The same machine behaves differently on the plains and at altitude, in winter and in summer. If these differences are found only after the delivery, the cost is usually much higher than asking about them before the order is placed. The parameters that are easily skipped in a selection discussion are exactly these conditional ones: they do not appear in the flow rate and power columns, yet they decide directly whether the machine can reach its figures once it is on site. This article lists the questions that need to be asked, by condition.
Altitude affects the vacuum level, not the flow rate
The first change brought by altitude is the drop in atmospheric pressure. The vacuum pump exhausts to the atmosphere, so the exhaust back pressure is the local atmospheric pressure, and once the back pressure changes the pumping characteristics of the same pump change with it. The figures -0.08 ~ -0.0999 MPa for the working vacuum and ≤5 Pa for the ultimate vacuum are given under standard atmospheric conditions. At a high-altitude site a deviation between the measured values and the nameplate values is normal, and it cannot be recovered by adjusting parameters on site.
The first step in the selection stage is therefore to write the site altitude into the enquiry conditions and have the supplier answer clearly: at the local altitude, on what basis are the working vacuum and the ultimate vacuum each given, and are they supported by test records or converted from standard atmospheric conditions. If this question is not settled, the later acceptance has no reference point.
Ambient temperature affects the heating time and the temperature window
The ambient temperature condition has to be read at both ends. The ambient temperature marked for the TYA series is -20–45 °C, and the meaning of that range is the boundary of the machine's application: a value below the lower limit or above the upper limit falls outside the rated range and has to be raised during selection, not dealt with on site afterwards. Inside the range there is a difference as well.
At the low end, the starting oil temperature is low, so the same heating power takes longer to bring the oil to the lower end of the temperature control range, and the viscosity of the oil is higher and the load on the pump heavier. What the selection stage has to confirm is whether this preheating time fits into the working window. At the high end, the margin for heat dissipation is smaller, and whether the upper end of the temperature control range can be reached has to be checked separately. The temperature control range is 45–80 °C, with the upper limit pulled down to 70 °C when the water content of the oil is high. Whether both upper limits are reachable at the actual ambient temperature has to be settled before the order is placed.
Different power structures, different heating performance
Within the ZYD series the power structure differs considerably between models: the total power of the ZYD-100 is 72 + 5 kW, the total power of the ZYD-200 is 175 kW of which 160 kW is heating, and the total power of the ZYD-300 is 110 + 11 kW. With different power structures, the time needed to reach the temperature control range at the same ambient temperature differs as well. How the ZYD-100 splits its power between heating and vacuum has to be taken from the nameplate and the drawings.
Only when this is read together with the flow rate is the selection judgement complete: the ZYD-100 has a flow rate of 6000 L/h, the ZYD-200 12000 L/h and the ZYD-300 18000 L/h. With different flow rates, the heat demand and the working cycle have to be scheduled separately against each power structure; one work schedule cannot be applied to all of them.
Site conditions: footprint, weight and power supply
Apart from temperature and altitude, there are site conditions to confirm during selection. Dimensions and weight: the ZYD-100 is 1200×1400×1800 mm, approx. 720 kg; the ZYD-200 is 1800×1600×2100 mm, 1950 kg; the ZYD-300 is 2200×1800×2200 mm, approx. 1400 kg. High-altitude sites are often colder and more remote, so the manual handling and lifting conditions have to be checked against the weight in advance: if the door opening, the foundation or the access route is missing, the machine will not go in.
Power supply: three-phase 380V / 50Hz is the power supply specification for these models. Phase loss and phase-sequence protection on the supply side is one of the fitted items, configured on the machine, but the actual state of the distribution board on site still has to be checked before the order is placed.
| Site condition | Indicator to check | What to ask before ordering |
|---|---|---|
| Site altitude clearly above standard atmospheric conditions | Working vacuum -0.08 ~ -0.0999 MPa, ultimate vacuum ≤5 Pa | On what basis are these two figures given at that altitude, and are there test records |
| Lowest winter ambient temperature close to -20 °C | Lower end of the 45–80 °C temperature control range, heating power | How long does it take to rise from the ambient temperature to the lower end of the temperature control range |
| Highest summer ambient temperature close to 45 °C | Reachability of the upper end of the temperature control range | With a high water content the upper limit is 70 °C; can that actually be reached |
| High altitude combined with a high water content in the oil | Temperature control upper limit 70 °C and the load on the vacuum side | When both constraints apply at the same time, does the throughput have to be adjusted |
| Handling and power supply conditions are restricted on site | Overall dimensions, machine weight, power supply | Do the door opening, the foundation and the lifting arrangement match the dimensions and the weight, and does the supply meet three-phase 380V / 50Hz |
- Write the site altitude and the winter and summer ambient temperatures into the enquiry, not only the flow rate.
- At acceptance, check the vacuum level readings against the site altitude instead of applying the nameplate values directly.
- Put the preheating time for the cold season into the work plan separately; do not estimate it at normal temperature.
- For oil with a high water content, check the temperature control upper limit of 70 °C together with the ambient temperature on site.
- Check the weight and the door opening against the civil works contractor and the handling party before the contract is signed.
Altitude and temperature do not change what the machine is able to do; they change what it is able to achieve at your site. The selection is only complete once the conditions have been settled.
