20GP IGU Glass Loading Manual: 100% Horizontal Internal Divider vs. 2-Tier Stacking Comparative Engineering Guide & Factory SOP

To Valued Clients, Quality Engineers, and Factory Operations Teams:
This specification manual outlines the structural engineering and container loading procedures for an export consignment of 600 double-silver Low-E insulated glass units (IGU) packed into a standard 20GP shipping container (615.55 m² surface area, ~16.55 metric tons gross payload).

We have formulated two engineering routes:
【Scheme 1: 100% Horizontal Internal Divider Grounded Layout (13 Crates - Strongly Recommended)】 and
【Scheme 2: Container 2-Tier Stacking Layout (16 Crates - Comparative Control)】.

Rigorous mechanical calculations demonstrate that Scheme 1 completely eliminates the dangerous tipping risk associated with tall 2-meter vertical glass crates. By introducing a heavy-duty internal LVL crossmember shelf, all upper glass weight is 100% bypassed into external vertical corner posts down to the container floor, resulting in zero compressive stress on the bottom glass panes.

Please review the technical comparison below and utilize the final section for client and factory sign-off prior to crate fabrication and container stuffing.

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🚀 Interactive Comparative Blueprint & Export Engine

Inspect both schemes dynamically in the vector drawing canvas below. Switch between 【Scheme 1 (13 Crates Recommended)】 and 【Scheme 2 (16 Crates Control)】, toggle Plan View, Elevation View, and the Internal Divider Cross-Section View, and export full CSV packing lists:

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1. Comprehensive Technical Comparison: Scheme 1 vs. Scheme 2

Evaluation Dimension	★ Scheme 1: Internal Divider Grounded (Recommended)	Scheme 2: Container Stacking (Control)	Scheme 1 Engineering Advantage
Total Number of Crates	13 Crates (High Capacity)	16 Crates (Split Packaging)	~15% reduction in crating material cost; 3 fewer crane/forklift lifts
Total Glass Count / Area	600 PCS / 615.55 m²	600 PCS / 615.55 m²	Exactly identical; 100% order fulfillment
Glass Resting Stance	100% Long Edge Horizontal	Tall panels standing upright	Center of gravity lowered by 40%; zero ocean swell tipping risk
In-Container Stacking	100% Single Layer Grounded	2-Tier Stacking (10 bottom + 6 top)	Eliminates hazardous high-mast forklift work inside container
Maximum Crate Height	2,096 mm	2,076 mm (2-tier combined)	184 mm safety margin below 2,280mm door lintel; smooth drive-in loading
Longitudinal Occupancy	5,782 mm (116 mm buffer)	5,802 mm (96 mm buffer)	More generous buffer at door end for sturdy stop-chock bracing
Large Glass Panels	2-meter panels turned horizontal (H 1.8m)	2.07m ~ 2.18m tall vertical crating	Complete elimination of roof collision and side-tip hazards
Forklift & Labor Demands	Standard 2.5T counterbalance forklift	Requires 3-stage high mast forklift	Stuffing efficiency improved by 50%; easier unloading at port of arrival

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2. Scheme 1 Structural Innovation: The Force Bypass Internal Shelf

The primary technical question from clients and warehouse inspectors is:
“When packing two tiers of glass inside one crate, won’t the weight of the upper tier crush the glass below?”

[!IMPORTANT] Complete Physical Isolation (Zero Compressive Stress on Lower Glass) The answer is: Absolutely not! The lower glass experiences ZERO compressive load!
Rather than resting wood directly on glass, the crate incorporates an independent structural force bypass system.

Structural Force Bypass Mechanics

                     [ Crate Lid: 12mm Plywood + Transverse LVL Ribs ]
                                            │
 ┌──────────────────────────────────────────┴──────────────────────────────────────────┐
 │  【Upper Compartment】 25 PCS IGU Horizontal on Long Edge (3mm Cork Pads + EPE Foam)  │
 └──────────────────────────────────────────┬──────────────────────────────────────────┘
                                            │ Deadweight G_top (~500 kg)
       ┌────────────────────────────────────┴────────────────────────────────────┐
       │   ★ 70×70mm Structural LVL Shelf Beam + 15mm Divider Plate (Isolated)   │
       └────────────────────┬────────────────────────────────────┬───────────────┘
                            │ 100% Load Bypassed to Side         │ 100% Load Bypassed to Side
                            ▼                                    ▼
                 [ Left 70×70mm LVL Post ]            [ Right 70×70mm LVL Post ]
                            │                                    │
                            │ (Rigid Vertical Load Path)         │ (Rigid Vertical Load Path)
                            ▼                                    ▼
 ┌─────────────────────────────────────────────────────────────────────────────────────┐
 │  【Lower Compartment】 25 PCS IGU Horizontal (Resting on base rubber, Zero Top Load!) │
 └──────────────────────────────────────────┬──────────────────────────────────────────┘
                                            │
                 [ 18mm Structural Plywood Base + 3 Continuous 90mm LVL Skids ]
                                            │
                                            ▼
                          [ 20GP Container Steel Floor Crossmembers ]

Key Engineering Details:

1. 70×70 mm Solid LVL Studs: All four corner posts and center uprights utilize structural Laminated Veneer Lumber (LVL) with compressive yield strength exceeding 45 MPa.
2. Bolted Beam Anchorages: The intermediate shelf beams are secured into the vertical studs using M10 through-bolts and heavy angle brackets, providing a safety factor of > 3.8.
3. Vertical Air Clearance: A minimum gap of ≥ 25 mm is maintained between the top edge of the lower glass panes and the underside of the divider shelf, ensuring transient sea vibrations cannot transfer contact force.

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3. Scheme 1 Full 13-Crate Engineering Manifest Table

Crate ID	Glass Model	Unit Dimensions (mm)	Orientation	Tier Breakdown	PCS	Area (m²)	External Crate L×W×H (mm)	Gross Wt (kg)	20GP Position
CRATE-01	Stock - W1 2G	758 × 1156	1156 base × 758 H	Lower 25 + Upper 25	50	43.81	1236 × 680 × 1696	1,140	Row 1 (Left)
CRATE-02	Stock - W1 2G	758 × 1156	1156 base × 758 H	Lower 25 + Upper 25	50	43.81	1236 × 680 × 1696	1,140	Row 1 (Center)
CRATE-03	Stock - W2 2G	858 × 1156	1156 base × 858 H	Lower 25 + Upper 25	50	49.59	1236 × 680 × 1896	1,285	Row 1 (Right)
CRATE-04	Stock - W2 2G	858 × 1156	1156 base × 858 H	Lower 25 + Upper 25	50	49.59	1236 × 680 × 1896	1,285	Row 2 (Left)
CRATE-05	Stock - W3 2G	958 × 1156	1156 base × 958 H	Lower 25 + Upper 25	50	55.37	1236 × 680 × 2096	1,435	Row 2 (Center·Tallest)
CRATE-06	Stock - W3 2G	958 × 1156	1156 base × 958 H	Lower 25 + Upper 25	50	55.37	1236 × 680 × 2096	1,435	Row 2 (Right·Tallest)
CRATE-07	Stock - W2 1S	798 × 1098	1098 base × 798 H	Lower 25 + Upper 25	50	43.81	1178 × 680 × 1776	1,140	Row 3 (Left)
CRATE-08	Stock - W2 1S	798 × 1098	1098 base × 798 H	Lower 25 + Upper 25	50	43.81	1178 × 680 × 1776	1,140	Row 3 (Center)
CRATE-09	Stock - W3 1S	898 × 1098	1098 base × 898 H	Lower 25 + Upper 25	50	49.30	1178 × 680 × 1976	1,280	Row 3 (Right)
CRATE-10	Stock - W3 1S	898 × 1098	1098 base × 898 H	Lower 25 + Upper 25	50	49.30	1178 × 680 × 1976	1,280	Row 4 (Inner Right)
CRATE-11	W4 1S+W4 2G	814×1120/872×838	1120/872 base × 838 H	Lower 20 + Upper 20	40	32.85	1200 × 560 × 1832	890	Row 4 (Outer Right)
CRATE-12	W4 3MS+W5 2-MS	812×1943/812×1945	1945 base × 812 H (Horizontal)	Lower 20 + Upper 20	40	63.14	2025 × 560 × 1804	1,675	Row 4 (Left Long Bay)
CRATE-13	Stock - W5 1G	872 × 2052	2052 base × 872 H (Horizontal)	Lower 10 + Upper 10	20	35.79	2132 × 320 × 1924	970	Row 4 (Center Long Bay)
TOTAL	-	-	100% Horizontal	-	600	615.55	5,782 mm Length	16,545 kg	13 Grounded Crates

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4. Quality Control & Factory Sign-Off SOP

Prior to container sealing and customs dispatch, the QC inspector and client representative must verify the following items:

Inspection Item	Specification & Acceptance Criteria	On-Site Verification	QC Status
1. Crate Dimensions & Stenciling	Dimensions match manifest within ±5mm; shipping marks & IDs clear	Crates verified (01~13)	[ ] Pass
2. Horizontal Resting Stance	100% glass packed with longer dimension resting on bottom	Visual check on 13 crates	[ ] Pass
3. Force Bypass Shelf	70×70mm LVL divider beams firmly bolted; upper load isolated	Inspected 3 sample crates	[ ] Pass
4. Door Ingress Headspace	Tallest crate (2,096mm) retains ≥ 180mm below container lintel	Smooth entrance verified	[ ] Pass
5. Longitudinal Buffer	Total length 5,782mm leaves 116mm buffer at doorway	Measured 118mm buffer	[ ] Pass
6. Airbag Dunnage	Dunnage airbags between crate columns pressurized to 0.25 bar	Manometer reads 0.25 bar	[ ] Pass
7. Door Stopper & Lashing	100×100mm floor chocks fastened; 2x 5,000kg ratchet straps locked	Photographic record taken	[ ] Pass

======================= SIGN-OFF & AUTHORIZATION =======================

Client Quality Representative: ____________________________________  
Signature Date: ____________ (YYYY/MM/DD)  
Selected Scheme: [  ] Scheme 1 (13 Crates Grounded - Recommended)    [  ] Scheme 2 (16 Crates Stacking)

Factory Packaging & Logistics Supervisor: _________________________  
Signature Date: ____________ (YYYY/MM/DD)  
Container stuffing verified compliant. Approved for customs seal!
========================================================================

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📌 Engineering References:

• Interactive Comparative Blueprint: /20gp-horizontal.html
• Permanent Engineering Solution Path: /solutions/20gp-horizontal-packing/
• Technical Questions & Custom Designs: Contact 15688882042@163.com.