Back-to-Back Double Cartridge Multi-Spring Mechanical Seal

Product Overview; 

The DC650 is a precision‑engineered back‑to‑back double cartridge multi‑spring mechanical seal developed for centrifugal and API 610 process pumps operating with hazardous, volatile, corrosive and high‑temperature process fluids. In this back‑to‑back configuration, two mechanical seals are arranged with their faces oriented away from each other and operated with a pressurised barrier fluid, providing maximum containment and reliable sealing for critical services in accordance with dual‑seal best practice and API 682 Arrangement 3 concepts. 

 

The DC650 employs hydraulically balanced seal faces and a multi‑spring distributed loading system to maintain uniform face pressure, minimise heat generation and ensure stable operation under fluctuating pressure and temperature conditions. Its cartridge‑mounted configuration, with the seal pre‑assembled on a sleeve and gland plate, eliminates on‑site setting of working length and reduces the potential for installation errors, enabling fast, repeatable installation in conventional stuffing boxes regardless of pump manufacturer. 

 

Designed for severe‑duty applications in petrochemical plants, refineries, fertilizer units, pulp and paper mills, pharmaceutical facilities, mining, steel, and wastewater treatment, the DC650 provides dependable sealing for hydrocarbons, aggressive chemicals, solvents, slurries and other hazardous media. The robust multi‑spring design resists clogging and maintains effective lubrication at the seal faces, supporting continuous‑duty operation even in demanding process conditions. 

 

The seal is fully compatible with pressurised barrier‑fluid systems and supports a wide range of API 682 piping plans for dual seals (such as Plans 53A/53B/53C and Plan 54), enabling optimised cooling, lubrication and emission control tailored to each installation. With its heavy‑duty construction, enhanced containment capability and user‑friendly cartridge design, the DC650 delivers a long‑lasting, high‑integrity sealing solution for the most critical process pump applications. 

 

Key Features; 

• Available in both metric and inch shaft sizes, ensuring compatibility with a wide range of pump specifications and international standards. 

• Bi‑directional operation, independent of shaft rotation direction, enabling versatile use across different pump types and variable rotational conditions. 

• Springs located outside the process fluid path (where applicable) to resist clogging and fouling, improving reliability in contaminated, viscous or particulate‑laden services. 

• Back‑to‑back double cartridge configuration providing maximum containment and reliable leakage prevention for hazardous and high‑pressure process applications. 

• Optional flushing and quench connections, fully compatible with API 682 seal support systems including Plans 52, 53A, 53B and 54, to enhance cooling, lubrication and environmental containment. 

• Cartridge construction – factory assembled and tested, supplied as a preset unit for quick installation and easy removal, minimising alignment errors, shaft‑setting issues and maintenance downtime. 

• Hydraulically balanced seal faces with rotating multi‑spring / wave‑spring loading ensure uniform face pressure distribution, reduced heat generation and extended seal life under fluctuating operating conditions. 

• Robust, refurbish-able construction suitable for high‑pressure, hazardous process environments, offering long service life and cost‑effective overhauls through replacement of wear components rather than the complete seal. 

 

Service Overview; 

Parameter	Value
Equipment	Process Pumps, API Pumps, Mixers, Agitators, Reactors
Fluid	Hydrocarbons, Chemicals, Solvents, Slurries, Process Fluids
Service Nature	Hazardous, Corrosive, Volatile, High-Temperature
Operating Mode	Continuous Duty / Heavy Industrial Service

 

Specifications; 

Item	Min	Max	Typical / Notes
Shaft Size	20 mm (0.750”)	300 mm (12.000”)	Custom sizes available
Pressure	Vacuum	40 bar (580 psi)	Higher on request
Temperature	-40°C (-40°F)	+220°C (+428°F)	Depends on elastomer selection
Speed	—	3600 RPM	Application dependent

 

Materials; 

Component	Standard Material	Optional Material	Comment
Seal Faces	Carbon vs Silicon Carbide	Silicon Carbide vs Tungsten Carbide	Selected per fluid abrasiveness
Elastomers	FKM (Viton)	EPDM / PTFE / FFKM	Chemical compatibility dependent
Metal Parts	SS 316	Duplex SS / Hastelloy / Alloy 20 / Titanium	Corrosion-resistant options
Springs	SS 316	Hastelloy C	External multi-spring arrangement

 

Applications; 

• Pulp and paper stock pumps 

• API 610 and ANSI process pumps 

• Fertilizer and agrochemical plants 

• Sugar and distillery process pumps 

• Power plant auxiliary rotating equipment 

• Water and wastewater treatment systems 

• Petrochemical and refinery process pumps 

• Steel and mining slurry handling equipment 

• Pharmaceutical and chemical processing systems 

• Food processing and hygienic fluid transfer systems 

 

Operating Limits; 

Parameter	Value
Pressure	Up to 40 bar (580 psi)
Temperature	-40°C to +220°C (-40°F to +428°F)
Speed	Up to 3600 RPM
Size Range	20 mm to 300 mm (0.750” to 12.000”)

 

Engineering Note; 

Technical values shown are typical engineering guidelines for double cartridge multi-spring seals and should be verified against actual operating conditions, fluid properties, and API piping plan selection before final specification.