Bulk LPG Tanker (in)accuracy

Flintman

The rate of change of liquid depth is as you say, sinusoidal. But the rate of change in float arm rotation with dcepth is also sinusoidal, hence they cancel each other out to give linearity. However, evenn if I am wrong about this,it is irrelevant since there is no correlation between variance and tank depth. It would certainly not explain why in Nov 24, 786 L was delivered to fill my tank from 31.5% full while this year, it took 931 L to fill it from 31.5%.

Powapa

https://forums.moneysavingexpert.com/discussion/comment/81873167#Comment_81873167

Hello, interesting reading this. I had a LPG delivery last year and it was very odd compared to my previous deliveries of the past 8 years. My tank is 2100 litres and we had 2099 litres delivered, the tank only read 85% and when the LPG was being delivered I could smell a really strong gas smell as if the pipe wasn't connected properly.

I contacted the company who said basically it was within tolerance and it is normal to be able to smell gas on delivery. I just paid up and got on with it but still to this day it doesn't sit right with me.

Flintman

Smell during tank filling only ccurs if the driver opens the tank vent excessively. They should only do this as the tank approaches 85% to ensure no liquid is expelled. (Guarding against a sticking tank meter). However, this will not cause a serious deviation. When my tank was filled with a 22% error, the driver was very good. If your tank was 20% full before topping up to 85%, you would only need 1,365 litres. There is no way they could get 2099 litres into it. I would challenge the supplier.

Thank you for your input, I am not alone!

Flintman

To be able to get 2099 litres into a 2100 litre tank would require that the tank was completely empty and 100% full after delivery. I assume that the former is not the case and if the tank meter is sticking at 85% when it is 100% full, it should stay at that value for some weeks until the gas level has fallen to less than 85%. Also, if the tanker driver did his job correctly and checked for liquid ejection (instead of gas) from the vent on top of the tank, it could not be 100% full. You therefore have a cast iron case against your supplier for an excessive charge. Whether the cause is a faulty tanker meter or administrative glitch in the billing process can be determined by the delivery note that you must have been given after the tank was filled. If you still have this note, keep it safe because if that showed 2099 L was delivered, it is 100% proof that the tanker meter was incorrect.

If your tank was empty and filled to 85%, you would have needed 1785 L. In your position, I would present these figures demand a plausible explanation for the 2099 L. If they did not come clean, I would threaten legal action because the case is so strong. I wish you good luck

One final question, do you order manually, or let the supplier take responsibility for filling the tank when they think it necessary?

Powapa

https://forums.moneysavingexpert.com/discussion/comment/81877084#Comment_81877084

Thank you very much for the information, I’ll draft an email to the company tonight and give them a call tomorrow. This was their response to my initial query last year - “This means that if you were empty, we could deliver approx. 2040 ltr to 85% depending on temperature ect.”

I order manually and on this occasion was at 5% reading when delivery took place.

Flintman

You mentioned that this delicvery was way above the norm. It would be interesting to know rouighly how much you normally get. Since your tank has a capacity of 2,100 litres, each % in it is equivalent to 20.1 L. Since the delivery took the level from 5 to 85%, 80 % of the tank's capacity was added to it; this equates to 1,680 L . Temperature has no effect because the tanker meter measures volume and not weight. In my opinion they are not treating you with respect. Please keep in touch.

Diophantos

I’m new to the world of LPG having just taken over my parents’ account. I too found many anomalies, a specimen one being a 1114 litre tank filled from 301 litres (27%) litres to 936 litres (84%). Since usage is reported in increments of 1%, I thought I could allow 0.5% each way and calculate that between 623 and 647 would have been delivered. However, the bill was for 697 litres, nearly 10% above the midrange of what was expected. At current prices, around £50 above what might be expected.

The gas company told me, after a few attempts, that the float guage in the tank is only accurate to plus or minus 10% - so a tank filled to 85% could be anything between 75-95% filled. I don’t know how to get independent verification of that, but if true it makes a mockery of the usage data they provide - it becomes so vague as to be worthless if the amount in the tank could be out by 110 litres or so. The usage page on their website says nothing about the level of accuracy, so is very misleading. There’s no way to challenge their billing if the possible ranges are so broad.

QrizB

There’s no way to challenge their billing if the possible ranges are so broad.

Keeping a gauge calibrated for billing purposes is relatively expensive. It's much more reasonable for the LPG company to calibrate the gauge on their tanker rather than the gauges on hundreds of tanks.

If you're being billed based on the calibrated gauge on the tanker, you're being billed correctly.

Diophantos

Let’s say then that the gauge is calibrated and the bill is correct - adding 697 litres to the 301 already in there (give or take 5) would leave the 1114 litre cylinder 89-90% full, but the usage page says it’s 84% (they don’t fill above 85%, they say). Where’s that 5% (approx 55 litres) gone? If it’s down to the inaccuracy of the float gauge, what’s a reasonable margin of error?

QrizB

Let’s say then that the gauge is calibrated and the bill is correct

Yes, let's. That's almost certainly a true statement.

adding 697 litres to the 301 already in there (give or take 5)

You don't know there was 301 already in the tank. All you know is that the gauge indicated 301. It might've been 250. It might've been 350. There's no way to know as the gauge is neither accurate nor precise.

Where’s that 5% (approx 55 litres) gone?

It hasn't gone anywhere. It never existed.

If it’s down to the inaccuracy of the float gauge, what’s a reasonable margin of error?

The float gauge is for indication only. Asking for anyone to suggest "a reasonable margin of error" shows that you're still thinking of it as being accurate. It isn't.