Evaluation of the Surge and Fatigue Resistance of PVC and PE Pipeline Materials for use in the UK Water Industry [PVC, PE]

System Experience & Training # 1998 Gothenburg

Many early brittle failures in PVC water and sewerage pipelines, where repeated surge events are thought likely to induce embrittlement, were attributed to fatigue. The concerns of pipeline engineers led to the adoption of the British Standard Code of Practice CP 312 (ref. 1) by the UK water industry, which gives maximum and minimum pressure ratings for various pipe classes.
‘Surge and Fatigue’ are often combined as a collective term. However although both phenomena arise from the same events (valves closing quickly, pump shut down etc.) they should : be considered separately siice they describe different effects on the pipe material.
Rapid closure of a valve or a pump Starting up may give rise to a rapid increase in pressure to a level well in excess of the steady state condition. This is commonly known as surge. Surge ‘events’, generally occur over a very short time-scale and it is known that many PVCu pipe failures followed surges in pressure in pumped systems.
Fatigue is associated with the repetition of such events, where the fluctuatrons in pressure cause a loss in the long-term strength of the pipe material.
Because it was believed that the combined effect of over-pressurization from surge and loss in properties caused by fatigue could have serious implications on the lifetimes of PVCu pipelines, a design code was introduced. in 1977 (BS CP312). The-advice for design from both CP312 and the PMSM is that in a dynamic loading situation, the difference between maximum and minimum pressures must be less than 0.5*Static Rating. An additional criterion is that the maximum pressure must always be less than the pipe rating. In many pumping situations, the maximum pressure may rise to twice the steady state condition and drop to zero. This means that the stress range is twice the siatic case and hence via CP312 criteria the wall section must be increased by a factor of four. Increasing wall sections of pipes has clear cost implications, since the cost of plastics is directly proportional to the weight of material used. It is also well known that increasing wall thickness promotes the generation of a state of plane strain in the wall section and this will reduce resistance to crack growth under static loading.
The Water Industry adopted the CP312 code for PVCu in the PVC Guidance Manual and the Water Research Centre (WRc) extended the range of materials affected to include PE pipe materials in the Pipe Materials Selection Manual (PMSM). There was no service evidence to suggest that fatigue was a problem for PE; the criteria were adopted as a conservative measure awaiting experimental evidence to demonstrate whether the properties of PE are affected : by cyclic loading. Since there is also considerable evidence to suggest that the major problems with PVCu were associated with static overloading rather than fatigue, clarification of the U.K. design position was sought by the water utilities. Laboratory research on the fatigue of PVC and PE materials has thus been carried out by Pipeline Developments via a commission from UK. Water Industry Research Ltd. (UKWIR) to define the position for the range of tough polymers currently in use in the UK Water Industry.

Please note that the whole article content is available on PPCA website onlySource : 1998 Gothenburg


Related papers

Very High Molecular Weight Polyethylene Resins with Improved Chemical and Abrasion Resistance

Author(s) : Dr. Dane Chang, Dr. David Marshall, Chris Cox 2014 Chicago

Plastic pipe applications often require polymers to have adequate abrasion resistance during usage. Although typical polyethylene resins have reasonably good resistance to abrasion and can be broadly used with a variety of chemicals, there are some demanding applications that require a resin with enhanced abrasion and...

Smart Solutions for the Design of Rehabilitation with Plastics Pipes

Author(s) : Marshall, Morley, Pearson 1998 Gothenburg

The Water Industry in England and Wales has responsibility for an approximate length of 300,000km of water main, ~nuchof which was laid over 70 years ago using cast iron.Subsequently, asbestos cement, PVCu and cement lined ductile iron have been used. The old iron pipe systems that were installed in many of the...

Improvements in Electrofusion Welding in the UK Water Industry

Author(s) : Marshall, Hepburn, Netherwood 1995 Edinburgh

The adoption of polyethylene as a pipe material by both the gas and water indusmes has undoubtedly led to several sigruf~cant economic and operational advantages. The development of narrow trenching techniques and insertion refurbishment methods only became viable once a complete fusion jointed polyethylene system was...

The Crack Growth Resistance of PVC and PE

Author(s) : Marshall, Ingham, Brogden 1995 Edinburgh

When clients purchase plastics pressure pipes, they have frequently made that decision because they know that plastics do not corrode and they assume that if they do not exceed the pressure rating then a long lifetime should be assured. (Low cost has also been known to be a factor). It is thus of concern for the...

The Development of a Mains Pressure Test for PE & PVC Pressure Pipes

Author(s) : Marshall, Birch, Morley 1995 Edinburgh

Many UK Water Companies are now using PE pipe systems because it 1s believed that use of an all-welded pipe will minimise the number of mechanical fittings employed and therefore will reduce potential sources of leakage. With pipes such as ductile iron and PVCu, which are joined in short lengths, it is often...

The Abrasion Resistance of Polymers Used in Slurry Transport Systems

Author(s) : Lowe, Marshall 1988 Bath

A Rotating Pipe Drum Test has been developed to assess the abrasion performance of plastics pipes to an extpnt where most test variables are understood. The procedure involves the rotation of relatively short pipe lcngths containing slurry on a conventional bail mlll. In the rest, the pipe surface repeatedly passes...

The Correlation of Fast Fracture Resistance of Polyethylene with Impact Toughness

Author(s) : Marshall, Birch-Kisbenyi, Youd 1988 Bath

A complete analysis of the Charpy impact system has been made to relate measurements of impact toughness to the geometry of samples. Using data obtained on pipe grade polyethylenes, Gc values at 20°C and 3°C have been found to correlate wel! with measurements of resistance to fast fracture in pressurised pipe...

The Renovation of Trunk Mains and Distribution Pipes in NWWA by Cold Drawn Swage Lining with MDPE

Author(s) : Young, Thomas, Marshall 1988 Bath

Within the Water Industry in England and Wales, there is an estimated length of 295,000 km of water main, much of which was laid in unlined cast iron prior to 1940. Subsequently, asbestos cement, UPVC and cement lined cast/ductile iron has been uscd. It is kn-that a substantial number of...

Specifying High Toughness in PE Pressure Pipes

Author(s) : Marshall, Birch 1985 York

It is proposed that present Specifications for PE Pressure pipes are essentially undemanding and tests do not simulate service conditions. Perfect pipes are assessed rather than pipes which have sustained handling and installation ‘damage’.Flaws and defects have caused many problems with other thermoplastics pipes...

The Abrasion Resistance of Polymers in Slurry Environments

Author(s) : Lowe, Marshall 1985 York

A new test has been developed to evaluate the abrasion performance of different pipe materials. The Rotating Pipe Test simulates sliding bed flow of a slurry and gives quite excellent data reproducibility. The influence of sample geometry and slurry changing frequency and particle size have been assessed. The effects...

Assessment of the Influence of Processing on Medium-High Density PE Pressure Pipes

Author(s) : Marshall, Taylor, Dickinson 1982 York

A study has been carried out which has sought to establish the influence of processing conditions on the properties of medium and high density polyethylene. Residual stress and fracture toughness measurements have been carried out on hdpe pipe, from which predications of the influence of diameterlwall thickness on the...

Criteria for High Toughness in UPVC Pressure Pipes

Author(s) : Birch, Marshall 1982 York

The mechanics of failure of uPVC pipe materials have been investigated using fracture mechanics test methods to induce brittle failure. It has been found that brittle failure can be quantified and test procedures have been developed which are capable of being used as quality control methods for classifying pipe. High...

The Use of Fracture Mechanics for the Prediction of Failure of Thermoplastics Pipes

Author(s) : Birch, Howarth, Marshall 1979 Brigthon

The paper is a brief resum of a large project which has sought to investigate the use of fracture mechanics in evaluating the failure properties of a number of common thermoplastics pressure pipe materials. In this outline, the results of tests made on uPVC and YDPE pipes are described. Pre-notched pipes have been...

The Analysis of practical failures of plastic pipelines

Author(s) : Marshall, Williams 1974 Southampton

During the last ten years, it has often been predicted that plastics will be used in increasing quantities as true engineering materials, Whilst there has been an increased acceptance of GRP as a positive alternative to metals in many applications, the use of thermoplastics for major load bearing structures has been...

Members of the Association

BOREALISBOROUGEFormosa Plastics CorporationINEOS O&PIRPCKorea Petrochemical IND. Co., LTD (KPIC)LyondellBasellPetroChina Dushanzi Petrochemical CompanyPRIME POLYMERSABICSCG Chemicals & Thai PolyethyleneSinopecTASNEE
TOP