Test rigs environmental

To help lessen the complications of product testing, a common approach is to separate mechanical and environmental testing. The mechanical properties can be tested on the product, using a relatively simple product test rig, while environmental degradation is studied on samples of the material. For time dependent mechanical properties, the degree of mechanical deterioration of the product is then increased by a factor reflecting the... 

An example of a basic environmental test bed would be a temperature controlled tank of a liquid, perhaps sea water. This basic structure is applicable to a considerable range of products and can involve acceleration by using more severe conditions than in service. In one use of such a rig, the insulation on oil riser pipes is tested by circulating hot oil through the pipe whilst it is immersed in the tank. 

Oilfields in the North Sea provide some of the harshest environments for polymers, coupled with a requirement for reliability. Many environmental tests have therefore been performed to demonstrate the fitness-for-purpose of the materials and the products before they are put into service. Of recent examples [33-35], a complete test rig has been set up to test 250-300 mm diameter pipes, made of steel with a polypropylene jacket for thermal insulation and corrosion protection, with a design temperature of 140 °C, internal pressures of up to 50 MPa (500 bar) and a water depth of 350 m (external pressure 3.5 MPa or 35 bar). In the test rig the oil filled pipes are maintained at 140 °C in constantly renewed sea water at a pressure of 30 bar. Tests last for 3 years and after 2 years there have been no significant changes in melt flow index or mechanical properties. A separate programme was established for the selection of materials for the internal sheath of pipelines, whose purpose is to contain the oil and protect the main steel armour windings. Environmental ageing was performed first (immersion in oil, sea water and acid) and followed by mechanical tests as well as specialised tests (rapid gas decompression, methane permeability) related to the application. Creep was measured separately. 

Where a number of properties are relevant to a product the testing may be carried out with a sequence of tests without superimposing any ageing. Where environmental effects have to be accounted for they are applied separately and the rig tests repeated. An example of this approach is artificial sports surfaces where such characteristics as ball bounce, energy absorption, dynamic stiffness and spike resistance are measured using specifically developed rigs. 

Automotive companies have used a four-poster road simulator rig with environmental conditioning to establish correlations with conventional adhesive testing methods [71]. 

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