RILSAN® Polyamide 11 in Oil & Gas Off - HCL Fasteners Ltd

PERMEABILITY (G.MM/M 2.DAY)
1000
100
10
1
METHANOL PERMEATION DATA
Temperature in °C 4 23 40 50
PA11 unplasticized 6 18
PA11 plasticized 13.5 40 115 190
units: g mm/m 2 day atm
The activation energies for the unplasticized and plasticized
grades are respectively:
39.4 kJ mol-1 and 43.1 kJ mol-1. Fig. 13 Methanol permeability
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• BESNO TL
■ BESNO P40TL
50°C 40°C 30°C 20°C 10°C 0°C
1/TEMPERATURE
Pressure effects on permeability have been observed. As a
general rule, a tenfold increase in pressure results in a three-fold
increase in methanol permeation.
Conclusions:
• Methanol has a finite permeation rate through PA11 which has
to be taken into account in design.
•Liquid methanol efficiently extracts the plasticizer from PA11
plasticized grade “P40”. For umbilicals, this extraction has no
consequence on the integrity of the pipe.
• Methanol induces a softening and also polymer breakdown at
higher temperatures. We suggest 70°C as the maximum continuous
use temperature and 90°C for occasional temperature
peaks in the case of hydraulic hoses. For offshore flexible
pipes, the extraction of plasticizer and the modification of the
flexiblity can further reduce the continuous use temperature.
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3.7 Influence of monoethylene glycol and ethylene
glycol-based hydraulic liquids on mechanical
properties
Monoethylene glycol and other ethylene glycols mixed in
different ratios with water are used as constituents of hydraulic
liquids in offshore applications. These liquids can extract plasticizer
from polyamide resin because the plasticizer has a rather
high solubility in glycol/water mixtures. This effect is shown in
the graph below. The tensile yield shifts to higher
modulus with the departure of the plasticizer.
To some extent glycol/water mixtures act as plasticizer themselves
when absorbed by polyamide 11 resin.
All these phenomena are well known today and experience has
shown that they do not cause any particular problem in the
functioning of the subsea installation under ordinary working
conditions.
In the following, the phenomena are described in detail so that a
thorough understanding of the prevailing material behavior can
be developed.
STRESS AT YIELD (MPa)
40
35
30
25
20
15
10
5
Fig. 14 Evolution of tensile stress of BESNO P40 TL 12mm bore
hoses in water/glycol 60/40
0 200 400 600 800 1000
TIME (DAYS)
40°C
70°C
19