API TR 17TR2:2003 pdf download

API TR 17TR2:2003 pdf download.The Ageing of PA-11 in Flexible Pipes.
B.2 Oxidation
Oxidation is primarily of concern in laboratory ageing tests rather than in the field. If no special care is observed during laboratory ageing tests, two different degradation mechanisms will be present. and oxidative degradation will occur in addition to the hydrolysis. The use of higher temperature in laboratory testing than in real service conditions (in order to reduce experiment times can also contribute to emphasise the influence of oxidation processes.
As a result, a pmprr oxygen removal procedure is required for any laboratory study devoted to PA-Il ageing in field conditions.
To ensure the absence of oxygen in ageing experiments. high purity nitrogen or argon (>99.999w) should be bubbled through the solution until the residual oxygen in the outlet gas is< lOppm. Even with proper fluid replacement and oxygen removal procedures. perfomied at each sampling time, some very low residual amounts of oxygen are nevertheless present after nitrogen bubbling. This results in conservative ageing data. Any gas used as the ageing environment should likewise have oxygen content < ID ppm. B.3 Open or Closed System Another difliculty coiieming the relation between laboratory and field conditions is linked to the flowing service encountered in the field compared to the static conditions mostly employed in laboratory tests. False interpretation can result from species either accumulaled or exhausted as a direct consequence of the closed. static laboratory environment. e.g.. when experiments are carried out with an ageing medium comprising only limited percentage of l)allicUlarlY “active” species for PA-I I degradation, such as water with acids, or oil with well-defined TAN. It is then of primary importance to consider carefully the ratio between the asailable amount of such chemicals and polyamidc in contact. Indeed, if the medium is no regularly renewed, exhaustion of the concerned species will occur, and polymer degradation will be slowed down—and ultimately stopped — exclusively due to laboratory test conditions. It should be noted that the rate of plasticiser loss can be affected by regular change-out of water, due to limited solubility of plasticiser in water. B.2 Oxidation Oxidation is primarily of concern in laboratory ageing tests rather than in the field. If no special care is observed during laboratory ageing tests, two different degradation mechanisms will be present. and oxidative degradation will occur in addition to the hydrolysis. The use of higher temperature in laboratory testing than in real service conditions (in order to reduce experiment times can also contribute to emphasise the influence of oxidation processes. As a result, a pmprr oxygen removal procedure is required for any laboratory study devoted to PA-Il ageing in field conditions. To ensure the absence of oxygen in ageing experiments. high purity nitrogen or argon (>99.999w) should be bubbled through the solution until the residual oxygen in the outlet gas is< lOppm. Even with proper fluid replacement and oxygen removal procedures. perfomied at each sampling time, some very low residual amounts of oxygen are nevertheless present after nitrogen bubbling. This results in conservative ageing data. Any gas used as the ageing environment should likewise have oxygen content < ID ppm. B.3 Open or Closed System Another difliculty coiieming the relation between laboratory and field conditions is linked to the flowing service encountered in the field compared to the static conditions mostly employed in laboratory tests. False interpretation can result from species either accumulaled or exhausted as a direct consequence of the closed. static laboratory environment. e.g.. when experiments are carried out with an ageing medium comprising only limited percentage of l)allicUlarlY “active” species for PA-I I degradation, such as water with acids, or oil with well-defined TAN. It is then of primary importance to consider carefully the ratio between the asailable amount of such chemicals and polyamidc in contact. Indeed, if the medium is no regularly renewed, exhaustion of the concerned species will occur, and polymer degradation will be slowed down—and ultimately stopped — exclusively due to laboratory test conditions. It should be noted that the rate of plasticiser loss can be affected by regular change-out of water, due to limited solubility of plasticiser in water.