We have hydrogen plant consists of hydrogen generators and compressors which is using as cooling for Gas turbine generators. However, we have eight hydrogen pressure vessels for storage purpose. These vessels have only one inlet valve and at the same time it is using as outlet. The arrangement of the vessels consists of to two rows and each row consists of four vessels. in front of these vessels there is a common hydrogen header hydrogen pressure coming from the compressor. We are looking what is the suitable facility to purge these vessels in order to attend the thickness measurement and relief valve calibration.