For the liability conscious straight from the Code of Federal Regulations (CFR):
49 CFR 173.302 - Charging of cylinders.
(b) Filling limits (Ref. 173.301 (e)): "Container pressure. The pressure in the container at 70°
F. must not exceed the service pressure for which the container is marked...". That's straightforward enough that no one should have any trouble understanding it.
Now let's examine what the actual reduction in tank life that filling an OMS (Faber) LP80 (3AA) to 3300 psig is versus the DOT stamped rating of 2400 psig.
From the OMS cylinder specification page:
1. The Hydrostatic test pressure is 4000 psig
2. The design life is 10,000 cycles at 4,000 psi
The water jacket test (commonly referred to as a hydrostatic test) is in effect a yield strength test. Where the yield strength is the stress required to produce a small-specified amount of plastic deformation. (plastic deformation is when the material will not return to it's original dimensions).
The mechanical response to stress for metals is commonly plotted on a stress-strain curve. The curve is linear for the 3AA tank from the zero point to the yield strength. What does this mean? That there is a proportional relationship to the behavior of the material at different pressures up to the yield strength. So a fill of 2400 psig in the OMS LP80 with a design life of 10,000 cycles at 4000 psig has an expected life of (4000/2400)*10,000 or 16,667 cycles. At 3300 psig it becomes 12,121 cycles = (4000/3300)*10,000. A reduction of the expected life by 4,546 fills or 12.5 years at one a day. 12,121 fills is one a day for 33 years.
And for what it is worth
The tensile strength or the ability of this tank to withstand tensile loads without rupture is a minimum of 5970 psig. Where does this figure come from? DOT regulations for the 3AA tank state that " the wall stress at the minimum specified test pressure may not exceed 67 percent of the minimum tensile strength of the steel as determined from the physical tests required " [49CFR 178.37 (f) (2)] The physical test required is the water jacket test which we know from the OMS spec page is 4000psi. (4000/0.67) = 5970 psi. For the curious you can get into the spec for the water jacket test if you want as well at 49CFR178.
omar
49 CFR 173.302 - Charging of cylinders.
(b) Filling limits (Ref. 173.301 (e)): "Container pressure. The pressure in the container at 70°
F. must not exceed the service pressure for which the container is marked...". That's straightforward enough that no one should have any trouble understanding it.
Now let's examine what the actual reduction in tank life that filling an OMS (Faber) LP80 (3AA) to 3300 psig is versus the DOT stamped rating of 2400 psig.
From the OMS cylinder specification page:
1. The Hydrostatic test pressure is 4000 psig
2. The design life is 10,000 cycles at 4,000 psi
The water jacket test (commonly referred to as a hydrostatic test) is in effect a yield strength test. Where the yield strength is the stress required to produce a small-specified amount of plastic deformation. (plastic deformation is when the material will not return to it's original dimensions).
The mechanical response to stress for metals is commonly plotted on a stress-strain curve. The curve is linear for the 3AA tank from the zero point to the yield strength. What does this mean? That there is a proportional relationship to the behavior of the material at different pressures up to the yield strength. So a fill of 2400 psig in the OMS LP80 with a design life of 10,000 cycles at 4000 psig has an expected life of (4000/2400)*10,000 or 16,667 cycles. At 3300 psig it becomes 12,121 cycles = (4000/3300)*10,000. A reduction of the expected life by 4,546 fills or 12.5 years at one a day. 12,121 fills is one a day for 33 years.
And for what it is worth
The tensile strength or the ability of this tank to withstand tensile loads without rupture is a minimum of 5970 psig. Where does this figure come from? DOT regulations for the 3AA tank state that " the wall stress at the minimum specified test pressure may not exceed 67 percent of the minimum tensile strength of the steel as determined from the physical tests required " [49CFR 178.37 (f) (2)] The physical test required is the water jacket test which we know from the OMS spec page is 4000psi. (4000/0.67) = 5970 psi. For the curious you can get into the spec for the water jacket test if you want as well at 49CFR178.
omar
