Quick answers
Size a spiral accumulator by storage length: required storage length ≥ mill line speed × time for one complete coil change and joint × 1.2 to 1.5, and check the refill after the joint. A horizontal accumulator uses one main motor to turn the whole disc, plus a separate feeder motor. A floor-type accumulator drives its outer rollers in groups, usually with one motor fewer than the number of groups. The release speed follows the mill, and the feeding speed must be higher than the mill speed so the accumulator can refill. Storage and feeding use variable-frequency drives (VFDs). Details follow below.
How much strip does a spiral accumulator store, and how do I calculate it?
Storage depends on the diameter, strip width, strip thickness and winding method. For selection, work backward: first calculate how much storage you need, then choose the type and diameter. Required storage length ≥ mill line speed × time for one complete coil change and joint × safety factor (usually 1.2 to 1.5).
Example (calculation method only; the inputs are assumptions, not the performance of any particular machine): at a line speed of 80 m/min and one complete coil change and joint of 5 minutes, you need 80 × 5 = 400 m; with a safety factor of 1.3, about 520 m.
A storage figure in tons changes with strip width and thickness and does not show whether the coil-change time is covered, so storage should be checked as a length in meters.
How should I estimate the coil-change time?
Count the complete cycle, from the moment the uncoiler stops feeding until strip feeding restarts. With a single-head uncoiler, loading the new coil falls inside this time, whether the coil is loaded by overhead crane or by coil car. A double-head uncoiler can load the next coil on its other arm while the current coil is running, so the cycle is mainly turning the uncoiler, threading the strip head, cutting, aligning, welding and resetting. Aligning the strip ends at the shear and butt welder, the coil loading method and the number of operators all affect this time; with manual welding and a single-head uncoiler, one coil change often takes several minutes or longer. On an existing line, time several real coil changes on site and use those figures to check the storage.
How many motors does a horizontal spiral accumulator have?
The accumulator body has one main motor. It turns the whole disc through a reducer and a large open gear, while the outer ring stays fixed. The feeder has its own motor. So a horizontal accumulator is driven by a main motor plus a feeder motor. Motor power is chosen for the diameter, strip width and thickness and is listed in the technical proposal.
How many motors does a floor-type spiral accumulator have?
The base of a floor-type accumulator does not rotate. Its outer horizontal rollers are divided into groups around the circle. The usual design gives each group its own geared motor and leaves one group undriven, so the number of driven motors = number of groups − 1. For example, with 12 groups there are 11 geared motors. The number of groups depends on the diameter and strip width. For heavy, thick strip, a floor-type unit can use one large motor with a central drive instead. The feeder has a separate motor, used mainly for threading.
What is the speed of a spiral accumulator?
There is no single speed figure. Look at two speeds: the release speed, which follows the tube mill line speed, and the feeding (filling) speed, which must be higher than the mill speed so the accumulator can refill after the joint. The feeding speed is set in the technical proposal from the maximum mill speed, the storage length and the required refill time. Mill line speeds are listed in each tube mill model's specification table; actual speed depends on pipe size and wall thickness.
How are the controls configured?
Storage and feeding use VFD speed control. Motors and controls are configured for the grid voltage and frequency at your site, so please state them in your inquiry. The supply in China is generally 380 V/50 Hz; common supplies on export projects include 415 V/50 Hz, 440 V/60 Hz, 460 V/60 Hz and 480 V/60 Hz. A strip length display is available as an option. If you have other specific requirements for operator displays or for signals between the accumulator and the tube mill, include them in your inquiry and our engineers will confirm them in the technical proposal.
What if the accumulator and the tube mill are at different heights?
Entry-section equipment commonly works at a strip center height of about 900 mm (reference value), while the tube mill's pass line is set by the mill design, and the two are often different. The high turnover stand at the accumulator exit bridges the difference; if needed, a two-roll pinch unit is added after it. So before an accumulator or entry section is matched to an existing mill, confirm the mill's pass-line (center) height. Final elevations follow the project layout and foundation drawings.
Can you add or replace an accumulator on an existing tube mill? What do you need from me?
Yes. Spiral accumulators can also be supplied as single machines. The standard scope covers the flat support stand, the adjustable twist stand, the feeder, the accumulator body, the high turnover stand and the electrical control cabinet. To match the new accumulator to your existing equipment, please send:
- Existing tube mill model, pass-line (center) height and feed direction (left-hand or right-hand)
- Maximum and normal line speed of the mill
- Strip width and thickness range, material grade, and yield and tensile strength
- Type of your current uncoiler and shear and butt welder, and the measured coil-change time
- Floor length and width available for the accumulator, and the position of the machines before and after it
- Local voltage and frequency
Horizontal or floor type: which should I choose?
As a general rule, narrower and thinner strip with moderate storage needs points to a horizontal accumulator, which is compact. Wider or thicker strip, or a large storage requirement, points to a floor-type accumulator, which is built as a fixed accumulator or a variable accumulator depending on strip thickness and material strength. There is no fixed cut-off for every project; our engineers decide from strip width, thickness, material strength, line speed and storage length. See our guide Horizontal vs. Floor-Type Spiral Accumulator: How to Choose.
Are spiral accumulators used only on tube mills?
No. Tube mills are the main use, but spiral accumulators are also used on other continuous strip lines, such as slitting, pickling and cold-rolled galvanizing lines. For lines other than tube mills, the accumulator is evaluated separately for the process, speed and strip size of that line.
How much does a spiral accumulator cost?
Each accumulator is configured for strip width, thickness, material, line speed and storage requirement, so pricing is configured to order and quoted separately. Please tell us the strip width and thickness range, material grade and strength, mill line speed, coil weight, joining method, local voltage and frequency, and whether it is a new line or an upgrade. We quote each machine as a separate item.
About this article
Prepared by the InGen Engineering Team. This is a general technical guide, not a specification or performance guarantee for any project. Final parameters are set in the project's technical proposal and technical agreement.