Refractory Anchors & Fastening Systems: Types, Selection & Installation

Why Anchors Are Critical to Refractory Performance

Refractory anchors are welded metal fixtures — most commonly V-shaped SS304 or SS310 stainless steel — embedded in a monolithic lining to hold it against the steel shell, since unlike brick, monolithic castable has no self-supporting structure of its own. Without correctly selected and installed anchors, gravity on roofs and vertical walls, thermal-cycling stress, vibration from rotating equipment, and process forces will eventually detach the lining, causing spalling and unscheduled shutdowns. Anchor material grade must match furnace temperature: carbon steel below 400°C, SS304/310 above it. Anchor spacing and embedment depth are equally critical — correct anchoring is one of the highest-leverage, lowest-cost decisions in monolithic refractory design.

A monolithic refractory lining (castable, gunning, or plastic) is only as good as the anchoring system that holds it to the steel shell or structure. Unlike brick linings that are self-supporting through gravity and arch action, monolithic linings rely entirely on anchors to resist:

• Gravity: On roofs, inclined surfaces, and vertical walls, the lining's own weight would cause it to fall without anchors
• Thermal cycling: Repeated heating and cooling causes the lining to expand and contract, generating stresses that can detach it from the shell
• Vibration: In rotating equipment (kilns, calciners) or equipment near heavy machinery
• Process forces: Gas velocity, material impact, and turbulence

Anchor failure leads to lining detachment (peeling, spalling, or falling), which causes unscheduled shutdowns, safety hazards, and expensive repairs. Selecting and installing anchors correctly is one of the most important aspects of monolithic refractory engineering.

Types of Refractory Anchors

V Anchors

The most common and versatile anchor type. Shaped like the letter V, with two legs welded to the shell at the tip and the open ends embedded in the castable.

• Material: Typically AISI 304 (SS304) or 310 (SS310) stainless steel for oxidation resistance at high temperature. Carbon steel is used only for low-temperature applications (< 400 degC).
• Wire diameter: 6, 8, 10, or 12 mm depending on lining thickness and weight
• Height: Usually 60–80% of the lining thickness. The top 20–40% of the lining should be anchor-free to prevent hot spots at the anchor tips.
• Best for: Flat surfaces, gentle curves, vertical walls, roofs with moderate lining thickness (50–200 mm)

Y Anchors

Similar to V anchors but with a third leg, providing better hold in thick linings and on roofs where the castable must resist higher gravitational pull.

• Material: SS304 or SS310
• Best for: Thick linings (> 150 mm), roof applications, areas with high vibration
• Advantage over V: More holding power per anchor point; better resistance to peeling failure

Bullhorn Anchors

Cast or fabricated anchors shaped like curved horns, with a wide paddle at the embedded end. Used for heavy-duty applications.

• Material: Cast SS310, Inconel 601, or heat-resistant alloy depending on temperature
• Best for: Very thick linings (> 250 mm), high-temperature applications (> 1,200 degC), cement kilns, incinerators

Ceramic Fiber Anchors (Cup Anchors)

Specifically designed for ceramic fiber blanket and module systems. A cup-shaped metal disk on a stud or threaded rod, capped with a ceramic fiber washer.

• Material: SS304 or SS310 stud with metal cup
• Best for: Ceramic fiber blanket and module installations on flat or gently curved surfaces

Hex Metal (Tortoiseshell) Anchoring

A continuous grid of hexagonal cells welded to the shell, filled with refractory. Not technically individual anchors, but a complete anchoring system.

• Material: SS304, SS310, or Inconel strips
• Best for: Extreme erosion conditions (FCCU cyclones in refineries, transfer lines), thin linings under high gas velocity

Pipe Anchors

A short length of hollow steel pipe, sometimes fitted with a ceramic tip, welded to the shell in place of a solid rod. The hollow section carries less metal mass to the hot face than a solid anchor of the same diameter, so it conducts less heat back to the shell.

• Material: SS304/SS310 pipe, sometimes ceramic-tipped
• Best for: Very thick linings or linings with a steep hot-face-to-cold-face temperature gradient, where a solid metal anchor spanning that gradient would otherwise act as a thermal bridge and create a cold spot on the shell exterior directly behind it

Ceramic Anchors (Rod/Pin Form)

Distinct from the ceramic fiber cup anchor covered below, a ceramic rod or pin anchor is used in castable and plastic refractory linings the same way a metal V or Y anchor is, but in zones that exceed the temperature range any metallic anchor grade can survive — typically 1,500 degC and above. Because ceramic anchors cost more and are harder to fix reliably to a steel shell than a welded metal anchor, they are normally used selectively at specific hot spots (burner blocks, slag lines) rather than across an entire lining, with metallic anchors handling the general field of the lining around them.

Which Anchor Type Should You Use? Quick Selection Guide

The five types above serve different jobs. This table summarises the selection logic from the sections above in one place, for a fast first-pass comparison before you get into material-temperature and spacing detail.

Anchor Type	Material	Best Suited For	Key Advantage
V Anchor	SS304 / SS310 (carbon steel only below 400 degC)	Flat surfaces, gentle curves, vertical walls, roofs with moderate lining thickness (50–200 mm)	Most versatile, lowest cost, suits the majority of applications
Y Anchor	SS304 / SS310	Thick linings (> 150 mm), roof applications, high-vibration areas	More holding power per anchor point; better resistance to peeling failure than V
Bullhorn Anchor	Cast SS310, Inconel 601, or heat-resistant alloy	Very thick linings (> 250 mm), high-temperature service (> 1,200 degC), cement kilns, incinerators	Wide paddle end gives the strongest hold for the heaviest, hottest linings
Ceramic Fiber (Cup) Anchor	SS304 / SS310 stud with metal cup	Ceramic fiber blanket and module installations on flat or gently curved surfaces	Purpose-built for fiber systems, not adaptable for castable/gunning use
Hex Metal (Tortoiseshell)	SS304, SS310, or Inconel strips	Extreme erosion conditions (FCCU cyclones, transfer lines), thin linings under high gas velocity	Continuous grid protects the whole surface, not just discrete points
Pipe Anchor	SS304/SS310 pipe, sometimes ceramic-tipped	Very thick linings or steep temperature gradients	Hollow section reduces thermal bridging back to the shell versus a solid rod
Ceramic Anchor (Rod/Pin)	Ceramic	Hot spots beyond metallic anchor range, typically 1,500 degC and above	Only anchor type usable where every metallic grade would fail

For most standard furnace, kiln, and vessel linings, V anchors are the default starting point; move to Y or bullhorn as lining thickness and temperature increase, and to hex metal only where erosion, not gravity or thermal cycling, is the dominant failure mode.

Material Selection Guide

Anchor Material	Max Service Temp	Typical Application
Carbon steel (MS)	400 degC	Low-temperature ducting, storage vessels
AISI 304 (SS304)	850 degC	Most industrial furnace applications
AISI 309 (SS309)	1,000 degC	Higher temperature furnaces
AISI 310 (SS310)	1,150 degC	Cement kilns, incinerators, high-temperature reactors
Inconel 601	1,250 degC	Extreme temperature and carburizing/sulfidizing environments
253MA	1,150 degC	High-temperature with good creep resistance

Critical note: The anchor material must be compatible with the operating temperature at its location in the lining, which is significantly cooler than the hot face temperature. A lining with a 1,400 degC hot face may have only 800–1,000 degC at the anchor tips, depending on thickness and insulation. Calculate this before specifying the anchor material.

Anchor Spacing Guidelines

Anchor spacing determines how many anchors per square meter and how evenly the lining load is distributed:

Lining Thickness (mm)	Anchor Spacing (mm)	Approx. Anchors/m2	Anchor Wire Dia. (mm)
50–75	150–200	25–45	6
75–100	200–250	16–25	6–8
100–150	225–300	11–20	8–10
150–200	250–350	8–16	10–12
200–300	300–400	6–11	12

For roof applications, use 20–30% closer spacing than for walls. At edges, openings, and penetrations, use 50% closer spacing. Always orient V-anchors with the open end pointing down on vertical surfaces (so they catch the lining if it starts to slide).

Welding Requirements

Anchor welding is a critical quality control point. Poor welding is a common cause of anchor failure:

• Welding process: MIG (GMAW) or TIG (GTAW) for stainless steel anchors. Stick welding (SMAW) with appropriate electrodes is acceptable if qualified.
• Electrode/filler: Use matching or over-alloyed filler metal. For SS310 anchors, use 310 or 310L filler.
• Weld size: The weld throat must be at least equal to the wire diameter. A 10 mm anchor needs a 10 mm fillet weld.
• Preheat: Not required for austenitic stainless steel. For carbon steel shell, preheat if the shell is thick (> 25 mm) to avoid hydrogen cracking.
• Inspection: Visual inspection of every weld. Bend test (hammer test) on random samples: try to bend the anchor 15 degrees away from the shell — the weld must not crack. A failure rate above 2% indicates a welding quality problem.

Installation Sequence: Castable vs Gunned Linings

The anchor itself does not change between a cast and a gunned lining, but the sequence around it does, and mixing up the two sequences is a common site error.

Castable Anchors: Installation Sequence

Castable anchors are welded to the shell first, formwork is erected around them to the finished lining thickness, and the anchor sits fully embedded in the wet castable as it is poured and vibrated into place. Because the castable flows and self-compacts around the anchor under vibration, embedment is generally more uniform than in a gunned application — provided vibration is adequate near the anchor itself. A poorly vibrated pour can leave a void right around the anchor base, which is the one place a void does the most damage.

Gunning Installation

Anchors are welded to the shell, and the gunning material is sprayed on in multiple passes that build up thickness progressively. The anchor must be positioned so it ends up correctly embedded within the finished thickness — not buried so deep it does nothing for the working face, and not left standing proud where it will be exposed once gunning is complete. Because gunned material is generally less dense and more variable than a vibrated cast lining, gunned installations typically run a slightly tighter anchor spacing than the equivalent castable application at the same lining thickness.

Common Anchor Installation Mistakes

1. Wrong material: Using carbon steel anchors in a 900 degC application. The anchors oxidize, lose strength, and the lining falls.
2. Anchors too tall: If anchors protrude to the hot face, they create thermal bridges (hot spots on the shell) and initiate spalling at the anchor tip. Keep anchors at 60–80% of lining thickness.
3. Poor welding: Undersized welds, porosity, lack of fusion. The anchor looks attached but fails under thermal cycling.
4. Wrong orientation: V anchors installed with the open end pointing up on a wall allow the lining to slide down. Open end should point down.
5. No anchor coat (tip cap): For stainless steel anchors above 1,000 degC, the anchor tip should be coated or capped with a small piece of ceramic fiber — this protective layer is what's called the anchor coat — to allow differential expansion between the anchor and the castable. Without it, the castable cracks around the anchor tip.
6. Inconsistent spacing: Clustering anchors in some areas and leaving gaps in others leads to uneven support and localized failure.

Special Considerations

Rotating Equipment (Kilns)

In rotating kilns with castable-lined sections, anchors see cyclic loading as the kiln rotates. Use Y anchors or bullhorn anchors for better fatigue resistance. Weld quality is even more critical because the welds see cyclic stress.

High-Velocity Gas Areas

In areas where hot gas velocities exceed 15 m/s (such as cyclone preheaters and transfer ducts), the castable surface erodes from the anchor tip outward, eventually exposing the anchor. Use hex metal systems or embedded studded anchors in these areas.

Ceramic Fiber Module Systems

Fiber modules use a different anchoring philosophy: each module has its own internal stud or rod that mounts to the shell. The key is ensuring that the stud is properly attached and that adjacent modules are compressed tightly together to prevent gap shrinkage during operation.

Anchors by Industry

The selection logic above (shape by thickness and load, material by temperature) holds everywhere. What changes industry to industry is which failure mode actually shows up first — and that's usually not the one a generic spec sheet leads with.

Oil & Gas and Petrochemical

FCC units, reformers, Claus sulphur recovery furnaces and thermal oxidisers commonly run reducing or sulphur-bearing atmospheres. Standard 300-series stainless anchors that handle plain oxidation well can still suffer accelerated sulphidation attack in an H₂S-bearing atmosphere at a temperature well inside their normal oxidation rating — the atmosphere, not just the temperature, decides the anchor material here. Tell us the process gas composition alongside the operating temperature so we can recommend accordingly.

Marine

Ship-board boilers and MARPOL waste incinerators see two failure modes a land-based furnace doesn't: chloride-driven external corrosion of any anchor hardware exposed to the salt-air environment (not just the hot-face side), and continuous low-level vibration from the vessel's own machinery. Weld integrity and any exposed metal outside the lining matter as much here as the anchor's hot-face rating.

Forging

Batch and car-bottom forge furnaces cycle far more often than a continuously-run kiln, and the anchors nearest the charge door also take direct mechanical impact from billet handling. That combination of thermal cycling and mechanical knock is exactly what Y and bullhorn anchors (see above) are for — concentrated at the opening, with standard V anchors sufficient away from it.

Heat Treatment (Carburising / Controlled-Atmosphere Furnaces)

Carburising and nitriding furnaces run a deliberately non-oxidising, carbon- or nitrogen-rich atmosphere by design. That atmosphere can carburise standard stainless anchors over time, diffusing carbon into the metal and making it brittle — a distinct degradation mode from the oxidation resistance a general anchor material table is built around. Atmosphere-specific alloy selection matters more here than in a simple fuel-fired furnace running ordinary combustion gas.

Refractory Anchors vs. Refractory Anchor Bricks

Refractory anchors and refractory anchor bricks are related but different components, and the two terms should not be used interchangeably. Refractory anchors, covered throughout this guide, are metal anchoring components used to mechanically secure refractory linings, particularly monolithic/castable linings, and are welded directly to the equipment shell. Refractory anchor bricks are a separate product: fired refractory ceramic shapes designed for suspended or mechanically supported brick lining systems, particularly kiln roofs, arches and vaults, and are hung rather than welded. As a shaped, fired brick, an anchor brick belongs to the same general product family as SAPL's other shaped refractory bricks, rather than the metal-fastener family covered elsewhere in this guide. Neither their materials, their installation method, nor their typical applications are the same.

Term	Material	Physical Form	Installation	Typical Application	Primary Function	Procurement Terminology
Refractory Anchors	Metal — stainless steel (SS304, SS310) or heat-resistant alloy (e.g. Inconel)	Fabricated metal fastener (V, Y, bullhorn or grid shapes)	Welded directly to the steel shell, then embedded in poured or gunned castable	Walls, roofs and general surfaces of monolithic (castable / gunning / plastic) linings	Mechanically holds a monolithic lining against the shell	Specified by material grade, wire diameter and quantity
Refractory Anchor Bricks	Fired refractory ceramic (a shaped brick, not metal)	Shaped, fired refractory brick unit	Embedded in castable and mechanically hung, not welded to the shell	Suspended/overhead linings — kiln roofs, furnace vaults and arches	Provides a hung, brick-based structural support for overhead linings	Specified by application, required dimensions and quantity, like other shaped bricks

Looking for refractory anchor bricks for a suspended kiln roof, arch or vault lining? These are a different product from the metal anchors described throughout this guide, shaped, fired refractory bricks rather than metal fasteners. Send us your drawing, dimensions, application and quantity. Our technical team will review the requirement and advise on the appropriate refractory shape and grade.

Furnace and kiln roofs are also sometimes built with arch bricks (including end arch and side arch shapes) — a further, separate shaped-refractory category. Unlike an anchor brick, which is hung from the shell, an arch brick is self-supporting: it holds itself and adjacent bricks in place through arch action, wedge-shaped so the load locks the ring together rather than relying on a hanging point. Arch bricks are distinct from both refractory anchors and refractory anchor bricks and should not be confused with either. See our shaped refractories range for more on arch brick shapes and how to specify one for your project.

Custom & Application-Specific Refractory Shapes

Industrial refractory requirements are not always limited to standard catalogue shapes. If your project needs a refractory anchor brick, or another shaped refractory component that isn't a standard listed product, SAPL's technical team can review the application, dimensions, drawing and specification, and evaluate the appropriate refractory shape, grade and fulfilment route for the requirement. Have a shape that isn't in our standard catalogue? Send us the drawing, dimensions, application and quantity, and our technical team will advise on the appropriate refractory solution.

SAPL: Complete Anchoring Solutions

Shanker Agencies supplies refractory anchors in all types and materials — V, Y, bullhorn, hex metal, and ceramic fiber anchoring systems. We provide anchors manufactured to your specification in SS304, SS310, Inconel, and other heat-resistant alloys. Our technical team can assist with anchor layout design, spacing calculations, and material selection based on your application temperature and conditions. Anchors are supplied to match the specific lining they hold: see our low cement castable, ultra low cement castable, conventional castable, plastic refractory, and ceramic fiber product ranges for the corresponding lining system. Contact us for a quotation or to discuss your anchoring requirements for an upcoming project.