DESMI PUMPING TECHNOLOGY A/S P a g e | - 30 -Tagholm 19400 Nørresundby - DenmarkPhone.: +45 96 32 81 11Fax : +45 98 17 54 99E-mail: desmi@desmi.comwww.desmi.com10.7.2 Flange couplingFlange couplings must always be undertaken by skilled professionals.Achieve parallelism between the flanges and observe the maximum tightening torqueto prevent tension in the pump casing1. Before connecting the flange, check that the flanges are parallel, as any variance inparallelism will create tension in the pump casing. Parallelism is achieved by aligning thepipe system or fitting compensators.2. Select the bolt size for the flanges on the basis of the pump size in the table in Figure 22.You should not use bolts with a yield stress of more than 240 N/mm2, corresponding toquality 4.8 – for pumps manufactured in grey cast iron, material code “1”.3. Find the maximum tightening torque in the table in Figure 22.Please note that the table contains the maximum tightening torque.The necessary tightening torque depends on: packing, form, material and the pump liquid’stemperature.The values in column A are valid for pumps manufactured in grey cast iron – material code“1”.The values in column B are valid for pumps manufactured in steel – material codes “3” or“4”.3. Cross-tighten the bolts using the uniform tightening torque shown in the table below.Bolt size / max. tightening torquePump size Bolt * Max. tightening torqueA B26 M12 30 Nm 80 Nm33-126 M16 75 Nm 200 Nm151-202 M20 145 Nm 385 NmFigure 22:The bolt sizes available for connecting flanges, together with the maximum tightening torquedepending on the pump size and material stated.Column A contains the maximum tightening torque for pumps manufactured in grey/nodular cast iron – material code“1”/”5”.Column B contains the maximum tightening torque for pumps manufactured in steel – material codes “3” or “4”.*You should not use bolts with a yield stress of more than 240 N/mm2, corresponding to quality 4.8, for pumpsmanufactured in grey cast iron – material code “1”.
