Propane Tank Recertification

[bobsallyh]

Dutch12078, they open the bleed screw when beginning filling and when the spitting starts, shut the screw and pump off. If a #20 cylinder is empty, it usually cuts off at 4.3. A #30 usually shuts off at 6.9. Both depending on weather and temps. Of course, the pump is stickered by the county for accuracy. just pumps like at service stations. I just got propane yesterday, and the owner now has a cage there with 20, 30, and 40 pounders in it for exchange. I don't know if this still true but a number of years ago propane regulations etc. in Texas were controlled by the Railroad Commision. I knew immediately why the differences from other states.

Edited October 5, 2022 by bobsallyh

[Dutch_12078]

1 hour ago, bobsallyh said:

Dutch12078, they open the bleed screw when beginning filling and when the spitting starts, shut the screw and pump off. If a #20 cylinder is empty, it usually cuts off at 4.3. A #30 usually shuts off at 6.9. Both depending on weather and temps. Of course, the pump is stickered by the county for accuracy. just pumps like at service stations. I just got propane yesterday, and the owner now has a cage there with 20, 30, and 40 pounders in it for exchange. I don't know if this still true but a number of years ago propane regulations etc. in Texas were controlled by the Railroad Commision. I knew immediately why the differences from other states.

I'm glad to see that's how they were doing it. I'm well aware of how the Fixed Liquid Level Gauge works, Bob, having used it many times when filling both DOT cylinders and ASME tanks. I mentioned it to the attendant at Tractor Supply, but he said he was filling my 30 lb cylinder the way he was trained. I don't know who did their training, but clearly something was skipped. It's not a store I'm likely to use for refills very often, but it'll be interesting to see if anything has changed the next time I stay at the state park in the area. It's good to see they have the larger sizes available for exchange. I wish more refillers would do that.

Edited October 5, 2022 by Dutch_12078
typo, clarity

[Customer1]

On 10/3/2022 at 11:44 AM, Ray,IN said:

OPD valve limits filling over 80%, 16# =3.4G is maximum capacity.

They hold 80% WC (water capacity) the typical BBQ size bottle is at 80% WC when it contains 20# of lpg.  Yours is a common mistake.

[Ray,IN]

On 10/12/2022 at 10:42 PM, Customer1 said:

They hold 80% WC (water capacity) the typical BBQ size bottle is at 80% WC when it contains 20# of lpg.  Yours is a common mistake.

This Measurement Technology paper has a different explanation.

[mptjelgin]

There are two different measurement types to consider.  When the 80% term is being used, it is based on volume. That is, only 80% of the volume of the tank is filled with liquid propane to allow 20% gas volume above the liquid. 

The paper that you refer to is based on weight. Since liquid propane weighs much less than water (4.1 - 4.2 pounds per gallon, depending on temperature vs. water at 8.3 pounds per gallon) the fill percentage numbers based on weight are much different. 

The 42% of WC referred to in the referenced paper corrects for the weight difference between the two liquids as well as the 80% fill volume. So the maximum weight of liquid propane is 42% of the full liquid weight of water. Volume-wise, that is about 80% full of propane. 

 

[Customer1]

3 hours ago, Ray,IN said:

This Measurement Technology paper has a different explanation.

"Cylinders Filled By Weight

Following the visual exterior bottle inspection, the bottle filler will look for two other things prior to hooking up the fill hose with the cylinder on the scale. These two things are the water capacity and tare weight. The water capacity is how much water the propane bottle will hold in pounds. The "WC" stamped on the bottle followed by a number such as "47.6" means the bottle will hold 47.6 pounds of water. The tare weight (empty weight) indicated by a "TW" is also followed by a number such as "18" meaning the bottle weighs 18 pounds when empty. The numbers here would likely be found on a five gallon propane bottle (also known as a 20 pound cylinder) used for a barbeque grill.

The bottle filling station will generally have a cylinder filling chart that converts water capacity (WC) to pounds of propane that the filler will refer to before filling the bottle. The chart will show that 47.6 pounds of water converts to 20 pounds of propane. In other words, a propane bottle that will hold 47.6 pounds of water will hold 20 pounds of propane. This indicates that the scale needs to be set a little over 38 pounds (20 lbs + 18 lbs = 38 lbs) to obtain the weight of the bottle when it reaches its allowable capacity."

https://www.propane101.com/propanecylinderfilling.htm