EagleBurgmann H74-D Balanced Dual Pusher Mechanical Seal

A balanced dual pusher seal for toxic, hazardous and poorly lubricating media

The EagleBurgmann H74-D is a balanced dual (double) pusher seal for stepped shafts with rotating multiple springs, based on the seal concept of the H7 range. The datasheet lists it for low-solids and low-abrasive media, toxic and hazardous media, media with poor lubrication properties and adhesives, in the process, oil and gas, refining, petrochemical, chemical, power plant and pulp and paper industries, and for chemical standard pumps. The seal is independent of the direction of rotation and is insensitive to low solids contents.

Connection dimensions follow EN 12756 for shaft diameters d1 up to 100 mm. A variant with pumping screw, the H74F-D, is available.

Technical specifications

How the dual arrangement is built

The dimension table covers shaft diameters from 14 mm upward; for example the 14 mm seal has an installed length l1 of 73 mm and the 33 mm seal 79 mm. The table is the reference for the seal chamber depth when fitting a dual seal, since a dual arrangement needs more axial space than a single seal.

Selection and installation notes

A dual seal needs a barrier or buffer fluid system, so decide the support-system arrangement together with the seal: the barrier liquid keeps the product from reaching the atmosphere and lubricates the faces when the product itself lubricates poorly. Choose the face and seat pairing for the product (silicon carbide for abrasive traces, carbon for clean lubricating liquids), and check the elastomer for temperature and compatibility. EagleBurgmann gives its data as guide values, and the exact application conditions must be notified before a guarantee can be given for a specific case.

For a single pusher seal of the same family see the EagleBurgmann H7N, and for another dual arrangement the Flowserve ISC2 cartridge seal; more seals are in the pumps category.

Selection checks for an H74-D application

Gather the full duty data before a size is confirmed: product name and concentration, any solids content, operating and maximum temperatures, seal chamber pressure, shaft speed and the shaft diameter and step at the seal position. Compare these with the operating limits in the table, noting that the permitted pressure falls as shaft diameter increases. Check the available axial space in the seal chamber against the installed length in the dimension table, and confirm how the barrier or buffer fluid will be supplied, circulated and monitored. Material codes for faces, seats, secondary seals and metal parts should be chosen together, since the pairing affects both wear behaviour and chemical resistance.

Installation good practice

Mechanical seals are precision components, so cleanliness during fitting is essential. Inspect the shaft and seal chamber for damage, burrs and sharp edges, and check shaft run-out and end play against the pump manufacturer’s limits. Lubricate O-rings only with a lubricant compatible with the chosen elastomer, avoid touching the lapped faces, and set the working length according to the dimension table and the EagleBurgmann instructions before tightening the set screws. Connect the barrier or buffer fluid lines before the pump is filled, and make sure the support system is vented so no gas pocket remains around the seal faces.

Commissioning and in-service care

Pressurise the barrier system and confirm it is stable before starting the pump, then fill and vent the pump casing. Never run the seal dry. During the first hours of operation, watch the barrier fluid level, pressure and temperature, since these are the earliest indicators of seal behaviour. In service, regular recording of barrier fluid consumption and condition helps distinguish normal wear from a developing leak on the inboard or outboard side, and allows planned replacement rather than an unplanned stop.

Heat, dust and humidity at GCC sites

Refineries, petrochemical plants and power stations in Oman and the wider GCC often run pumps outdoors under strong sun. High ambient temperatures raise the temperature of the barrier fluid and the support system, so check that cooling of the barrier circuit remains adequate in summer and that the barrier fluid stays within the limits of the selected elastomers. Fine dust can collect around the atmosphere side of the seal and on support system instruments, so keep these areas clean during routine rounds, and protect barrier reservoirs and lines from contamination by sand and humid coastal air.

Documents and quotation

The EagleBurgmann H74-D data sheet (6 pages, EN) lists the operating range, materials, parts list, seat options, torque transmission and the dimension tables is attached to this page and is the manufacturer’s own document, not a Seven Star summary.

Before ordering confirm the shaft diameter and shaft step, barrier fluid arrangement, liquid, temperature, pressure and speed, and the face, seat and elastomer codes. Seven Star LLC, an independent supplier in Muscat, quotes the EagleBurgmann H74-D 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.