English to Portuguese Tech/Engineering Mechanics / Mech Engineering flow sleeve spacer

Prezados tradutores,
Gostaria de saber qual seria a tradução mais adequada para o termo "flow sleeve spacer" que encontrei num texto que fala sobre válvulas manuais:

"The lips of the balance seal set must be facing the holes in the retainer sleeve,
Install flow sleeve spacer, # 4 in the retainer sleeve, # 2.
Install the seat seal, # 6, seat ring, # 7, and o- ring, # 8 in the trim stack cartridge, # 5."

Obrigado,

Sergio Medina