BS EN 253:2009 pdf download – District heating pipes — Preinsulated bonded pipe systems for directly buried hot water networks — Pipe assembly of steel service pipe, polyurethane thermal insulation and outer casing of polyethylene
The carbon black shall be finely dispersed in the material. When tested in accordance with 5.2.3,the followingrequirements shall be met:
Carbon black agglomerates, bubbles, voids or foreign matter shall not exceed 100 um in diameter. No white orblack stripes or smears may occur.
126.96.36.199 Melt mass-flow rate
The melt mass-flow rate(MFR), in g/10 min, of black PE materials used for the manufacturing of casings shall liewithin 0,2≤MFR≤ 1,4 g/10 min determined in accordance with EN ISO1133,condition T(5kg,190 °C).
Black coloured PE materials conforming to 188.8.131.52,which do not differ more than 0,5 g/10 min in MFR shall beconsidered fusible to each other.
Casings made of PE materials outside this MFR range of 0,5 g/10 min may be fusion welded provided that the pipemanufacturer has demonstrated fusion compatibility by preparing a but fusion joint using the parameters asspecified in Annex A of lS0 11414:1996.The requirement of fusion compatibility is a ductile failure mode of the jointwhen tested at 23 C in accordance with lSo 13953.
184.108.40.206 Thermal stability
The thermal stability is determined by oxygen induction time (OIT) of the black coloured PE material and shall be atleast 20 min when tested at 210C according to EN 728.
220.127.116.11 Use of rework material
Only clean,not degraded, rework material, generated from the manufacturer’s own production of pipes, shall beused.
18.104.22.168 Nominal outside diameter
The nominal outside diameter of the casing should be selected from Table 5.
The actual outside diameter shall be measured in accordance with EN ISO 3126.
The wall thickness of the casing shall be in accordance with Table 5.
The actual wall thickness shall be measured in accordance with EN ISO 3126.
22.214.171.124 Appearance, surface finish, pipe ends
The internal and external surfaces 1) of the casing pipe shall be clean and free from such grooving or other defects that might impair its functional properties (see 5.2.1).
The pipe ends shall be cleanly cut and shall be square within 2,5° with the axis of the pipe.
126.96.36.199 Elongation at break
The elongation at break determined in accordance with 5.2.2 shall not be less than 350 %.
The test is to be applied only on casings that are produced partly or fully from rework material.
188.8.131.52 Heat reversion
When tested in accordance with EN ISO 2505, the longitudinal length at any position on the pipe shall not changeby more than 3 %.On inspection after testing, the pipe shall not show any faults, cracks, cavities or blisters.
184.108.40.206Stress crack resistance
When tested in accordance with 5.2.4, the time to failure shall not be less than 300 h.
4.4Polyurethane rigid foam insulation (PUR)
The manufacturer of the pipe assembly shall be responsible for the choice of raw materials,composition andmanufacturing conditions.
The manufacturer shall keep records, documenting the raw materials used, the prescribed mixing ratio and thetests performed.
The records shall demonstrate that the foam from the production of pipe assemblies is of the same composition asthe foam sample used for the ageing test in 5.4.3 and meets the requirements of 4.4.
4.4.2Voids and bubbles
The average area of voids and bubbles determined on the five cross sections in accordance with 5.3.2 shall notconstitute more than 5 % of the nominal cross sectional area of the PUR foam.No single void shall leave less than1/3 of the nominal insulation thickness between the steel service pipe and the casing.
The compressive strength or the compressive stress at 10 % relative deformation as defined in IS0 844 shall benot less than 0,3 MPa in a radial direction when tested in accordance with 5.3.3.
All requirements are valid including the diffusion barrier, if any.4.5.2 Pipe ends
Both ends of the service pipe shall be free from insulation for a minimum of 150 mm. The tolerance on the declaredvalue shall be ±10 mm.Service pipe ends shall be prepared for welding in accordance with EN ISO 9692-1.