Tubing assembly

Omnifit has developed a tubing assembly with leak-tight gripper fittings for fluid transfer in spectrophotometers. Each flow cell consists of a glass tube held in an aluminium housing. The requirement was for a PTFE tubing assembly with fittings that would seal to the glass surface of the flow cell while accommodating variations in the alignment between the cell and its housing. The dimensions of the flow cell tubing were 1.6 mm OD and 1.0 mm ID.

The solution is a gripper fitting with a stainless steel case and a PTFE seal insert. When assembled onto the glass tube of the cell, the PTFE 'cold flows', forming a secure seal on the glass surface. There were slight variations in the alignment of the glass within the cell which could have made sealing difficult; this was overcome by fitting an O-ring between the gripper and the tube end fitting, allowing the gripper to align with the cell independently of any variations in the alignment of the housing. The end of one fitting was also made slightly longer than the other to allow easy assembly, and the fittings were colour-coded for simple identification.