B-gap - The radial gap between the impeller outside diameter (OD) and tip of volute lip (or diffuser lip in a diffuser pump). It is also referred to as the volute lip clearance or cutwater clearance.
Inadequate B-gap may result in high vibration level at impeller vane pass frequency especially with high energy density centrifugal pumps.
BA - The width of the impeller opening at its outside diameter (OD). It is the width of the impeller at its OD excluding the impeller shroud (wall) thickness.
The impeller BA is a significant parameter because it is proportional to the pump capacity, and it also proportional to its hydraulic radial load.
Back-to-back - When referring to impellers, a back-to-back arrangement is when two adjacent impellers in a two-stage or multistage pump, are arranged so that the backs of the impellers are adjacent to each other, and their suctions are on opposite sides facing away from each other.
When referring to ball thrust bearings, a back-to-back arrangement is when two adjacent bearings are arranged so that the back, or high shoulder of the of the outer rings, are next to each other. The bearing contact angles diverge inward to the shaft. See definition of face-to-face.
Base circle - A reference circle in a volute development that is used as a basis for sizing the volute cutwater diameter. The base circle diameter usually corresponds to the maximum impeller diameter for which a volute is designed for.
"Bad actor" pump - The term used to a pump whose mean time between failures (MTBF) is so poor that the pump suffers from chronic failures and high operating and maintenance cost. A "bad actor" pump is a prime candidate for hydraulic re-rate or mechanical upgrade.
Balanced seal - A mechanical seal arrangement where the seal is designed to change the effect of the hydraulic pressure in the seal chamber on the seal face closing force, typically based on the seal balance ratio of less than 1.
Ball shuttling - A phenomena whereby balls in an inactive, or unloaded, bearing rotate perpendicular to their rolling axis due to gyroscopic forces causing them to lose contact with the raceway momentarily. Ball shuttling can cause premature bearing failure due to the acceleration of microscopic wear, and is characterized by the appearance of polished or burnished raceway. Also known as ball sliding.
Ball sliding - See ball shuttling.
Barrel pump - A horizontal pump of a double casing type consisting of an inner casing and an outer barrel. The inner casing, containing the rotor, is under compressive pressure from the liquid in the barrel which is under full discharge pressure. A similarly designed vertical pump is usually referred to as vertical canned-pump.
Barrier liquid - a liquid injected between pressurized double mechanical seals to isolate the process liquid from the atmosphere. The pressure of the barrier liquid is always higher than that of the process liquid being sealed. See buffer liquid.