In offshore oil production FMC Subsea systems use a product called cap. The cap´s mainly task is to protect hubface and seal areas on inboard hub against dirt, corrosion and mechanical damage under installation of a Subsea system. A new model of a cap has been designed and analysed using finite element method. The model is called KC3-12 and has a new function, emergency release, which is a backup method for the ROV (remote operated vehicle) to release the cap from the hubface when it is placed under water. The cap KC3-12 was found to fulfil the criteria under the test load pressure, according to ASME VIII, div2.