API TR 17TR2:2003 pdf download

API TR 17TR2:2003 pdf download.The Ageing of PA-11 in Flexible Pipes.
Consideration of using either the partial pressure (and/or fugacity) of acid gases or pH of the water phase in determining the effect of acid gases on PA-i 1 ageing is currently under further investigation. Within this document. p11 calcukited using full water analysis is employed.
There may also be a contnbution to the p1-I of the water phase from acids in the oil phase. although there may also be other elkets of such acids, as described in the following section.
2.4 THE EFFECT OF DIFFERENT CRUDES
Ditferent crude compositions may aftcct IA-l I dittcrcrnly. The most important ageing effect is derived from the so- called TAN (Total Acid Number) of the crude. rather than pH. which applies only to the water phase. TAN is a gross measure of the amount of organic acids, typically naphthcnic carboxylic acids, within the crude41.
The effects of TAN are generally secondary relative to the effects of water and pH. The principal effect of these high molecular weight acids, which are not soluble in water, is to give an extra “skin” effect, effectively a highly aged surface layer. on top of the p1-I effect. Specific age ing testing may be required for very highly acidic crudes (TAN > 3.5;.
In order to quantify the effect of a specific crude on PA-Il it may be necessary to gain a more detailed knowledge of the acid species. Different ageing effects have been observed at similar TAN numbers.
2.5 THE EFFECT OF HYDRATE TREATMENT CHEMICALS
hydrate treatment chemicals may affect the ageing of PA-Il.
Pure, liquid methanol diffuses easily and quickly through PA-I I and very effectively extracts plasticiser and swells the material.
As a hydrate prevention and rernediation measure, methanol is typically introduced either by continuous injection or in hatch treatments. In continuous injection, the temperature is typically high. e.g.. the production temperature if injected at a production welihead, but the concentration is low. In kuch treatments, the average exposure temperature may he lower thaii the production temperature. but the methanol is in high concentrafion. It should be noted that methanol used in the field varies in its water content, and is typically only specified to be > 95% methanol. The contribution of methanol to the ageing of a PA-Il internal pressure sheath must take account of all these factors.
For continuous injection, at low concentrations, typically 10 to 2tNJ ppm. field experience suggests that methanol is 1)01 a problem. For PA-I I pressure sheath service life prediction under these conditions the effect of methanol can be neglected.
For batch treatment, an estimation of cumulative exposure time and temperature must be made.