The booster pump is a component that is easily mistaken for another kind of vacuum pump. In fact it does not remove any gas itself; what it does is compress the gas. The role of the roots blower JRP-500 in this system is to raise the pressure on the vacuum chamber side of the fore pump, so that the pump that actually does the pumping works in a more comfortable range.
First, separate three concepts
The pumping speed is the volume of gas that the pump can remove per minute at a given pressure; the usual units are m³/h or L/s. It describes the handling capacity, which is a different matter from the lowest pressure that can finally be reached.
The ultimate vacuum is the lowest absolute pressure that the complete system can reach under the specified conditions, determined by the pumping speed curve of the pump, the sealing, the cleanliness of the pipework and the leaks. A pump with a high pumping speed can usually take the ultimate vacuum deeper, but in the low pressure region the pumping speed falls noticeably.
The booster pump (roots blower) is a dry rotary pump: a pair of rotors compresses the gas and discharges it, and the gas never comes into contact with oil. It does not discharge the gas to the atmosphere, it discharges it to the suction inlet of the fore pump.
What the booster pump actually boosts
An ordinary fore mechanical pump has an awkward feature: it works best in the range from close to atmospheric pressure down to medium vacuum, and once it enters the high vacuum region its pumping speed falls sharply and the efficiency deteriorates. With the booster pump fitted between the two, the gas in the chamber is compressed to a level close to atmospheric pressure and then pushed on to the fore pump, so the fore pump always works in the range where its efficiency is highest and the pumping effect is amplified.
The result is that the system can take the ultimate vacuum deeper. The booster pump therefore does not add capacity in the sense of the total volume of gas handled; what it changes is the pressure distribution, so that each stage does what it is good at. This is also where the mistaken idea of an additional pumping pump comes from.
Seen from another angle, it is more like an efficiency amplifier than a capacity amplifier: on the same fore pump it may push the ultimate vacuum that the system can reach a long way further, but the volume of gas actually removed per minute has not increased in the same proportion.
When it is needed and when it is not
The typical signs that a booster pump is needed are these three together: a large throughput, a high initial gas content, and a target gas content of ≤0.01% with an ultimate vacuum at the ≤5 Pa level. In this kind of duty, simply adding another stage of pumping is often less effective than letting the fore pump work in its high-efficiency range.
The cases where a booster pump is not needed are just as clear: a small throughput, clean oil at the start and a duty whose main objective is dehydration; or a target working vacuum of the order of -0.08 MPa. For equipment such as the TYA-50 (2000 L/h) and the TYA-100 (4000 L/h), the money is better spent on the flow rate and the temperature control.
There is one hard constraint as well: the booster pump cannot pump on its own. When the system has just started and the vacuum chamber is still at atmospheric pressure, the booster pump can only push the air forward to the fore pump; a fore pump has to be establishing the suction behind it, and the opening sequence of the pipework and the valves has to be designed on that logic.
| Concept | Meaning | Unit or form | Effect on the degassing |
|---|---|---|---|
| Pumping speed | The volume of gas removed per unit of time | m³/h or L/s | Determines the processing capacity and the depth that can be reached |
| Ultimate vacuum | The lowest absolute pressure the system can reach | Pa | Determines whether the dissolved gas can be removed completely |
| Booster pump | Compresses the gas and pushes it to the fore pump | Roots blower JRP-500 | Lets the fore pump work in its high-efficiency range |
- Ask about the objective first: a target gas content of ≤0.01% and a duty that only removes water call for completely different equipment configurations.
- Then ask about the starting condition: the dirtier the oil and the higher its gas content, the greater the pumping speed and the depth of vacuum that are needed.
- Finally ask about the conditions: whether the power supply, the space and the maintenance interval on site can support one more pump.
- Mobile applications have to be assessed separately: equipment such as the TYG-100 is more sensitive to weight and to the power supply, and the principle behind the configuration trade-off is unchanged.
The booster pump does not produce vacuum, it only makes the vacuum easier to achieve; whether to have one depends on how far the target is from where you are now.