafts. The raw material enters on the upper part of the vertical shaft, and 50% of the total oil content of the raw material can be extracted from the vertical shaft. The remaining part is squeezed on the horizontal axis, and the rotational speed of the horizontal axis is about 1/2 of the vertical axis. In the complete squeezing of rapeseed, the horizontal axis is 28r/min and the vertical axis is 56"min. In the pre-expression extraction, the speed can be increased to 40 r/Hlin and 80 r, min.


(2) Laughing at French Company

Laughing French company’s oil presses are mostly characterized by horizontal-axis screw presses. But the press shaft can be divided into a fast rotating part and a low speed rotating part. The raw material xj enters the fast-rotating low-pressure part for squeezing oil, and then sequentially enters the low-speed rotating high-pressure part for squeezing oil.


(3) Simon oil press

The Simon-Rosdowns oil press is also a high-pressure screw press, and is equipped with a double screw feed. The inner surface of the machine is treated with stellite. The general processing capacity is 40 t, d-65 continents, and the power is 112 kWh-150 kWh. The residual oil in the cake is 4% to 6% when fully squeezed, and 10% to 18% when pre-squeezed. "


(1) British Simon-Rosdans series screw press

The squeezing screw shaft adopts a water-cooled structure to prevent the ejected cake from burning, to ensure the quality of the oil, and to reduce the axial force caused by thermal deformation. The feeding device is composed of a metering drive and an independent drive forcing screw device. Double screw feeding is used, which is conducive to forced feeding and self-cleaning.

Snail squeezing: For oil with low fiber content, quenching snails are used; for oil with high fiber content, stellite with high surface strength is used.

The crushing cage adopts a vertical center split hinge structure. The surface of the pressed sliver is coated or welded with a layer of alloy with high wear resistance.


(2) American Francis high-pressure water-cooled screw oil press

The squeezing screw shaft adopts a double-speed squeezing shaft, and the feeding part has a high speed, so that the oil is compressed and compacted; the squeezing part has a low rotation speed and a powerful squeeze. The used screw shaft can be turned around and used, which doubles the life span. Feeding device: It adopts variable speed screw conveyor and slide pipe to form an independent feeding device.


(3) American Anderson screw oil press

The squeezing screw adopts a water-cooled hollow squeezing screw. Snails: 8 sections of snails, of which 1.2 sections have the same diameter, which are the pre-pressing sections; 3.4, 5.6, and 7.8 sections of the snails have the same outer diameter and the same size between each section of the snails. Equipped with a cone-shaped village circle. Press chamber: There are two horizontal and vertical press chambers. Domestic 200A-3 type oil press: the screw shaft consists of a mandrel with a length of 1960mm. It is composed of 7-section snail and 6-section lining ring. The first section of the screw is a double-threaded thread, and there is a hanging knife on the lining ring. The pressing chamber has 7 stages, the first stage is pre-pressing, the 2.3 stage is the main pressing stage, and the 7th stage is the cake output stage. The gap of each section of the press chamber is different, and the gap is adjusted according to the different oil material to adapt to different oil materials.