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Defective assembly with Expansion Inserts. Notice the Inserts pulled out of the host component.

Efficient assembly with CL800 Compression Limiters (left) and Series 20 Inserts (right).

Standard HP machine used to install the Inserts.

Compression Limiters and Inserts for Plastics
Application: Plastic Filter Pump Assembly

A pump and valve manufacturer contacted SPIROL to help solve an issue with their filter pump. The filter pump consisted of a cover fixed to the pump housing. With internal pressure and applied torque, the assembly needed to resist 22 N-m. They were using six Expansion Inserts with M8 bolts within 30% glass filled polypropylene plastic. A sub-contractor was manually installing each Insert at the perimeter of the housing flange. When required pressure was applied, the Inserts were coming off with the bolts resulting in the pump opening up. The client was looking for a reliable and efficient solution to meet his specifications.

After review of the application, SPIROL Engineering determined that the diameters of the cover’s holes were bigger than the diameter of the Inserts; thus creating a jack-out condition. It was recommended that the customer use SPIROL’s Series 20 Headed Heat Installed Inserts combined with CL800 Compression Limiters. This style of Insert offers the greatest ease of alignment and installation with the added benefit of a head for increased bearing surface to prevent jack-out. It also has higher torque and pull-out values than Expansion Inserts. The Compression Limiters offer added bearing surface to avoid jack-out and prevent plastic creep during assembly life.

SPIROL also suggested that the customer use a semi-automatic HP Model Heat Installation Machine to install the Inserts.

This solution provided a high quality product and an efficient assembly process while exceeding the application’s performance requirements.

Our staff of engineers will review your application needs and work with your design team to recommend the best solution. One way to start the process is to select Inserts in Plastic in our Optimal Application Engineering portal.