FINAL DRAFT UGANDA 
STANDARD  
  FDUS 945-2
First Edition
2012-mm-dd
 
 
 Reference numbe r
FDUS 945-2: 2012
© UNBS 2012 
  
Pre-insulated flexible pipe systems — Part 2:  Non bonded 
system with plastic service pipes, requirements and methods of  
test 
 FDUS 945-2: 2012 
ii © UNBS 2012 – All rights reserved
 Compliance with this standard does not, of itself confer immunity from legal obligations 
A Uganda Standard does not purport to include all necessary provisions of a contract. Users are 
responsible for its correct application  
© UNBS 2012  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilised in any 
form or by any means, electronic or mechanical, in cluding photocopying and microfilm, without prior written 
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: 256 414 505 995 
Fax: 256 414 286 123 
E-mail: unbs@infocom.co.ug  FDUS 945-2:2012 
© UNBS 2012 – All rights reserved  iii
 Contents Page 
Foreword  .............................................................................................................................. .............................. iv  
1  Scope  .............................................................................................................................. ........................ 1  
2  Normative references  ............................................................................................................................ 1  
3 Terms and definitions  .............................................................................................................................. ....... 2 
4 Classification  .............................................................................................................................. ..................... 2  
4.1 Operating temperatures and service life .................................................................................................... 2  
4.2 Operating pressures  .............................................................................................................................. ...... 2 
4.3 General requirements  .............................................................................................................................. .... 3 
4.4 Service pipes and fittings  ............................................................................................................................ 3  
4.4.1 Quality  .............................................................................................................................. .......................... 3  
4.4.2 Oxygen tightness  .............................................................................................................................. ........ 3 
4.5 Sealing in linear direction  ............................................................................................................................ 3  
4.6 Water vapour permeation  ............................................................................................................................ 3  
5 Test procedures  ............................................................................................................................... ................ 3  
5.1 General  .............................................................................................................................. ............................ 3  
5.2 Temperature cycle test  .............................................................................................................................. .. 4 
Annex A (informative) Application of Miner's Rule  ......................................................................................... 5  
Annex B (normative) Specifications for crosslinking of pipes in service  .................................................... 6  
B.1 Introduction  .............................................................................................................................. .................... 6  
B.2 General  .............................................................................................................................. ............................ 6  
B.3 Requirements  .............................................................................................................................. ................. 6  
B.3.1 Pipe system  .............................................................................................................................. ................. 6  
B.3.2 Determination of the ability to crosslink  ................................................................................................ 7  
B.3.3 Service test  .............................................................................................................................. .................. 7  
B.4 Marking  .............................................................................................................................. ........................... 7  
B.5 Example  .............................................................................................................................. .......................... 8  
 
 FDUS 945-2: 2012 
iv © UNBS 2012 – All rights reserved
 Foreword 
Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry  of Tourism, Trade and 
Industry established by the Act of Parliament of 198 3, of the Laws of Uganda.  UNBS is mandated to co-
ordinate the elaboration of standards and is  
(a) a member of International Organisation for Standardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex A limentarius Commission on Food Standards, and  
(c) the National Enquiry Point on TBT/SPS Agr eements of the World Trade Organisation (WTO). 
The work of preparing Uganda Standards is carried out through Technical Committees. A Technical 
Committee is established to deliberate on standards in a gi ven field or area and consists of representatives of 
consumers, traders, academician s, manufacturers, governme nt and other stakeholders. 
Draft Uganda Standards adopted by the Technical Committ ee are widely circulated to stakeholders and the 
general public for comments. The committee reviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council.  
Committee membership 
The following organizations were represented on t he Building and civil engineering standards Technical 
Committee (UNBS/TC 3), during the development of this standard: 
• Department of Geological Mines and Surveys 
• East African Distributors Ltd 
• Institution of Surveyors of Uganda 
• Kyambogo University 
• Multiple Industries  
• Uganda National Association of Building and Civil Engineering Contractors 
• Uganda National Bureau of Standards  
• Uganda National Plumbers Association 
 
 FINAL DRAFT UGANDA STANDARD FDUS 945-2: 2012
 
© UNBS 2012 – All rights reserved  1
 Pre-insulated flexible pipe systems – Part 2: Non bonded 
system with plastic service pipes, requirements and methods of 
test  
1 Scope 
This Final Draft Uganda  Standard s pecifies the  requirements and methods of test for flexible, pre-insulated, 
direct buried district heating pipes with plastic serv ice pipes and no bonding between the layers of the pipes. 
This standard is valid for maximum operating temperat ures of 95 °C and maximum operating pressures up to 
10 bar for a design lifetime of at least 30 years. 
This standard does not cover surveillance systems. 
NOTE For higher temperatures or for t he transport of other fluids, for example potable water, additional requirements 
and testing may be needed. Such requirements  are not specified in this standard.  
2 Normative references 
The following referenced documents are indispensible for the application of this standard. For dated 
references, only the edition cited applies. For undated references, the latest edition of the referenced 
document (including any amendments) applies. ISO 9080, Plastics piping and ducting systems — Determinat ion of the long-term hydrostatic strength of 
thermoplastics materials in pipe form by extrapolation   
ISO 10147, Pipes and fittings made of crosslinked polyeth ylene (PE-X) — Estimation of the degree of 
crosslinking by determination of the gel content  
ISO 10508;  Plastics piping systems for hot and cold water installations — Guidance for classification and 
design  
ISO 13760, Plastics pipes for the conveyance of fluids under pressure — Miner's rule — Calculation method 
for cumulative damage   
ISO 15875-1, Plastics piping systems for hot and cold water in stallations — Crosslinked polyethylene (PEX) 
— Part 1: General  
ISO 15875-2, Plastics piping systems for hot and cold water in stallations — Crosslinked polyethylene (PE-X) 
— Part 2: Pipes  
ISO 15875-3, Plastics piping systems for hot and cold water in stallations — Crosslinked polyethylene (PEX) 
— Part 3: Fittings  
ISO 15875-5, Plastics piping systems for hot and cold water in stallations — Crosslinked polyethylene (PE-X) 
— Part 5: Fitness for purpose of the system  
ISO 15876-1, Plastics piping systems for hot and cold water installations — Polybutylene (PB) — Part 1: 
General   FDUS 945-2: 2012 
2 © UNBS 2012 – All rights reserved
 ISO 15876-2, Plastics piping systems for hot and cold water installations — Polybutylene (PB) — Part 2: 
Pipes   
ISO 15876-3, Plastics piping systems for hot and cold water installations — Polybutylene (PB) — Part 3: 
Fittings   
ISO 15876-5, Plastics piping systems for hot and cold water installations — Polybutylene (PB) — Part 5: 
Fitness for purpose of the system  
ISO 17455, Plastics piping systems — Multilayer pipes — Determination of the ox ygen permeability of the 
barrier pipe  
ISO 21003:1:  Multilayer piping systems for hot and cold water installations inside buildings — Part 1: General   
ISO 21003-2, Multilayer piping systems for hot and cold water installations inside buildings — Part 2: Pipes  
3 Terms and definitions 
For the purposes of this standard, the terms and definitions given in FDUS 945-1:2011 apply.  
4 Classification 
4.1 Operating temperatures and service life 
Pipe systems according to this standard are designed fo r a service life of at least 30 years when operated at 
the following temperature profile: 
29 years at 80 °C + 1 year at 90 °C + 100 h at 95 °C. Other temperature/time profiles can be applied in ac cordance with ISO 13760 (Miner's Rule). Further 
information is given in ISO 10508 and ISO 21003-2. The maximum operating temperature shall not exceed 95 °C. 
4.2 Operating pressures 
Pipe systems according to this standard are designed fo r continuous operating pressures of 6 bar, 8 bar or 10 
bar. Table 1 defines maximum SDR ratios of the serv ice pipe required to withstand the operating pressures. 
Table 1 — SDR ratios required for different operating pressures 
Service pipe Operating pressure 
6 bar 8 bar 10 bar 
PE-X SDR 11 SDR 9 SDR 7.4 
PB SDR 13.6 SDR 11 SDR 9 
Multilayer pipes Wall thicknesses shall be calculated according 
to the methods defined in ISO 21003-2 
 
The SDR ratios in Table 1 are based on the regressi on curves of ISO 15875 series and ISO 15876 series. 
Higher SDR ratios may be applied, if they are based on regression curves developed in accordance with EN 
ISO 9080. FDUS 945-2: 2012 
© UNBS 2012 – All rights reserved  3
 5 Requirements 
5.1 General  
In addition to the general requirements defined in ISO 21 003-2, the product specific requirements in 5.2 – 5.4 
shall apply. 
5.2 Service pipes and fittings 
5.2.1 Quality 
Plastics service pipes and fittings shall comply with: 
• ISO 15875-1, ISO 15875-2, ISO 15875-3 and ISO 15875-5 for pipes made of cross linked 
polyethylene (PE-X, for PE-Xb see also Annex B), 
• ISO 15876-1, ISO 15876-2, ISO 15876-3 and ISO 15876-5 for pipes made of polybutylene (PB), and 
• for multi-layer pipes, ISO 21003-2. 
Deviating from these standards, temper ature cycle tests on pipe systems and fittings shall be carried out with 
test cycle numbers specified in 6.2. 
5.2.2 Oxygen tightness The oxygen diffusion of service pipes shall not exceed 3.6 mg/m²d at 80°C when tested in accordance with 
ISO 17455. 
NOTE The value of 3.6 mg/m2d is state of the art at general heating ap plications. A maximum diffusion rate of 0.8 
mg/m2d is recommended for district heating purposes. 
5.3 Sealing in linear direction 
The manufacturer of the system shall offer components to stop leakage in the linear direction at the end of 
each pipe section. These components shall be water tight  when tested according to water tightness test of 
ISO 9080 (without the box load test). 
5.4 Water vapour permeation 
The pipe supplier shall give information about the risk of the water accumulation in the insulation dependent 
on the service conditions. 
NOTE PE-X and PB pipes are slightly open for diffusion of water from the media to the insulation. The rate of 
diffusion is increasing with the temperature. The casing is lik ewise open for diffusion from the insulation to the soil. The 
rate of this diffusion is depending upon the casing temperat ure and the water vapour partial pressure difference over the 
casing wall. For pipes installed under the ground water table there will always be a certain build up of water directly under 
the casing. Experience shows that this build up is limited and not detrimental to the function although a certain loss of 
insulation capacity may be expected. 
6 Test procedures 
6.1 General 
Unless stated otherwise, all tests are to be carried out: 
a)  no sooner than 72 h after production; FDUS 945-2: 2012 
4 © UNBS 2012 – All rights reserved
 b)  at room temperature; and 
c)  on samples taken from coiled pipes. 
6.2 Temperature cycle test 
The minimum test cycles and the cycle times for se rvice pipe system tests are given in Table 2. 
Table 2 — Test cycles 
Service pipe outer diameter d 2, 
mm Test cycles Cycle times,  
min 
d2 ≤ 32  2 000 30  
40 mm ≤  d2 ≤ 110 1 000 30  
d2 > 110  250 60  
 FDUS 945-2: 2012 
© UNBS 2012 – All rights reserved  5
 Annex A 
(informative) 
 
Application of Miner's Rule 
For plastic service pipes the lifetime is influenced by  the temperature profile. For this European Standard a 
calculatory temperature profile has been used. The lifeti me is calculated by applying Miner's Rule. For other 
temperature profiles new calculations have to be made. 
District Heating systems are usually operated at various flow temperatures according to the necessary heat 
load. When the actual temperature profile is deviating from the standard profile, the system supplier should 
provide calculations applying Miner's Rule based on the information given in Table A.1. 
Table A.1 — Examples for applying Miner's Rule 
Operating temperature, 
°C Example 1 
Operating time per year, 
h Example 2 
Operating time per year,  
h Example 3 
Operating time per year, 
h 
95 3.3 0 0 
90 292 50 50 
85 0 100 1 000 
80 8 468 200 3 450 
75 0 2 000 1 000 
70 0 2 410 0 
65 0 4 000 0 
60 0 0 0 
total 8 763.3 8 760 5 500 
 The total operation time should comply with the annual operation time (max. 8 760 hours). For systems 
operating only for the heating period, the annual operation time might be below 8 760 hours. 
Example 1 is taken from the temperature profile in F DUS 945-1 which means a total life time of 30 years and 
100 h. 
When calculated in accordance with Miner's rule Exampl e 2 gives an estimated life time of more than 50 years 
for a service pipe and Example 3 an estimated life time of more than 40 years. FDUS 945-2: 2012 
6 © UNBS 2012 – All rights reserved
 Annex B 
(normative) 
 
Specifications for crosslinking of pipes in service 
B.1 Introduction 
The PE-X service pipe material may be crosslinked by any  process (peroxide, silane, electron beam and azo) 
which changes the chemical structure in such a way that  the polymer chains are connected with each other to 
a three-dimensional net by chemical bonds (commonly termed cross linking). Cross linking is carried out 
during or after the manufacture of the pipe (see ISO 15875-2:2003, 4.1). 
Silane cross linked polyethylene (PE-Xb ) pipes are not fully crosslinked when being extruded. Crosslinking 
occurs in contact with water, at a rate dependent on time and temperature. 
The crosslinking of pipes in contact with water can either be carried out as a part of the production process or 
allowed to occur during the commissioning and the first short period of service. 
The purpose of this annex is to specify the requiremen ts and test procedures of the pipe systems cross linked 
during service to ensure that they comply with the specifications of Clause 4. 
Pipes that are covered by this annex are curing so rapidly, that under ambi ent conditions they are curing partly 
during storage. They are therefore like all fully  crosslinked PE-X pipes unsuited for butt-welding. 
Since not sufficient experience with electrofusion fittings  is available, this annex does not cover pipe systems 
with electrofusion fittings. 
B.2 General 
The degree of crosslinking shall meet the minimum r equirement of 65 % specified in ISO 15875-1. The time 
needed for reaching this crosslinking level is dependent upon the formulation of the material, the dimensions 
of the pipe and the temperature of the water. 
A pipe system fulfilling the requirements of B.3 may be installed directly and put into operation at the working 
temperatures and pressures given in Clause 4. 
The recommendations of the piping system producer shall be followed. 
B.3 Requirements 
B.3.1 Pipe system 
The pipe and fitting system shall be specified by the pr oducer and only such fittings which have been tested 
together with the pipes in accordance with the service test specified in B.3.3 shall be used with the pipes in 
the system. Pipe systems shall comply with the thermo cycling test  specified in ISO 21003-2, 6.2 and the pullout-test 
according to of ISO 15875-5, 4.4 without prior conditioning. FDUS 945-2: 2012 
© UNBS 2012 – All rights reserved  7
 B.3.2 Determination of the ability to crosslink 
A test piece of 2 mm thickness taken from the pipe or from the pipe or the fitting shall be conditioned in hot 
water at 95 ° C for 24 h. 
The degree of crosslinking of the conditioned sample when tested in accordance with ISO 10147 shall be ≥ 65 
%. The degree of crosslinking test shall be a quality control test. 
B.3.3 Service test 
The pre-insulated pipe systems shall meet requirement s at both temperatures sp ecified in Table B.1, 
minimum 24 h and maximum seven days after production of  the service pipe, when stored at 23 °C ± 3 °C and 
an air humidity of 50 % ± 10 %: 
a) a test piece of a minimum 1 m length shall be fitted with a connection fitting at both ends in 
accordance with the supplier’s instructions. The fittings to be used for the test shall be those 
belonging to the commercial system;  
b)  the test pieces shall be placed in  air at room temperature and filled with water at room temperature, 
and subject to internal pressure for thirty minutes at 1.3 times the pressures given in Table B.1; and 
c)  the pressure shall then be set and the temperatur e shall be increased to the values given in Table 
B.1 and held constant for the periods of time giv en in Table B.1. The water circulation shall be 
adequate to maintain the specified temperature accuracy in the entire test sample.  
Table B.1 — Pipe testing for various SDR values 
SDR value Test pressure, 
bar Testing time at (50 ± 1) °C, 
h Testing time at (95 ± 1) °C, 
h 
SDR 11 6 3 000 1 000 
SDR 9 8 4 000 1 000 
SDR 7.4 10 8 760 1 000 
 
If it can be shown that a crosslinking degree of 65 % is reached earlier than the times stated in Table B.1, the 
test may be interrupted when 65 % is reached. 
After the tests according to Table B.1: 
a) there shall be no visible failures or leakages; and b) the pipes shall comply with ISO 15875-1. 
The service test shall be a type test. 
B.4 Marking 
The marking of the service pipe shall include minimum information concerning material or material code 
according to the relevant standard  for crosslinkable PE-Xb pipes. FDUS 945-2: 2012 
8 © UNBS 2012 – All rights reserved
 B.5 Example 
The common operating temperatures are 70 °C or 80 °C and common pipe dimensions are diameters 32 and 
63 with SDR 11. Larger dimensions are av ailable (for example, 110 SDR 11). 
Considering these parameters and a typical PE-Xb material on the market, the necessary time to achieve 65 
% of crosslinking in operation is given in Table B.2. 
Table B.2 — Testing of pipe diameters 
Diameter, 
mm SDR value 
 Test temperature, 
°C Testing time at 80 °C, 
h Test temperature, 
°C Testing time at 70 
°C, 
h 
32 11 
80 16 
70 32 
63 11 45 90 
110 11 105 210 
 
Pipes can be operated at the maximum serv ice pressure during crosslinking. 
 FDUS 928-2: 2012 
© UNBS 2012 – All rights reserved  9
 Certification marking 
Products that conform to Uganda standards may be  marked with Uganda National Bureau of Standards 
(UNBS) Certification Mark shown in the figure below.  
The use of the UNBS Certification Mark is gove rned by the Standards Act, and the Regulations made 
thereunder. This mark can be used only by those licens ed under the certification mark scheme operated by 
the Uganda National Bureau of Standards and in co njunction with the relevant Uganda Standard. The 
presence of this mark on a product or in relation to a product is an assurance that the goods comply with the 
requirements of that standard under a system of supervision, control and  testing in accordance with the 
certification mark scheme of the Uganda National  Bureau 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.  
 
 FDUS 945-2: 2012
 
ICS 23.040.20  
Price based on nn pages 
© UNBS 2012 – All rights reserved