UGANDA STANDARD  
  DUS 2031  
First  Edition  
yyyy-mm-dd  
 
 
 Reference number 
US 2031-: 2019 
© UNBS yyyy  
  
Metering Assemblies  — Lease Automatic Custody Transfer 
(LACT) Systems  
 
 
 
 
 
 
 
 
 
 
 DUS 2031: 2019 
ii © UNBS yyyy – All rights r eserved
 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 yyyy  
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 2031:2019 
© UNBS yyyy – All rights reserved  iii
 Contents Page  
Foreword .......................................... ................................................... ................................................... ............ iv  
1 Scope ............................................. ................................................... ................................................... ... 1 
2 Normative references .............................. ................................................... ........................................... 1  
3 Terms and definitions ............................. ................................................... ........................................... 1  
4 COMPLIANCE ........................................ ................................................... ............................................. 2  
5 Field of Application .............................. ................................................... .............................................. 2  
6 Requirements for All LACT Systems ................. ................................................... ............................... 2  
7 SPECIFIC REQUIREMENTS ............................. ................................................... .................................. 3  
9 Procedures for proving meters ..................... ................................................... .................................... 4  
10  Meter system operation ............................ ................................................... ......................................... 5  
11  Maintaining allowables ............................ ................................................... .......................................... 6  
12  Monitoring quality ................................ ................................................... .............................................. 6  
13  Sampling .......................................... ................................................... ...................................................  6 
A.1  Operation Sequence ................................ ................................................... ........................................... 7  
A.1.1  Case A-Normal Delivery to a Gravity Flow Pipeline i n Nonscheduled Operation ..........................  7 
A.1.2  Case B-Normal Delivery to a Pressurized Pipeline in  Nonscheduled Operation ...........................  7 
A.1.2  Case C-Normal Delivery to a Pipeline in Scheduled O peration .......................................... .............. 7  
A.2  NONMERCHANTABLE OIL INTERRUPTION .................. ................................................... .................. 7  
Bibliography ...................................... ................................................... ................................................... ............ 9  
 
. DUS 2031: 2019 
iv © UNBS yyyy – All rights r eserved
 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 2031:2019 
© UNBS yyyy – All rights reserved  v
 Introduction 
LACT equipment includes a meter (displacement, turb ine, ultrasonic and Coriolis), a proving system (ei ther 
fixed or portable), devices for determining tempera ture and pressure and for sampling the liquid, and a means 
of determining non merchantable oil 
A LACT system is an arrangement of equipment design ed for the unattended custody transfer of liquid 
hydrocarbons from producing leases to the transport ing carrier. The system must determine net volume a nd 
quality, provide for fail-safe and tamperproof oper ation, and meet requirements of accuracy and depend ability 
as agreed to by mutually concerned parties. 
 DRAFT UGANDA STANDARD DUS 2031: 2019 
 
© UNBS yyyy – All rights reserved  1
 Metering Assemblies — Lease Automatic Custody Trans fer 
(LACT) Systems  
1 Scope  
This Draft Uganda Standard has been prepared as a g uide for the design, installation, calibration, and  
operation of a lease automatic custody transfer (LA CT) system. 
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. 
FDUS ISO 2714:2017 – Liquid hydrocarbons -- Volumet ric measurement by displacement meter systems 
other than dispensing pumps 
FDUS ISO 2715:2017 - Liquid hydrocarbons -- Volumet ric measurement by turbine meter system 
US 1733:2017 Practice   for   Automatic   Sampling   of   Petroleum   and   Petroleum Products 
US 1732:2017 Practice   for   Manual   Sampling   o f   Petroleum   and   Petroleum Products 
FDUS ISO 8222: 2002 Petroleum measurement systems - - Calibration -- Temperature corrections for use  
when calibrating volumetric proving tanks 
DUS ISO 12242:2012 Measurement of fluid flow in clo sed conduits -- Ultrasonic transit-time meters for liquid 
DUS ISO 10790:2015 Measurement of fluid flow in clo sed conduits — Guidance to the selection, installat ion 
and use of Coriolis flowmeters (mass flow, density and volume flow measurements) 
3 Terms and definitions  
For the purposes of this document, the following te rms and definition apply.  
3.1  
ALACT system 
an arrangement of equipment designed for the unatte nded custody transfer of liquid hydrocarbons from 
producing leases to the transporting carrier.  
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 2031: 2019 
2 © UNBS yyyy – All rights reserved
 4 COMPLIANCE 
The compulsory verb form “shall," while not necessa rily binding for all conditions, has been used when  a 
deviation from the standard is likely to adversely affect the satisfactory operation of a system that is designed 
for optimum operation under typical producing condi tions. 
5 Field of Application 
The field of application of this Draft Uganda Stand ard is the unattended and automatic measurement by meter 
of hydrocarbon liquids produced in the field and tr ansferred to a pipeline in either a scheduled or a non 
scheduled operation. 
6 Requirements for All LACT Systems 
The requirements for all LACT systems are as follow s: 
When hydrocarbon liquids are measured and transferr ed, the fluid should be stable to permit subsequent  
storage during transportation without abnormal evap oration losses. 
During custody transfer, provisions shall be made f or determining net standard volume.  
Temperature measurements, recordings, or correction s applicable to volumetric measurement shall be mad e 
in accordance with FDUS 8222. 
Temperature and pressure measurements (either recor ded or indicated) shall be taken, and corrections 
applicable to volumetric measurements shall be made . The method of performing temperature compensation  
is a matter of negotiation but should be accomplish ed by use of volume-weighted temperature averaging 
devices or temperature compensators for optimum acc uracy. 
A representative sample of transferred oil for dete rmining density (API gravity), sediment and water c ontent, 
and any other physical properties required shall be  obtained. 
The merchantability of hydrocarbon liquids should b e established when they are transferred; that is, w hen the 
liquids are within a specified density (API gravity ) range, do not contain more than a specified sedim ent and 
water percentage, are at an acceptable temperature,  and are of an acceptable Reid vapor pressure. A me ans 
shall be provided to stop the flow of oil to the ca rriers system and to the sampling system if the oil  becomes un 
merchantable. 
A means should be provided to control flow rates, p eriods of flow, and net quantities of oil delivered  into the 
carriers system. 
A means shall be provided to stop the flow of oil i nto the carriers system at or before completion of delivery of 
the leases assigned allowable capacity. 
The control and recording system shall include fail -safe components to prevent mismeasurement or 
hazardous operating conditions in the event of a po wer or system functional failure of any of the syst em's 
components required for the LACT. 
All components of the system that require periodic calibration and/or inspection shall be accessible f or 
inspection by all parties involved in the custody t ransfer transaction. Adjustment, repair, or replace ment will be 
performed by those responsible for the operation of  the system. The design of the system shall provide  a 
means for readily detecting leakage throughout the system, for example, double-block and bleed-type va lves, 
sight drains, or pressure instruments. DUS  2031: 2019  
© UNBS yyyy – All rights reserved  3
 The piping system shall not have connections or byp asses that would permit liquids to be transferred w ithout 
measurement and shall be designed or equipped so th at a reverse flow of liquid through the measuring d evice 
cannot occur. 
A means shall be provided to lock or seal component s that affect control or indicate measurement of qu antity 
or quality. Unless this requirement has been specif ically waived, such components shall be unlocked or  
unsealed only after prior notice to and consent of the parties concerned. 
System malfunctions shall be anticipated, and deliv eries that could occur during such periods shall be  
estimated. This requirement may be met by independe nt gross fluid delivery-recording systems, that is,  by 
using a dual-head meter and temperature recorder, b y using a meter in series, or by recording temperat ure or 
pressure or other instruments that indicate periods  of flow. In installations where such apparatus is not used, 
prior agreement shall be established for calculatin g or estimating procedures that will be followed in  instances 
of measurement system malfunction. 
Sediment and water content and density (API gravity ) measurements shall be made from composite samples  
obtained by automatic samplers of acceptable design . Samplers shall be installed in accordance with US  
1733:2017  
7 SPECIFIC REQUIREMENTS 
LACT systems that use meters shall maintain fluid p ressure throughout the measurement system in excess  of 
the product bubble-point pressure by an amount suff icient to prevent the formation of vapour. If vapou r is 
introduced into the measurement system, the measure ment will be inaccurate. 
When vapour removers are specified, they shall be s ized for releasing vapour to the atmosphere or to a  
suitable vapour recovery system at rates equal to o r greater than the normal flow rates of the liquid.  Vapour 
outlet lines from removers shall comply with safety  standards. When the design of storage facilities e nsures 
fluid-packed line conditions leading to the meter, vapour removers may not be required. 
When the installation of the dielectric or capacita nce instrument (water monitor) is required, this sh all be 
located upstream from the meter and shall be in ope ration at all times during delivery. The carrier sh all specify 
the maximum water setting of the instrument. 
The water monitor shall automatically stop or diver t flow before liquid is delivered to the meter when  the 
carrier's specifications are not met 
Meters shall be operated within the manufacturer's recommended flow rates and at a rate as near as pos sible 
to the rate at the time of the meter proving when t he meter factor was obtained. A back-pressure contr ol valve 
is necessary to maintain a constant flow rate and p ressure independent of downstream conditions.  
Meters shall not be subjected to pressure pulsation s, flow rate surges and shall not be subjected to s hock 
pressures caused by quick-closing valves. 
When temperature compensators with density selector s are used, they shall be adjusted for the density (API 
gravity) of the metered liquids. When temperature v ariations result in mismeasurement, temperature 
stabilization and monitoring may be required. The c arrier may require that a pressure surge and/or suc tion 
tank be installed upstream from the LACT system to ensure that fluid-packed line conditions lead to th e meter 
and to protect the meter from flow rate surges. 
"Weathering" the crude oil, expansion chambers, and  other such requirements may be required by the car rier 
to prevent unstable metering conditions. 
When system pressure requires the use of the oil co mpressibility factor and pressure may not remain 
constant, flow weighted pressure-averaging devices or pressure recorders may be required.  DUS 2031: 2019 
4 © UNBS yyyy – All rights reserved
 When required by operating conditions that change s ufficiently to alter the meter factor beyond accept able 
limits, such as temperature variations and the asso ciated viscosity changes, the oil temperature shall  be 
maintained reasonably constant and shall be approxi mately the same as the proving temperature . 
8 Installation 
LACT systems that use meters shall be installed in accordance with applicable industry codes or standa rds. 
Figure 1 is a schematic flow diagram showing the pr incipal components of a meter-equipped LACT unit. A ll 
items shown may be used in an installation, but if certain components are not required for the integri ty of 
quantity and quality control, they may be omitted. 
 
Figure 1  field LACT typical components 
9 Procedures for proving meters 
Proving procedures for each LACT location shall be agreed to by the parties concerned. Copies of the 
agreement should be furnished to both the operating  personnel and proving personnel. Such procedures 
should include: 
a. A step-by-step method to be followed at the loca tion. 
b. A procedure for checking valves for leakage befo re and during the proving operation. 
c. A preliminary inspection or operation of the pro ving equipment. 
d. The locations and specifications of seals to be inspected at time of proving. 
e. The notification and witnessing required when se als, are broken for maintenance purposes. 
f. The location, type, scale division, and methods for reading the thermometers used in the proving 
process. 
g. The location, type, scale division, and methods of reading pressure instruments used in proving. 
h. The specifications of a proving run, such as: DUS  2031: 2019  
© UNBS yyyy – All rights reserved  5
 1) The number of times the prover tank should be fi lled. 
2) Specifying the number of runs for a pipe prover.  
3) Defining a minimum time and/or volume if the mas ter-meter method is used. 
i. The repeatability criteria for runs to be used a nd the number of runs to be averaged to obtain a ne w 
meter factor. 
j. The normal period between required meter proving s. The period between provings may be 
established either on a through put or on an elapse d-time basis. This period may be amended based 
on individual location meter performance records. 
k. The normal date and time of provings or the noti ce to be given to witnessing parties when a proving  
schedule is established. 
l. L. The witnessing required for provings. 
m. The standard of consistency desired between mete r factors obtained from consecutive provings. 
n. The procedure to be followed when the desired co nsistency is not obtained, either in the results of  
consecutive runs during an attempted proving or in meter factors obtained from consecutive provings. 
o. The frequency of inspection or the frequency and  method of recalibration or calibration verificatio n of 
the basic proving device. 
p. The content for the forms to be used to record m eter-proving data, complete with sample calculation s 
and references to tables used for correction factor s and conversions. 
q. The proving record for each meter shall be kept on file for at least the same period as the meter 
tickets to which it applies or for a period mutuall y agreed to by the parties concerned, at least one 
copy of each official proving record should be supp lied to each party concerned. 
10 Meter system operation 
The operation of a meter system will vary depending  on the characteristics of the liquid, the design o f the 
installation, the type of pipeline facility connect ion, and the operating schedule of the pipeline.  
For meter system using ea displacement meter, with equipment arranged to meet the requirements defined  in 
this standard shall meet specifications in FDUS ISO  2714 
For meter system using a turbine meter, with equipm ent arranged to meet the requirements defined in th is 
standard shall meet specifications in FDUS ISO 2715   
For meter system using a Coriolis meter, with equip ment arranged to meet the requirements defined in t his 
standard shall meet specifications in DUS ISO 10790  
For meter system using an Ultrasonic meter, with eq uipment arranged to meet the requirements defined i n 
this standard shall meet specifications in DUS ISO 12242 
 
 DUS 2031: 2019 
6 © UNBS yyyy – All rights reserved
 11 Maintaining allowables 
When regulatory agencies apply production allowable s, runs from the LACT system shall conform to but s hall 
not exceed these allowances. Automatic means shall be used to accomplish this requirement.  
The system shall be fail-safe, tamperproof, and sea led so that neither the producer nor the carrier ca n change 
the arrangement without the consent and/or knowledg e of the other party. 
System devices shall be capable of being pre-set an d verified for a predetermined volume that will app roach 
but not exceed the lease allowable. When the predet ermined volume has been reached, the arrangement 
used must prevent any further movement of oil from the lease until it is manually reset. The arrangeme nt shall 
be adjustable so that changes in production allowab les are accommodated. 
Registers and counters shall be readily visible so that oil deliveries can be checked at any time. 
12 Monitoring quality 
Means shall be provided to prevent water-contaminat ed oil or slugs of water from entering a carrier's system. 
The parties shall agree on the maximum permissible sediment and water content of the crude oil. One su ch 
satisfactory automatic device which detects water i s an instrument that measures capacitance (dielectr ic 
constant of the liquid stream).  
This BS&W should be installed in a vertical riser i n the piping before the meter and should be used to  actuate 
controls so that water-contaminated oil is not deli vered to the pipeline. A time-delay element should be 
incorporated into the monitor system. 
13 Sampling 
The relevant sampling procedure given in US 1733:20 17 or in US 1732:2017 shall be used to provide samp les 
for testing. 
When, accounting for a crude oil run is to be deter mined on the basis of net standard volume, which in cludes 
corrections for meter factor, temperature, pressure , and sediment and water content, the composite sam ple 
accumulated in a run period and any portion used fo r the determination of density (API gravity) and se diment 
and water content must represent all crude oil deli vered during that run period. 
When density (API gravity) and sediment and water c ontent are based on a sample from the composite 
sample of the run, the procedures used shall ensure  that this secondary sample is representative of th e 
composite sample. The sampling should be proportion ed to the flow rate through the meter. 
. DUS  2031: 2019  
© UNBS yyyy – All rights reserved  7
 Annex A 
(informative)  
 
DISPLACEMENT AND TURBINE METER SYSTEM OPERATION 
A.1 Operation Sequence 
Before an installation is completed, operating sequ ences shall be checked to ensure that the requireme nts of 
all interested parties have been met. The following  cases are typical, and the items to be checked are  
suggested as guides for system studies  
A.1.1 Case A-Normal Delivery to a Gravity Flow Pipe line in Nonscheduled Operation 
a) When the liquid level in the delivery tank reach es the normal high working level, the charge pump 
starts and the control valve opens to the pipeline,  admitting flow through the meter. 
b) When the valve reaches its open-to-pipeline posi tion, the automatic sampler begins sampling as soon  
as the meter starts turning. 
c) Under normal conditions, delivery to the pipelin e continues until the liquid level reaches the norm al 
low-level position. 
d) The back-pressure valve then closes the pipeline  outlet; the charge pump stops, and the automatic 
sampler stops sampling when the meter stops turning . 
A.1.2 Case B-Normal Delivery to a Pressurized Pipel ine in Nonscheduled Operation 
a) When the liquid level in the delivery tank reach es the normal high working level, the charge 
pump starts and the control valve opens to the pipe line, admitting flow through the meter. 
b) When the valve reaches its open-to-pipeline posi tion, the pipeline shipping pump starts and the 
automatic sampler begins sampling as soon as the me ter starts turning. 
c) Under normal conditions, delivery to the pipelin e continues until the liquid level reaches the 
normal low-level position. 
d) The charge pump stops, the back-pressure valve c loses the pipeline outlet, and the pipeline 
shipping pump is shut down. 
A.1.2 Case C-Normal Delivery to a Pipeline in Sched uled Operation 
Some pipeline systems are operated on a schedule wh ereby it is desirable to admit oil only during a ce rtain 
interval. For this arrangement, the operation seque nce shall be the same as for non-scheduled delivery  
(6.1.6.4.1 and 6.1.6.4.2) except that a time-interv al controller shall be added to the circuit that ov errides the 
normal high working level control. 
A.2 Non merchantable oil interruption 
In each of the three cases, the following procedure s shall be followed: DUS 2031: 2019 
8 © UNBS yyyy – All rights reserved
 a) After delivery to the pipeline has begun, if non  merchantable oil flows continuously past the water  
monitor for a predetermined time interval, the char ge pump is automatically stopped unless the pump 
is required to circulate oil for treatment 
b) The valve closes, stopping flow to the pipeline.  
c) The automatic sampler remains energized in case of inadvertent flow through the meter 
d) The controls lock out the transfer of oil to the  pipeline until the non merchantable oil has been t reated 
to meet specifications. 
The LACT unit can be designed to restart automatica lly after a period of recirculation. DUS  2031: 2019  
© UNBS yyyy – All rights reserved  9
 Bibliography 
[1] API MPMS Chapter 18.2 Custody Transfer of Crude  Oil from Lease Tanks Using Alternative 
Measurement Methods 
[2] API MPMS Chapter 12 - Calculation of Petroleum Quantities, Section 2-Calculation of Petroleum 
Quantities Using Dynamic Measurement Methods and Vo lumetric Correction Factors, Part 2 - 
Measurement Tickets, Third Edition 
[3] API 11N : 1994 Specification for Lease Automati c Custody Transfer (LACT) equipment 
[4] API MPMS Chapter 7 Temperature Determination 
[5] API MPMS 12.2 Manual of Petroleum Measurement S tandards Chapter 12—Calculation of Petroleum 
Quantities  
 
 
. DUS  2031-n: yyyy  
© UNBS yyyy – All rights reserved  11
 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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