The time limit for. shipping a POV is the same as for travel and HHG transportation limits (JTR Para 5366, POV. Transportation Time Limitation), 1 year from the date of retirement/separation with severance. pay or 180 days from the date of separation.
The envelope is the large bag that holds the helium gas. The envelope is generally cigar-shaped, for aerodynamic purposes, and made of a durable, airtight, lightweight fabric (polyester composites) that is much like the fabric of a space suit.
Helium is also one of the lightest gases around and only 1,5 kg will fit into a 50 litre at 200 bar. This makes the distribution of helium so much more challenging as the cylinder weighs 70kg. For this reason helium is shipped from the origin to the cylinder filling plant in liquid form and then pumped into cylinders. The helium is extracted in a few places in the world, namely USA, Algeria, Russia and Qatar â the largest contributors of helium to the world markets.