COMPARISON OF API BB1 vs BB2

API 610 Designation Comments

Volute casing Axially Split Radially Split

Casing MAWP 16 or 24 bar.g

Operating conditions

H2S Service & Sealing

Mounting Foot mounted or Near centreline Centreline mounted

Yes Yes

Axially Split Pump API Type BB1

Radially Split Pump API Type BB2

BB2 is barrel case and therefore more robust design, originally designed for Hydrocarbon Applications as per API 610 compared to BB1 pumps which were historically designed as water pumps and have been converted to comply where possble with API 610

40 or 50 bar.gThe case and cover design is suitable for higher working pressure than an axial split case pump due to its smaller bolting area, symmetrical bolting pattern, and confined gasket design

BB2 designed as per API (min 40 barg)BB1 is limited to lower working pressure due to the difficulty in bolting with a flat, unconfined, and irregular case gasket, and due to the non-symmetrical volute and suction areas between the upper half and lower half casing.

Temperature - No more than 200 °C (400 °F)Density - No less than 0.7

Temperature - No restriction Density - No restrictionDisch. Pr - No restriction

It is typically limited to 400 °F operating temperature due to thermal expansion consideration as there is significant differences in the case metal thickness between the upper half and lower half of the pump resulting in differences in thermal expansion;

Flat gasketNot preferred by end-user for H2S application

Viton O-ringsAllows for better sealing and is better suited for H2S service for avoiding any leaks

BB1 uses compression gasket or liquid gasket and is more dependent on correct bolt torque sequence to prevent leakage. BB1 pumps require careful cleaning of top and bottom half casing faces before every assembly (to remove old gasket material)

Pump cannot be supported at the shaft centerline where the pump casing is split in half (at best, it can be supported at near-centerline only). This results in asymmetrical thermal expansion between the upper half and lower half casing.

Pump Maintenance without disturbing Suction/Discharge Pipework

Both BB1 and BB2 allow for rotor removal / maintenance without disturbing pipework

Sulzer BB2 pump rotor removal is achieved in a similar manner to that for a BB1 pump - using eye-bolt for lifting the NDE end-cover (as opposed to lifting the top-cover) and slings for the rotor. No special tools are required