DRAFT UGANDA STANDARD  
  DUS 2030-1  
First  Edition  
yyyy-mm-dd  
 
 
 Reference number 
DUS 2030-1: 2019 
© UNBS yyyy  
  
Proving Systems — Methods of Calibration for Displa cement 
and Volumetric Tank Provers — Part 1: Introduction to the 
Determination of the Volume of Displacement and Tan k Provers  
 DUS 2030-1: 2019  
ii © UNBS 2019 – All rights reserved
 Compliance with this standard does not, of itself c onfer immunity from legal obligations 
A Uganda Standard does not purport to include all n ecessary provisions of a contract. Users are 
responsible for its correct application  
© UNBS 2019  
All rights reserved. Unless otherwise specified, no  part of this publication may be reproduced or util ised in any 
form or by any means, electronic or mechanical, inc luding photocopying and microfilm, without prior wr itten 
permission from UNBS. 
Requests for permission to reproduce this document should be addressed to 
The Executive Director 
Uganda National Bureau of Standards 
P.O. Box 6329 
Kampala 
Uganda 
Tel: +256 414 333 250/1/2/3 
Fax: +256 414 286 123 
E-mail: info@unbs.go.ug  
Web: www.unbs.go.ug  DUS 2030-1:2019 
© UNBS yyyy – All rights reserved  iii
 Contents Page  
Foreword .......................................... ................................................... ................................................... ............ iv  
1 Scope ............................................. ................................................... ................................................... ... 7 
2 Normative references .............................. ................................................... ........................................... 7  
3 Terms and definitions ............................. ................................................... ........................................... 7  
4 Symbols (and abbreviated terms) ................... ................................................... .................................. 8  
5 APPLICATIONS ...................................... ................................................... ............................................. 9  
5.1  Prover Calibration ................................ ................................................... .............................................. 9  
5.1.2  Portable provers .................................. ................................................... ............................................... 9  
5.1.3  Recalibration frequencies ......................... ................................................... ........................................ 9  
5.2  Temperature measurements .......................... ................................................... ................................... 9  
5.3  Pressure indicators ............................... ................................................... ........................................... 10  
5.4  Hoses, pumps and connections ...................... ................................................... ............................... 10  
6 Field standard test measures ...................... ................................................... .................................... 10  
6.1Procedure of use of Test Measures .............. ................................................... .......................................... 10  
7 Master meter ...................................... ................................................... ............................................... 11  
8 Master prover ..................................... ................................................... ............................................... 11  
9 Mobile equipment .................................. ................................................... ........................................... 11  
10  Documentation and Record Keeping .................. ................................................... ........................... 11  
11  Calibration Troubleshooting Guide ................. ................................................... ............................... 13  
12  calibration witnesses ............................. ................................................... .......................................... 14  
Annex A (informative)  Supplementary information on  meters ........................................... ........................ 15  
A.1  Types Of Provers .................................. ................................................... ............................................ 15  
A.1.1  Unidirectional—Sphere Provers with Mechanical Detec tors .............................................. ............ 15  
A.1.2  Displacement type bi-directional provers with free displacers ........................................ .............. 15  
A.1.3  Displacement type meter provers with captive displa cers .............................................. ............... 15  
A.1.4  Displacement type meter provers with multiple volum es ................................................ ............... 16  
A.1.5  Atmospheric tank provers .......................... ................................................... ..................................... 16  
A.2  Equipment ......................................... ................................................... ................................................ 16  
A.2.1  Prover detector switches .......................... ................................................... ....................................... 16  
A.2.2  Launching chambers and transfer chambers .......... ................................................... ..................... 16  
A.2.3  Sphere interchanges ............................... ................................................... ......................................... 17  
A.2.4  Four-way valves ................................... ................................................... ............................................. 17  
A.2.5  Displacers ........................................ ................................................... ................................................. 1 7  
A.2.6  Valves, relief valves, drains and vents ........... ................................................... ................................ 17  
A.2.7  Solenoid valves and logic circuits ................ ................................................... .................................. 17  
APPENDIX B (Informative) CALIBRATION WITNESSES .... ................................................... ....................... 19  
Bibliography ...................................... ................................................... ................................................... .......... 21  
. DUS 2030-1: 2019  
iv © UNBS 2019 – All rights reserved
 Foreword 
Uganda National Bureau of Standards (UNBS) is a par astatal under the Ministry of Trade, Industry and 
Cooperatives established under Cap 327, of the Laws  of Uganda, as amended.  UNBS is mandated to co-
ordinate the elaboration of standards and is  
(a) a member of International Organisation for Stan dardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex Alimentar ius Commission on Food Standards, and  
(c) the National Enquiry Point on TBT Agreement of the World Trade Organisation (WTO). 
The work of preparing Uganda Standards is carried o ut through Technical Committees. A Technical 
Committee is established to deliberate on standards  in a given field or area and consists of key stake holders 
including government, academia, consumer groups, pr ivate sector and other interested parties.  
Draft Uganda Standards adopted by the Technical Com mittee are widely circulated to stakeholders and th e 
general public for comments. The committee reviews the comments before recommending the draft standard s 
for approval and declaration as Uganda Standards by  the National Standards Council. 
The committee responsible for this document is Tech nical Committee UNBS/TC 16 , Petroleum , Subcommittee 
SC 2, Drilling, Development and Production Equipment and Materials . DUS 2030-1:2019 
© UNBS yyyy – All rights reserved  v
 Introduction 
Provers are precision devices, defined as volumetri c standards, which are used to verify the accuracy of liquid 
volumetric meters used for custody transfer measure ment. Both displacement and tank provers are used t o 
prove a meter in order to obtain its meter factor, which is then used to correct for meter error cause d by 
differences between the metered volume and the true  volume. The base volume of a displacement or tank 
prover, determined by calibration, is an essential requirement in the determination of these meter fac tors. 
. 
 DRAFT UGANDA STANDARD DUS 2030: 2019 
  
vii  
 Proving Systems — Methods of Calibration for Displa cement 
and Volumetric Tank Provers — Part 1: Introduction to the 
Determination of the Volume of Displacement and Tan k Provers  
1 Scope  
This draft Uganda standards covers procedures requi red to determine the field data necessary to calcul ate a 
Base Prover Volume (BPV) of either Displacement Pro vers or Volumetric Tank Provers.  
It will enable the user to perform all the activiti es necessary to prepare the prover, conduct calibra tion runs, 
and record all the required data necessary to calcu late the base volumes of displacement and tank prov ers. 
Evaluation of the results and troubleshooting of ma ny calibration problems are also discussed. 
2 Normative references  
The following referenced documents referred to in t he text in such a way that some or all of their con tent 
constitutes requirements of this document. For date d references, only the edition cited applies. For u ndated 
references, the latest edition of the referenced do cument (including any amendments) applies. 
1 FDUS ISO 7278-2:1988 Liquid hydrocarbons — Dynami c measurement — Proving systems for 
volumetric meters — Part 2: Pipe provers 
3 Terms and definitions  
For the purposes of this document, the following te rms and definitions apply.  
3.1 
Authorised Authority:  
Responsible personnel/institution as indicated or s pecified in the Petroleum (exploration, development  and 
production) (metering) Regulations, 2016 and subseq uent revisions 
3.2  
Base Prover Volume (BPV)  
The volume of the prover at base conditions, as sho wn on the calibration certificate package, and obta ined by 
arithmetically averaging an acceptable number of co nsecutive Calibrated Prover Volume (CPV) 
determinations 
3.3  
calibration certificate package  
A document package stating the Base Prover Volume ( BPV) together with the physical data used to calcul ate 
the BPV. It also includes the witnessed field data,  summary calculations, and the traceability documen tation 
3.4  
Calibrated Prover Volume (CPV):   
The volume at base conditions between the detector switches of a unidirectional prover, or the volume of a 
prover tank between specified “empty” and “full” le vels, as determined by a single calibration run. Th e DUS 2030-1: 2019  
viii © UNBS 2019 – All rights reserved
 calibrated volume of a bi-directional prover is the  sum of the two volumes displaced between detectors  during 
a calibration round-trip. 
3.5  
4 double block and bleed valve  
A high-integrity valve with double seals that has p rovision for determining whether either seal is lea king 
3.6  
prover calibration pass  
A single movement of the displacer between two pred etermined detectors. 
3.7  
6 prover calibration run  
One pass of a unidirectional prover or one round tr ip of a bi-directional prover, or one emptying or f illing of a 
volumetric tank prover, which provides the data whi ch allows the calculation of a single value of the Calibrated 
Prover Volume (CPV). 
3.8  
targeted BPV  
A term associated with atmospheric tank prover cali bration, and refers to adjusting the scales to an e ven 
nominal value, such as 500 barrels or 1000 barrels 
3.9  
traceability  
The property of the result of a measurement, or the  value of a standard, whereby it can be related to stated 
references, usually National or International Refer ence Standards, through an unbroken chain of compar isons 
all controlled, and having stated uncertainties. It  should be noted that traceability only exists, whe n 
scientifically rigorous evidence is collected, on a  continuing basis, showing that the measurement is producing 
documented results, for which the total measurement  uncertainty is quantified 
3.10  
HOME position  
The combination of one OUT pass followed by one BAC K pass of the displacer in a bi-directional meter 
prover. The OUT pass refers to the flow of the liqu id in the FORWARD direction while the displacer mov es 
away from the HOME position. The BACK pass refers t o the flow of the liquid in the REVERSE direction w hile 
the displacer returns to the HOME position. 
3.10 
Witness  
Representative of an associated company or organisa tion having operational, financial or other interes ts in the 
custody transfer functions at that facility 
4 Symbols (and abbreviated terms) 
1 UNBS 
Uganda National Bureau of Standards 
 
ISO and IEC maintain terminological databases for u se in standardization at the following addresses: 
— ISO Online browsing platform: available at http:/ /www.iso.org/obp DUS 2030-1:2019 
© UNBS yyyy – All rights reserved  ix
 5 APPLICATIONS 
5.1 Prover Calibration 
A prover calibration shall be done in accordance to  FDUS ISO 7278-2:1988 by the authorized authority a fter it 
has been installed at the operating facility and re gular calibrations shall be performed according to a 
predetermined schedule. 
All provers shall be re-calibrated at regular inter vals. Some provers are to be re-calibrated more fre quently 
than others to minimize the risk of measurement err ors or to limit the level of measurement loss by lo wering 
the overall uncertainty of the prover volume. The f requency of use of the prover and the volume throug hput 
measured at the facility should be considered when determining the appropriate frequency for recalibra tion.  
5.1.1 Establishing the possible loss exposure and m easurement risk 
When establishing the possible loss exposure and me asurement risk, and determining a required frequenc y of 
calibration for all provers the following items sho uld be put into consideration: 
• Volume through the metering system associated wit h the prover between prover calibrations 
• Number of meters regularly proved by the prover a nd their frequency of proving 
• The total yearly value of each product metered 
• Service conditions and properties of products bei ng metered and proved 
• Whether the prover is portable or stationary 
• The different types of products being metered 
• The range of properties of liquids being metered 
• The required yearly maintenance and repair 
• The total overall condition, including detectors and sphere displacer 
5.1.2 Portable provers 
Portable provers subjected to more severe condition s of operation and the total yearly road usage shou ld be 
looked at when considering a recalibration frequenc y.  
5.1.3 Recalibration frequencies 
Recalibration frequencies for provers shall range f rom one year up to five-year cycles and in some ext reme 
cases prover recalibrations on three month or six m onth cycles shall be carried out if necessary. 
5.2 Temperature measurements 
Temperature measurements are required to be taken a t the location where the liquid being displaced exi ts the 
prover. Temperature measurements shall be made usin g certified or calibrated mercury-in-glass 
thermometers or calibrated electronic temperature d evices. 
A certified or calibrated thermometer shall be on-s ite with a certificate of calibration accuracy. The  certificate 
of calibration shall be traceable to UNBS or other appropriate national metrology institute. The certi fied 
thermometer shall be used to verify the accuracy of  all the other thermometers (working thermometers) used 
in the calibration procedures. The certified or cal ibrated thermometer and the working thermometers mu st 
agree within ± 0.1°F (± 0.05°C). Alternatively, wor king thermometers that have been certified to have been 
verified at three points (e.g., high, mid and low r ange points) within one year and a day of the time of the DUS 2030-1: 2019  
x © UNBS 2019 – All rights reserved
 prover calibration by a thermometer that has a cali bration traceable to a national standard may also b e used 
providing that all of them agree among themselves w ithin ± 0.1°F (± 0.05°C). 
Electronic temperature measurement devices may be u sed in the calibration if there is agreement betwee n all 
the represented parties and as part of the requirem ent, these device shall be verified before each cal ibration, 
this verification shall be carried out against a ca librated or certified thermometer, accurate to ± 0. 1°F 
(0.05°C)... 
5.3 Pressure indicators 
For water draw calibrations, a pressure measurement  is required downstream of the displacer. A connect ion 
to fit a pressure measuring device shall be provide d between the water outlet from the prover and the pipe 
work prior to the water entering the test measures.  Because of the very low flow rate when the water i s flowing 
only through the solenoid valve, and the resulting minimal pressure drop at that time, it is acceptabl e to install 
the pressure measuring device on the calibration un it. 
Pressure measurements are usually made using a cali brated dial type pressure gauge that is accurate an d 
readable to one pound per square inch (1-psig) incr ements, and shall have with it on-site a certificat e of 
calibration accuracy. This certificate of calibrati on shall be traceable to UNBS or other appropriate national 
metrology institute and shall be considered valid i f within one year and a day of the date of calibrat ion of the 
pressure gauge. Electronic pressure devices or digi tal pressure gauges may be used in the calibration if there 
is agreement between all the represented parties. T heir readability and verifiable accuracy shall have  exactly 
the same requirements as those specified for dial t ype pressure gauges, including an on-site valid cer tificate 
of calibration accuracy. All electronic pressure re adings shall be rounded to the nearest one pound pe r square 
inch (1-psig) for recording. 
5.4 Hoses, pumps and connections 
All hoses and connectors used shall operate leak fr ee and be suitable for the liquid used in the calib ration and 
for the maximum pressures to be expected throughout  the calibration. Hoses used for calibrations shoul d be 
wire-wound to prevent collapse and to minimize any inflation due to pressure. However, for calibration s using 
water, soft hoses may be used (if approved by user company policy) on the inlet side, since inflation of the 
inlet hose has no impact on the calibration. The to tal length of hoses in use should be kept as short as 
possible so that the volume of liquid contained in these hoses is minimized. 
The pump (or pumps) used to circulate water through out the system during calibrations should be in goo d 
working condition with no leaks. An electric motor driven centrifugal pump works best, since the flow rate can 
be easily varied or stopped with the outlet pressur e remaining relatively low 
6 Field standard test measures 
Field standard test measures shall be used as the v olumetric standards in the calibration of liquid pr overs and 
shall be used for the water draw calibration method  
A field standard test measure shall meet specific d esign criteria and is to be calibrated by UNBS or o ther 
appropriate national metrology institute. The test measures will typically range in volume from two li tres to 
4000 litres, with 2000 litres being the largest siz e in regular use.  
6.1 Procedure of use of Test Measures 
Test measures may have a “to contain” and/or a “to deliver” volume. When the “to deliver” volume is us ed, the 
test measures are filled and drained, and then left  in a wetted condition before use. Only the “to del iver” 
volume of a test measure shall be used in a calibra tion. The “to contain” test measure volumes are not  used in 
prover calibrations, because then the test measures  must be completely clean and dry before every fill ing, 
usually an impractical field operations requirement . DUS 2030-1:2019 
© UNBS yyyy – All rights reserved  xi
 Two permanently mounted, adjustable spirit levels o ften installed and located at right angles to each other, on 
the body of the upper cone of the test measure. The se spirit levels are usually equipped with adjustin g 
screws, capable of being sealed, which have protect ive covers. As part of the preparation of a field s tandard 
test measure for calibration, it is recommended tha t it be filled with water and adjusted until level (usually 
using the legs). This level position shall then be verified by placing a precision machinist's spirit level across 
the top of the neck and verifying that the test mea sure is level in two directions, 90 degrees apart. 
After verification, it may be necessary to more fin ely adjust the test measure position for level by a dditional 
changes to the leveling system. The permanently mou nted spirit levels shall then be adjusted so that t hey 
agree exactly with the precision machinist's spirit  level as described above. Once set, the permanentl y 
mounted spirit levels should be sealed in place and  covered for protection. 
This test measure level verification and adjustment  procedure is recommended for all test measures pri or to 
them being delivered to the authorized authority fo r calibration. This is to ensure that the levels on  the field 
standard measure are in agreement with the precisio n machinist's spirit level when placed across the n eck of 
the standard. On smaller size test measures, circul ar type bubble levels are sometimes used. 
In all cases the UNBS Report of Calibration of a fi eld standard test measure, shall provide the criter ia for 
determining the level state of any given test measu re when filled with water. In case of any disagreem ent 
between the use of the permanently mounted levels a nd the use of a precision machinist's spirit level across 
the top of the neck, the UNBS Report of Calibration  definition of the level position for that test mea sure shall 
apply 
7 Master meter 
Master meters with very good linearity and repeatab ility shall be used for master meter proving. These  meters 
shall be inspected annually to insure their integri ty. Master meter performance (review of master mete r 
calibration factors) shall be routinely checked to determine if the master meter is performing properl y.. 
Pressure and temperature instrumentation shall be i nstalled in the meter run. 
8 Master prover 
A master prover should be designed and sized to wor k in conjunction with the master meter. The master 
prover shall not be calibrated by the master meter method. The master prover should be equipped with 
pressure and temperature instrumentation on inlet a nd outlet of the prover. All drain and vent valves on the 
master prover shall either be of the block and blee d type or have other means for checking leakage. 
9 Mobile equipment 
The prover calibration equipment if mounted on a tr uck or trailer shall be rigidly constructed and sec urely 
mounted on the truck or trailer to prevent deformat ion or damage during transportation, usage, or stor age. 
10 Documentation and Record Keeping 
All observation data shall be hand written in ink; or collected, recorded, and reported automatically by a flow 
computer with audit trail capability. All of the ob servation data shall be proof read against the data  input for the 
calculations before signing any documents. In case of discrepancies or errors discovered at a later da te the 
hand written observation data shall be used to corr ect the final volume. 
The calibration certificate package issued by the a uthorized authority shall include the Calibration R eport with 
the date of the prover calibration prominently disp layed on the front of the Calibration Certificate P ackage. 
Other items applicable to the calibration shall als o be recorded in the Calibration Certificate Packag e as 
follows: 
For the Water draw, Master Meter and Gravimetric Me thods: 
a) the location of the prover DUS 2030-1: 2019  
xii © UNBS 2019 – All rights reserved
 b) the serial number of the prover 
c) the serial number or seal number for each detect or switch 
d) the owner or operator of the prover 
e) the type of prover 
f) the material of construction of the prover 
g) the inside diameter of the prover 
h) the wall thickness of the prover 
i) the temperature indicators and pressure indicato r used 
j) Calibration Certificates for all the temperature  and pressure indicators used 
k) the displacer type, the size, and the durometer (if applicable) 
in the case of multi-volume displacement provers 
l) a clear identification of the detectors used for  this calibration 
m) the physical location of each detector 
n) A copy of the handwritten observation documentat ion (signed by all parties as witness to the origin al 
observation data); 
o) A copy of the calculation and summary generated documentation 
For the Water draw Calibration Method: 
a) the field standard test measures used 
b) copies of the UNBS Reports of Calibration for al l of the field standard test measures used. 
For the Master Meter Calibration Method: 
a) the serial number of the master prover 
b) the type of master prover 
c) the material of construction of the master prove r 
d) the inside diameter of the master prover 
e) the wall thickness of the master prover 
f) Calibration Certificate Package for the Master P rover 
g) the type of master meter 
h) the size of master meter 
For the Gravimetric Calibration Method: 
a) Calibration Certificates of the Standard Weights  DUS 2030-1:2019 
© UNBS yyyy – All rights reserved  xiii
 b) Calibration Certificate(s) of the Weigh Scale 
Note: This method under development so list is inco mplete 
11 Calibration Troubleshooting Guide 
Full records of the complete data collected during all the calibration runs, whether valid or invalid,  shall be 
recorded and kept in a systematic manner. 
The primary source of a questionable measurement ca n normally be identified as one or more of the foll owing 
as specific to the calibration method: 
a) Air in the system 
b) Hydrocarbons in the system (when water is the ca librating medium) 
c) Leaks in the system 
d) Temperature or pressure instability 
e) Errors in determining test measure measurements 
f) Malfunctioning isolating valves 
g) Malfunctioning solenoid valves 
h) Damaged or under-inflated sphere displacer 
i) Damaged or improperly fitting seals 
j) Wear in the piston displacer 
k) Contamination to the circulating (calibration) m edium 
l) Damaged or contaminated field standard test meas ures (for the waterdraw method) 
m) Damaged master meter or master prover (for the m aster meter method) 
n) Damaged weighing device or weight standards (for  the gravimetric method) 
o) Damaged temperature and pressure measuring devic es 
p) Malfunctioning prover detector switches 
q) Damaged or deteriorating internal surfaces of th e prover 
r) Damaged or leaking sphere interchange 
s) Damaged or leaking four-way valve 
t) Human error 
u) Measuring equipment errors 
Each of the above sources must be carefully examine d until the cause of the abnormal measurements is 
found. DUS 2030-1: 2019  
xiv © UNBS 2019 – All rights reserved
 12 calibration witnesses 
The Authorised Authority/OFFICER shall perform the calibration in the company of several others who ar e 
designated as the witnesses.  
All the parties attending the calibration as witnes ses (representatives of other involved interests), shall be 
equally responsible for the successful outcome of t he calibration. It follows that all the witnesses s hould, 
therefore, be involved in all the required calibrat ion activities 
 
 
 
 
 DUS 2030-1:2019 
© UNBS yyyy – All rights reserved  xv
 Annex A 
(informative) 
 
Supplementary information on meters 
A.1 Types Of Provers 
A.1.1 Unidirectional—Sphere Provers with Mechanical  Detectors 
These types of unidirectional provers are subdivide d into the following two categories depending on th e 
manner in which the displacer is handled.. 
A.1.1.1 The manual-return unidirectional prover 
The manual-return unidirectional prover, sometimes referred to as the measured distance, is an element ary 
form of an in-line prover that uses a section of pi peline as the prover section. Prover detector switc hes that 
define the calibrated volume of the prover section are placed at selected points along the pipeline. A  
displacer-launching device is placed upstream from the prover section, and receiving facilities are in stalled at 
some point downstream from the prover section. Conv entional launching and receiving scraper traps are 
usually used for this purpose. To make a proving ru n, a displacer (a sphere or specially designed pist on) is 
launched and allowed to displace the reference volu me before being received downstream and manually 
transported back to the launching site. This type o f prover is no longer in common use. 
A.1.1.2 The circulating-return unidirectional prove r 
The circulating-return unidirectional prover, often  referred to as the endless loop, has evolved from the prover 
described above. In the endless loop, the piping is  arranged so that the downstream end of the loop cr osses 
over and above the upstream end of the looped secti on. The interchange is the means by which the displ acer 
is transferred from the downstream to the upstream end of the loop without being removed from the prov er. 
The displacer detectors are located inside the loop ed portion at a suitable distance from the inter-ch ange. 
Continuous or endless prover loops may be automated  or manually operated. 
A.1.2 Displacement type bi-directional provers with  free displacers 
There are three types of bi-directional provers: th e sphere prover with mechanical detectors; the pist on prover 
with magnetic detectors and check valves; and, the piston prover with mechanical detectors and check v alves. 
These types of bi-directional provers have a length  of pipe through which the displacer travels back a nd forth, 
actuating a detector switch at each end of the cali brated section. Suitable supplementary pipe-work an d a 
reversing valve or valve assembly that is either ma nually or automatically operated make possible the reversal 
of the flow through the prover. The main body of th e prover is often a straight piece of pipe, but it may be 
contoured or folded to fit in a limited space or to  make it more readily mobile. A sphere is used as t he 
displacer in the folded or contoured type; a piston  or sphere may be used in the straight-pipe type.. 
A.1.3 Displacement type meter provers with captive displacers 
A prover having a captive displacer has an attached  shaft or rod, which moves with the displacer. The 
displacement of the shaft is constant except that i t moves into and out of the calibrated section duri ng a 
calibration run. Thus a prover with a captive displ acer and a shaft attached to one end will have an u pstream 
and a downstream volume. If a shaft is attached to both sides of the displacer and they have equal are a 
displacement, the upstream and downstream volumes a re equal. There is often one or two other detector 
and/or guide rods attached to the captive displacer . DUS 2030-1: 2019  
xvi © UNBS 2019 – All rights reserved
 Since these type provers have externally mounted op tical detectors, the thermal effect on the steel ma y not be 
the same for the area aspect as for the linear aspe ct. For example, if both the prover chamber and the  
mounting that defines the linear distance between t he detector(s) were the same, the thermal effects w ould be 
the same. But in many cases, a prover chamber might  be made of a type of stainless steel while the 
detector(s) mounting which defines the linear dista nce between the detector(s) might be made of a spec ial 
alloy having a different thermal coefficient of exp ansion. In terms of a prover calibration, the main effect is that 
it is necessary to obtain both a prover barrel temp erature and a detector temperature 
A.1.4 Displacement type meter provers with multiple  volumes 
If a displacement prover has multiple volumes, each  volume shall be considered to be a stand-alone and  
independent prover volume. 
Each of these prover volumes shall be calibrated by  a separate and independent calibration. Each calib ration 
shall meet the same criteria as described in the de tailed calibration procedures.  
A.1.5 Atmospheric tank provers 
An atmospheric tank prover is a volumetric vessel w ith an upper neck, upper sight glass, upper scale, and an 
upper and lower cone usually separated by a cylindr ical section. Different types are identified by the  way in 
which their bottom "zero" is defined. 
Atmospheric tank provers are described below: 
• Bottom-weir type: This prover has a bottom neck b eneath the lower cone. The bottom neck may or may n ot 
have a sight glass and scale, but in any case it ha s a fixed bottom “zero” defined by the weir. 
• Dry-bottom type: This prover usually does NOT hav e a bottom neck under the lower cone. The closed 
bottom drain valve defines the bottom “zero” just a s on a field standard test measure. 
• Wet-bottom type: This prover has a bottom neck be neath the lower cone. The bottom neck always has a 
sight glass and scale. The bottom “zero” is defined  by the “zero” on the scale. In practice, readings above and 
below the “zero” in the lower neck are common 
A.2 Equipment 
A.2.1 Prover detector switches 
A detector switch is a high precision device mounte d on a prover, which is used to detect the passage of a 
displacer. The calibrated volume of a prover is the  amount of fluid that is displaced between two dete ctor 
switch positions. Additional detector switches may be used if more than one calibrated volume is requi red on 
the same prover, or they can also be used to signal  the entrance of a displacer into the sphere restin g 
chamber. Several types of detector switches are des cribed below. 
• Mechanically Actuated Detector Switches 
• Proximity-Type Magnetically Actuated Detector Swit ches 
• Optically Actuated Detector Switches.. 
A.2.2 Launching chambers and transfer chambers 
In both unidirectional and bi-directional provers, an area must be provided in which the displacer can  rest 
when not in use. In bidirectional meter provers, th is space is defined as a launching chamber. Bi-dire ctional 
provers using sphere displacers require launch cham bers at both ends of the prover pipe. Piston type b i-
directional provers do not require expanded launch chambers at either end of the prover pipe because t he DUS 2030-1:2019 
© UNBS yyyy – All rights reserved  xvii
 flowing stream does not go around the piston, but i s diverted upstream of the launch chambers by means  of 
check valves. On unidirectional meter provers, a tr ansfer chamber is used in combination with one or m ore 
valves, to store the sphere away from the flowing s tream, and to provide a means to re-launch the disp lacer 
when required. 
A.2.3 Sphere interchanges 
On unidirectional provers, the sphere interchange p rovides a means for transferring the sphere from th e 
downstream end of the proving section to the upstre am end. Transfer of the sphere may be accomplished with 
several different combinations of valves or other d evices to minimize bypass flow through the intercha nge. A 
leak-tight seal between the upstream and downstream  sides is essential and must be verified before the  
sphere reaches the first detector switch of the pro ving section.. 
A.2.4 Four-way valves 
The four-way diverter valve is used on bi-direction al provers to change the flow direction through the  prover. It 
is designed to handle low-pressure differentials, a nd has a double block and bleed feature to verify t he sealing 
integrity of the valve. 
A.2.5 Displacers 
In a displacement prover, the displacer is used to form a seal so that the flow pushes it through the measuring 
section. This seal prevents flow from bypassing the  displacer, which is critical to the accurate calib ration of the 
prover. The displacer actuates detector switches, w hich define the volume of the prover. There are thr ee 
common types of displacers. 
• Sphere Displacers 
• Piston Displacers 
• Captive Displacers—Piston with Shaft (Rod).. 
A.2.6 Valves, relief valves, drains and vents 
The unidirectional prover sphere handling interchan ge, the bi-directional prover four-way valve, and a ll valves 
located between the calibrated section of the prove r and the calibration unit, shall seal without any visible 
internal or external leakage when in a closed posit ion 
All valves located on the prover system and in-line , up to the test measures, that are part of the cal ibration, 
and operating in an open position, shall be regular ly inspected for any signs of external leakage. Any  leakage 
will cause an error in the certified volume. 
A.2.7 Solenoid valves and logic circuits 
Solenoid valves and logic circuits may be used for any method of prover calibration. The discussion be low is a 
short introduction to the subject. 
A.2.7.1 Water draw calibrations 
Solenoid valves, used in water draw calibrations, a re a combination of an electromagnetic plunger and an 
orifice to which a disc or plug can be positioned t o either restrict or completely shut off a flow. Or ifice closure 
occurs when the electromagnet actuates a magnetic p lunger. Typical orifice sizes range from 3/32 to 1/ 4 inch. 
Solenoid valves may be two-way or three-way acting.  
Solenoid valves are actuated by detector switch clo sures and are usually arranged to stop the water fl ow to 
drain and divert it into the test measure or vice-v ersa. The use of a solenoid valve reduces the uncer tainty in 
valve closure to stop the test measure filling when  the displacer contacts the second detector switch.  Other DUS 2030-1: 2019  
xviii © UNBS 2019 – All rights reserved
 uses of the solenoid valve during the prover calibr ation permit the recording of the stop/start sequen ce at the 
same exact repeatable conditions every time. Soleno id valves control the final approach of the displac er so 
that it arrives at the same exact position each tim e that it actuates the detector switch.. 
A.2.7.2 Water draw, master meter and gravimetric ca librations 
A logic circuit is defined as an electronic device or devices used to govern particular sequences of o perations 
in any given system. 
They can gate or inhibit signal transmission in acc ordance with the application, removal, or combinati on of 
input signals. They have become a necessary aid in calibration and provide assistance in locating and 
tracking the position of the displacer. At the actu ation of a detector switch, the logic circuit is pr ogrammed to 
notify the operator, generally by means of visible or audible signals, of the position of the sphere d isplacer. 
Solenoid valves mounted above the test measures wor k in conjunction with the prover detector switches 
through the logic circuit as follows: 
• A single cable to both prover detector switches. 
In this configuration any time a detector switch is  gated the logic circuit will NOT tell the operator  specifically 
which detector switch was actuated. 
• A separate cable to each prover detector switch. 
In this configuration any time a detector switch is  gated the logic circuit will tell the operator spe cifically which 
detector switch was actuated. 
It is possible to perform prover calibrations witho ut the use of logic circuits by direct wiring betwe en the prover 
switches and the solenoid valves. Careful observati on of the activation of the detector switches and t he 
solenoid valves will be necessary by the operator t o continuously track and follow the location of the  sphere 
displacer, since external-signaling devices will no t be available in this situation. General industry practice, 
however, is to make use of logic circuits when they  are available DUS 2030-1:2019 
© UNBS yyyy – All rights reserved  xix
 APPENDIX B 
(Informative) 
CALIBRATION WITNESSES 
One technician usually performs the calibration in the company of several others who are designated as  the 
witnesses. Company employees from the same or other  divisions are often involved and occasionally fede ral, 
state or local government officials will be present . However, all the parties attending the calibratio n as 
witnesses (representatives of other involved intere sts), shall be equally responsible for the successf ul 
outcome of the calibration. It follows that all the  witnesses should, therefore, be involved in all th e required 
calibration activities. 
Some of these required items are listed below. Gene rally, all the witnesses shall be ready to assist, advise, 
and participate in whatever tasks are necessary to produce a speedy, successful and accurate calibrati on: 
• Validate the traceability of equipment by checkin g the calibration dates and the availability of val id calibration 
certificates and other records. 
• Witness the cleanliness and interior condition of  the prover. 
• Witness the inspection and sizing of the sphere d isplacers or pistons. 
• Witness the inspection and all maintenance of the  detector switches. 
• Witness the verification of the temperature and p ressure devices. 
• Witness all general set-up activities including s etting up the liquid circulation, venting of the ai r, and leak 
checking. 
• Witness patrolling of the area for leaks during t he calibration runs. 
• Witness checking the integrity of block valves du ring runs. 
• Witness checking the integrity of four-way valves  during runs. 
• Witness checking the integrity of sphere intercha nges during runs. 
• Witness the filling and general operation of the test measures (waterdraw) or the general operation of the 
master meter and master prover. 
• Witness the filling and general operation of the prover being calibrated. 
• Witness and check that the test measures are leve l when read (waterdraw). 
• Witness test measure scale readings and interpola tions (waterdraw). 
• Witness temperature and pressure readings and int erpolations. 
• Witness the draining of test measures and the adh erence to draining times (waterdraw). 
• Witness the accurate determination of necessary t emperatures and pressures. 
• Keep or witness the recording (hand written) of a ll the calibration data as log entries. 
• Where requested, offer advice in troubleshooting all problems and difficulties, and assist with the reading of 
thermometers and gauges. DUS 2030-1: 2019  
xx © UNBS 2019 – All rights reserved
 • In general, witness the resolution of all the ope rations, processes and problems encountered. DUS 2030-1:2019 
© UNBS yyyy – All rights reserved  xxi
 Bibliography 
[1] API MPMS 4.9.1 1st Edition, October 2005 Manual  of Petroleum Measurement Standards Chapter 4-
Proving Systems Section 9-Methods of Calibration fo r Displacement and Volumetric Tank Provers Part 
1-Introduction to the Determination of the Volume o f Displacement and Tank Provers [2] ISO #####-
##:20##, General title — Part ##: Title of part  
. DUS 2030-1: 2019  
xxii © UNBS 2019 – All rights reserved
  DUS 2030-1:2019 
© UNBS yyyy – All rights reserved  xxiii
 Certification marking 
Products that conform to Uganda standards may be ma rked with Uganda National Bureau of Standards 
(UNBS) Certification Mark shown in the figure below .  
The use of the UNBS Certification Mark is governed by the Standards Act, and the Regulations made 
thereunder. This mark can be used only by those lic ensed under the certification mark scheme operated by 
the Uganda National Bureau of Standards and in conj unction with the relevant Uganda Standard. The 
presence of this mark on a product or in relation t o a product is an assurance that the goods comply w ith the 
requirements of that standard under a system of sup ervision, control and testing in accordance with th e 
certification mark scheme of the Uganda National Bu reau of Standards. UNBS marked products are 
continually checked by UNBS for conformity to that standard.  
Further particulars of the terms and conditions of licensing may be obtained from the Director, Uganda  
National Bureau of Standards.  
 
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