What Is the Coiling Method vs Plate-by-Plate Method?
The coiling method erects a welded tank by building the top shell course at ground level and jacking the structure upward course by course, welding at working height. The plate-by-plate method erects each course with cranes from the bottom up. Both build API 650 tanks; they differ in speed, crew access, and site constraints.
The Two Classic Tank Erection Methods
In the coiling or jacking method — historically the Soviet-era coil of panels welded at ground level, today the hydraulic jacking system — the tank grows downward: the top course is assembled at grade, hydraulic jacks lift the whole shell, and the next course is fitted and welded underneath at ground level. Welders work at comfortable height inside an enclosed system, cranes are minimal, and wind exposure is limited because the structure stays low.
The plate-by-plate method is the traditional sequence: the bottom is laid, the first shell course is fitted plate by plate, girth welds close it, and each successive course is lifted into place by crane. It needs no jacking equipment, handles very heavy plate and large nozzles naturally, and remains the default on massive tanks and wherever jacking capacity would be exceeded.
Choosing the Erection Method Is a Real Decision
The method chosen touches schedule, weld quality, crane logistics, and safety. Neither is universally superior — the right choice falls out of tank size, site access, and labor economics.
l Jacking keeps welders at grade but is limited by total lifted weight and jack capacity.
l Crane erection tolerates heavy courses but exposes every weld to work-at-height conditions.
l Wind regimes and site confinement often decide the question before cost does.
How Each Method Runs
The two sequences differ structurally:
1. Coiling/Jacking Sequence: Roof and top course are built at ground level; hydraulic jacks raise the assembly on trestles; the next lower course is fitted and welded at grade; repetition proceeds to the bottom course.
2. Plate-by-Plate Sequence: Bottom plates are laid and tested; first course is erected plate by plate; girth welding closes each ring; cranes set the next course above it to full height.
3. Common Welding and NDE Core: Both methods weld under qualified procedures with radiographic examination per the code shot plan, differing only in where the welder stands.
4. Common Closeout: Hydrostatic testing with settlement monitoring and data-book completion finishes either method identically.
Coiling/Jacking vs Plate-by-Plate Erection
Technical Parameter | Coiling (Jacking) Method | Plate-by-Plate (Crane) Method |
Welder Working Position | Ground level inside the shell, safe and weather-shielded | Work at height on scaffolding as the tank rises |
Crane Requirement | Minimal — jacks carry the structure | Full crane program throughout erection |
Height and Weight Limits | Constrained by jack capacity and lifted weight | Effectively unlimited for very large heavy tanks |
Wind Sensitivity | Low profile during most of the work | Open shell exposed to wind at all heights |
Typical Best Use | Mid-size tanks, confined sites, high-labor-cost regions | Large-diameter and heavy-plate tanks, big-tank terminals |
Where Each Method Fits
l Jacked erection of mid-size fuel and water tanks in confined plants
l Crane erection of large-diameter terminal crude tanks
l Jacking in high-wind coastal or desert sites
l Plate-by-plate work on heavy-wall high-temperature tanks
l Tank farms with repetitive tank designs benefiting from jacking cycles
l Reconstruction and raising projects using hybrid sequences
Key Advantages of Each Method
1. Coiling/Jacking: Safety and Speed at Grade
Ground-level welding with enclosed access cuts scaffolding cost, reduces weather downtime, and shortens programs — the productivity reason jacking dominates repetitive mid-size tank farms.
2. Plate-by-Plate: No Weight Limit on Ambition
Crane erection handles the plate thicknesses, nozzle weights, and diameters that jacking systems cannot lift, keeping the method essential at terminal scale.
3. Both: Identical Code Outcome
Whichever method is used, the finished tank is welded, examined, and tested to the same code — the data book does not record which ladder the welder used.
Quality Standards and Proven References
Center Enamel provides design, fabrication, construction, and aftermarket services for storage tanks and silos under ISO 9001 and ISO 45001 certified quality systems, with EN 1090 structural steel certification. With three decades of experience and projects delivered to more than 100 countries — including biogas and wastewater references for Paques and Veolia and industrial references for PetroChina and Sinopec — the company supports tank assets from commissioning through decades of inspection-driven service.
Frequently Asked Questions (FAQ)
Q: Is the coiling method allowed by API 650?
A: Yes. API 650 governs materials, design, welding, and examination; erection method — jacked or crane-set — is a contractor's means and methods choice within code tolerances.
Q: Which method is faster?
A: Jacking is usually faster for mid-size tanks with repetitive designs; crane erection competes strongly on very large tanks where jacking capacity is exceeded.
Q: Can methods be combined on one project?
A: Yes — hybrid sequences, such as crane-erecting heavy lower courses and jacking the upper shell, are common on heavy-wall tanks.
Q: What is the expected lifespan of a professionally engineered steel tank?
A: Steel tanks designed and built to recognized codes (API 650, API 620, AWWA D100, or ASME Section VIII) and maintained under scheduled inspection, coating, and repair programs routinely deliver service lives exceeding 30 years — and tanks managed under API 653-class integrity programs commonly remain in safe service for 50 years or more.
