A 10-ton positioner is not a specification. It is a starting number that has cost more fabrication shops money than any other line on the quotation. The rated load is only meaningful with a stated centre of gravity, a table size, a tilt angle, a duty cycle and a foundation. If the supplier will not put those on the drawing, do not sign the purchase order.
Rated load is a mass at a stated centre of gravity
The EWP two-axis range is listed at 1, 2, 4, 6, 8 and 10 t rated load, with table diameters from 900 to 2,500 mm and maximum rotation diameters from 1,500 to 3,200 mm. Those figures do not mean you can bolt any 10 t fabrication onto the table and tilt it. They mean 10 t at the centre of gravity condition the maker used. Put the centre of gravity 300 mm above the table and you have changed the job from a load problem to a moment problem.
For a 6 t workpiece with its centre of gravity 300 mm above the table, the static overturning moment is about 17.7 kNm before you add weld oscillation, clamp offset or a heavy fixture. At 10 t and the same 300 mm offset, it is about 29.4 kNm. The tilt gearbox and brake see that moment every time you index.
A unit that is honest at 6 t with the load sitting on the table can be marginal at 6 t with a 300 mm offset. Ask for the load curve at 0 mm, 150 mm, 300 mm and 500 mm offset. If the answer is only rated load 6 t, walk away.
What a 300 mm offset does to the tilt gearbox
The tilt gearbox is not usually the part that fails first in a clean, slow application. It is the part that fails after months of reversed torque, backlash and brake wear. At a 120 deg tilt on the larger EWP frames, the load can swing past top dead centre and reverse the torque direction.
The brake must hold that reversal, not just the static load. Specify holding torque at the worst tilt angle, not only at horizontal. Specify the maximum offset in two directions: above the table and out from the table centre. A 300 mm offset on a 4 t job is 11.8 kNm static; that is enough to expose a gearbox selected on mass alone.
The small EWP frames tilt 0135 deg. Above 4 t, the range is 0120 deg. If your process needs 135 deg with a 6 t load, do not buy that frame and hope. It will not do it. Change the fixture, change the process, or buy a different machine.
Duty cycle limits are thermal limits
Duty cycle is not a sales margin. It is a motor and gearbox thermal limit. The EWP rotation power range is 1.12.2 kW, and those motors are not sized for continuous rotation at rated load with no rest. If your cell runs 20 hours a day with a 2-minute load, 8-minute weld and 1-minute unload, that is 6 cycles per hour and 60 starts in a 10-hour shift.
Add a 300 mm offset and the tilt starts become harder than the weld rotation. Ask for the duty cycle at rated load, the ambient temperature, the starts per hour and the allowable reversing frequency. A 60% duty rating on a 10-minute cycle means 6 minutes powered and 4 minutes cooling, not 6 minutes welding and 4 minutes holding a load on the brake.
For pipe rotators, the SAR range covers 5100 t capacity, vessel diameters 2506,000 mm, wheel speeds 0.11 m/min and motor power 0.755.5 kW. If your procedure needs 2 m/min wheel speed, do not buy a standard SAR and expect the drive to turn up. If you need continuous rotation at 100 t for 24 hours, that is a duty-cycle conversation before it is a price conversation.
Table diameter is not workpiece clearance
A 2,500 mm table with a 3,200 mm maximum rotation diameter leaves only 350 mm radial clearance. That is fine for a round shell with no clamps, cables or fixtures. It is not fine for a box section with a fixture plate, a torch liner and a welders hand.
The table diameter should match the fixture footprint and the T-slot layout, not just the load. A 900 mm table can carry a 1,500 mm diameter flange if the centre of gravity is supported and the rotation clearance is checked, but you will hate the clamping arrangement every shift.
Check the swing path at the worst tilt angle, not just at horizontal. On a small frame at 135 deg, the workpiece can swing below the table and into the floor. On a large frame at 120 deg, it can swing into the operator side. The maximum rotation diameter is a clearance number; the table diameter is a fixturing number. Do not confuse them.
Foundation above 10 tonnes is a civil design item
The EWP catalogue tops out at 10 t. Above that you are into SAR territory, up to 100 t, or a custom frame. A 10 t positioner with a 300 mm offset can put tens of kNm into the floor. Four 16 mm wedge anchors into a 150 mm slab is not a foundation. Above 10 tonnes, require a reinforced concrete block, anchor bolts designed for uplift and shear, a grout bed and a soil-bearing check.
Put the foundation cost in the budget before you compare machine prices. If the civil work is not funded, do not buy the positioner.
Do not buy when: the quote has no centre-of-gravity envelope; the load curve stops at rated load; a 6 t job needs 135 deg; a 10 t job sits on a 300 mm offset with no holding-torque figure; the duty cycle is 24/7 at rated load; or the largest workpiece is 6,000 mm diameter and you are looking at an EWP with a 3,200 mm maximum rotation diameter. Those are not negotiation points. They are wrong-machine cases.
For the catalogue figures and selection limits behind these rules, see welding equipment technical specifications.
Elevating Welding Positioner (EWP Series)
Technical Specifications:
| Model | Rated Load (tons) | Rotation Power (kW) | Tilt Power (kW) | Table Dia (mm) | Max Rotation (mm) | Tilt Angle | Weight (tons) |
|---|---|---|---|---|---|---|---|
| EWP1 | 1 | 1.1 | 1.5 | 900 | 1500 | 0-135 | 1.2 |
| EWP2 | 2 | 1.1 | 1.5 | 1200 | 2000 | 0-135 | 1.6 |
| EWP4 | 4 | 1.5 | 2.2 | 1400 | 2100 | 0-120 | 2.8 |
| EWP6 | 6 | 2.2 | 3.0 | 1500 | 2500 | 0-120 | 5.0 |
| EWP8 | 8 | 2.2 | 4.0 | 1600 | 2800 | 0-120 | 6.5 |
| EWP10 | 10 | 3.0 | 5.5 | 1800 | 3000 | 0-120 | 7.8 |
| EWP15 | 15 | 3.0 | 5.5 | 2000 | 3200 | 0-120 | 12 |
| EWP20 | 20 | 4.0 | 7.5 | 2200 | 3400 | 0-120 | 18 |
Note: Variable rotation speed. Height adjustable column. Remote pendant control. CE certified options available.
For detailed specifications and pricing, contact us at [email protected] or visit https://biqee.cn.
Conclusion
Choosing the right welding automation solution is key to improving productivity and quality in your fabrication operations.
