The system resistance met by a compressor can vary from a constant discharge pressure to a variable relationship as shown in the generalized system resistance curves of Figure 100-9.
Examples of the three types of curves are:
Type 1 – Constant Pressure
• Gas Lift
• Gas Injection
• Plant/Air Instrument Air
Type 2 – Combined Constant Pressure and Friction Process with piping and equipment plus constant pressure drop through catalyst bed.
Type 3 – Predominately Friction
Systems with only piping, fittings, and equipment such as heat exchangers.