EagleBurgmann MFL85N Metal Bellows Mechanical Seal

A metal bellows seal for extreme temperatures from -40 C to 220 C with no dynamic O-ring

The EagleBurgmann MFL85N is a single, balanced, rotating metal bellows mechanical seal for unstepped shafts. Because the bellows unit replaces the dynamically loaded secondary seal and spring, there is no sliding O-ring on the shaft, which EagleBurgmann lists among its advantages together with the self-cleaning effect and the option of a short installation length. The datasheet gives a shaft diameter range of 16 to 100 mm, an operating temperature range of -40 C to +220 C and a sliding velocity of 20 m/s, and names hot, cold and highly viscous media as recommended applications in the process, oil and gas, refining, petrochemical and chemical industries.

The seal follows EN 12756. The datasheet states that a stationary seat lock is necessary, and it gives different pressure ratings depending on whether the seal is pressurised externally or internally.

Technical specifications

Variants and typical dimensions

The dimension table, printed in millimetres for every shaft size, shows that the installed length l1K rises from 42.5 mm for the 16 mm seal to 65 mm for the 90 to 100 mm seals; the 16 mm seal is marked as longer than the EN 12756 length. The G16 seat gives an l1K shorter than EN 12756.

Selection and installation notes

Select a metal bellows seal where the temperature or the liquid would attack elastomer secondary seals, where the shaft or sleeve is prone to fretting from a sliding O-ring, or where the product tends to coat and clog a dynamic elastomer. Remember that the pressure rating differs by direction: the 25 bar figure is for external pressurisation, and an internally pressurised seal drops to 10 bar below 120 C and 5 bar below 220 C. Fit the stationary seat lock where the datasheet requires it and check that the shaft is unstepped. The datasheet reminds users that its technical data are guide values and that the exact conditions of application must be notified before any guarantee for a specific case can be given.

For an elastomer bellows alternative see the John Crane Type 2100 unitized bellows seal, or browse the pumps category.

How the EagleBurgmann MFL85N works

The seal has a rotating metal bellows with a carbon or silicon carbide face. A fixed seat faces it, and the bellows pushes the faces together. The bellows replaces the spring and the dynamic O-ring, so nothing slides on the shaft.

Where the MFL85N is used

• Process industry pumps
• Oil and gas
• Refining
• Petrochemical and chemical plants
• Hot, cold and highly viscous media

Selection checklist for the MFL85N

• Shaft diameter
• Medium and temperature
• External or internal pressure
• Sliding velocity
• Face and seat material
• Bellows material
• Need for a pumping screw
• Seat lock

Installation, commissioning and maintenance notes for the MFL85N

Check the shaft size and the surface finish before fitting. Fit the stationary seat lock where the datasheet calls for it and set the seal to the installation length. Run the pump only with the seal wetted and inspect for leakage at regular intervals.

Requesting a quotation for the EagleBurgmann MFL85N

Please send the shaft diameter, the medium, the temperature and the pressure. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

MFL85N seal type

It is a single, balanced, rotating metal bellows seal.

MFL85N shaft type

It is for unstepped shafts.

MFL85N rotation

It works independent of the direction of rotation.

MFL85N secondary seal

The bellows unit replaces the dynamically loaded secondary seal and spring.

MFL85N no sliding O-ring

There is no sliding O-ring on the shaft.

MFL85N self-cleaning

EagleBurgmann lists a self-cleaning effect among its advantages.

MFL85N short length

A short installation length is possible.

MFL85N shaft diameter

The shaft diameter range is 16 to 100 mm.

MFL85N temperature

The temperature range is minus 40 to plus 220 degrees C.

MFL85N sliding velocity

The sliding velocity is 20 m/s.

MFL85N external pressure

Externally pressurised, it takes up to 25 bar.

MFL85N internal pressure

Internally pressurised, it takes up to 10 bar below 120 degrees C.

MFL85N hot internal pressure

Internally pressurised, it takes up to 5 bar below 220 degrees C.

MFL85N seat lock

A stationary seat lock is necessary.

MFL85N seal face

The seal face is carbon graphite antimony impregnated or silicon carbide.

MFL85N seat

The seat is silicon carbide.

MFL85N short seat

A G16 short-installation seat is offered.

MFL85N bellows

The bellows is Inconel 718 hardened or Hastelloy C-276.

MFL85N metal parts

Metal parts are CrNiMo steel, duplex or Hastelloy C-4.

MFL85N torque transmission

Torque is transmitted by set screws.

MFL85N pumping screw

A pumping screw is available for highly viscous media.

MFL85N viscous variant

That version is the MFL85F, and it depends on the direction of rotation.

MFL85N retrofit

The pumping screw can be retrofitted.

MFL85N related variant

The MFL90N is internally pressurised to 16 bar for shafts of 20 to 100 mm.

Seal records for the MFL85N

Record the shaft size, the installed length and the date of each leakage check.

Choosing the right MFL85N variant

Choose the variant from the medium viscosity and from the direction of pressure.

Documents and quotation

The EagleBurgmann MFL85N data sheet (4 pages, EN) lists the operating range, materials, variants, seat options and the dimension table by shaft diameter is attached to this page and is the manufacturer’s own document, not a Seven Star summary.

Before ordering confirm the shaft diameter, pressure direction, temperature, liquid and speed, and the face, bellows and seat codes. Seven Star LLC, an independent supplier in Muscat, quotes the EagleBurgmann MFL85N against your duty point and delivery requirement; send the document tag, flow, head and liquid so the right size can be confirmed before an offer is issued.