Copper tubes, as we are all aware, have

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1 CRITICAL REQUIREMENTS OF COPPER TUBES & FITTINGS FOR MEDICAL GAS PIPELINE SYSTEMS (MGPS) COVER STORY GURMIT SINGH ARORA Copper tubes, as we are all aware, have various applications including Airconditioning & Refrigeration, Deep Freezers, Bottle Coolers, Visi Coolers, Heat Exchangers, Water Geysers, Solar Heaters, Oil Coolers, Vapour Absorption Machine, etc. i.e. for various heat transfer/cooling applications. Copper tubes - Deoxidised High Residual Phosphorus Grade (DHP Grade) Copper tubes are now also widely used for plumbing since the last 70 years and for conveying both water & gases. One such application, which is the most critical in nature, is for Medical Gas application. The copper medical gas system in any hospital plays a vital role in the delivery of special gases such as oxygen, nitrogen, and nitrous oxide, as well as medical, vacuum and compressed air services to the patient s beds and to operating rooms. The tubes also take away scavenger gases back from the O.T.s. The interior surface of the medical gas system must be meticulously clean, and therefore, it is no surprise that copper tube is the material of choice for this application. In fact, copper is the only material permitted by codes for medical gas distribution lines. Copper tubes for medical gas lines are specially cleaned and are supplied to the installer capped or plugged. Apart from the obvious reasons to ensure the cleanliness of copper tubes for these applications, oxygen under pressure, for example; Medical Gas for Hospitals Piped Medical Gas in Hospitals 4 / September 2017 / Indian Plumbing Today

2 may cause spontaneous combustion of some organic oils which are residues of lubricating oils used during the manufacture of copper pipes and also pose a danger to the medical safety of patients. Copper tube is chosen for surgical vacuum systems, because of its resistance to corrosion and easily-cleaned internal surfaces and, when in use, detergents are periodically passed through to purge and sterilize the lines. This is because both copper tubes and fittings are the only solution for supplying medical gases with proper safety and cleanliness requirements conforming to various specifications. Safety standards for copper and other positive pressure medical gases require the use of copper tubes with special cleanliness. Copper tubes for medical gas line are furnished suitably degreased and inner diameter cleaned and capped or plugged. It is very important to take care to prevent contamination of the system when the caps or plugs of these tubes are removed while undergoing installation. The installer must satisfy himself and the inspection department, that the cleanliness requirement of desired codes is met. Copper tubes for Medical gas applications are specified under various standards. Since we do not have an Indian standard in place the standards applicable are given hereunder. 1) EN (European) : 13348, which is a standard for Copper & Copper Alloys Seamless, round Copper Tubes for Medical Gases or Vacuum 2) EN (European): 1057 (which now supersedes the BS: 2871) which is a standard for Copper and copper alloys seamless, round copper tubes for water and gas in sanitary and heating applications 3) AS/NZS (Australian) 1571 for copper tubes for Medical Gas Tubing 4) AS 2896 (1988) Medical Gas Systems installation & testing of non-flammable medical gas pipe line systems 5) ASTM B 819 (American) for Seamless Copper tubes for Medical Gas Systems 6) ASTM B 837 (American) for Seamless Copper tubes for Natural Gas and Liquefied Petroleum (LP) Gas Fuel Distribution Systems 7) BS 6017 (British) for Copper Refinery Shapes (For impurity levels in Copper tubes) In India since Medical Gas copper piping & fittings are specified in metric sizes (mm) we are following EN: along with EN 1057 now superseding BS 2871 along with the BS EN 1057/BS 2871 specifies copper tubes in 3 wall thicknesses - Tables X, Y, & Z. However, the commonly recommended sizes for medical gases are much thicker in nature due to both pressure requirements and design level factor of safety for medical gas installations. We have given below the working and burst pressures of Table X, Y & Z. Tube Size Outer Diameter maximum minimum Thickness TABLE 1 Table X (R 250) Inner Dia Calculated Burst Pressure Maximum Working Pressure (mm) (mm) (mm) (mm) (mm) (bar) (PSI) (bar) (PSI) Indian Plumbing Today / September 2017 / 5

3 Tube Size Outer Diameter maximum minimum Thickness Table Y (R 220) Inner Dia Calculated Burst Pressure Maximum Working Pressure (mm) (mm) (mm) (mm) (mm) (bar) (PSI) (bar) (PSI) Tube Size Outer Diameter maximum minimum Thickness Table Z (R 290) Inner Dia Calculated Burst Pressure Maximum Working Pressure (mm) (mm) (mm) (mm) (mm) (bar) (PSI) (bar) (PSI) The important aspects of testing copper tubes to EN: along with EN 1057 are given below. Most clients for medical gas tubing insist on certification by Lloyds or Bureau Veritas having to witness copper tubes undergoing Non-Destructive tests including pressure tests or Eddy Current test & its physical properties including Elongation, Ultimate Tensile Strength (UTS) & Flaring (Swaging/Drift test). Some clients, of course, accept tubes on factory certification. Important aspects in conformance to medical gas piping as per EN: along with EN 1057 are as follows:- COPPER TUBES 1) Dimensional Test Proper dimensional conformance because the tube has to be brazed and inserted into fittings to allow capillary action and joints with burst pressures higher than the tube itself. 2) Physical Test Conformance to physical properties to define proper workable and bendable copper tubes. Half hard physical properties in a copper tube give the tube enhanced bendability and 6 / September 2017 / Indian Plumbing Today

4 ductability factor without wrinkle formation or cracking, fatigue or failure. 3) Chemical Composition Chemical composition conforming to Copper DHP Grade also knowing as Deoxidised High Residual Phosphorus Grade, Alloy C 106 having minimum Copper percentage of 99.9% (Cu + Ag) and phosphorus levels of 0.015% to 0.040%. The equivalent to Alloy No. C106 or CW 024 A as specified in British/ EN specifications is Copper No. C confirming to ASTM B251. 4) Impurities Impurities in copper tubes are to be tested confirming to specification BS The chemical composition is very important as impurity contamination like lead or iron can lead to fatal circumstances in medical piping. Hazardous substance especially hexavalent chromium, mercury, lead and cadmium are to be restricted to PPM levels, even though the specification do not call for RoHS compliance. However, it is recommended that all the MGPS tubes are RoHS complaint. 5) Hydrostatic Test (As per EN : 1057) Test pressures are given below: Table 2 Nominal outside diameter Hydraulic Pressure mm bar Over upto and including Minimum ¹ including 6 Note: 1 bar is equivalent to 0.1 Mpa 6) Pneumatic Test (As per EN: 1057) The tubes under test shall be connected to a source of pressurized air. Air pressure at 4 bar shall be maintained in the tube. The tube shall be completely immersed in water for a minimum period of 10 seconds and inspected for the issue of bubbles from the tube. Should any bubbles be observed then the tube shall be rejected. If no bubbles (leakage) are observed then the tube shall be accepted. around the periphery of the tube to detect any flaw or blow hole which may not be visible to the naked eye. Note: EN: does not allow for a Hydrostatic or Pneumatic Test and it is mandatory to conduct an Eddy Current Test only. 8) Carbon Film & Carbon Content Test The determination of carbon content shall be carried out on the samples obtained in accordance with the specification per EN 723 and the detection and assessment of carbon film shall be carried out on the samples obtained. Note: EN: only mandates the tube to be tested for Carbon Content test up to and including 54 mm OD Tubes and not for Carbon Film. Residual and potential maximum carbon of 0.2 Mg/dm² is specified in the EN standards. FITTINGS Fittings are specified as per British standard BS 864 Part II, now superseded with EN Copper fittings are cleaned for oxygen service in accordance and must meet all requirements of NFPA-99 (American Specification). It is pertinent to note that there are copper fittings manufactured in India, none of which confirm to these standards and therefore fittings are to be confirming to EN Very few manufacturers supply fittings as degreased to meet the requirements for medical gas applications. Copper Equal Elbow Copper Coupling 7) Eddy Current Test In lieu of hydrostatic or pneumatic pressure tests an eddy current test has been specified in EN: and EN 1057 to be in accordance with EN Eddy current test is a computer aided test wherein the tube passes through a probe and an electro magnetic field is created Copper Equal Tee Copper End Cap Indian Plumbing Today / September 2017 / 7

5 INSTALLATION AND TESTING OF MEDICAL GAS PIPING SYSTEMS Tubes, for use in oxygen and other medical gas piping, are required by International standards to have exceptional internal cleanliness in order to prevent gas contamination or potential explosions. Oxygen under pressure may cause spontaneous combustion of residual organic drawing oils if left inside tubes after manufacture. Oils or other contaminants could cause severe patient problems if not removed prior to installation. Hence the specification calls for a carbon content/film test to test residual and potential carbon in a tube (as given above): 1. All piping, valves, fittings and other components for use in all non-flammable medical gas systems must be thoroughly cleaned by the manufacturer to remove oil, grease and other readily oxidizable materials as if they were being prepared for oxygen service. Use particular care in storage and handling. Such material must be capped or plugged to prevent recontamination before final assembly. Just prior to final assembly, the material must be examined internally for contamination Cleaning must be done in accordance with the provisions of CGA Pamphlet G-4.1, Cleaning Equipment for Oxygen Service 2. All brazed joints in the piping shall be made up using brazing filler metals that bond with the base metals being brazed and that comply with Specification for Brazing Filler Metal, ANSI/AWS A5.8 Copper-to-copper joints shall be made using a copper-phosphorus brazing filler metal (BCuP series) without flux Dissimilar metals such as copper and brass shall be joined using an appropriate flux with either a copper-phosphorus (BCuP series) or a silver (BAg series) brazing filler metal. Apply flux sparingly to the clean tube only and in a manner to avoid leaving any excess inside of completed joints. (NOTE: Ensure proper ventilation. Some Bag series filler metals contain cadmium, which, when heated during brazing, can produce toxic fumes and must not be used at all) During brazing, the system shall be continuously purged with oil-free dry high purity moisture free nitrogen to prevent the formation of scale within the tubing. The purge shall be maintained until the joint is cool to the touch It must be noted that all MGPS Piping must be joined by the process of brazing and not soldering The outside of all tubes, joints and fittings shall be cleaned by washing with hot water after assembly to remove any excess flux and provide for clear visual inspection of brazed connections A visual inspection of each brazed joint shall be made to assure that the alloy has flowed completely around the joint at the tube-fitting interface. Where flux has been used, assure that solidified flux residue has not formed a temporary seal that could hold test pressure All tubes will be recapped wherever open to prevent the entrance of any contamination in the tube ID All tubes will be visible and clamped and will not in any way be put in a chase 3. Threaded joints in piping systems shall be tinned or made up with poly tetra fluoro ethylene (such as Teflon) tape or other thread sealants suitable for oxygen services. Sealants shall be applied to the male threads only STANDARD OPERATING PROCEDURE FOR MEDICAL GAS SYSTEMS 1. The staff installing medical gas lines should first trace the line being connected to the point where they can be assured that it is the proper gas to be dispensed 2. Proper labeling as per colour codes should be placed on all pipes to assure that lines are appropriately identified, carrying different gases 3. Actual construction of the piping to medical air and the oxygen outlets will require the use of oxygen grade copper. The material is cleaned with caps plugging the ends prior to use 4. Nitrogen will be introduced into piping while silver soldering is taking place to ensure that 8 / September 2017 / Indian Plumbing Today

6 the inside of the pipe remains clean 5. All cut sections of pipe should be closed and covered with plugs or tape to preclude any foreign material from contaminating the new line 6. Hangers should be installed as required for support of all piping. If a pipe is left hanging in place awaiting soldering, it should be capped off to maintain cleanliness of the material 7. After a new line is installed, it should be purged with a blast of the same gas that the line is delivering. Then, a Millipore filter screen with white filters should be connected to test for any possible dirt that remains in the system. If particulate/dirt is still present in the system, purging should continue with retesting until the system is free of all contaminants 8. The staff installing outlets should contact the appropriate Respiratory Therapy Department in the Hospital to attest to final inspections and approval 9. The staff should document all testing of installations made by the staff and document this appropriately. Contractors/Workmen are held to the same standard as the staff 10. All MGPS pipe lines will be installed at least 1 meter below the electrical lines 11. All copper pipe work to pass through a wall or any solid structure, will pass through a sleeve to ensure free movement of the pipe work due to change in temperature, allowing for a co-efficient of linear expansion and contraction In conclusion, as we can see from the above that copper tubes and fittings are a very important aspect of medical gas piping and comprise the critical application of supplying lifesaving oxygen to patients and therefore specifications, testing or certification should not be ignored and depending on client requirement, the test(s) should be clearly specified. However, the minimum and mandatory testing must be conducted and certified by the Authority Having Jurisdiction (AHJ). ipt Mr. GURMIT SINGH ARORA is Managing Director, Rajco Metal Industries Pvt. Ltd., Mumbai; National President, IPA and Co - Chair, IGBC Mumbai Chapter & Exec. Board Member, IGBC. He can be contacted at rajco@ rajcogroup.com Indian Plumbing Today / September 2017 / 9