Challenge :
Replacing the sealing system of a butterfly valve consisting of an inflatable seal with a 40-mm diameter by a single-piece elastomer seal.

Context :
The client had encountered a reliability problem in relation to maintaining the air pressure inside the inflatable seal.

This seal was firstly replaced by a full ring seal. As no adjustment was possible on this type of arrangement, unlike the possible grades with the inflatable seal, the seal was rapidly worn due to excess friction and generated leaks.

The client asked PXL SEALS to find a solution on a single-piece seal, which is adjustable on the valve body.

On the other hand, it was important for the client to restrict machining of the valve body.

The PXL SEALS solutions :
In order to best meet the specifications of EDF, PXL SEALS designed the sealing system in 4 steps :

1.    Study of the equipment : Expertise of the solution existing on the EDF site and engineering offices,

2.    Recommending sealing solutions : Drafting a technical file including the analysis of existing equipment, the advantages of the new solution compared to the old equipment, 3D and 2D drawings of the entire valve as well as drawings representing the parts to be re-machined with the machining dimensions and tolerances,

3.    Manufacturing the sealing system : mould manufacturing, vulcanisation tests between the lens and trunnion, then manufacture of the single-piece seal in the PXL SEALS workshop,

4.    Contribution to the shop-test assembly of the seal on the valve at EDF’s subcontractor. Adjusting and testing the lens to ensure optimal contact over the entire circumference of the valve body.

The implemented sealing solution was a moulded seal with a diameter exceeding 2,000 mm, which was entirely vulcanised and fitted onto the valve without bonding.

The moulded single-piece seal solved all leakage problems. Thanks to the installation of a spreader, the seal profile could be adjusted over the entire periphery of the valve body by means of set screws.

This autumn, the valve was reclassified and put back into service. The outcome: no leaks occurred during the re-commissioning of the valve. The mission was successful for PXL SEALS!