What is the difference between Type A valves and Type B valves (check valves) in API 594?
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What is the difference between Type A and Type B valves as specified in API 594?
Putting aside the materials, the main difference is that type A is of the clamp-type with lugs and double flanges, while type B has flange ends and weld ends
Look at the standard Scope; it’s written very clearly. According to this standard, Type “A” check valves have short face-to-face dimensions. – The body design can be wafer type, wafer type with lugs, or double flanged. – The obturator can be of single or dual plate design, or it can be a swing disc or a pivoting disc. – Body materials include gray iron and ductile iron, as well as those specified in ASME B16.34. – Refer to the typical illustrations in Annex C, Figures C.1, C.2, C.3, C.4, and C.5. Type “B” check valves have either long or short dimensions depending on the face-to-face or end-to-end spacing, in accordance with ASME B16.10. – The body can be flanged or have butt-welded ends. – The obturator can be a swing disc or a pivoting disc. – Body materials are listed in ASME B16.34. – Refer to the typical illustration in Annex C, Figure C.5.
Type A is a double-disc check valve, while Type B is a single-disc check valve. The structure is completely different.