Setting the final dimensions of your DuPont™ Vespel CR-6100 component
We have discussed how to measure your pump, prepare the metal parts, and establish the press fit for your Vespel® CR-6100 installation. The final two dimensions you need to establish are the part length and the clearance.
The Part Length
Vespel® CR-6100 has an extremely low coefficient of thermal expansion in the radial plane (perpendicular to rotation). This is one of the principal reasons it performs so well in centrifugal pump components. The low coefficient of thermal expansion is achieved through the use of radially-oriented, long carbon fibers.
Conversely, the coefficient of thermal expansion along the axis is relatively high. Therefore, the part length for a Vespel® CR-6100 component should account for the axial thermal expansion at operating temperature. Table 4 of our installation guide provides the details on how to make this adjustment.
The clearance for the part is set depending on the diameter and component type. Tables 2a and 2b in the installation guide show the clearance recommendations for horizontal pump components such as pump wear rings, throttle bushings, center bushings, inter-stage rings, balance bushings, and throat bushings.
Tables 3a and 3b show the clearance recommendations for vertical pump components like vertical pump shaft bearings, wear rings, and throat bushings.
The best way to set the clearance is to press the component into place, and then final machine the bore to the desired clearance. This is shown in steps 5a-7a in our installation guide, pages 8-9.
Where final machining after the press fit is not practical, you can design the component to have the correct clearance after the press fit. For most component geometries, you can assume the Vespel® CR-6100 will reduce at a 1:1 ratio with the press fit. This method is shown in steps 5b-7b in our installation guide, page 9.
Some sites have implemented a hybrid method. They measure the inside diameter of the Vespel® CR-6100 case wear ring after installation, and then machine the metal impeller wear ring to set the desired clearance.
Installing Vespel® CR-6100 is an easy upgrade to make your pumps more reliable, safe, and efficient. Follow the steps in our installation guide and you can make your pump even better than the day it was new. If you need material, Boulden carries inventory of stock sizes in the USA, Europe, and Singapore.