Decide what enters the package
A dedicated high-pressure compressor takes its specified inlet supply and produces the required outlet duty. A booster relies on an upstream supply that must also be defined. State inlet pressure, available flow, temperature and air quality if you are buying a booster. Include the upstream compressor and its auxiliaries when comparing the total installation input and scope.
The quotation should identify which equipment is included: compressor stages, receiver, cooler, dryer, filters, drains and controls. Do not assume that a booster quote includes the low-pressure air supply. Equally, do not assume that every 30 bar oil-free enquiry requires a separate low-pressure screw and booster.
Use a documented configuration without combining range endpoints
The CMN CM/GPV medium-pressure family provides an example of configurations that need careful reading. Its reviewed CM130GPV entries include a 2.0–3.0 MPa band with 5.4–13.5 m³/min, and a separate 2.0–4.0 MPa band with 4.0–10.2 m³/min. These are configuration intervals. Neither row proves maximum flow at its maximum pressure.
If considering this family for a 30 bar duty, ask CMN, Taizhou for the exact pressure convention, selected-pressure delivery, volume reference and complete current model. Preserve the separate drive ratings from the offered data sheet and request measured package input. A model name is not a motor-rating calculation.
Define what “oil-free” must establish
Specify the required oil limit, evidence and sampling point, together with separate water and particle requirements. Ask for a current report or certificate covering the offered configuration and relevant conditions. A description of oil-free compression does not establish the complete treatment duty or prove that lubricants are absent from every gearbox or bearing in a package.
Include the dryer, filters, receiver and pipework in the air-quality review. Confirm the pressure rating and operating limits of every item, plus the condensate and maintenance arrangements. Agree where delivered air will be sampled and the acceptance method before placing the order.
For PET blowing, provide the production duty
Give bottle size, cavity count, cycle, simultaneous machines and the blowing machine's pressure and consumption requirements. Describe any air-recovery arrangement and the existing storage concept. If the process is unrelated to PET, identify the actual air or gas application instead of assuming that a PET package is suitable.
Ask for delivery during the relevant production cycle, pressure losses, receiver selection, control sequence and cooling requirements. Compare the same duty and package boundary across offers. A listed 35 or 40 bar PET product is not automatically evidence of a confirmed 30 bar rating.
Send a 30 bar oil-free enquiry. Change the gauge-pressure assumption in the enquiry if your process requires an absolute-pressure specification. The manufacturer must confirm the selected machine and air-treatment arrangement.