Not always. Some AC fitting tubes are smooth / near smooth for easy hose assembly and the ferrule is locked / crimped to the fitting with the shape of the crimp mimicking a " barb " or " rings " , this prevents hose blow off.

Hydraulic hoses fittings are built this way as well.

Old style field install hose fittings have barbs to prevent hose blow off when used with a screw clamp. " AC " spec hose clamps have a leg that gives proper spacing so pressure is applied to a smooth area just past the barb. Standard non leg clamps are fine if the spacing is properly set.

When replacing factory ferrules with crimped on ones, be sure that the ferrule is crimped to the notch on the fitting.


RE: R290 = " propane "


From Lindie a major industrial gas supplier.

R290 (CARE 40) Propane | Linde Gas

MSDS / SDS sheet.

http://www.refrigerants.com/pdf/SDS%20R290%20Propane.pdf


I would not use R290 in a mobile application, propane would be hazardous in a crash that punctures the system. It would be fine in a household fridge, the chances for a sudden leak are low and the system volume small compared to a car.