Shifts change, and the day crew heads on out. Five thousand pickups bound for honky-tonk heaven. The night shift rumbles in, dusty trucks and dinner pails and ''Hey, Bob, ya ready for another night?'' Dust settles in the parking lot. Shifts change, and the sun slips behind the refinery in one meltdown of a sunset. Waste crude in holding tanks reflects the burning colors - Texaco red, sulfur yellow, the blue of natural gas. Workers trickle in to the rhythm of the punching clocks. Shift's changed, and the stars come out, 10,000 sodium vapor lights cluster in a man-made galaxy. Quiet on the horizon, the supertankers take their bearings from these newer constellations. Throughout the night they bring ships safely into port. Until shifts change.