| dc.description.abstract | Two main problems must be solved in the planning and execution of compressor sets to be installed within refrigeration loops. The use of several compressors with different sidestream admissions calls for the installation of a control system for optimizing the parallel operation of the machines, even if there are differences in their performance curves, due to reactions to the pipework, minor manufacturing tolerances, or the use of varying frame sizes. To ensure uniform loading of the stage groups and the same distance from their respective surge limits in the case of constant discharge pressures, throttle valves are installed in the compressor intake pipes for actuation by the control system presented. Protection from surging is provided by an anti-surge control system, which includes a dynamic control line to respond to sudden changes in the duty point, as well as an additional anti-surge safety line preceding the surge limit. Unlike in other turbomachinery applications, the startup operation must be carefully studied early in the project planning stage of the refrigeration loop. In view of the great number of parameters affecting the starting procedure, these studies must resort to mathematical simulation for variation of the plant parameters, with the aim of minimizing the driving torque and, thus, the motor frame size. One way in which these problems can be solved will be detailed by reference to a compressor set for a propane loop, consisting of three machines each having three stage groups and two sidestream admissions. | en |
