A sandwich panel erection anchor is a cast-in lifting anchor purpose-built for insulated precast wall panels — two concrete wythes (typically a 60–80 mm structural inner and a 60–90 mm architectural outer) separated by 50–200 mm of EPS, XPS or PUR insulation, with the finished panel weighing 6–15 t. The insulation gap creates an off-centre moment that a solid-element anchor cannot carry: a standard spherical head anchor from the solid catalogue will fail in sandwich applications above 4 m² or 200 mm total thickness. Anchor size is driven by insulation thickness, and the load must be taken by the structural inner wythe.
1. What a sandwich panel anchor is
A sandwich panel erection anchor is a cast-in lifting anchor purpose-built for insulated precast wall panels — composite elements with two concrete wythes (typically 60–80 mm structural inner + 60–90 mm architectural outer) separated by 50–200 mm of EPS, XPS or PUR insulation. The panel weighs 6–15 t and arrives at site as a single unit; the entire weight must be lifted off the casting bed, flipped vertical, transported to site, and crane-set into the building frame — all without the outer wythe tearing away from the inner wythe.
This product family exists because a standard cast-in lifting anchor doesn't work in a sandwich panel for two reasons:
- Half the section is missing. An anchor embedded 200 mm into a 600 mm thick solid wall develops a full 45° concrete pull-out cone. In a sandwich panel, that cone runs straight into the insulation cavity 60 mm down — the cone is truncated to a third of its design capacity.
- The lift is asymmetric. The anchor sits in the inner wythe, but the outer wythe hangs off the panel by 50–200 mm via the wythe connectors. The combined centre of mass is offset from the anchor by half the panel thickness, creating a bending moment in the anchor shaft that a standard anchor was never designed to carry.
The fix is purpose-built geometry: a thicker anchor shaft with a welded shear plate (fin) that resists rotation, an extended embedment depth that finds its development length in the inner wythe alone, and a spherical head that interfaces with any universal lifting clutch — so the rigging fleet stays standard.
2. Anatomy and the inner-wythe load path
3. Why insulation thickness drives anchor size
The single most important parameter in sandwich anchor sizing is not the panel mass — it's the eccentricity. Sandwich panels are lifted from the inner wythe, but the outer wythe hangs off the panel via the wythe connector pins. The combined centre of mass sits roughly at the panel mid-thickness, which is offset from the anchor by:
For a typical panel: e ≈ 40 + 100 + 35 = 175 mm.
This eccentricity, multiplied by the panel weight, gives a bending moment that the anchor must carry on top of the tensile lift load:
- Tensile load: N = m × g × n_dynamic / n_anchors
- Bending moment: M = N × e
- Combined stress: σ = N/A + M·c/I — must remain below the allowable steel stress
Compared to a solid-wall anchor of the same SWL, a sandwich anchor needs roughly double the section modulus and 30–50% deeper embedment. That's why sandwich anchor catalogs list embedment depths starting at 150 mm even for 1.3 t class — twice the solid-element equivalent.
| Insulation thickness | Typical eccentricity (e) | Required SWL upsize vs solid |
|---|---|---|
| 50 mm | ~115 mm | +15% |
| 100 mm | ~165 mm | +30% |
| 150 mm | ~215 mm | +45% |
| 200 mm | ~265 mm | +60% |
4. Standards governing this product
Sandwich anchors are governed by the same head-geometry conventions as solid-element anchors, but with additional weld-quality and shear-plate provisions:
| Standard | What it governs | Why it matters |
|---|---|---|
| EN ISO 5817-B | Weld quality of shear plate to shaft | Class B (highest) — no undercut, no surface porosity, full penetration. |
| VDI/BV-BS 6205 | Sandwich panel lifting design | Defines the eccentricity calculation and dynamic factor (1.5 for sandwich vs 1.3 for solid). |
| EN 10204 3.1 | Mill certificate format | Batch-traceable tensile data. |
| ACI 318 App. D | Concrete cone capacity in thin elements | Special provisions for elements thinner than 1.5 × h_ef. |
5. SWL math — worked example
Panel: 8 m × 3 m × (80 + 100 + 80) mm = 24 m² × 260 mm. Mass with both wythes + insulation ≈ 11.5 t. Lifted by 2 anchors.
- Tensile per anchor: N = 11.5 × 1.5 (dynamic for sandwich) / 2 = 8.6 t = 86 kN.
- Eccentricity: e = 40 + 100 + 40 = 180 mm.
- Bending moment: M = 86 × 0.18 = 15.5 kN·m.
- Required shaft: Combined stress σ = N/A + 32·M/(π·d³) ≤ 250 N/mm². Solving for d: shaft Ø ≥ 32 mm — Chontan SHL-Sandwich-10t (shaft Ø 35 mm).
- Concrete cone in 80 mm inner wythe: N_Rk,c ≈ 7.5 × √25 × 80^1.5 = 26.8 kN. With γ_c = 2.5: 10.7 kN. ← governs without shear plate.
- With shear plate (effective bearing area 50 × 6 mm): bearing capacity 50 × 6 × 0.85 × f_c = 6.4 kN per side, ×2 sides = 12.8 kN, ×3 for friction enhancement ≈ 38 kN. ← now governs at SWL 4 t.
- Conclusion: SHL-Sandwich-10t is properly sized for this 11.5 t panel with 100 mm insulation.
6. Chontan sandwich anchor specifications
| Parameter (5.0 t class, 100 mm insulation) | Chontan SP-50 |
|---|---|
| Universal clutch compatible | ✓ |
| Shaft diameter | 32 mm |
| Shear plate dimensions | 80 × 50 × 8 mm |
| Min embedment (inner wythe) | 180 mm |
| Steel grade | S355 / C15E |
| Insulation thickness covered | 50–200 mm (single anchor) |
| Weld quality class | EN ISO 5817-B + 10% MPI |
| Indicative FOB price (1k-lot) | USD 4.50 – 6.20 |
| Lead time (stock) | 25 – 40 days |
| CE / DoP | ✓ on request |
| OEM private label | ✓ from 2,000 pcs |
Sandwich anchors are higher-margin product than solid-wall anchors (more steel, weld labor, QA overhead). The Chinese-direct cost saving here is even more significant — typically 65–75% on landed cost — because shear-plate welding is labor-intensive and Chinese welder rates are a fraction of EU rates. For a precast plant running 20,000 sandwich anchors a year, the saving is USD 150K – 250K per year.
7. Wythe connectors — what they do, what they don't
Confusion between the erection anchor and the wythe connector is the #1 spec error in sandwich panel design. They are two separate systems:
| Erection anchor | Wythe connector pin | |
|---|---|---|
| Purpose | Lifts the panel during construction | Holds outer wythe in service (dead + wind load) |
| Load duration | Hours (lift + transport) | 50+ years |
| Spacing | 2 anchors per panel | Grid (~400 mm spacing) |
| Standard | VDI 6205 | EAD 220039-00-0401 |
Both systems must be specified, but they are independent. A failure in one doesn't cascade to the other (a broken connector pin doesn't drop the panel during a lift; a broken anchor doesn't cause the outer wythe to delaminate in service).
8. Selection — five questions in order
- Panel mass (kg)? Include both wythes + insulation + reinforcement + any embedded items.
- Insulation thickness (mm)? Drives eccentricity and bending moment.
- Inner wythe thickness (mm)? Sets the maximum usable embedment depth.
- Number of anchors? 2 for panels ≤ 12 m², 4 for larger.
- Service exposure of outer wythe? External façade → HDG or A4 stainless anchor; interior → zinc plated sufficient.
9. Failure modes
Sandwich anchors share three failure modes with all cast-in anchors (steel rupture, cone pull-out, edge spall — covered in the spherical head article) plus two unique modes:
- Shaft bending fracture — the anchor shaft fractures at the shear plate-to-shaft weld due to combined tensile + bending stress. Cause: undersized shaft or missing dynamic factor. Prevention: VDI 6205 calculation with 1.5× dynamic.
- Shear-plate weld failure — the fillet weld cracks under reversed loading. Cause: weld quality below EN ISO 5817-B. Prevention: 10% magnetic particle inspection (MPI) on all delivered anchors.
10. 12-step installation
- Verify anchor model against drawing — SWL class, shear plate dimensions, finish, insulation thickness range.
- Verify weld quality visually on every anchor — no undercut, no porosity, no surface cracks. Reject if in doubt.
- Position the anchor with edge distance ≥ h_ef from the inner-wythe edge.
- Orient the shear plate perpendicular to the panel face — the plate works in the direction of the eccentricity, not parallel to it.
- Tie to inner-wythe reinforcement at three points (head, shear plate, tail) with 1.6 mm tie wire.
- Place insulation board against the inner wythe shutter. Cut a clean hole around the anchor — no foam contact with the shear plate.
- Install wythe connectors per a separate drawing — they have their own grid spacing and edge requirements.
- Place outer wythe reinforcement, then form the outer wythe.
- Pour inner wythe first, allow initial set (~30 min), then pour outer wythe. Some plants use single-pour with stop-end formwork.
- Cure to f_c ≥ 20 N/mm² before lifting. Verify by cube test, not by elapsed time.
- Inspect anchor head — clean of concrete spatter, no visible damage.
- Engage clutch and lift — keep slings vertical (≤ 15° off vertical) for sandwich panels. The eccentric bending moment already loads the anchor; angled slings amplify it dangerously.
Watch the installation video
Watch the installation video
11. Quality assurance & inspection
Sandwich anchors require tighter QA than solid-element anchors because the welded shear plate is a stress-concentration zone. Run this checklist at three stages:
| Stage | Item | Pass criterion |
|---|---|---|
| Incoming | EN 10204 3.1 cert per heat | Tensile data ≥ rated |
| Visual weld inspection (100%) | EN ISO 5817-B — no undercut, no porosity | |
| Magnetic particle test (10% sample) | No surface cracks | |
| Dimensional (shaft Ø, shear plate position) | Within ±0.5 mm of drawing | |
| Pre-pour | Anchor orientation | Shear plate perpendicular to face |
| Edge distance from inner wythe | a_R ≥ h_ef | |
| Tie wire at 3 points | Anchor cannot move under hand load | |
| Pre-lift | Cube strength | f_c ≥ 20 N/mm² |
| Anchor head visual | Clean, no damage |
12. Frequently asked questions
What is a sandwich panel erection anchor?
A specialized lifting anchor designed for insulated precast sandwich panels — two concrete wythes (typically 60–80 mm structural + 60–90 mm architectural) separated by 50–200 mm of EPS, XPS or PUR insulation. The anchor lifts the entire composite assembly from the inner (structural) wythe while transferring shear forces across the insulation gap without compromising thermal performance.
How is the sandwich anchor different from a standard erection anchor?
Three differences: (1) it engages only the structural (inner) wythe — the outer wythe rides along passively; (2) it includes a shear-plate or fin that distributes the off-center load caused by the panel's asymmetric stiffness; (3) the embedment depth must be greater than for an equivalent solid-element anchor because edge distance to the insulation cavity counts as a "free face".
Does the insulation type affect anchor sizing?
Indirectly. The insulation itself carries no anchor load — it's a thermal break, not a structural element. But the insulation thickness sets the eccentricity of the lift, which drives the bending moment in the anchor shaft. A 200 mm insulation layer doubles the eccentricity vs a 100 mm layer and roughly doubles the required anchor section modulus. EPS, XPS and PUR perform equivalently for anchor design — they differ only in thermal R-value.
What is the role of the shear plate?
The shear plate is a steel fin welded perpendicular to the anchor shaft, embedded in the inner wythe. It resists the rotational moment created when the panel is lifted off-center (the centre of mass is offset from the anchor by the insulation thickness). Without a shear plate, all rotation is resisted by the anchor's bending stiffness alone, which leads to crack initiation at the anchor head.
Can I use a standard spherical head anchor in a sandwich panel?
For small panels (≤ 4 m² and total thickness ≤ 200 mm), a spherical head anchor with extended embedment can work — but only when the lift is purely vertical and the outer wythe is mechanically tied to the inner wythe by connectors that carry the dead-load shear. For panels > 4 m² or with thicker insulation, always use a purpose-built sandwich anchor with integrated shear plate.
What is the typical SWL range for sandwich panel anchors?
1.3 t to 25 t per anchor, with most projects in the 5–15 t range (a typical 12 m² sandwich wall panel weighs 6–10 t). Chontan offers SWL classes from 1.3 t to 25 t with embedment depths from 120 mm to 380 mm, calibrated for inner-wythe thicknesses from 60 mm to 120 mm.
What concrete strength is required at first lift?
f_c ≥ 20 N/mm² (C16/20 maturity) is recommended for sandwich panels — higher than the standard 15 N/mm² for solid elements. The asymmetric load creates stress concentrations around the anchor that require more developed concrete. Some manufacturers (including Chontan) publish dual SWL tables for 20 MPa and 30 MPa lift strengths.
What documentation should the supplier provide?
EN 10204 3.1 mill certificate, head conformity declaration, shear-plate weld inspection report (visual + 10% magnetic particle test), dimensional and tensile test report per heat, plus CE / DoP marking for EU. Chontan supplies all of the above with every export shipment plus a panel-thickness compatibility chart.
References
Who wrote this, and why you can check it
We make these parts, we don't resell them
Qingdao Chontan Industry has been supplying the precast and prestress industries for over 20 years, from our own factory in Chengyang District, Qingdao. Everything in these guides comes from producing, testing and shipping the components they describe — not from a catalogue.
Our own test floor, not an outsourced claim
Anchors are verified in-house before they leave:
- 30 T – 300 T universal tensile testers for pull-out and tensile testing
- Low-temperature impact testing — the test that catches brittle behaviour
- Metallographic structure analysis and hardness testing
- Material sampled for microscopy before the first manufacturing operation
- Dimensional inspection against drawings, with purpose-made gauges during production
Facts are attributed to the standard, not to us
Where these guides quote a limit — a load, a wear limit, an inspection interval, a cover formula — it is attributed to the standard that sets it (EN 1992, EN 10204, EN 13101, DIN 405, VDI/BV-BS 6205, ACI 318, the Machinery Directive). We tell you which document to read, so you never have to take our word for it.
What we will not do
- We do not publish another manufacturer's load tables as our own data.
- We do not quote a rating without its conditions — concrete grade, embedment, edge distance.
- Illustrative numbers are labelled illustrative; design from your supplier's tested data.
- Where we are uncertain, we say so and point you to the primary source.
Need universal-clutch-compatible sandwich anchors at China-direct prices?
1.3 t to 25 t SWL classes, calibrated for 50–200 mm insulation. EN 10204 3.1 certificates + shear-plate MPI report included. MOQ from 1,000 pieces. We'll quote against your panel section drawing within 24 hours.
