Rajkot makers build screw oil expellers in a wide range of sizes, plus filter presses, seed preparation equipment and complete small to medium oil mill lines. The industry grew around the groundnut and cotton seed crushing of Saurashtra.
Machines from the area crush groundnut, mustard, sesame, sunflower, cotton seed, copra and castor, among other seeds. Seed refining is a separate plant and a different kind of supplier.
How a screw expeller works
A worm shaft turns inside a cage made of steel bars with small gaps between them. As seed moves along the shaft, the space narrows and pressure rises. Oil drains out through the gaps between the bars, and pressed cake leaves at the end.
Expellers are made for cold pressing or hot pressing. For hot pressing, the seed first goes through a cooker or conditioner that heats and moistens it, which usually raises oil yield. Cold pressing gives a different oil quality and usually leaves more oil in the cake.
Capacity is normally stated in tonnes of seed per day. The figure depends on the seed, its moisture and whether it is pre-treated.
Filter presses and clarification
Oil from the expeller carries fine solids. It usually settles in tanks first and then passes through a filter press. Plate and frame presses and recessed plate presses push the oil through filter cloths under pump pressure. Larger mills may use pressure leaf filters instead.
Check the filter area, the plate material, the cloth type and how easily the press opens for cleaning. Ask how many cloths come with the press, since they wear and clog and need regular replacement. A press that is too small for the expeller becomes the bottleneck of the whole mill.
What to check before you buy
- Capacity measured on your seed, not on a different seed the maker usually runs.
- Residual oil in the cake, measured by a lab on cake from a trial, because this decides your yield.
- The motor rating, the gearbox type and whether the gearbox runs in an oil bath.
- The hardness and material of wear parts such as worm sections and cage bars.
- Whether the quote covers only the expeller or also seed cleaning, cooking, filtering and conveying.
- Guards over moving parts and the electrical standards your country requires.
Wear parts and spares
Worm sections and cage bars wear steadily, and their condition affects yield. Keep a set in stock, as explained in spare parts for processing machinery. If you need a full mill, compare single supply against separate makers using turnkey processing lines.
Oil sold as food must also meet food safety rules in your country. That is the producer's responsibility, so confirm the requirements with your local food authority.
Next step
We find and audit expeller makers in Rajkot, arrange trials with your seed and have cake samples tested. See our machinery page, or book a free sourcing review.