Features: 1) Design and manufacture of product according to ANSI B 16.34 and API 600 2) Compact structure, small bulk, perfect rigidity, safety and reliable 3) Blow down part (disc) utilize flexible structure, can automatically compensate distortion of body due to abnormal burden or temperature, so seal credible and prevent wedge being blocked 4) Manual valve with DN over or equal to NPS10", class 400 pounds and DN over or equal to NPS 16", class 600~2500 pound equip with rolling bearing to operate easily 5) Material of main body, material of trims, packing, washer, material of fastener can logically combine according to customer's requirement or actual work status 6) Exchangeable seat, random combine the material of surface of blow down part to meet the requirement of work status, prolong service life 7) Material: cast iron/ductile cast iron/WCB/CI/stainless steel