Flowserve BX Series Metal Bellows Mechanical Seal API 682

BX Series balanced metal bellows seal to API 682 Type B

The Flowserve BX Series is a family of balanced metal bellows mechanical seals available in single and dual configurations. It is made for corrosive and non-corrosive liquids and especially for fluids that crystallise or coke when exposed to the atmosphere, where a conventional spring seal tends to clog. The BX meets the requirements of API 682 Type B.

Seven Star LLC supplies BX series seals in Oman and the GCC as an independent supplier in Muscat. The BX is a series: the exact variant, shaft size and materials are set from your pump and process data.

BX Series technical specifications

How the BX bellows seal works

A welded metal bellows replaces the springs and the dynamic elastomer of a pusher seal. The bellows provides the axial flexibility and the closing force, so the faces follow shaft movement without any part sliding on the shaft. With no spring coils and no dynamic O-ring, there is less to hang up in dirty or crystallising fluid.

The bellows rotates, so centrifugal action helps clear the convolutions and prevent debris build-up. A thin 0.20 mm bellows resists corrosion, shaft vibration and centrifugal forces. On dual seals an integrated circulating device moves barrier fluid across the faces to keep them cool, and a circulating device can also be fitted to single seals on fluids above 75 °C. An optional multi-port flush spreads the flush evenly round the faces.

BX, BXQ, BXB, BXLS and BXR variants

Where the BX seal fits in the pump

The BX is a cartridge-style seal for the seal chamber of API 610 pumps such as the HPX, HPX-V and WCC, and similar process pumps. Part interchangeability between the single and dual arrangements keeps spares inventory small. A single seal gives Arrangement 1, a dual unpressurised seal gives Arrangement 2, and a pressurised dual seal gives Arrangement 3; the BXB is the form for Arrangement 3.

BX Series selection and ordering checklist

• Shaft or sleeve diameter and seal chamber dimensions from the pump drawing.
• Pumped fluid, specific gravity, vapour pressure, solids and tendency to coke or crystallise.
• Seal chamber pressure and temperature, including upset conditions.
• Shaft speed, to check surface speed against 23 m/s, or BXR above that.
• Single, dual unpressurised or dual pressurised arrangement and API 682 flush or barrier plan.
• Face and metal materials for the fluid.
• Emission requirements, for example the BXQ for hydrocarbons.
• Pump make, model and standard (API 610, DIN).

Installation and maintenance of BX seals

Check shaft runout and seal chamber face squareness before fitting, as bellows seals tolerate shaft movement but not poor machining. Set the cartridge using the manufacturer’s setting clips, and remove them only after the pump is assembled. Vent the chamber fully, start the flush or barrier system before the pump, and watch barrier fluid level and pressure on dual seals.

Leakage that is slowly growing usually means face wear; sudden leakage can come from dry running or a flush failure. Keep a spare cartridge for critical pumps, and record the flush plan with the pump file so replacements match.

BX Series applications in Oman and the GCC

Typical uses are hot oil and heat-transfer fluids, hydrocarbon services at refineries and gas plants, caustic and acid transfer in petrochemical units, and desalination chemical dosing. High ambient temperature and dust make the cooling arrangement and flush system worth checking early in selection.

Metal bellows seals are also used where fluid tends to polymerise or solidify at the atmospheric side of the faces. Because the bellows has no sliding elastomer to stick, the seal keeps working after long idle periods, which suits standby pumps that wait weeks between starts. State whether the pump is duty or standby, and how often it starts, so that the right flush plan is proposed.

Seal support systems for the BX

A metal bellows seal performs best when its environment is controlled. API 682 piping plans define how the seal chamber is flushed, cooled or quenched: Plan 11 or Plan 13 recirculates product, Plan 23 cools hot water or hydrocarbon in a closed loop, Plan 32 injects a clean external flush, and Plan 62 provides a steam or nitrogen quench on the atmospheric side to prevent coking or icing. For dual arrangements, Plan 52 or Plan 53 supplies buffer or barrier fluid. Choosing the right plan, together with bellows material and face combination, affects seal life as much as the seal itself.

Information to send with a BX RFQ

• Pump make, model and shaft diameter, with the seal chamber drawing.
• Fluid and operating data: pressure, temperature, speed.
• Required arrangement, plan and variant (BX, BXQ, BXB, BXLS or BXR).
• Materials, emission requirements and quantity.

Documents and quotation

A manufacturer datasheet for the BX is attached on this page for reference. Please send the duty data and the options you need, and we will prepare a quotation.

Seven Star LLC is an independent supplier in Muscat serving Oman and the GCC. Delivery time and availability are confirmed per enquiry.