In the delivery documents or the spare parts list of a vacuum oil purifier, two pumps appear in the vacuum system: an X-100 vacuum pump and a JRP-500 Rootes pump. This is not a redundant configuration but two components in fixed positions within a two-stage vacuum structure, each taking on one part of the task. Understanding what they each do is more useful than remembering the model codes, because when something goes wrong on site, which of the two to look at depends on the working state the machine was in.
Two-stage vacuum: pressure boosting at the front stage, extraction at the rear stage
The working principle of a Rootes pump is to boost the pressure rather than to draw directly down to the ultimate vacuum. Placed at the front stage of the system, it first handles the large volume of gas coming out of the vacuum tank, raises the pressure by one stage and then passes it on to the rear-stage vacuum pump to draw away. The advantage is that, for the same volume of gas extracted, the rear-stage vacuum pump works against a lower pressure and has more margin in its pumping speed. The ultimate vacuum of the ZYD-100 is ≤5 Pa and the working vacuum is -0.08 ~ -0.0999 MPa; these two figures describe the pressure level of this two-stage system in its different working states.
The division of the two stages brings one convenience for judgement on site: when the oil starts entering the tank and the gas load in the tank rises, the front stage is the first to struggle; if the exhaust capacity of the front stage is insufficient, then even with the rear stage in good condition the working vacuum is held back. The reverse also holds: if the front stage is clear but the efficiency of the rear-stage vacuum pump has fallen or there is a problem in the oil circuit, the ultimate vacuum cannot be reached.
Why both pumps are in the standard configuration
The reason for making the two-stage structure the standard configuration lies in the degassing process itself. During degassing the oil feed is continuous, and the quantity of dissolved gas entering the vacuum tank follows the quantity of oil: the higher the flow rate, the more gas is released, and a single-stage structure is easily held back by the gas load in continuous operation. The two-stage configuration keeps the system with margin during continuous processing, which is what the flow rates of the ZYD-100 at 6000 L/h, of the ZYD-200 at 12000 L/h and of the ZYD-300 at 18000 L/h require.
The other practical reason is maintenance. Pumps are wear parts, and having both pumps held as supplied spare parts is much faster than waiting until one of them has failed completely and then ordering. This appears in the spare parts list as specific items rather than as a vague vacuum pump assembly.
What to check at delivery and on site
When the machine arrives, there are several checks relating to the vacuum system that are worth making. First, check that both pumps are present and that the models fitted are the corresponding ones; second, check that the pipework between the pumps and the vacuum tank has been completed as shown and that no blanking-off has been left in the pipework; third, check that the model designation on the nameplate matches the one in the delivery documents; fourth, check that the power supply and the wiring have been brought in line with the three-phase 380 V / 50 Hz requirement, where the phase-failure and phase-sequence protection comes into play.
After the machine has been in use for a while, there is also a fixed order for deciding which pump to look at first: if the working vacuum cannot be reached and the pressure in the tank falls faster than normal, look first at the running state and the exhaust of the front stage; if the ultimate vacuum does not reach its target, then look at the rear-stage vacuum pump and the condition of the pump oil. The order is not absolute, but it halves the range of the investigation before anything else.
| Check or investigation item | Corresponding component | What to confirm |
|---|---|---|
| Completeness of the supplied configuration | X-100 vacuum pump | The model, the nameplate and the delivery documents all use the same designation |
| Completeness of the supplied configuration | JRP-500 Rootes pump | Installation position, pipework connections and confirmation of the direction of rotation |
| Working vacuum -0.08 ~ -0.0999 MPa | Front-stage exhaust and rear-stage pumping speed | Look at the front-stage load first, then at the margin of the rear-stage pumping speed |
| Ultimate vacuum ≤5 Pa | Rear-stage vacuum pump and pump oil | The condition of the pump oil and the leakage of the system |
| Three-phase 380 V / 50 Hz | Power distribution and protection | Whether the phase-failure and phase-sequence protection is effective |
- When checking on delivery, find the pumps by position: first establish on the frame which one it is, and then check the model.
- Record the condition of the vacuum pump oil at regular intervals; the change in the oil shows up before the noise of the machine does.
- When the working vacuum is abnormal, work through the front stage and then the rear stage; do not skip a stage in the judgement.
- Write the spare parts list with both the model and the position, so that a service request can say clearly which pump it refers to.
- Switch the machine off and isolate the power before working on the couplings and flange positions of the pumps.
The two pumps are not in a standby relationship with each other; they divide the work between them. Once it is known which step each one stands at, the site can put them in an order.
