Since NatGas and LPG pipelines evacuate relatively quickly and vaporize to atmosphere leaving scarcely a trace, nobody is interested in trying to crimp a broken LPG or NatGas pipeline. By the time the equipment gets out there, it's already departed to upper atmosphere.
What kind of leaks are you trying to stop. You say leaks, yet you talk about crimping a pipeline, which wouldn't be appropriate for anything but line breaks. Well blowouts are kind of another problem. They only have one control point to worry about and put a valve there.
Freezing the pond??? What pond? LPGs vaporize. Robots installing vents. No time for that. Product vaporizes well before you get the robot to site. An installed vent might not be any safer than a natural vent. No ignition source nearby = no worries about ignition, no matter what kind of vent you have.
The best technique to minimize LPG loss found so far is to have closely spaced block valves, perhaps remotely activated? although remote control hasn't been proven to be particularly useful either.
Do you have a problem with the existing clamping solutions, or are you just fishing for new, cheaper or better methods to evaluate? Are they too general for your needs? Do you need a specific solution? Tell us more specifically about what it is exactly that you need to accomplish.
Technology is stealing American jobs. Stop visas for robots.