2-Ear Pinch Clamp, Zinc Plated Steel, 0.315 - 0.433 Inch Clamping Range, 0.276 Inch Width

Go by the clamping range, not the “3/8” nickname. This one clamps from 0.315 to 0.433 inch, so it works as long as your hose outside diameter where the clamp sits falls in that window.

These Oetiker 2-ear clamps are indeed suited for steam lines, as well as air, fluid, and gas lines, especially in industrial settings where there's a lot of vibration. The zinc plated steel construction provides good corrosion resistance for those applications.

Your coworker's right on that one. Close the first ear all the way, then work the second ear down until the first ear opens back up just a little, roughly 1/16 of an inch. That slight gap is what gives the clamp its holding strength. It creates a spring-like tension that helps the clamp resist pressure, vibration, and hose shrinkage over time. If you close both ears completely flat, you've likely got too big a clamp for the job and should move down to the next smaller size.