A refinery customer had a series of Ingersol-Rand VOC vertical pumps with clamshell couplings (as seen in the original IR manual below). Clamshell couplings are common in vertical pumps because they are relatively easy and inexpensive to manufacture because of their simple geometry. Unfortunately, the simple geometry can also lead to poor misalignment and high vertical pump runout because of the loose fits.
On these units, the seals were failing very quickly, causing more downtime and frustration. During every seal change, the clamshell coupling would be disassembled and reassembled. During the installation process, the mechanics would check the runout on the pump shaft, and they typically found values of 0.030” to 0.040” (0.76mm – 1mm). Unfortunately, there was no good way to adjust the couplings to correct the runout consistently. It became clear over time that the poor alignment was the primary cause of the premature seal failures.
The plant discovered the CCA Vertical Clamp Coupling, viewing it as a potential solution to their problem. This patented device uses a mechanical shrink fit to connect the hubs to the shafts. Then the spacer sleeve attaches to the hubs with a piloted fit to ensure excellent concentricity. This fit helps to ensure consistent alignment between the motor and pump. Additionally, the coupling has a feature that allows the user to make some minor alignment adjustments to get the vertical pump runout close to zero or eliminated.
One note of caution – the adjustment capability of the coupling does not take the place of performing an alignment between the motor and pump. Instead, it gives the mechanic a simple way to get the alignment and runout nearly perfect.
The plant started with one new coupling. The pump shaft runout was less than 0.010” (0.25mm) once installed before any adjustments were made. The mechanics used the alignment adjustment capability of the Vertical Clamp Coupling to make some minor adjustments. Within minutes, the pump shaft runout was reduced to 0.002” (0.05mm).
With that success, the plant has begun to change the pumps to the Vertical Clamp Coupling.