A port-installed damper (100) for trimming a flow of a substance through a pipe (101), the pipe (101) having a port formed therein, that includes a fitting (104) that attaches to the pipe (101) about the port, a port assembly (106) that attaches to the fitting (104) and includes an actuator (118), and means for trimming the flow of a substance through the pipe (101). The actuator (118) may be connected to the means for trimming by one or more connectors. The port may have a predetermined size such that, during installation of the port-installed damper (100) and the means for trimming may pass through the port. In some embodiments, the port may not extend beyond half of the circumference of the pipe (101).