Introduction
Edible oils. An important part of the global food supply chain. From sunflower oil to palm oil, groundnut oil, olive oil and many more, edible plant-based oils are used in homes and restaurants for cooking. They're used to manufacture many of the packaged foods we consume. Edible oils and the by-products from their production are also important feedstocks for industries like green fuels, oleochemicals, animal feed, and energy generation.
At the centre of all these processes and industries lies a singular activity: edible oil extraction, typically carried out using oil expeller machines, solvent extractors, specialty equipment, or a combination of these machines. At the centre of most oil extraction operations lies a singular type of equipment: edible oil expeller press machines.
Oil expeller presses are usually used for the mechanical extraction of oil (more on this soon). Nonetheless, even when edible oil manufacturers rely on solvent extraction or other extraction techniques, they often use oil expellers to pre-press the oil-bearing material, retain the nutritional qualities of the oil, and maximise oil yield.
This isn't the only reason why oil expellers are so important. You may have seen or read about vegetable oils in the news in recent times because of some of the negative impacts associated with them - deforestation as land use patterns shift to accommodate feedstock cultivation; the high carbon footprint of some oils; the waste generated during the production and refining of oils. Addressing these ESG i.e. environmental, social, and governance concerns is important as they affect human and environmental health.
Nonetheless, edible plant-based oils are incredibly important. In 2020, a report by the Ministry of Foreign Affairs of The Republic of Indonesia highlighted the important contribution that vegetable oils have made towards fulfilling the United Nations' Sustainable Development Goals (UN SDGs). From improving food and protein supply in service of SDGs 2 and 3 (zero hunger and good health and well-being) to contributing to job creation, smallholder farmers, and GDP (SDG 1: no poverty and SDG 8: decent work and economic growth), edible oil production is crucial to human health, economic growth and sustainable development.
In this delicate balance, edible oil manufacturers must find sustainable methods to extract oil. Methods which prioritise people, planet and profits. Understanding how oil expellers work and investing in the right one is critical to achieving this mission.
So in this article, we're taking a deep dive into all things edible oil expeller press, starting at the very beginning.
What is mechanical extraction?
In the edible oil extraction industry, manufacturers largely rely on two methods to extract oil from plant-based oil-bearing materials: mechanical extraction and/or solvent extraction.
Mechanical extraction is a relatively older approach to oil extraction. It involves using mechanical pressure to squeeze oil out from the seed, nut, fruit, or other part of an oleaginous (oil-producing) crop. Traditionally, mechanical extraction was carried out using fairly simple machines - for instance, ghanis in India and other manual or animal-operated machines in Africa and other parts of the world. This involved crushing say, groundnuts, between two stones to expel oil.
Today, oil manufacturers who use the mechanical extraction process rely on more sophisticated machines called oil expellers (also referred to as expeller press or oil press machines). These expellers may be either hydraulic presses or screw presses (more on this later).
The other most common technique for industrial edible oil extraction is solvent extraction. This technique relies on the use of organic solvents like hexane to dissolve the oil content of seeds, bran, etc. Even when this is the primary method to extract oil, manufacturers will often use an oil expeller to pre-press the raw material. This not only expels some of the oil but also reduces the size of the feed, making it more compact to ensure high efficiency in the solvent extraction or specialty extraction process.
As you can see, no matter the type of extraction process, mechanical techniques and oil expeller machines are mainstays of the edible oil industry.
Anatomy of an oil expeller press machine
An oil expeller press is the heart and soul of any oil extraction operation. This essential piece of equipment uses pressure to separate oilseeds, nuts or fruit into oil and meal.
Typically, an edible oil expeller will consist of a chamber into which the prepared raw material is fed. Using a screw, piston or other machine component, pressure is exerted onto the raw material, expelling the oil from it. The oil is collected, filtered and refined while the remaining cake is either sent to a solvent extraction plant for further extraction or to another industry where this by-product has a productive application.
Expeller machines differ in size, capacity and design. The capacity of an expeller is generally expressed in terms of the weight of raw material that it can process every hour. Simple expellers for commercial use may have capacities of anywhere between three kilograms and 100 kilograms of input material per hour. Larger industrial machines and plants have much higher per-hour capacities; their production capacity is often expressed as tonnes per day (TPD).
Now that we've understood the need, basic operations, and general anatomy of expellers, let's jump into the two types of technologies that these machines use to exert force on oil-bearing materials to expel oil. The next section will focus on the distinction between hydraulic oil expellers and screw oil presses.
In the previous section of this blog post, we got an introduction to the fundamentals of mechanical extraction and expeller press machines. Now, it's time to go a step further - into the two broad categories of expeller press machines.
Types of expellers: Hydraulic press vs screw press
Broadly, there are two types of expeller machines, differentiated based on the mode of pressure applied.
Hydraulic expeller presses use hydraulic pressure i.e. they use liquid as a medium to pressurise the oil-bearing material and extract oil. Screw presses, on the other hand, use mechanical pressure from a rotating screw to press the oil-bearing material against the walls of the shaft or chamber.
These foundational differences in design and operation impact oil yield, oil quality, processing capacity, and several other factors during edible oil extraction. No one expeller type is objectively better than the other - depending on the quantity, quality and type of oil you are extracting, you may choose to invest in either type of expeller.
Let's look at the factors and product features which would affect your choice of expeller type.
Hydraulic press
Anatomy and operation
Hydraulic press-based expellers use the principle of liquid (generally oil) pressure transmission to squeeze the oleaginous material and extract oil from it.
A hydraulic press system typically comprises a hydraulic cylinder, a piston within a pressing chamber, a hydraulic pump station, a control valve, an electrical cabinet, a motor, a frame, and other components. The oilseeds, nuts etc. are placed inside the chamber, after which hydraulic pressure is applied to crush them and expel oil. The expelled oil is collected through a filter and drainage system to separate it from the remaining solids or cake.
Pros of hydraulic pressing
Hydraulic oil presses are ideal for producing high-quality, cold-pressed oils in small batches. Hydraulically pressed oil generally preserves its natural nutrients and flavours and has minimal impurities. While hydraulic expeller machines operate more slowly and have higher labour requirements, compared to screw presses, they are quieter and easier to operate.
Here's a quick list of advantages of using hydraulic presses:
- Advanced, highly efficient technology
- Easy to operate
- Produces less noise compared to screw press
- Needs no heat or chemicals for edible oil extraction, retaining natural oil properties
- Produces clean oil with minimal need for treatment/refining
- Ideal for producers of cold-pressed walnut, sesame, peanut etc. oil
Challenges associated with hydraulic expellers
Using a hydraulic oil expeller also has some drawbacks:
- Low oil yield rate
- Small processing capacity: Since hydraulic expellers are only suitable for batch processing and not continuous processing, they have limited applications in large-scale operations.
- Difficulties in operations and maintenance: Using a hydraulic press can be labour-intensive because of the frequent need for manual intervention. Moreover, if there is even a small oil leakage in the hydraulic system, the expeller cannot be used until repairs are completed. In short, hydraulic expellers have high maintenance requirements.
- Relatively large sizes, high weight, and slow operations
- Higher costs for purchase and installation
Pro tip: Choose the right hydraulic oil for your hydraulic press
The right hydraulic oil can benefit your expeller machine through smoother operation, lower maintenance, and increased reliability.
When operating a hydraulic press machine, ensure that you are using a hydraulic oil which improves the efficiency of the process and extends the life of the equipment. The right oil has the optimal viscosity and additives that reduce corrosion and wear and tear. It also prevents leaks, facilitates stable performance, and reduces maintenance costs by minimising sludge formation.
Given the high value of environmental and human health and safety, you should also consider using biodegradable and/or fire-resistant fluids.
Screw press
Anatomy and operation
Screw oil presses use mechanical pressure from a screw to expel oil from oleaginous materials.
Screw presses typically consist of an expeller screw, screw shaft enclosed in a cylindrical barrel, seed hopper, press head, press nozzle, gearbox, control cabinet, oil canals, frame, slag outlet, and other components.
The seed hopper, generally made of metal, directs the raw material into the press. The gearbox converts the speed and torque of the motor into the appropriate settings for the expeller machine. The screw rotates within its cylindrical cage to press the oil-bearing materials against the side of the chamber or cage. The resultant friction not only breaks down the raw material to expel oil but also increases the temperature in the system - this heat, combined with high pressures, aids in oil extraction. The expelled oil seeps through a screening surface while the residual solids continue to move through the machine, from where they are removed as cake or meal.
Pros of screw pressing
Screw-based oil expellers are ideal for large-scale operations requiring high throughput and versatility.
Most screw presses offer the following benefits:
- High oil yield, as the same oilseeds get pressed three to four times
- Can be used for various oilseeds
- Relatively simple operations
- Durability and stability, due to the simple mechanical structure of the system
- Suitability for full continuous edible oil processing lines
Challenges associated with screw-based expellers
Screw presses have some drawbacks:
- Higher nutrient loss compared to hydraulic presses: Screw presses generate more heat during the pressing process. This causes nutrient loss in the oil, making screw presses unsuitable for delicate oils. However, this isn't an issue for cooking oils since they are heated when used in the kitchen.
- More impurities: Screw-pressed oil has more impurities compared to hydraulically pressed oil. It must be filtered well using a centrifugal or other type of oil filter before it can be used. This adds to the cost and time of edible oil production.
That's all for the differences between hydraulic and screw presses. In the next and final section of this post, we're going to dive deep into the decision-making process - how you can make a smart investment, one that will stand the test of time.
Now that you know the basics of mechanical extraction and the types of screw presses you may find on the market, it's time to go another step further.
Let's get into how you can translate these learnings into an informed decision. From expeller press machine features, finances, business planning and relationship-building, we'll explore all it takes to set up a successful mechanical extraction plant.
Assessing expeller press machine features
We've said it before and we'll say it again: when it comes to edible oil expeller machines, there is no one-size-fits-all solution.
If you're setting up, say, a groundnut oil extraction plant, your facility and equipment will be a bit different compared to if you were setting up a coconut oil or palm kernel oil production unit. Your choice of expeller will depend on not only the oil content and hardness of the raw material but also your desired production capacity and product quality.
Before you can decide which edible oil expeller is best for your specific purposes, you need to examine and assess some of the basic features and components of the oil expeller. So that's exactly what we'll walk you through in this part of this ultimate guide to oil expeller machines.
Let's dive right in.
Material of construction. Technically, edible oil expellers can be built with aluminium, cast iron, or any other strong metal. But high-quality edible oil expellers are built using materials which ensure safety and efficiency in addition to durability.
The right material of construction for an oil expeller press depends on the climatic conditions in which it is used. The right material is resistant to rust and corrosion. It has the robustness to not only hold the system together but also withstand the high temperature and pressure conditions generated during edible oil production.
In most cases, high-quality stainless steel is the best option. It's an option that we, at Kumar, swear by. The right stainless steel - especially when specially treated - is durable, has lower wear and tear, has lower maintenance and repair costs, aids in extending the life of the machine, and works out more economical than cheaper materials in the long run.
Gearbox. The gearbox powers your oil expeller's operations by converting the speed and torque of your electric motor into the speed and pressure settings you want for your expeller.
A good quality gearbox will help you to accurately control the motor speed, essential not only for effective production and equipment longevity but also for the safety of your workforce. The gearboxes of all high-quality expellers are equipped with failsafe mechanisms.
Ideally, you should invest in an expeller with a high-efficiency external gearbox. This will enable easier maintenance, repair and adjustments without having to dismantle the entire machine.
Worm shaft and pressure worm. Worm shafts come in many variations, but the best are usually those which can be removed quickly and easily, without disturbing the gearbox assembly. Ideally, you should opt for pressure worms with thick, hard, uniform, and durable parts. As icing on the cake, you can go for pressure worms with special welding electrodes which help you achieve the desired hardness easily.
Main cages. The best expellers have hinged main cages so that when it's time for cleaning, repairs or maintenance, you can open up the equipment safely and effortlessly. As a bonus, look for clamping bars and bolts which are easy to tighten as well as remove - this can do wonders for the speed of your cleaning and maintenance work.
Oil collection and filtration mechanisms. Some expellers feature a drainage section in the inlet feed hopper, where raw materials are introduced to the press, to prevent oil from flowing back and clogging the machine. For instance, Kumar expellers have the standout feature of built-in screw conveyors. These fully enclosed systems efficiently transport oil while maintaining a clean work environment and ensuring smooth operations.
Additionally, when oil is extracted using an expeller, it often contains some impurities. To produce a high-quality product, the oil typically requires further refinement to remove impurities such as free fatty acids and metal contaminants, and to undergo bleaching and deodorization. However, a high-quality expeller press will include filtration technology to handle initial impurity removal. Vibro separators and filter presses are ideal for filtering crude oil, producing a clean oil output that needs minimal further refining.
As you assess expeller machines, have a look at the options we provide at Kumar. With applications for plants of various scales and oil-bearing materials of different kinds, there is no oil extraction need these machines can't fulfil.
The Kumar X' Press Series Oil Expeller Max 200, currently the largest in the range, delivers world-class performance and reliability. It requires a minimum investment while providing benefits like an independent gearbox system, automatic cone adjustment, and a built-in adjustable conveyor.
The Kumar New Super Press Series Oil Expeller is ideal for small and mid-sized mechanical extraction plants. It boasts of a low maintenance system, hard-faced wear parts, and mechanisms to prevent shaft damage.
The PK Series Expeller is specially designed for the efficient extraction of palm kernel oil. It boasts of all the benefits of our other expellers and more.
Finally, we have the Kumar New Oil-N-Oil Series Oil Expeller. Designed for small and mid-sized mechanical extraction plants, this expeller is equipped with an independent gearbox, an independent adjustable conveyor, a frequency drive to control the speed of feeding screws, and a reducer motor to drive the feeding screw.
The information we've provided above should help you to decide which type of machine is best suited to your particular context, constraints, and requirements.
Beyond expeller machine specs
Yes, the features and quality of an expeller machine are important factors affecting your purchase decision. Still, there are some factors beyond machine specifications that you should consider before you settle on a piece of machinery.
Your desired production capacity. You may have certain oil production goals to meet demand in the market of your choice. Achieving these goals will depend on the financial investment you are willing to make and the scale at which you are willing you operate. Therefore, selecting an expeller machine of the right capacity depends not only on what your engineering partner has to offer but your own ambitions and constraints.
Make sure you have a clear idea of the desired scale of your project and the specifications of the oil extraction process, be it for cottonseed oil, castor oil or shea butter, before you purchase any equipment. Most oil mills have capacities ranging from 1 TPD to 5000 TPD. However, the right oil expeller manufacturer will be able to adapt to your requirements.
Estimated ROI. We always recommend that you make a purchase decision based on the value you are getting rather than the price of the product or service. Nonetheless, we cannot deny that financial constraints and demands have a very real impact on purchase decisions. This is why we recommend that you first assess the return you can expect on the expeller machine price that you shell out. You should factor in not just capital expenses but also operating costs like raw material and utility consumption, maintenance costs etc. when you input your expeller machine price.
Your engineering partner. Purchasing an oil expeller press is about a lot more than just buying a machine. It is about building a relationship with your engineering partner. This is particularly important because your engineering partner will not only make or supply you with the oil expeller but also be involved in other activities - commissioning, installation, maintenance, repair, spare parts supply, etc. - in the entire lifecycle of the machine. They may also help you with procuring related equipment. Your relationship with your expeller manufacturer/seller will be a long and meaningful one; make sure it is a symbiotic partnership with shared values and approaches to doing business.
Expeller machine prices
The pricing of expeller machines varies based on several factors - production capacity, product quality, brand name, the cost of inputs like stainless steel, the logistical expenses involved in making the machine, etc.
In some markets, expeller machine prices for small businesses can cost as little as USD 500, going up to about USD 5,000. For larger commercial operations, with the need for sophisticated automation and industrial-scale capacity, expeller machine prices can range from USD 5,000 to USD 20,000 and even higher.
The variability in expeller machine prices is because of the large variability in expeller machines. To assess whether a certain piece of equipment justifies a certain price tag, here are a few factors you can consider.
Capacity and throughput. The expeller's capacity and throughput i.e. how many TPD it can process will play a major role in determining its price. Given all other factors are constant, the expeller machine price will increase if it can produce larger quantities of oil in less time.
Material quality. For oil expellers, the raw material used in construction is key to cost but also quality. Manufacturers typically choose stainless steel for the body of the equipment due to its durability, ease of maintaining hygiene, and exceptional performance. In some cases, carbon steel can also be a suitable alternative. However, these high-quality materials come at a premium price, which can fluctuate based on market conditions. As a result, oil press machines made from stainless steel tend to be more expensive.
This isn't a bad thing. The higher cost is justified by exceptional product quality, improved durability and lifespan, and simplified operations, repairs, and upkeep.
Technical complexity. Oil mills vary in their level of technological advancement, which influences their complexity, degree of automation, mechanization, and labour needs. Advanced automated machines often come equipped with state-of-the-art features such as digital control panels, automatic temperature regulation, built-in safety systems, and integrated oil filters. These modern technologies, resulting from intelligent engineering and design, typically deliver superior performance, higher yields, and an enhanced user experience.
Opting for a high-tech oil expeller with automation and advanced features ensures improved efficiency. Naturally, the cost of such an automated or highly complex oil press machine will be higher than that of a simpler model.
Where you buy. Where you buy your expeller from will affect the price you pay for it. If you source a screw press from say, a dealer, you will likely pay a markup over the manufacturer's price to cover the dealer's cost of operations and profit. Whenever you can, go straight to the expeller press manufacturer to get a competitive price.
A final word
Ultimately, selecting the right oil expeller press is critical for the success of any edible oil production operation. Whether you're looking for a hydraulic press or a screw press, each type of expeller offers distinct benefits and challenges depending on your production needs and the type of oil you wish to extract.
By choosing the right expeller, you not only enhance efficiency but also ensure long-term sustainability and profitability in your oil extraction process. At the end of the day, understanding the technical aspects and making informed decisions about your expeller press will contribute significantly to the success of your edible oil production business. Choose well.
You might find these interesting:
The price of oil expeller machine: What you need to know before buying
A buyer's guide to navigating the oil expeller market
The ultimate guide to finding the best oil expeller manufacturer
