Proper selection, handling, installation of tubing when combined with the proportion of WESMEC Double Ferrule Compression Tube Fittings are essential for reliable tubing system. Although, WESMEC is not tubing manufacturer, we feel it is our duty to impress on our customers the vital importance of careful selection of high quality tubing in order to install safe and leak free systems. Selection of tube is based on materials, hardness, wall thickness and surface finish. The ASTM specification for various tubes covers material, hardness and wall thickness. Finished tubes shall be reasonably straight and have smooth ends free from burrs. They shall be free from defects and shall have workman like finish.



Tubing must be always softer than the fitting material by using the suggested hardness of the tubes as explained in tubing specification you will ensure joints which work perfectly.


The most misunderstanding about tubing hardness are in the area of stainless steel tubing WESMEC Double Compression Tube Fittings are made from stainless steel have been tested successfully with tubing hardness up to HRB 90, the maximum hardness allowed under ASTM A213 and ASTM A269. Although such tubing hardness is permissible and WESMEC Double Compression Tube Fittings perform satisfactorily on such tubing they will not give maximum advantage and performance for tubes of hardness above HRB 80. Hence it is suggested that when purchasing stainless steel tubes to ASTM A213/A269, you specify that the hardness of the tube should not exceed HRB 80. Better still we have found that the best results are obtained where the stainless steel tubing hardness is in the range HRB 70-74.Such tubing (HRB 70-74) lowers installation costs because it is easily bent and installed. Tubing installers should be particularly careful the full suggested one and quarter turns after snug tight be performed to ensure the proper joints. This will give the maximum performance. This is especially so in the case of harder tubing where higher torques is required. We again repeat that HRB 80 maximum hardness is suggestion and not a restriction against the use of WESMEC Double Compression Tube Fittings in stainless steel to increase the performance of the fitting.



The allowable pressure rating of tubing for the wide range of wall thickness is calculated from “S” values as specified by ASME Code B31.1The range of tubing wall thicknesses varies from 0.028” to 0.083” in the inch OD series. These wall thicknesses are generally preferred for tube sizes up to 1”.



For maximum safety and the prevention of surface defects in any gas system, it is recommended that tubing wall thicknesses are not less than those shown in this table:





• Scratches on tube OD are a potential source of problems in leak-tight tubing systems. Good handling practices can greatly reduce scratches and protect tubing surface finish. Tubing should never be dragged out of a tubing rack. Particularly in sizes 3/4” and larger, the weight of the tubing being retrieved is sufficient to gouge the OD if there are any burrs on the ends of the other tubes in the rack.


• Tubing should never be dragged across cement, asphalt, gravel or any other surface, which could scratch the surface and create potential leak paths. Sharp tube cutters should be maintained and tube ends should always be deburred. This allows easier entrance of the tube into the fitting bore and helps to assure that the tubing will go all the way through the ferrules without damaging the ferrule’s sealing edge.




Seamless, annealed 304 or 316 Stainless Steel tubing to ASTM A 269 or A 213 or equivalent is recommended (ERW tubing use is not recommended). 4-1 safety factor considering tensile strength of 75,000 PSI at room temperature. Tube hardness should not exceed HRB 80. The preferable hardness range is HRB 75-80. Tubing should be suitable for bending and flaring, and should be free of any surface defects and imperfections.



Annealed, soft, seamless copper tubing to ASTM B75 or equivalent. 5-1 safety factor considering tensile strength of 30,000 psi at room temperature. Maximum hardness of the tubing is not to exceed HRB 50. Preferred hardness range is HRB 40-45.



Fully annealed Monel 400 seamless tubing confirming ASTM B165 or equivalent and based on ultimate tensile strength of 70,000 psi and with temperatures 20°C to 90°C.










*** Note: For your safety the system designer and user have the sole responsibility to select products suitable for their special application requirements and to ensure the proper installation, operation and maintenance of the product. Please consider application details, material compatibility and product ratings when making your selection. Improper use or selection of products can cause property damage or personal injuryperformance during peak times.