I have a specs of gate Valve with BLOCK & BLEED service. I think there is no service called BLOCK & BLEED. I think BLOCK & BLEED should be the design. Please advise.
If you need a double block and bleed valve you have plenty of choices. Expanding gate valves gives you mechanical sealing, a slab gate can also do this as long as you have floating seats. Ball valves can also give you the correct sealing. Just be sure that you differentiate between double block and bleed (DBB), and double isolation and bleed ( DI&B).