Why can't you fill a LPG storage tank up to 100%

As you may concern that the LPG storage tank’s filling volume is 80-85% of capacity. Is the gas company is short-changing you? No. Because a vapor space must be left in the tank to avoid an explosion, which may happen caused by not leaving sufficient room for for expansion of the liquid fuel as temperature of the liquid propane increase during the delivery process.

Liquid propane has a comparatively high coefficient of expansion. As the temperature increase liquid propane can expand 5-10%. For example, if you would fill a tank to 100% in the morning when it’s 60 ˚F and the temperature during the day increases to 90 ˚F. The liquid propane would expand to the point that the relief valve would release the liquid that will not fit in the tank.

And if a tank is filled to 100% of capacity, then increases in temperature would result in pressure increases on the tank of hundreds, or possibly thousands, of PSI, and possibly cause a very severe mechanical failure resulting in a massive fire or chemical explosion.

This is because LPG gas has very little compression ability.

So considering the safety, leaving vapor space in the tank is necessary. Then moderate pressure increases due to moderate temperature increases are safely absorbed, or buffered, allowing only moderate pressure increases to the tank.

It is theoretically possible of physically and totally fill a tank, but if proper safety valving and filling techniques are used, then there will always be a "head-space" for safety in the tank at all times.

So how to know the filling level? A good quality level gauge is needed to monitor the inner tank.

And also the temperature gauge and pressure meter are typically equipped with LPG tanks. Since temperatures can change while delivering. And the pressure changes, too. When the pressure rises up to a level which the tank can’t hold it, the safety valve would rise up to release pressure.

Also the LPG gas would leak with the pressure, too, until the pressure in the tank recover to the standard level.

So make sure don’t fill LPG storage tanks up to 100%. It’s really dangerous. And do purchase high quality tanks and accessories from reliable manufacturer. Chengli factory’s LPG tanks are manufactured strictly based on the pressure vessel standards. And the ASME certificate has been approved.