Diaphragms
Fenner Precision offers two types of Crux Diaphragm Closures, one for the purpose of auxiliary buoyancy provision and the other to prevent the ingress of seabed material into the grout annulus.
The Crux Buoyancy Diaphragm is the most commonly used diaphragm worldwide.
Buoyancy or Crux 'Heavy Duty' Diaphragm Closures
Diaphragm closures, as required for the provision of auxiliary buoyancy purposes, are made from rubber reinforced with polyester fabric. Fixing is achieved by clamping a solid nylon core, around which the laminations of polyester fabric are wrapped between two machined flanges. The required diaphragm strength for specified application is achieved by provision of appropriate fabric strength and number of plies.
Crux 'Heavy Duty' Diaphragms are unique in that they are manufactured with one side of the diaphragm flat. The diaphragm is then deformed to fit into the fixing grooves within the flanges by torquing the fixing bolts. This forced deformation of the diaphragm ensures that a seal is obtained, even at early stages of bolt torquing. Tolerance to flange distortion resulting from welding is much better than with other competitor diaphragms.
Mud-Exclusion Diaphragms
Mud-Exclusion Diaphragms are used to prevent seabed material from entering the annulus between the pile and pile sleeve or structure leg prior to pile insertion. This type of diaphragm is used in conjunction with Grout Seals where there are soft seabed conditions, such as encountered in the Gulf of Mexico. The combined action of the Mud-Exclusion Diaphragm and Grout Seal ensures that no seabed material ever enters the annulus.
These relatively lightweight diaphragms are provided with a keeper plate fixing similar to that used for Grout Seals. Similar keeper plate geometry to that used for Grout Seals of similar size is maintained, thus providing consistent can configuration. This type of diaphragm is manufactured without any tooling requirement and at low cost. The avoidance of flange machining, as required for other types of diaphragms, leads to major cost savings.