[Music] meters measure the volume of petroleum or petroleum product that flows through them in G or barrels the meter register tells how much oil or product has been bought sold or transferred to another's custody so a meter must give accurate readings however a meter doesn't always deliver exactly the volume it says it did to understand why let's look closer at a meter many types of meters are available but a common type is the positive displacement meter in this type liquid flows through the meter and turns either a rotor or loed impellers these rotating elements form a measuring chamber of fixed volume the rotation of the chamber is transmitted through gears to the meter register above since each chamber has a fixed volume it divides the liquid stream into precise or positive segments thus it is termed a positive displacement meter one limitation in a meter's performance has to do with its design clearance between the rotor blades or the impeller and the meter housing is needed so that the rotor or impeller can rotate freely as a result some liquid slips through these clearances and is not registered another problem is wear as the rotor or impeller rotates wear on these moving Parts causes changes in the meter's performance clearances tend to increase and gears and other moving Parts become worn so because meters don't always deliver exactly the volume they register they must be calibrated they must be proved to prove a meter you precisely determine a volume of liquid either before or after it's run through the meter then you compare the meter's indicated volume with the known volume if the meter has over or under registered you can mechanically adjust the meter itself or you can calculate a special number a meter factor to correct the meter's reading now a meter factor is found by dividing the known volume by the volume registered by the meter then the meter's registered volume is corrected by multiplying it by the meter factor for for example suppose the meter's registered volume is 10,000 barrels if the meter factor is 9964 then the corrected volume is 9,964 barrels on the other hand mechanical adjustment is done by adjusting the calibrator of the meter adjusting the calibrator changes the ratio between the rotor or impeller and the meter register to to correct the register both mechanical adjustment and a meter Factor are accurate ways to correct the meter's registration so why are two methods available well it depends on where the meter used for example this meter is at a truck loading facility such meters are usually mechanically adjusted because even if it can be adjusted to only 99.9 8% accuracy 99.99% accuracy introduces an error of only plus or minus 1/2 gallon in loading a 2,000g truck compartment since such transactions are rounded to the nearest gallon anyway such a small error is insignificant on the other hand this meter measures the transfer of large volumes of petroleum or product in a pipeline operation in this case 100% accuracy is required because of the large volumes involved here's why in a run of let's say 200,000 barrels a meter accuracy of only 99.98% produces an error of 40 barrels now this is a significant error therefore where large volumes are involved use the meter factor to correct the meter registration to 100% accuracy if you have workbooks stop the tape and work exercise one then return to the program to determine a meter factor or to know how much to adjust a meter you need a meter prover a device with a precisely known Volume Two basic types of provs are available the open tank prover and the pipe Pro also sometimes a Master Meter is used to prove another meter a Master Meter is simply a meter with known performance you compare the performance of the meter being proved against the known performance of the master meter but let's concentrate on pipe provs and open tank provs an open tank PR is often used to prove meters at a truck loading rack because using the prover is similar to loading a tank truck since the prover is open to the atmosphere or to a vapor recovery system and is not under pressure it's called an open tank prover to prove a meter with an open tank prover the liquid is flowed through the meter and into the tank a graduated gauge glass on the prover gives a precise reading of the volume of liquid the meter delivers into the tank now this reading should be to the nearest .01 gallon or .001 Barrel you compare this actual volume delivered into the tank with the volume the meter register then you either mechanically adjust the meter the usual case or use a meter factor to correct the meter's registration however before you can make an accurate comparison of the two volumes you must calculate temperature and pressure corrections to explain petroleum and petroleum product volumes change with temperature and pressure for instance 10,000 barrels of oil at 75° F occupies about 10,50 barrels at 85° F and 10,000 barrels of oil at 500 PSI occupies about 10,030 barrels at 0 psi also prover volume changes with temperature and pressure changes steel expands or contracts with increases and decreases in temperature and pressure therefore to accurately compare the volume the meter registered with the volume in the prover you must correct both volumes to standard temperature and pressure usually standard temperature and pressure is 60° fah and Zer PSIG in other words regardless of what the volume volumes are at their actual temperature and pressure they're converted to what they'd be if they were at 60° F and 0 PSIG now to convert volumes at actual temperature and pressure to volumes at standard temperature and pressure you use correction factors these correction factors are correction for the temperature of steel CTS correction for the temperature of liquid CTL correction for the pressure on steel CPS and correction for the pressure on liquid CPL in open tank proving we're mainly concerned with CTS and CTL the temperature Corrections now this is because with open tank provs the liquid is under no pressure except for the atmosphere so it's already at 0er PSIG and if no pressure correction is applied to the meter the pressure correction is automatically included when the meter is adjusted but you still must determine CTS and CTL the temperature Corrections tables are provided by API to find these factors now this one is for CTS as an example if the observed temperature of the prover steel IS 78° F this Falls between 73 3.5 and 78.8 de F so the CTS value is 1.03 you use similar tables to find CTL both for the liquid in the prover and at the meter when the observed volumes are multiplied by these factors the volumes are corrected to standard temperature but a word of caution some meters are temperature compensated a device automatically corrects the metered volumes to 60° Fahrenheit if so you don't have to determine CTL for the meter a pipe is often used to prove meters in pipelines because using a pipe is similar to pipeline operations now many types of pipe provs are available but a common one is the B directional U type with this prover you divert flow from the main line into the prover either before or after the liquid goes through the meter now here the prover is Downstream from the meter but it could just as likely be Upstream this is a bidirectional pipe prover because one proving run is not complete until flow goes through it first in One Direction and then the other the accurately calibrated part of the approver is its base volume the base volume is calibrated and certified to deliver a very specific roundtrip volume of liquid like 5.28 barrels for example using a four-way valve you direct flow through one side of the prover here to the right a ball or displacer sphere contacts a detector switch when contacted by the displacer the detector switch starts an electronic counter the counter counts pulses put out by a pulse generator on the meter the number of pulses on the counter represents the metered volume the pulse generator is attached to the meter and puts out a large number of of pulses for every barrel the meter registered as the displacer travels through the PR's base volume portion the electronic counter continues to operate and accumulate the meter's indicated volume when the displacer reaches the other detector switch it trips the switch and the counter stops registering pulses the displacer then goes into the left receiver trap but the this is only half the run to complete it you send the displacer back the other way the displacer hits the detector switch and the counter starts counting meter pulses again adding to the number already counted in the first half of the Run finally the displacer travels past the other detector switch and the counter stops registering pulses now you read the total pulses on the counter here it's 85356 when this number is converted to barrels it tells you the volume the meter registered now this registered volume is corrected to standard temperature and pressure and compared with the base volume of the prover after it is corrected to standard temperature and pressure temperature and pressure Corrections are made after finding values for CTS s CTL CPS and CPL then using a meter Factor the meter's registered volume is corrected if you have workbook stop the tape and work exercise two then return to the program regardless of the type of prover several requirements must be met to ensure valid proving results first prove the meter under the same conditions at which it normally operates for example prove the meter at its normal flow rate don't change the flow rate during approving and expect the job to be valid second the prover must have a capacity large enough to provide proving runs of adequate duration for example an open tank prover has to be large enough to hold at least the volume of liquid the meter delivers in a 1 minute period at its normal flow rate and preferably the pr should have 1 and A2 to two times this capacity third you must make enough runs to establish the validity of the proving enough runs to establish repeatability here 10 runs were made and requirements in this case called for the pulse counts for five consecutive runs to be very close to the same figure here the pulse counts for the last five runs meet the requirements fourth the prover must be calibrated with the National Bureau of Standards certified field standard test measures a certificate of calibration should ACC the prover fifth all the liquid that passes through the meter must also pass through the prover in other words you must carefully check all connections fittings and valves for leaks any liquid that leaks out won't go into the prover and isn't accounted for inaccurate proving is the result finally you must accurately and carefully fill out approv proving report it's a very important document so let's take a closer look this one from the API is for an open tank proving a report for a pipe prover is similar but let's use this one as an example it has spaces for such data as the location tender number type of liquid its API gravity and so on it also has spaces for such prover data as its nominal volume at 60° fah and 0 PSIG and its serial number spaces are also provided for data from previous reports an important part as you'll see later meter data such as its serial number manufacturer size flow rate and so on is is also recorded PR tank volume data and run data is also recorded here data for up to four runs can be written down the proved meter data section has spaces for final and initial meter readings indicated volume by the meter temporary at the meter pressure at the meter and so on finally spaces are provided for signatures date and companies represented now the completed report has several uses for one thing it gives the information needed to mechanically adjust the meter to the required accuracy or it gives the information needed to calculate a meter factor in addition the report becomes a matter of record a record to use for petroleum or product transactions also it's a record to use for meter evaluation for example let's say you prove a meter and determine a meter Factor now this current Factor may be different from the factor determined the last time the meter was proved let's say 9988 versus 9984 now in this case the previous and current factors are very close to the same probably well within the tolerance set by your company however suppose the previous factor is 9988 versus 9940 for the current proving now 0 n940 is quite a bit different from 9988 and is probably out of the tolerances set by your company in such a case the question why is the factor out of Tolerance must be asked all right first check to be sure the proving job is good all the recommended methods and procedures must be followed and all data must be accurately recorded in any proving job the tolerances are close and poor quality work can cause mismeasurement and unnecessary expense but if the proving job is good then consider that the meter may be worn to the point of repair as meters are used they become worn and their performance changes a badly worn meter may fail to repeat within required tolerance when considering where think about these points in general a meter in constant use wears faster than one used only occasionally also a new or overhaul meter tends to wear faster than one that's been in use for some time items other than wear can also be the cause of a change in meter performance for instance changes in the flow rate of liquid through a meter change its performance or meter Factor typically increased flow rate increases the meter Factor decreased flow rate rate decreases the meter Factor now here's why with a low flow rate the amount of liquid that slips through the clearances in the meter is low thus the meter factor is lower conversely with a high flow rate the amount of liquid that slips through is high thus the meter factor is higher so if the factor is out of Tolerance it could be that the flow rate has changed changed since the last proving changes in the temperature of a liquid also change meter performance petroleum and petroleum products generally become less viscous thinner with increases in temperature and thinner liquids slip through clearances easier than thicker liquids so the higher the temperature the higher is the meter Factor thus changes in the temperature of the liquid flowing through the meter can account for Factor changes changes in the API gravity of the liquid also changed the meter Factor because in general a high-gravity liquid is less viscous thinner than a low-gravity liquid so high-gravity liquids because they are thinner slip through clearances easier than thicker low gravity liquids thus plus an increase in gravity causes an increase in the meter factor or a decrease in gravity causes a decrease in the meter Factor now this is why you always check the liquid's gravity in all proving jobs if you have workbooks stop the tape change the slide tray and work exercise 3 then return to the program the prover can also be a source of inaccuracy in approving job let's look at some examples first remember that no leakage can occur every drop of approving run must be contained in the proving system otherwise the proving is invalid you can check for external leaks by simply checking connections but you need internal Leak Detectors to see if valves are leaking internally here a small valve at the base of the main valve is opened after the main valve is closed if liquid flows out of the small valve then the main valve is leaking and needs repair before proving can continue now just because the meter can repeat with intolerance with a small leak don't make the mistake of ignoring it here's why the volumes used in proving a meter are relatively small so a leak of let's say only one gallon for a th000 gallon proving run may not seem like much however if you ignore the loss of 1 gallon per 1,000 in a proving run the error adds up to 1,000 gallons for every million gallons through the meter now that's a lot also even the leakage of one pint is significant a pint of leakage adds up to 125 gallons for every million gallons and when it comes to pipe provs where the base volume for one run can be about Five Barrels or less leakage is even more critical for aover of this size the leakage of less than 1 o half a shot glass can cost you one barrel per 10,000 or 100 barrels per million so always check for leaks even small ones now one problem open tank provs have is buildup inside the tank buildup causes the prover to contain less volume than indicated on the gauge glass so inspect the interior frequently and if necessary flush it with an approved solvent a common proving error is in temperature determination thermometer reading errors inaccurate or damaged thermometers or poor installation can all Lead You astray how important is accurate temperature measurement well let's look at 1° fight of error with liquids that range from 30° to 65° API a range that covers most of the crude and products we meter depending on the gravity the correction for one degree temperature ranges from four to around six barrels per 10,000 all right this means that someone gets taken by four to six barrels per 10,000 for each one degree of temperature error in aing job so always be sure that the thermometers are accurate and installed properly if you don't a temperature error could go undetected for years if air or vapor in a liquid also causes errors air or vapor like liquid imparts motion to the meter's roor so the air or vapor is registered as though it was Liquid slippage through the meter is also increased further if the air or vapor goes through the metering system in slugs the meter probably won't repeat within Tolerance on the other hand if the air or vapor is evenly distributed in the liquid it may go undetected during the proving and the meter may or may not repeat with intolerance in any case air or vapor eventually causes losses as it escapes from the liquid when the liquid finally reaches a tank so when air or vapor is present approving error results look for the source of the eror vapor and correct the process problem for instance maybe a leaking gland or seal on the suction side of a pump is pulling air in it'll have to be repaired before continuing the proving job in a tank prover you can actually see the air Vaper in the sight glass or in the top neck in a piper You Can't See Arrow Vapor but you can tell if it's there when you bleed it between runs if it's there every time you bleed chances are good you've got got a problem in summary remember these key points about conducting or evaluating approving first always follow the recommended methods and procedures as set forth by your company and API second check and double check each step in the proving don't assume anything third be precise in all observation ations and calculations and fourth and finally always report to your supervisor the use of any procedures not covered by the company instruction manual if you have workbooks work exercise [Music] 4 [Music]
