Dual Metal Bellows Double Cartridge Mechanical Seal

Product Overview; 

The BD750 is a premium metal bellows double cartridge mechanical seal featuring both inboard and outboard welded bellows elements, engineered for critical high‑temperature and hazardous process applications where maximum reliability, emission control and operational safety are mandatory. This non‑pusher, elastomer‑free dual‑bellows configuration provides a fully cartridge‑mounted solution that delivers consistent sealing performance in corrosive, thermally unstable and slurry‑laden media. 

 

The inboard metal bellows seal functions as the primary process seal, offering superior thermal stability, resistance to coking and excellent sealing performance under severe temperature fluctuations and chemically aggressive fluids typically encountered in hot‑oil, thermic‑fluid, hydrocarbon and solvent‑handling duties. By eliminating dynamic elastomer movement along the shaft, the bellows design removes common pusher‑seal failure modes such as O‑ring hang‑up, hardening and thermal degradation. 

 

The outboard metal bellows seal acts as the containment or secondary barrier seal, providing an additional level of safety and redundancy. It is particularly effective in dual‑seal systems operating with pressurised barrier (API Plan 53) or unpressurised buffer (API Plan 52) fluids, where tight process‑leakage control and environmental compliance are vital. The dual‑bellows arrangement delivers excellent pressure‑handling capability and stable barrier‑fluid circulation, supporting high integrity in hazardous, toxic or volatile services. 

 

Supplied as a fully pre‑assembled double cartridge, the BD750 ensures precise axial setting, simplified installation and reduced commissioning errors on refinery, petrochemical and power‑generation equipment. Hydraulically balanced seal faces on both stages minimise face loading and heat generation, providing thermal stability and long service life under pressure fluctuations and thermal cycling commonly found in high‑energy process pumps and other critical rotating machinery. 

 

With its dual metal bellows construction, non‑pusher design and API‑compatible dual‑seal capability, the BD750 offers a rugged, long‑lasting sealing solution for high‑temperature hydrocarbons, thermic fluids, fatty acids, volatile solvents and other aggressive process media in the most demanding industrial environments. 

 

Technical Features; 

• Bi‑directional operation, non‑dependent on shaft rotation direction, provides installation flexibility across clockwise and counter‑clockwise rotating equipment. 

• Industry‑standard design for use with API, ANSI and ISO pump arrangements, available in both metric and inch shaft sizes to integrate seamlessly into new or existing installations worldwide. 

• Factory‑assembled and pressure‑tested cartridge design ensures precise axial setting, minimises installation and commissioning errors, and supports quick installation and easy removal to maximise plant uptime. 

• Integrated cooling, flushing and quench connections offer built‑in ports for barrier fluid and cooling circuits, enhancing heat dissipation around the seal faces and extending seal life in high‑temperature and high‑duty applications. 

• Engineered for API process pumps, refinery units and other critical rotating equipment, providing state‑of‑the‑art leak‑tight performance, extended MTBF and reduced total cost of ownership in mission‑critical services. 

• Double‑seal arrangement is compatible with both pressurised (API Plan 53 variants) and unpressurised (API Plan 52) barrier/buffer systems, supporting stringent emission‑control and containment requirements in hazardous and toxic services. 

• Robust metal‑bellows technology delivers high corrosion and thermal‑fatigue resistance, making the seal suitable for acidic, caustic and hydrocarbon‑based media, as well as cyclic operation with frequent starts, stops and temperature swings. 

• Hydraulically balanced seal faces combined with the axial flexibility of the bellows deliver superior pressure‑handling capability, reduced heat generation and stable operation across wide operating windows, including thermally unstable and high‑viscosity fluids. 

• Double cartridge configuration with inboard and outboard metal bellows provides primary and secondary sealing in a fully integrated, pre‑assembled unit, delivering high reliability for volatile, abrasive and environmentally hazardous media from vacuum up to high pressure. 

• Dual non‑pusher metal bellows elements eliminate dynamic elastomers on both seals, reducing the risk of degradation or failure from thermal shock, chemical attack, swelling or secondary‑seal hang‑up, while offering excellent resistance to coking, crystallisation and polymerising fluids. 

Service Overview; 

Parameter	Value
Equipment	API process pumps, thermic fluid pumps, refinery pumps, hydrocarbon transfer pumps
Fluid	Hydrocarbons, thermic fluids, solvents, fatty acids, caustic and acidic media
Service Nature	Hazardous, high-temperature, corrosive, volatile process service
Operating Mode	Continuous duty with thermal cycling and pressure fluctuations

 

Specifications; 

Item	Min	Max	Typical / Notes
Shaft Size	20 mm (0.750”)	200 mm (8.000”)	Larger sizes available on request
Pressure	Vacuum	25 bar (362 psi)	Depending on seal arrangement and API plan
Temperature	-40°C (-40°F)	+400°C (+752°F)	Based on metallurgy and face selection
Speed	—	3600 RPM	Higher speeds available with application review

 

Materials; 

Component	Standard Material	Optional Material	Comment
Seal Faces	Carbon / Silicon Carbide	Tungsten Carbide / Reaction Bonded SiC	High-temperature compatible face combinations
Metal Bellows	SS 316L	AM350 / Hastelloy C276 / Inconel 718	Welded multi-ply construction
Secondary Seals	Graphite / Flexible Graphite	PTFE / Expanded Graphite	Suitable for elevated temperatures
Hardware	SS 316 / SS 316L	Duplex SS / Hastelloy / Titanium	Based on corrosion severity

 

Applications; 

• Petrochemical process pumps 

• Refinery hydrocarbon transfer systems 

• Solvent recovery and distillation systems 

• Acidic and caustic media transfer systems 

• Thermic fluid and hot oil circulation pumps 

• High-temperature reactor circulation pumps 

• LPG and hazardous chemical processing plants 

• Vacuum residue and heavy hydrocarbon services 

• Nuclear and thermal power station auxiliary pumps 

• Biochemical and specialty chemical processing units 

 

Operating Limits; 

Parameter	Value
Pressure	Up to 25 bar (362 psi)
Temperature	-40°C to +400°C (-40°F to +752°F)
Speed	Up to 3600 RPM
Size Range	20 mm to 200 mm (0.750” to 8.000”)

 

Engineering Note; 

Operating parameters and material selections shown are based on typical industry standards for double cartridge metal bellow seals used in refinery and petrochemical applications. Final seal selection should be verified against actual operating conditions, API piping plan requirements, fluid characteristics, and equipment configuration prior to procurement.