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CAPP International Research Project on the Effects of Chemical Ageing of Polymers on Performance Properties FLEXIBLE PIPES - PERMEATION OF METHANE, CARBON DIOXIDE AND WATER THROUGH TEFZEL ETFE - Experiments 1996 Prepared for: Prepared by: Document no: Document date: CAPP Joint Industry Project Per Arne Wang, Norsk Hydro 97Q-BG3.DOC CAPP/N.3 18 April 1997 9063 Bee Caves Road, Austin Texas 78733-6201, U.S.A. Tel: 1-512-263-2101 Tamworth Road, Hertford SG13 7DG, England
Transcript

CAPPInternational Research Project on the Effects of Chemical

Ageing of Polymers on Performance Properties

FLEXIBLE PIPES -

PERMEATION OF METHANE,CARBON DIOXIDE AND WATER

THROUGH TEFZEL ETFE -

Experiments 1996

Prepared for:

Prepared by:

Document no:

Document date:

CAPP Joint Industry Project

Per Arne Wang, Norsk Hydro

97Q-BG3.DOC

CAPP/N.3

18 April 1997

9063 Bee Caves Road, AustinTexas 78733-6201, U.S.A.Tel: 1-512-263-2101

Tamworth Road, HertfordSG13 7DG, England

_ Research CentrePorsgrunnREPORT

Classification: Internal

Title:

Flexible pipes.

Permeation of methane, carbon dioxide and water through Tefzel ETFE.

Experiments 1996.

Author(s):

Per Arne Wang

To:

T. Andersen, HRE

Copy:

Dr. Bob Campion, MERL

M. Tystad, T&U VK

B. Moursund, HRE

C. Hansteen, HRE

Reg./circ.

Front page:

K. Harg, HRE

R. Steen Hansen, HRE

F. Ellingsen, HRE

Date: 1997-04-18

File no.: 972.61

ProJ.no.: R23965.200

Arch. per.: Permanent

Doc.no.:

Pages/App.:

Ref.:

97Q_BG3.DOC

6/4

PAW:(VN)

Keywords:

PERMEABILITET VANN

METAN ETFE

KARBONDIOKSYD FLEKSIBLE ROR

Approved project [Approved project

leader: ] respo_

Guidelines for approval are descdbed in the Research Centre Quality Handbook (HRE-I-1)

Summary/Concluslon:

The permeation of a mixture of CH 4 and CO 2 (97% CH 4 and 3% CO 2) saturated with water

vapour through Tefzel has been studied at 95°C and 25 and 50 bars. Tefzel is the Du Pont

trademark of an ETFE (ethylenetetrafluorethylene) which is a copolymer of ethylene and

tetrafluorethylene. This material might be used as inner plastic lining of flexible pipes.

The permeability coefficients (P in cm2/sobar) for CH 4, CO 2 and water at the various

temperatures are found to be:

Permeability, (cm2/s.bar)

CH4 CO2 H203.65E-08 2.09E-07 1.62E-06

For methane and carbon dioxide, the permeability of Tefzel is higher than the deplasticized

PVDF (Polyvinylidenefluoride), but lower than the plasticized PVDF. For water, the situation

seems to be the other way round; Tefzel has a lower permeability than deplasticized PVDF.

Whether the permeability tests on Tefzel at higher temperatures and pressures will be pursued

or not, will be considered by the steering committee of the CAPP project in May.

Research CentreInternal

Page 2 of 6

. Introduction.

This document describes the permeation test of Tefzel ETFE (Ethylene Tetra Fluor

Ethylene) performed in 1996.

u Experimental and testing parameters.

The experiments are performed with a new pressure cell. One advantage of this cell

is the possibility of testing on various pipe dimensions, up to 90 mm OD. In principle

though, the same experimental set-up as described in the previous report was used in

these measurements (/1/,/7/). A drawing of this new cell can be found in App. 4.

The permeation is measured from a pressurised test gas inside a sealed pipe section.

The sample pressure is balanced with argon on the outside. The argon gas flushes

the outside and brings the permeated gases to a gas chromatograph and a moisture

detector for analysis. The saturation of the gas mixtures with water was performed at

the actual temperature.

The test series that were planned to be performed on Tefzel are shown in Table 1.

Due to system- and component failures, fewer test runs are performed in 1996 than

planned. Thus, there are no results ready yet for other pressures and temperaturesthan described in the table.

The CAPP steering committee will decide (May 1997) whether the tests on Tefzel

will be pursued according to plan or not.

Table 1. Overview of the planned testing parameters. One can see that only

the 25 and 50 bar at 95cC testing is finished. The gas mixture is

fluid B according to the CAPP nomenclature.

Gas mixture

(All saturated with water)

97% CH4/3% CO z

97% CH4/3% CO 2

97% CH4/3% CO z

97% CH4/3% CO z

Temperature

(oc)70

Pressure

25, 50, 75, 100, 120

95 25,50

95 75,100,120

120 25,50,75,100,120

Status

Pend!ng

Finished

Pending

Pending

The permeation rates and permeability coefficient were determined as described in

the previous reports/1/,/71. The permeability coefficients were calculated by using

equation 1, which applies to a cylinder.

P = q In(K) (Equation 1)t 2IrL(pl-p2 )

q/t = permeation rate, p_ and P2 are the high and low (inside and outside) partial

pressures. The dimension of the permeability coefficient is cmZ/sobar.

Research CentreInternal

Page 3 of 6

Results.

Methane and carbon dioxide.

The amount of each gas permeated through the sample and associated permeability

coefficients for methane and carbon dioxide at each pressure are given in App. 2.

A graphical presentation of permeation rates and concentrations as a function of time

can be found in App. 3. Table 2 below shows a summary of permeability data for the

gases.

On the 50 bar run, the flow of argon was increased from 20 to 50 ml/min in order to

improve the stability of the analysis. The effect of this was that the concentrations

increased, and thereby a higher permeability rate was found. However, the increment is

insignificant in the scales used for evaluation. Details can be seen on the concentration

and permeation charts in App. 3. No explanation could be found yet on this effect.

Table 2. Summary table for methane and carbon dioxide.

Run

95°C 25 bar95°C 50 bar I95°C 50 bar II

Average

Permeability

(cm2/s-bar)Methane C022.99E-08 1.82E-073.51E-08 1.94E-074.45E-08 2.50E-07

3.65E-08 2.09E-07

For comparative purposes, the average Tefzel permeability is plotted together with

the permeabilities of other materials previously tested (Figures 1-2). One can see that

for this particular temperature and pressures, the permeability of carbon dioxide and

methane through Tefzel ETFE is lower than through Solef and Coflon PVDF.

Research CentreInternal

Page 4 of 6

m"E.2

E.=

Permeability coefficients for carbondioxide.

1.0E-05

1.0E-06 =L 9 °01 !,o-- _L _ .... -- i

.J

0.0026 0.0027 0.0028 0.0029 0.003

1.0E-07

1.0E-08

0.0024 0.0025

1/T (l/K)

--Coflon DP • CoflonNHresult A Solef 1015/0078 DP• Solef 1015/0078 P • Tefzel

Figure 1. The figure shows the permeability coefficient of CO 2 through TefzeI at 95

cC. Coefficients for plasticized and deplasticized PVDF are also shown.

The Coflexip data (Coflon DP) are from/2�and the SoIvay data are from

/3/.

Permeability coefficients for methane.

1.0E-06m

.2

i E 1.0E-08

&

n

i'95°C I -_' t

t'°°cl---

++__

1.0E-09

0.0024 0.0025 0.0026 0.0027 0.0028 0.0329 0.003

1/T (1/10

--Coflon DP. • Coflon NH results ,_, Solef 1015/0078 DP.

• Soef 1015/0078 P. • Tefzel

Figure 2. Permeability coefficient of methane through Tefzel at 95 cC. Coefficients

for permeation of CH 4 through plasticized and deplasticized PVDF are

also shown. The Coflexip data (Coflon DP) are from/2�and the Solvay

data are from/3/.

Research CentreInternal

Page 5 of 6

3.2 Water permeation.

Details regarding the computation of water permeability, and a graphical presentation

of permeation rate of water, can be found in App. 1 and 3 respectively. Although

there is a relative small change, the water permeability is also in this case increased

when the flow rate of argon is increased. Table 3 summarises the permeabilitycoefficient for the various conditions.

Table 3. Summary table for water.

Run Permeability

(cmVs.bar)95°C 25 bar 1.48E-06

95°C 50 bar I 1.47E-0695°C 50 bar II 1.92E-06

Average 1.62E-06

The permeability coefficient is plotted together with previous data on PVDF in

Figure 3. From the figure, one can see that the permeability of water trough Tefzel is

lower than trough deplasticized PVDF.

Permeability coefficients for water

1.0E-04 ii r ' _1: _:' III

iiiiiii ii n L I1.0E-06

0.0024 0.0025 0.0026 0.0027 0.0028 0.0029 0.003

1/1" (l/K)

= Coflon NH results & Solef 1015/0078 DP mTefzel • PVDF ref. Ausimont

Figure 3. Permeability coefficient of water through Tefzel at 95 C. The coefficients

for permeation of water as a function of temperature through

deplasticized Coflon is also shown.

Porsgrunn, 1997-04-18

Per Arne Wa

Research CentreInternal

Page 6 of 6

w References

Ill J. I. Skar, "Permeabilty of methane and carbon dioxide through plasticized

polyamide (PA 11) and polyvinylidenefluoride (PVDF). Norsk Hydro Doc. No.

94R_DS6, 1994-09-02. (CAPP/N.1)

/2/ B. Radenac, "COFLON - A material for inner lining of Coflexip flexible pipe".

Coflexip report no. 93.05.06, September 1993.

/3/ "Solef PVDF for offshore applications". Presentation in Brussel by Solvay,

January 31. 1996.

/4/ Design Guide, "HALAR ECTFE" Ausimont USA. Inc. 1992.

/5/ G.J. Morgan and B. Campion, CAPP/M.4 Rev. B.

/6/ Giddings, Myers, McLaren, Keller, Science 162, 67 - 73 (October 1968).

/7/ Skar, Jan Ivar; Hansteen, Christoffer : "Flexible Pipes. Permeation of methane,

carbon dioxide and water trough polyvinylidenfluoride"; Report HRE;

96Q_DC8.DOC; File 972.61.

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Appendix 4

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