Investigating SiC Seal Face Grooves

Start with the operating sequence

Ask when leakage first appeared relative to commissioning, maintenance, a restart, loss of flow or restoration of liquid. Record priming and venting steps, low-level events and flush interruptions. An early failure deserves investigation, but short service life alone does not establish a material defect.

A pump containing liquid can still lose lubrication at the sealing interface. EagleBurgmann describes film failure caused by local vaporization and inadequate heat removal or reduced pressure. Vulcan Seals also identifies air pockets, interrupted flow and excessive seal compression as possible contributors. Check actual seal-chamber conditions and installed working length, rather than relying only on discharge pressure or tank temperature. [S4, S6]

Verify seal chamber venting after a shutdown

For a vertical pump returning to service, a priming record and a line labelled Plan 13 are not, by themselves, evidence that the seal chamber was vented and the required flush established. This is a review conclusion drawn from the manufacturer guidance below, not a diagnosis of a particular pump. Treat restart readiness as a documented system condition, rather than a property of the replacement SiC ring.

John Crane’s 8648VRS instructions, revised April 2020, require the chamber’s fluid paths, venting and liquid fill to be checked after equipment inactivity as well as after seal installation. That is a model-specific requirement, not a universal procedure. For the actual installation, obtain the applicable pump and seal instructions and identify which shutdown conditions trigger a renewed check. An accepted commissioning record does not establish the chamber’s condition after a later interruption. [S12]

The description “vertical pump” is also insufficient. A January 2018 FSA article by a Flowserve engineer distinguishes vertical turbine and wet pit, sump and slurry, and overhung arrangements. Their pressure paths differ; impeller features and the installed chamber arrangement matter. Ask for the actual pump type and as-built section before using discharge pressure as a substitute for seal-chamber pressure or assuming that a return line has adequate driving pressure. [S13]

EagleBurgmann describes Plan 13 as recirculation from the chamber to suction through an orifice. Its guide calls the arrangement self-venting but also specifies a high-point vent for a vertical pump’s chamber or gland, sufficient heat-removing flow and a suitable chamber-to-suction pressure difference. The practical inference is that a plan name alone cannot demonstrate pre-start venting or effective circulation. Have the responsible designer review the installed elevations and pressure basis; do not select an alternative piping plan from this article. [S14]

For the replacement review, organize existing evidence by three states: shutdown or idle, startup transition, and normal operation. Record the chamber and suction pressure basis, flush evidence, changes during inactivity, applicable acceptance criteria and the person responsible for confirmation. Keep the as-built drawing and shutdown history with the component drawing. Mark missing information as unknown; do not run equipment dry to obtain data.

Carry this evidence into the existing replacement enquiry below, rather than treating a material change as the system correction. FreeWill’s component review concerns the ceramic ring, drawing, grade and inspection needs. Qualified personnel responsible for the equipment must determine restart readiness under the applicable OEM instructions and site safety procedures. This section provides no vent-opening sequence, discharge arrangement, safety-critical design or operating clearance.

Establish where the particles came from

John Crane lists both inadequate lubrication and abrasives in the pumped liquid as possible explanations for high wear with continuous circumferential grooving. The visible pattern is therefore a starting point, not a verdict. [S5]

Self-generated debris is an important alternative. Grundfos describes hot-water conditions outside a seal’s stable-friction pressure and temperature range in which thermal fatigue can release SiC grains. Those grains then abrade the faces. Separately, a laboratory study of self-mated SiC under water-limited, reciprocating contact found severe abrasion that was aggravated by the resulting wear debris. This supports a possible mechanism, not a diagnosis of a rotating pump seal. [S1, S11]

Preserve the failed faces before cleaning or relapping. Compare deposits and debris from both rings with representative process-fluid and flush samples. Record where and when samples were collected. Qualified laboratory examination may help distinguish process particles, deposits and face-material debris; appearance alone may not establish their origin or the sequence of damage.

Use cracks and contact marks as supporting evidence

Crack patterns can help narrow the investigation. EagleBurgmann distinguishes relatively widely spaced, often radial thermal-shock cracks from closely spaced, usually shallow thermal-stress cracks. Sudden liquid arrival after dry-running overheating is one thermal-shock scenario; local surface overheating can produce heat checking. Neither description provides a universal crack-spacing threshold. [S2, S3]

Also inspect drive slots, anti-rotation pin contacts and chipped edges. AESSEAL identifies startup impact between metal pins and SiC as a possible source of stress cracking in some seal designs. A crack near a drive feature therefore warrants an installation and loading review alongside thermal explanations. More than one mechanism may be involved. [S7]

Keep material changes and system corrections separate

A replacement proposal should explain which observed mechanism it addresses. Identify both face materials, their grades, any special phases or coatings, and the seal assembly. Ask the seal designer to assess the complete pair against the fluid, solids, geometry and duty cycle.

In parallel, have the responsible equipment team review priming, venting, fluid supply, cooling, flush distribution and installation. A harder face will not restore an interrupted liquid supply. Any flush or separation change needs application-specific engineering review, including fluid compatibility and whether product dilution is acceptable.

Do not translate “graphite-loaded SiC” into an allowed dry-running time. Grundfos reports differing dry-running behavior between materials and variation even within a grade. If a proposed replacement carries a dry-run claim, request the tested face pair, geometry, load, speed, environment, duration and failure criterion. Ask whether testing included liquid return and repeated starts. A result from another seal or test rig is not an operating allowance for yours. [S1]

Prepare a focused replacement enquiry

The most useful first submission combines the component requirement with the evidence already available. Start with:

• An event timeline showing startup, interruptions, liquid return and first leakage.
• Photographs of both faces with scale and orientation, including cracks and drive features.
• Both material grades, the seal model, drawing revision and required quantity.
• Seal-chamber pressure and temperature, speed and duty cycle, including abnormal events.
• Fluid composition, known solids or deposits, and measured flush conditions.

Mark missing information as unknown. Ask the proposed supplier which explanations remain open, what evidence would distinguish them, and what acceptance criteria should govern the replacement. Coordinate failure analysis with the seal designer or equipment OEM before assigning a cause.

For a component enquiry, use the FreeWill Material Silicon Carbide Mechanical Seal Ring product page and include the drawing and evidence above. Keep the request specific to the component; grade suitability, inspection requirements and any validation work must be agreed for the application.

Only qualified personnel should remove or examine a seal after safe shutdown, isolation, depressurization and control of process-fluid hazards. Do not deliberately dry-run equipment or suddenly introduce cold liquid to an overheated seal to test a theory.

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