What are the safety issues when using flexible hoses that are continuously pressurized (but not cycled through pressures or moved very much) the way swap and drop tube trailer hoses would be?

Many methods are used to mitigate the risk of a tube trailer hose loss of containment incident. Examples that otherwise exceed code requirements are provided below. These have been deployed in various combinations depending on the risk analysis for a particular system: 

1. Installation of automatic shutoff valves on the tube trailer upstream of the hose to activate upon hose rupture. These can be operated in two modes:
   1. Always open and activated only with a manual and/or automatic emergency shutdown system or 
   2. Always closed and only opened when in use, in addition to being closed via activation of an emergency shutdown system. 
2. Over-design of the hose with a higher factor of safety than the 3:1 otherwise required. Using a hose with a 4:1 factor, or even higher, is common. 
3. Implementation of hose replacement frequency as part of a mechanical integrity program. An interval of three years for a tube trailer hose is frequently used. 
4. Use of anti-whip restraints to anchor each end of the hose. 
5. Implementation of leak detection equipment, using either external gas detection or internal pressure monitoring systems. 
6. System design that prevents abrasion, kinking, or stretching of the hose when in service. 
7. Implementation of anti-pull-away systems for the trailer when connected to the station. 
8. Use of a self-sealing hose in the event of a hose rupture. 9. Use of a double-ended breakaway system similar to those used on fueling hoses.