Plastic Pipe Systems Testing

Pressure Testing

WRc-NSF's pressure test facilities offer a comprehensive service for testing plastics pipes and fittings. The services offered cover a wide range, from a straight forward hydrostatic pressure test - where constant internal pressure is applied to evaluate the long term strength of the pipes and/or fittings, to the more complex test that can involve a combination of pressure and external loading. Regression analysis can also be conducted to evaluate new materials and production techniques and prove a minimum 50 year lifetime for a product when in service. WRc-NSF also has facilities for cyclic pressure testing of samples and vacuum testing of fittings.

WRc-NSF has several water baths dedicated to providing the correct temperature environment for long term pressure testing and regression analysis for plastic pipes and associated fittings. Each bath has its own individual temperature control, providing test temperatures from 20°C to 95°C to an accuracy of +/-1 degree Celsius. Water-chillers are available to provide lower temperatures and sub-zero temperature testing if required. The comprehensive range of test tanks are capable of accommodating pipes up to 1000mm in diameter and six meters in length. WRc-NSF has a compressed air distribution system capable of operating to 10 bar An additional high pressure compressed air source and intensifying equipment permits pressures up to 40 bar. Hydrostatic testing of larger pipes is carried out using dedicated pressure control equipment which monitors and controls the internal pressure in the sample under test at precisely defined limits. Testing is conducted using 'Water-in-Water' for safety.

WRc-NSF has comprehensive facilities for the evaluation of modern plastics plumbing pipe and fittings for hot and cold water use. These include cPVC, cross linked polyethylene, polybutylene and others. The facilities include several test rigs dedicated to carrying out thermal cycling tests to the requirements of the British Standard 7291 amongst others.

Mechanical Testing

WRc-NSF provides a comprehensive service for the determination of the mechanical properties of plastics pipes and fittings including weld strengths . The majority of the test equipment is equipped with microprocessor controls.

WRc-NSF has a purpose built 'pull-out' rig which is housed within a temperature controlled environment comprising three main component modules: a 200 tonne capacity, horizontally opposed, hydraulically operated tensile ram with precision pull-rate control; computer controlled data-logging equipment; and a heavy duty test bed, proof tested to 180 tonnes. Accuracy at lower loads is achieved using load cells whereas higher loads are measured by a calibrated pressure transducer. WRc-NSF also operates an Instron tensile test machine on which all routine mechanical tests - tensile, compression, fatigue and 3-point bend tests - can be conducted. WRc-NSF offers the complete size range of Accelerated Relaxation End Load (AREL) tests up to 500mm diameter in which pipe-fitting assemblies are tested under constant applied end loads. Additional mechanical tests available are fracture toughness (C-ring) and, combined loading profiles using internally applied pressures and externally applied loads

Characterisation

WRc-NSF offers a comprehensive characterisation service for plastics materials used in the manufacturing process of plastics pipes and fittings. The experimental techniques which are used range from infrared spectroscopy, for the identification of materials and additives, to techniques for determining through-pipe-wall profile distributions such as residual stress measurements by a layer removal analysis. WRc-NSF can offer a speedy thermal analysis result service using its Differential Scanning Calorimeter (DSC) which is particularly useful for those clients whose volume of work exceeds their company's capabilities. This service will be useful for those clients where thermal analysis is an essential part of their quality procedure, such as plastics pipes and fittings manufacturers with a requirement for Oxidation Induction Time and/or Temperature measurements. Analyses are carried out on a Du Pont Instruments 9900 Thermal Analysis System including an automatic gas change-over facility and all results are stored on disk enabling future retrieval if required, which can be useful for the comparison of samples worked on over periods of weeks, months or even years. Other characterisation facilities offered by WRc-NSF are: density columns; melt flow index apparatus and opacity measurements.

Failure Investigation

WRc-NSF offers an investigation service into the causes of failure of pipeline systems. Pipe failures are expensive and time consuming to repair. In many instances this expense could have been saved through correct installation procedures being followed. Pipeline systems in the most simple form comprise lengths of pipes of various diameters joined together by fittings which may be couplers, to join pipes of equal diameter; reducers, to join different diameter pipes; saddles or tees, for take-off or branch arms etc. Fittings can be of two types:- the fusion type, which needs a form of heating or solvent welding and the mechanical type, such as push-fit or clamp-style. Also in the case of large diameter pipe jointing, butt welding of pipe-to-pipe or pipe-to-flange with backing ring is used. All these procedures are reliable providing the manufacturer's jointing procedures are employed. Failure of the pipe itself is also a possibility through mishandling in the field causing scoring to the outer surface thus introducing a notch and a point of weakness. Point loading on the pipe surface through incorrect use of backfill material is an additional contributor to failure. WRc-NSF is able to investigate the causes of failure through techniques ranging from the careful dismantling of the failed part and close examination, to more complex investigations where the fracture surfaces are examined using optical or electron microscopy techniques. In cases where particle contamination is found these can be identified through EDAX analysis.

For further information contact Mr Ian Broad.

Last Updated: 13 June 2010

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