RILSAN® Polyamide 11 in Oil & Gas Off - HCL Fasteners Ltd
RILSAN® Polyamide 11 in Oil & Gas Off - HCL Fasteners Ltd
RILSAN® Polyamide 11 in Oil & Gas Off - HCL Fasteners Ltd
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20<br />
The physical picture of the <strong>in</strong>teractions<br />
In a physical description of the ensemble<br />
“umbilical filled with control fluid,” we<br />
have to consider a closed system with<br />
two phases, PA<strong>11</strong> and control fluid, and<br />
several components which, <strong>in</strong> time, can<br />
<strong>in</strong>terdiffuse between the two phases.<br />
These components are the plasticizer<br />
BBSA and constituents of the control<br />
fluid, ma<strong>in</strong>ly glycols.<br />
Control Fluid<br />
The effects can be described when the<br />
solubility parameters of the diffus<strong>in</strong>g<br />
species and the diffusion k<strong>in</strong>etics are<br />
known. The mathematics of diffusion <strong>in</strong> a<br />
plane sheet are well described (Crank).<br />
We will use some simple forms to illustrate<br />
the effects <strong>in</strong> a semiquantitative<br />
manner.<br />
For a particular umbilical, the ratio<br />
between the two phases may be different<br />
due to the particular tube dimensions.<br />
The approach is best described <strong>in</strong> a<br />
worked example.<br />
Standard 1 /2’’ hydraulic tube<br />
ID = 12 mm WS = 1.5 mm<br />
OD = 15 mm L = 100 mm<br />
...................<br />
...................<br />
OD ID<br />
...................<br />
...................<br />
BBSA BBSA<br />
We calculate:<br />
Fluid volume: <strong>11</strong>.3 ml<br />
Weight of tube (r = 1.05 mm): 5.4 g<br />
The plasticizer content is on average<br />
12.5% by weight of the res<strong>in</strong>.<br />
BBSA content <strong>in</strong> a tube<br />
with L = 100 mm: 675 mg<br />
L<br />
PA<strong>11</strong><br />
BBSA SOLUBILITY (G/L)<br />
14<br />
12<br />
10<br />
8<br />
6<br />
4<br />
2<br />
60°C<br />
22°C<br />
0 5 10 15 20 25 30 35 40 45<br />
GLYCOL CONTENT ( %)<br />
Fig. 15 The solubility of BBSA <strong>in</strong> glycol-based control fluids and its temperature<br />
dependence<br />
The maximum extractable amount of plasticizer adds up to approximately 6% by<br />
weight. For a hydraulic fluid conta<strong>in</strong><strong>in</strong>g 45% glycol, the maximum plasticizer solubility<br />
at ambient temperature is close to 6%. For a hydraulic fluid conta<strong>in</strong><strong>in</strong>g 25% glycol, the<br />
solubility limit is 2.2 – 2.5%. At temperatures over 60°C, the plasticizer will be extracted<br />
as it will become soluble <strong>in</strong> such a fluid.<br />
22°C 60°C<br />
pure water based, eg., Oceanic* HW 500 0.1 - 1 1.5 – 2.5<br />
approx 25% glycol, eg., Oceanic HW 525 2.2 – 2.5 6.8 – 7.4<br />
approx 40% glycol, eg., Oceanic HW 540 4.0 – 5.0 12.0 – 13.6<br />
*Hydraulic fluid manufactured by MacDermid Cann<strong>in</strong>g, PLC
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