Introduction: A fixed vacuum emulsifying machine splits one batch across three vessels so each ingredient group is prepared at the right temperature before the emulsion forms once, under vacuum.
Most people first meet this equipment as a photo of one large tank with two smaller tanks standing beside it, and the obvious question is why a single stirred pot would not do the same job. The answer lies in the order of operations rather than in the tank count. Two phases are heated and mixed separately, then drawn into a sealed main vessel that shears the combined mass and pulls air out of it. Once you follow the material from the small tanks into the big one, most of the layout decisions on the machine stop looking arbitrary.
The two side vessels are not storage. Each one is a working tank with its own jacket and its own agitator, sized to hold one half of the formula at the temperature that half needs. In the PROMAKE fixed series, the 200 L model lists an 80 L oil-phase tank and a 160 L water-phase tank, while the 10,000 L model lists 4,000 L and 8,000 L. The roughly one-to-two ratio between oil and water is the visible clue to what each tank is for: the water side carries the larger share because water, humectants, salts, and water-soluble polymers usually make up the bulk of a cream or lotion. Keeping the two apart is a chemistry decision, not a plumbing one. Oil-soluble ingredients such as emulsifiers, waxes, fatty alcohols, and emollient esters have to melt into a continuous oil body, while water-soluble ingredients have to dissolve or hydrate fully in water. Both processes need heat and time, and both need to finish before the two sides meet. Combine the phases too early and an emulsifier can contact water at the wrong temperature, hydrated polymer can form lumps that shear cannot remove, and part of the batch starts emulsifying before the rest has even melted. Temperature matching is the practical reason the tanks sit next to each other. Operators bring both phases to a similar point on the jacket controls, check that the oil side is clear and the water side is free of undissolved powder, and only then open the route to the main vessel. On the water side, quality matters as much as temperature, and the European Medicines Agency's guideline on water for pharmaceutical use shows how closely the aqueous input is controlled where the finished product is regulated.
The main vessel is sealed and evacuated before transfer begins. Once a phase tank is opened to the line, the pressure difference between a vessel at atmospheric pressure and a vessel under vacuum does the work, pulling liquid up the pipe and into the main tank without breaking the seal on the lid. Because the receiving tank is already below atmospheric pressure, air does not travel in with the liquid, which is the whole point of moving material this way instead of pouring it. Operators set the rate with a valve, and the order — water into oil or oil into water — follows the formula, because whichever phase receives the other becomes the continuous phase.
Once both phases are in, the rotor-stator head takes over. It spins at high speed, draws the mixture into the working zone, and drives it out through narrow slots, so droplets are stretched and broken again and again while the main agitator turns at 0–63 rpm to keep the whole body of material moving and to sweep the wall. Homogenizing motors on the fixed series run from 5.5 kW to 37 kW depending on vessel size, which is the part of the specification that governs how much shear is available at the moment the phases combine. Vacuum does a second job here: air entrained during transfer and mixing migrates to the surface and is removed rather than folded back into the cream. A figure of roughly 1 μm appears as a process reference under specific formulations and operating conditions, not as a fixed result for every recipe.
Consistency comes from the sequence being identical every time. Each phase is measured and heated in a known volume, the ratio is set by tank size rather than by an operator's judgement, and the emulsion begins at one identifiable moment when a valve opens. That matters during scale-up: the same three-step flow that describes a 200 L batch still describes a 10,000 L batch, so a formulator can compare runs without guessing where a difference came from. Vacuum emulsifier system manufacturers generally quote the three vessels as one working unit for exactly this reason, since the phase tanks are the first two stages of the process rather than accessories bolted on afterwards. Hygiene follows the same logic of a closed path. Ingredients travel through fixed piping rather than across an open floor, the main vessel stays sealed through transfer and homogenizing, and the phase tanks are covered working vessels in their own right. Standards work in the background here. ASME's bioprocessing equipment standard addresses hygienic piping design and drainability, and the FDA's GMP guidance for cosmetics centres on preventing cross-contamination between batches. Both explain why a closed, fixed three-vessel layout is easier to keep under control than an open pot filled by hand, and why most vacuum cosmetic homogenizer manufacturers treat tank configuration as a process decision rather than a packaging one.
The three vessels in a fixed vacuum emulsifying machine map onto three jobs: dissolve and heat the water phase, melt and heat the oil phase, then combine, shear, and deaerate inside a sealed main tank. Reading the machine that way makes the specification sheet far clearer, because tank volumes describe a ratio, jacket options describe how each phase reaches temperature, and the homogenizing motor describes the shear available at the moment of combination. Anyone comparing models can start from the listed water and oil tank volumes and work backwards into how a given batch would actually run. The PROMAKE fixed vacuum emulsifying machine page lists those volumes across its model range for readers who want to check the numbers.
A: Because the two ingredient groups need different conditions to be ready at the same time. Oil-soluble materials such as waxes, emulsifiers, and emollients must melt into a continuous oil body, while water, salts, humectants, and water-soluble polymers must dissolve or hydrate fully in the aqueous side. Heating them apart lets each phase reach a matched temperature before they meet, and it prevents premature contact that can create lumps, incomplete melting, or a partly emulsified batch that later shear cannot fully repair.
A: The main tank is sealed and pumped down below atmospheric pressure, while the phase tanks sit at normal pressure. When a valve on the connecting line opens, that pressure difference pushes the liquid up the pipe and into the main vessel without anyone opening the lid. Because the receiving tank is already evacuated, air is not drawn in with the material, so the transfer adds no foam. The operator controls the speed with the valve and chooses the order of addition according to the formula and which phase should end up continuous.
A: It removes the air that matters most — the bubbles entrained during transfer and mixing — as long as the vacuum is held long enough and the product is still moving so trapped air can reach the surface. A small residue can remain depending on viscosity, holding time, and how the batch is discharged, so the practical goal is a visually smooth, dense product rather than a mathematically bubble-free one. Vacuum level and deaeration time are set per formulation and machine configuration.
Quality of water for pharmaceutical use - Scientific guideline | European Medicines Agency (EMA)
Bioprocessing Equipment - ASME
Good Manufacturing Practice (GMP) Guidelines/Inspection Checklist for Cosmetics | FDA
