GASTEC QA Approval Requirement 197 197.pdf · COMPANY PROFILE GASTEC NV, Centre of Gas Technology,...

September 2000

GASTEC QA Approval Requirement 197

Corrugated stainless steel piping systems for indoor gas installations

COMPANY PROFILE

GASTEC NV, Centre of Gas Technology, is a technological support company with an international

reputation in the field of gas technology. Gastec is engaged in research and development, consultancy,

engineering, certification and training. Its customers include energy distribution companies, appliance and

distribution equipment manufacturers, installers and contractors. Gastec also works for fellow researchers

and institutions with a need for natural gas expertise. Gastec has about 350 employees in its subsidiaries

in the Netherlands, Italy, the UK and Bulgaria.

The services include advice about the procurement and sales of gas and the distribution of gas and heat.

In addition, Gastec provides know-how about energy utilisations in general and natural gas utilisations in

particular. Gastec tests and certifies gas technology products and quality management systems. Finally, it

develops and organises specialist courses and seminars.

GASTEC NV

Centre of Gas Technology

P.O. Box 137, 7300 AC Apeldoorn

Wilmersdorf 50, 7327 AC Apeldoorn, The Netherlands

Tel.: +31 555 393 393

Fax: +31 555 393 494

E-mail: [email protected]

© 2004, GASTEC NV, Apeldoorn

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or

published, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise,

without the prior written permission of GASTEC NV.

CONTENTS

PREFACE .....................................................................................................5

1. GENERAL.....................................................................................................6 1.1 Scope ............................................................................................................6

1.2 Pipe-fitting combinations ...............................................................................6

1.3 References ....................................................................................................6

2. CONSTRUCTIONAL REQUIREMENTS ......................................................8 2.1 Corrugated stainless steel pipe.....................................................................8

2.1.1 Dimensions and admissible tolerances.........................................................8

2.2 Coating ..........................................................................................................8

2.3 Tensile-resistant fittings ................................................................................8

2.3.1 Dimensions....................................................................................................9

2.3.2 Connections ..................................................................................................9

3. MATERIAL..................................................................................................11 3.1 Corrugated stainless steel pipe...................................................................11

3.2 Fittings.........................................................................................................11

3.2.1 Copper alloys ..............................................................................................11

3.2.2 Stainless steel .............................................................................................12

3.2.3 Rubber sealings ..........................................................................................12

3.2.4 Other sealing materials ...............................................................................12

4. PERFORMANCE REQUIREMENTS..........................................................13 4.1 Soundness of the connections at internal pressure....................................13

4.2 Resistance to pressure load .......................................................................13

4.3 Bending resistance of the pipe without coating ..........................................13

4.4 Bending resistance of the coated pipe........................................................13

4.5 Resistance to drop impact of the corrugated stainless steel pipe ..............14

4.6 Resistance to drop impact of the coating....................................................14

4.7 Resistance to tensile load ...........................................................................14

4.8 Pressure loss pipe.......................................................................................14

4.9 Pressure loss system..................................................................................14

4.10 Repeated assembly ....................................................................................15

4.11 Resistance to corrosion...............................................................................15

3

5. TEST METHODS ........................................................................................16 5.1 General........................................................................................................16

5.2 Soundness of the connections at internal pressure....................................16

5.3 Resistance to pressure load .......................................................................17

5.4 Bending resistance of the pipe without coating ..........................................17

5.5 Bending resistance of the coated pipe........................................................19

5.6 Resistance to drop impact of the corrugated stainless steel pipe ..............19

5.7 Resistance to drop impact of the coating....................................................21

5.8 Resistance to tensile load ...........................................................................21

5.9 Pressure loss...............................................................................................22

5.10 Repeated assembly ....................................................................................24

5.11 Resistance to corrosion...............................................................................24

6. MARKING AND INSTRUCTIONS ..............................................................26 6.1 Pipe marking ...............................................................................................26

6.2 Fitting marking.............................................................................................26

6.3 Instructions ..................................................................................................26

4

PREFACE

In the present paper no requirements are laid down for the permeability of coating

materials. Further research on this field is necessary. Requirements on permeability

may be added in future.

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1. GENERAL

1.1 Scope

The present approval requirements relate to plastic-coated flexible and pliable

corrugated stainless steel pipes and matching tensile-resistant fittings for indoor gas

installations.

The nominal internal diameter of the corrugated pipes is 10 through 28 mm.

The maximum admissible operating pressure is 200 mbar.

The system is intended for indoor use at operating temperatures ranging from

-20 °C to +60 °C.

1.2 Pipe-fitting combinations

All combinations of pipes and fittings mentioned in the manufacturer’s instructions

must comply with all requirements in the present paper.

1.3 References

In the present requirements reference is made to documents included in the list

below. Unless otherwise stated the latest editions, including any appendices and

revisions, apply.

NEN 2541 Fittings and connections for gas conduits

NEN 2542 Fittings and connections with outside thread for gas conduits

NEN 2543 Fittings for soldering for gas conduits

NEN 2544 Coupling nuts for fittings for gas and water conduits

NEN 2545 Packing rings for fittings for gas conduits

NEN 3084 Gasmeters with diaphragms; Type G 2.5, G 4, G 6 and G 10

EN 1982 Copper and copper alloys - Ingots and castings

DIN 17660 Wrought copper alloys; copper-zinc alloys; (brass); (special brass);

composition.

EN 549 Rubber materials for seals and diaphragms for gas appliances and

gas equipment

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EN 10088-2 Stainless steels. Part 2: Technical delivery conditions for sheet /

plate and strip for general purposes.

ISO 7 Pipe threads where pressure-tight joints are made on the threads.

Dimensions, tolerances and designation

ISO 272 Fasteners; Widths across flats for hexagon products


Fittings, couplers and parts for soldered and screwed connections


Squeeze fittings for copper pipe


Metal clamp fittings for galvanised steel precision pipes


Clamp fittings for the connection of copper pipes to steel pipes

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2. CONSTRUCTIONAL REQUIREMENTS

2.1 Corrugated stainless steel pipe

The surface of the stainless steel pipe shall be smooth both internally and externally

and shall not show any mill scale, loose oxide layers or acid residues.

The pipe ends shall be smooth and square.

2.1.1 Dimensions and admissible tolerances

No requirements are laid down for the dimensions of the coated corrugated stainless

steel pipe.

The dimensions and the admissible tolerances shall be in accordance with the

manufacturer’s specifications and shall be given on drawings.

2.2 Coating

The corrugated stainless steel pipe shall have a yellow coating which protects the

material against the impact of commonly used building materials such as concrete,

mortar, plaster, etc. The coating material shall not have a detrimental effect on the

corrugated stainless steel pipe. The manufacturer shall submit a written confirmation

of the above properties.

The coating shall be free from pores.

2.3 Tensile-resistant fittings

The surfaces of the tensile-resistant fittings shall be smooth both internally and

externally and shall show no blisters, pitting, notches or other defects.

Sharp transitions that may have a notching effect shall be avoided.

In fitting the tensile-resistant fitting, the stainless steel pipe and in particular the

welded seam shall not tear.

Fitting tools and aids shall not damage the pipe and tensile-resistant fitting.

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2.3.1 Dimensions

No requirements are laid down for the dimensions of the connection of the tensile-

resistant fitting with the corrugated stainless steel pipe.

The dimensions of the tensile-resistant fittings and the admissible tolerances shall be

in accordance with the manufacturer’s specifications and shall be given on drawings.

If the fitting features any spanner faces, these shall comply with ISO 272. Moreover,

the height of the spanner face shall comply with the values given in Table 1.

Spanner width

(in mm)

up to

22

24 and 27 30 and 34 36 and 41 46 and 50 55, 60, 65,

70 and 75

Minimum height of

spanner face (in mm)

4 5 6 7 8 9

Table A: Heights of spanner faces

The wall thickness of the body of the fittings and nuts shall at least comply with the

values given in Table 2.

Pipe diameter

DN (in mm)

Minimum wall thickness

(in mm)

Castings Other

up to and included

10

1.1 1.1

>10 through 12 1.2 1.2

>12 through 15 1.2 1.2

>15 through 22 1.8 1.5

>22 through 28 1.8 1.6

Table B: Minimum wall thickness

2.3.2 Connections

It is permitted to provide one end of the tensile-resistant fitting with one of the

following connections. The connection shall comply with the relevant requirements or

standards.

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- Gassound threads according to ISO 7 type R or Rp. The threads shall be smooth

and have rounded crests and roots.

- Compression fittings for copper pipe connections according to GASTEC QA

Approval Requirement 35

- Metal clamp fittings for galvanised steel precision pipes according to GASTEC

QA Approval Requirement 68

- Fittings, couplers and parts for soldered and screwed connections according to


- Union couplers according to NEN 2541, NEN 2542, NEN 2543, NEN 2544, NEN

2545 and NEN 3084

- Press fittings according to GASTEC QA Approval Requirement 186.

Other connections are permitted after consultation of the approval authority.

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3. MATERIAL

3.1 Corrugated stainless steel pipe

The pipe shall be made of a stainless steel grade corresponding to

- grade X5 CrNi 18-10; material no. 1,4301 according to EN 10088-2

- grade X2 CrNiMo 17-12-2; material no. 1,4404 according to EN 10088-2

- grade X6 CrNiTi 18-10; material no. 1.4541 according to EN 10088-2

- grade X6 CrNiMoTi 17-12-2; material no. 1.4571 according to EN 10088-2

The manufacturer shall submit a written confirmation of the above properties.

3.2 Fittings

The component parts of joints and couplings shall be made of the materials below.

Any materials used in joints and couplings shall not adversely affect each other.

3.2.1 Copper alloys

Any copper alloys applied shall be selected from:

- wrought brass CU-Zn 39 Pb3 according to DIN 17660

- wrought brass CU-Zn 40 Pb2 according to DIN 17660

- wrought brass CU-Zn 36 Pb1.5 according to DIN 17660

- wrought brass G C4-Zn 35 according to DIN 17660

- wrought brass G C4-Sn 5 Pb5 Zn5 according to DIN 1709

Or copper alloys of comparable quality.


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3.2.2 Stainless steel

Any stainless steel materials applied shall be selected from:

- grade X5 CrNi 18-10; material no. 1,4301 according to EN 10088-2




- grade X6 CrNiTi 18-10; material no. 1.4541 according to EN 10088-2

- grade X6 CrNiMoTi 17-12-2; material no. 1.4571 according to EN 10088-2

- grade G-XS CrNiMoNb 18-10;material no. 1.4581 according to EN 10088-2


3.2.3 Rubber sealings

If rubber seals are used, they shall comply with EN 549. The seals shall be minimally

of temperature class A2 according to EN 549.

3.2.4 Other sealing materials

Other sealing materials used, shall be resistant to gas.

The manufacturer shall submit a written confirmation of the above property.

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4. PERFORMANCE REQUIREMENTS

4.1 Soundness of the connections at internal pressure

After assembly, the pipe and fitting shall be capable of withstanding an internal air

pressure increasing from 0 bar to 1,5 bar at temperatures of -20 ºC and +60 ºC for a

period of 25 min. without showing any leakage.

The tests shall be carried out according to section 5.2.

4.2 Resistance to pressure load

After assembly, the pipe and fitting shall be capable of withstanding an internal water

pressure of 16 bar without showing any cracks or leakage.

This test shall be carried out according to section 5.3.

4.3 Bending resistance of the pipe without coating

After removal of the coating, it shall be possible to bend the corrugated stainless

steel pipe 10 times through an angle of 180° and the corrugated stainless steel pipe

and fittings shall show no leakage or kinks.


4.4 Bending resistance of the coated pipe

It shall be possible to bend the coated corrugated stainless steel pipe 5 times

through an angle of 180° and the coating shall show no pores.


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4.5 Resistance to drop impact of the corrugated stainless steel pipe

The corrugated stainless steel pipe shall be capable of withstanding a drop impact

caused by a striker falling perpendicular to the centre line of the pipe. Pipe and fitting

will show no leakage.


4.6 Resistance to drop impact of the coating

The coating of the corrugated stainless steel pipe shall be capable of withstanding a

drop impact caused by a striker falling perpendicular to the centre line of the pipe.

The coating shall show no pores


4.7 Resistance to tensile load

After assembly, the pipe and fitting shall be capable of withstanding a longitudinally

applied tensile load of 140 N per mm of internal diameter and an internal pressure of

300 mbar without showing any cracks or leakage.


4.8 Pressure loss pipe

The manufacturer shall provide a curve describing the relationship between airflow

and pressure loss per meter pipe. The curve shall cover pressure losses per meter

pipe ranging from 0 to 1.00 mbar per meter. The airflow shall be expressed in

standard cubic meters air (1013 mbar, 15°C) per hour.

The pressure losses measured by the approval authority shall be smaller than or

equal to the values measured by the manufacturer.

The measurements by the approval authority shall be carried out according to

section 5.9.

4.9 Pressure loss system

The manufacturer shall provide a curve describing the relationship between airflow

and pressure loss for a pipe system containing of a straight fitting with gassound

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tread according to ISO 7 type R, one meter pipe and an elbow 90° fitting with

gassound tread according to ISO 7 type R. The airflow shall be expressed in

standard cubic meters air (1013 mbar, 15°C) per hour.

The curve shall cover pressure losses for this system ranging from 0 to 1.00 mbar

per meter. The pressure losses measured by the approval authority shall be smaller

than or equal to the values measured by the manufacturer.

The measurements by the approval authority shall be carried out according to

section 5.9.

4.10 Repeated assembly

If ,according to the assembly instructions, the connection is fit for repeated assembly,

it shall, after being assembled and disassembled 10 times, comply with the

soundness requirements specified in 4.1.


4.11 Resistance to corrosion

Tubing and fitting assemblies shall show no leakage after exposure to a corrosive

environment.


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5. TEST METHODS

5.1 General

The fittings shall be assembled in accordance with the manufacturer’s assembly

instructions. Tools used for assembling or disassembling fittings and pipes shall be

provided to the testing authority.

Unless otherwise stated, all measurements shall be carried out at room temperature

23 °C ± 5°C.

The test shall be carried out three times, unless otherwise stated, using a

representative selection of the various sizes.

Unless otherwise stated, all temperatures shall be measured with an uncertainty of ±

0,5°C.

Unless otherwise stated, all pressure measurements shall be carried out with a

measuring error of 5% Rdg.

The specified dimensions shall be checked using measuring equipment that is fit for

its purpose and has a measuring error not exceeding 0.1 mm and angles with a

measuring error not exceeding 30'.

5.2 Soundness of the connections at internal pressure

For this test, a straight tensile-resistant fitting shall be connected to both ends of a

corrugated stainless steel pipe. The coating shall be removed. If the coating is

needed for the soundness of the connection of the fitting to the pipe, the coating shall

not be removed at the fitting. The distance between the fittings shall be at least 300

mm.

If an other non-metallic sealing material is used than described in section 3.2.3, the

connection shall be conditioned in water for 1000 h at 80°C. Otherwise no

conditioning is needed.

Immerse the test specimens horizontally to 100 ± 50 mm in a vessel containing a

fluid with a temperature of -20 °C ± 3 °C and condition it for at least 1 h.

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Expose the test specimens to an internal air pressure increasing from 0 bar to 1,5 ±

0,05 bar for a period of 25 min. The pipe and fittings are checked for leakage.

Repeat the test at 60 °C ± 3 °C.

5.3 Resistance to pressure load

For this test, a straight tensile-resistant fitting is connected to both ends of a



not be removed at the fitting. The distance between the fittings shall be at least 300

mm.

The corrugated stainless steel pipe is connected to a hydraulic system on one side

and sealed off on the other side.

The pipe is fully filled with water; making sure that the pipe is properly vented. A

water pressure of 16.0 ± 0.5 bar is exerted to the system and maintained for 300 s.

The pipe meets the requirement if no cracks or leakage are visible.

After completion of this test, the pipe and fittings shall still be gastight in accordance

with 4.1. In contrast to 4.1, the gastightness shall only be checked at a temperature

of 23 ± 5 °C.

5.4 Bending resistance of the pipe without coating

For this test, a straight tensile-resistant fitting shall be connected to both ends of a



not be removed at the fitting. The distance between the fittings shall be at least 300 ±

100 mm.

One of the fittings is connected to a test apparatus in such a way that the top of

fitting A is at equal height with the bottom of the arbors D as shown in figure A. In

case of a longitudinal weld the orientation of the corrugated stainless steel pipe shall

be such that the weld touches one of the arbors. The surface of the arbors shall be

smooth. The diameter of the arbors D shall be in accordance with the table C below.

Corrugated pipe internal diameter, DN in mm Arbor diameter in mm

10 through 12

>12 through 15

25

30

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>15 through 22

>22 through 28

45

50

Table C: Arbor diameters

The distance between the vertical centre lines of the arbors shall be such that the

arbors come as close as possible to the corrugation of the pipe without clamping it.

α

Figure A: Principle of bending test

A = fitting

B = starting position at the beginning of the test

C = position after one bending

D = arbor

Bend the pipe in the starting position depicted by the full lines and subsequently

bend the free end from position B to position C via the dash-dotted circular arch.

Angle α between positions B and C shall be 180 ± 10°. Moving from B to C is

regarded as one bending. Bend the pipe back from position C to position B. Moving

from C to B is regarded as one bending as well. Each bending is carried out at a

uniform speed in approximately 10 s. during each bending the pipe shall touch the

arbor through

90 .-10+0° °

° The corrugated stainless steel pipe shall be bent 10 times.

Only in case of a longitudinal weld, take a new sample. The orientation of the

corrugated stainless steel pipe shall now be such that the weld is in the middle of the

arbors. Again, the corrugated stainless steel pipe shall be bent 10 times.

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After the bending the corrugated stainless steel pipe and fittings shall show no

damage. The pipe and fittings shall still be gastight in accordance with 4.1. In

contrast to 4.1, the gastightness shall only be checked at a temperature of 23 ± 5 °C.

5.5 Bending resistance of the coated pipe

For this test, a straight tensile-resistant fitting shall be connected to a coated

corrugated stainless steel pipe. The free length of the corrugated pipe shall be at

least 300 ± 100 mm.

The fitting is connected to a test apparatus as shown in figure A.

In contrast to figure 1, this time there shall be a vertical spacing of 50 mm between

the fixed fitting and the arbors. The surface of the arbors shall be smooth. The

diameter of the arbors D shall be in accordance with the table 3.

The distance between the vertical centre lines of the arbors shall be such that the

arbors come as close as possible to the coating of the corrugated pipe without

clamping it.

Bend the pipe in the starting position depicted in figure 1 by the full lines and

subsequently bend the free end from position B to position C via the dash-dotted

circular arch. Angle α between positions B and C shall be 180 ± 10°. Moving from B

to C is regarded as one bending. Bend the pipe back from position C to position B.

Moving from C to B is regarded as one bending as well. Each bending is carried out

at a uniform speed in approximately 10 s. during each bending the pipe shall touch

the arbor through 90 .-10+0° °

°

After 5 bendings, the coating of the corrugated stainless steel pipe shall show no

pores. The absence of pores shall be determined using a holiday detector. The

detector shall be controllable and be able to supply such a voltage that the locally

adjusted spark length corresponds to a base voltage of 5.0 ± 0.5 kV plus 5.0 ± 0.5 kV

per mm of nominal layer thickness according the specification of the manufacturer.

5.6 Resistance to drop impact of the corrugated stainless steel pipe

For this test, a coated corrugated stainless steel pipe is used with matching straight

tensile-resistant fittings on both ends. The distance between the fittings shall be at

least 300 mm. The coating shall be removed. If the coating is needed for the

19

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soundness of the connection of the fitting to the pipe, the coating shall not be

removed at the fitting.

Place the stainless steel pipe stress-free on a flat horizontal plane.

In case of a longitudinal weld, the orientation of the pipe shall be such that the weld

is at equal height to the centreline of the pipe.

For this test a falling weight testing machine incorporating the following basic

components is used:

• main frame, with guide rails or a guiding tube fixed in the vertical position to

accommodate a striker and means to release it to fall vertically and freely. When

calibrated, the speed of the striker at the moment of hitting the steel block shall be

not less than 95% of the theoretical speed;

• striker, having a flat round striking surface with a diameter of 25 ± 1 mm and a

weight of 10.0 ± 0.2 kgf.

The impact shall be evenly distributed over the pipe over a length of 70 mm. This

length of 70 mm is realised by placing a rectangular steel block horizontally upon the

pipe. The distance between the steel block and the fitting shall be 10 ± 1 mm. The

dimensions of the block shall be 70.0 ± 0.1 mm x 70.0 ± 0.1 mm x 10.0 ± 0.1 mm.

The two ribs of the block touching the pipe shall be rounded off with a radius of

2.0 ± 0.5 mm. The steel block shall be kept in position without significantly

influencing the impact exerted on the pipe. From a height according to table 4

(calculated up to the horizontal plane), drop the striker on the steel block.

Corrugated pipe inside

diameter DN (mm)

Falling height in mm

±5 mm

10 through 12 400

>12 through 15 600

>15 through 22 800

> 22 through 28 1,000

Table 4 : Falling heights

In case of a longitudinal weld, the other end of the pipe is tested as well. This time

the orientation of the pipe shall be such that the weld is facing the steel block.

The pipe meets the requirement if no cracks or failures are visible and if in addition

the pipe and fitting are still gastight in accordance with 4.1 In contrast to 4.1 the

gastightness shall only be checked at a temperature of 23 ± 5 °C.

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5.7 Resistance to drop impact of the coating

For this test, a coated corrugated stainless steel pipe is used with a length of ± 500

mm.

Place the coated stainless steel pipe stress-free on a support consisting of a 120°

vee-block of length at least 200 mm, positioned so that the point of impact of the

falling weight is in the axis of the vee-block or not more than 2,5 mm from this axis.

For this test a falling weight testing machine incorporating the following basic

components is used:

• main frame, with guide rails or a guiding tube fixed in the vertical position to

accommodate a striker and means to release it to fall vertically and freely. When

calibrated, the speed of the striker at the moment of hitting the steel block shall be

not less than 95% of the theoretical speed;

• striker, having a hemispherical striking surface of 25 ± 1 mm diameter and a

weight of 250 ± 5 gr.

Condition the sample during 30 minutes at a temperature of 0 ± 2°C during 2 hours

in air.

During the testing, the sample shall not be outside the conditioning environment for

longer than 10 seconds shall. After this reconditioning for a period of 10 minutes is

necessary.

Put the sample on the vee-block and drop the striker from a falling height of 500 ± 5

mm. Carry out 10 separate impacts on sites at least 30 mm apart.

Test the impact sites within 30 seconds after impact with a high voltage holiday

detector. The detector shall be controllable and be able to supply such a voltage that

the locally adjusted spark length corresponds to a base voltage of 5.0 ± 0.5 kV plus

5.0 ± 0.5 kV per mm of the minimum layer thickness stated by the manufacturer.

5.8 Resistance to tensile load

For this test, a corrugated stainless steel pipe is used with matching straight tensile-

resistant fittings on both ends. The distance between the fittings shall be at least 300

mm. The coating shall be removed. If the coating is needed for the soundness of the

connection of the fitting to the pipe, the coating shall not be removed at the fitting.

The pipe is exposed to a constant internal pressure of 300 ± 10 mbar. A tensile

testing machine is used to exert for 300 s a tensile force corresponding to 140 ± 10

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N per mm of internal pipe diameter. The tensile force shall be measured with an

uncertainty of 5% Rdg.

The pipe shall be horizontally immersed to 100 ± 50 mm in water during the period in

which the tensile load is applied.

The pipe meets the requirement if during this 300 s period in which the tensile force

is applied no air bubbles are visible.

5.9 Pressure loss

The pressure losses measured by the approval authority shall be smaller than or

equal to the values measured by the manufacturer. The approval authority shall

measure pressure losses smaller than 2.00 mbar with a maximum measuring error

of 0.04 mbar. Pressure losses larger than 2.00 mbar shall be measured with a

maximum measuring error of 2% Rdg. Airflow’s smaller than 0.5 m3/hr shall be

measured with a maximum measuring error of 0.025 m3/hr. Airflow’s larger than 0.5

m3/hr shall be measured with a maximum measuring error of 5% Rdg.

The approval authority shall use the configuration in figure B for the measurement of

pressure losses.

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A A

Figure B: Principle of pressure loss test

Detail of damping tube A

For measuring the pressure loss of the pipe the total length between the connections

of the differential pressure gauge shall be 3.0 ± 0.1 m. The length between the

connections shall be measured with a maximum measuring error of 0.01 m. Bends in

the corrugated stainless steel pipe shall be avoided. The pressure loss per meter

pipe is calculated by dividing the measured pressure loss by three.

For measuring the pressure loss of the system the total length of the pipe between

the fittings shall be 1.0 ± 0.05 m. The fittings shall have a gassound thread according

to ISO 7 type R. The fittings shall be connected to the differential pressure gauges.

The length between the fittings shall be measured with a maximum measuring error

of 0.01 m. Bends in the corrugated stainless steel pipe shall be avoided.

Air of room temperature is pumped through the pipe. The overpressure of the air at

inlet, measured by the inlet pressure gauge, shall be 25.0 ± 1.0 mbar.

1 = inlet pressure regulator

2 = inlet pressure gauge

3 = differential pressure gauge

4 = test specimen

5 = flow meter

6 = control valve at outlet

Nominal size Internal diameter, d (mm) 1/8 6 1/4 9 3/8 13 1/2 16 3/4 22

1 28

11/4 35

11/2 41

23

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5.10 Repeated assembly

Disassemble and assemble the test specimens 10 times according to the

manufacturer instructions. Check if the requirements of 4.1 are met.

5.11 Resistance to corrosion

For this test, two coated corrugated stainless steel pipes are used with matching

straight tensile-resistant fittings on both ends. The ends shall be sealed gaslight. The

total length shall be at least 300 mm. The coating shall be removed. After removal of

the coating the corrugated stainless steel pipe shall be free of lime rests and grease.

If the coating is needed for the soundness of the connection of the fitting to the pipe,

the coating shall not be removed at the fitting.

The two test assemblies shall be immersed for 2/3 of its length in a solution by weight

of 20 percent sodium chloride, one percent sodium nitrate and 79 percent distilled

water. The temperature of the solution shall be raised to 100±2°C at atmospheric

pressure and maintained at that temperature for 14 hours. All boil-off vapour shall be

condensed and returned to the test solution.

After 14 hours in the boiling test solution, the test assemblies shall be removed from

the solution and cooled to room temperature. The assemblies shall then be

deformed according figure 4 from A to B. The bending shall take place at the

immersed part of the pipe. One assembly shall be bend with the weld on the inside of

the curve (position 1), the other assembly with the weld on the outside of the curve

(position 2).

After completion of this test, the pipe and fittings shall still be gastight in accordance

with 4.1. In contrast to 4.1, the gastightness shall only be checked at a temperature

of 23 ± 5 °C.

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Figure C: Bending test after corrosion

position 2

position 1

25

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6. MARKING AND INSTRUCTIONS

6.1 Pipe marking

The pipe shall be clearly and indelibly marked at intervals of not more than 5 m with:

- the GASTEC QA mark;

- the manufacturer’s mark;

- the DN of the pipe;

- the year and date of production (or a code representing these data).

6.2 Fitting marking

The fittings shall be clearly and indelibly marked with:

- the GASTEC QA mark;

- the manufacturer’s mark;

- the mating dimension of the corresponding pipes.

6.3 Instructions

The manufacturer shall provide in clear Dutch the following data:

• clear assembly instructions;

• a confirmation stating which combination of coated corrugated stainless steel pipe

and tensile resistant fitting can be used;

• the fitness for repeated assembly of the fitting;

• minimum bending radius (minimum allowable bending radius is equal to the

diameter given in table 3);

• a statement that during installation the corrugated stainless steel pipe shall not be

permanently elongated in longitudinal direction;

• a curve describing the relation between airflow and pressure loss per meter pipe;

• a curve describing the relation between airflow and pressure loss of a pipe

system containing of a straight fitting, one meter pipe and an elbow 90° fitting.

Date post:	03-Jul-2020
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GASTEC QA Approval Requirement 197 197.pdf · COMPANY PROFILE GASTEC NV, Centre of Gas Technology,...

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