tolerance on CH oil delivery meters

[jim]

There is over 5% discrepancy between the delivery tanker meter (on a printed roll) and the the amount I estimate/calculate as having being delivered by measuring the storage tank (rectangular steel).

Please, does anyone know what the allowed tolerance is on these meters? In other words if the printer roll on the tanker states

1000litres, how close to that is the actual delivered volume likely to be?

TIA

[Dave Liquorice]

Have you let the oil settle? I know it sounds daft but the delivery does introduce a lot of air into the oil that needs to settle out. I've noticed a 1cm drop in level in the 24hrs after a delivery when the useage hasn't been enough to account for that amount of drop. Also think about temperature and expansion/contraction, I feeling that it does make a measurable difference to the tank level.

Ask trading standards? Pah their central site is not very useful but it did lead me to an SI "The Measuring Instruments (Liquid Fuel delivered from Road Tankers) Regulations 2006" SI 2006 No.1269.

[The Medway Handyman]

I think HMRC have an interest here, they certainly inspect petrol pumps for accuracy. I'd guess the meters have to be checked & calibrated at regular intervals as well.

[fictitiousemail]

I'd imagine the Op is suggesting he got less than stated ,not more .

[Michael Chare]

My recent delivery was apparently a little short however this could be accounted for by the fact that the oil is cold, and would occupy a reduced volume.

[Vortex3]

Have a read of this:

"The Accuracy of Fuel Metering" from the National weights and measures lab.

Emphasis is vehicle fuels but I guess the regs must be pretty similar.

D

[Kevin]

but its sold/metered by volume not weight

[Rod]

I was thinking of replying along the same line. But then I thought Michael might have been meaning that the temperature (and hence volume) of the oil went down between the tanker and the tank. Maybe after a cold night? So checking the next day might suggest less oil. But as I CBA to check changes of density of heating oil due to a few degrees drop in temperature, I didn't...

[Alang]

The volume is calculated by reference to API tables and corrected for a temperature of 15 degrees C.

[Michael Chare]

No, I just happen to know that what your buying is litres at 15deg C. I should perhaps have included that point.

[jim]

//snip///

TFT - but what are the API tables? Please can you provide a pointer? Or perhaps post the fractional correction factors (or %) for say 0deg;

5; 10; 15 (assume that is 1.0); 20; & 25 please?

Thanks also to others for very interesting relevant postings. I did try TS but the concept of meter accuracy and measurement tolerance of a delivered volume was beyond their comprehension!

[Alang]

American petroleum institute tables for the correction of volume at 15 degrees C. The density therefore volume varies for change in temperature.

Or perhaps post the fractional correction factors (or %) for say 0deg;

I'm out the business over 10 years. Don't have them anymore and IIRC they are rather costly to purchase.

There are lots of companies involved in this but they tend to concentrate on larger volumes. Try a search on tank gauging.

[Steve Walford]

Have you allowed for the thickness of the walls when calculating Tanks are not allways square, sides can belly out leading to errors when calculating We used to have a 10,000 litre above ground DERV tank and suspected short deliveries and or delivery problems The tank had an external sight glass we affixed a couple of large metre rulers to the side one above the other(similar to what they use with (blackboards) (sorry chalkboard) Filled the tank up, when a 1,000 litres had been drawn off (dispensing pump accurate to 1%) marked the ruler, carried on doing this for each

1,000 litres. The markings were not same measurement for each 1,000 litres

[mick]

Also (from HM Revenue & Customs Reference: Notice 179 - November 2006):

4.10 What are your accuracy requirements? 4.10.1 General

You are responsible for the calibration and continuing accuracy of measuring equipment used to raise revenue accounts. You must comply with the following accuracy requirements (these requirements are referred to in the Energy Institute good practice document as "HM Revenue & Customs mandatory requirements").

Note that the following are minimum acceptable accuracy requirements. If your measuring equipment is capable of a better standard of accuracy that better standard should be applied.

4.10.2 Volumetric meters

The Maximum Permitted Error (MPE) of a meter used for revenue accounting (under its rated operating conditions) shall not exceed at any time:

• for unheated oils ±0.15% (±0.20%) * for heated oils ±0.20% (±0.20%)

Notes:

1. The Measurement Instruments Directive has set new standards of MPEs to replace current values for all equipment installed after 30 October 2006. These replacement values are shown above in brackets.

1. "Heated oil" means heavy oil having a temperature exceeding 15°C and shown to the satisfaction of HMRC to be artificially heated.

2. "Artificially heated" oils are those, which have been heated from an external source, such as steam heating coils, during storage or delivery, to facilitate handling. The temperature of these oils is normally kept substantially above 15°C. Oils which have not been intentionally heated subsequent to a production process, e.g. in a refinery, but which may retain some residual heat from that process, are not regarded as being "artificially heated".

4.10.3 Automatic tank level gauges (ALGs/ ATGs)

The accuracy of an automatic tank level gauge (ALG) used for revenue accounting, over the working range in which it is installed must be within ±8mm of a measurement made by reference manual gauging. Again, under the provisions of the Measurement Instruments Directive, we have agreed that for all equipment installed after 30 October 2006, this accuracy level will be ±5mm.

ALGs (sometimes referred to as Automatic Tank Gauges - ATGs) are used to measure the depth of oil in tanks. Technical information on the various types of ALG is below. With a temperature probe as additional equipment, they can also measure temperature. Such equipment can be set to read in and/or convert to volume at 15°C. Setting-up and servicing ALGs requires a high degree of care. Experience has shown that their reliability depends on the trader?s observing the full maintenance procedure recommended by the manufacturer. In addition to the readings given on tank-side indicators, some types of equipment may be connected to electronic units, which transmit information to a central control room. Traders? schedules of measurement methods used at duty points will indicate those gauges used for duty accounting. Tank gauges will usually be used for receipt accounting of bulk volumes taken into storage tanks and for stock control.

When properly installed and serviced, ALGs provide rapid and accurate tank dips and temperatures for operational and stocktaking purposes without interrupting the processes. They contribute to safety and to the economic use of traders? manpower by reducing the need to climb tanks for manual dipping.

4.10.4 Manual gauging

The accuracy of a working dip-tape used for revenue accounting must lie within ± 2mm throughout each 30m length (±1.5mm when new).