Forklift truck

01

Read the rated capacity at its load centre

Appendix A of the US OSHA powered industrial truck standard explains stability by moments: a counterbalanced truck tips forward about its front wheels when the load moment (load weight times its distance from the front wheels) exceeds the vehicle moment. Makers therefore rate a truck for a maximum load at a stated load centre, the distance from the fork face to the load's centre of gravity; the appendix's worked example below uses a 24-inch load centre. It describes the stability triangle formed by the three-point suspension that "almost all counterbalanced powered industrial trucks have"; the truck is stable while the line of action of the combined centre of gravity falls inside it. [2]

The appendix works an example: a 3,000 lb truck rated at a 24-inch load centre has a maximum load moment of 72,000 inch-pounds, so a 60-inch-long load with a 30-inch load centre may weigh at most 2,400 lb. It adds that braking, cornering, lifting, tilting and lowering create dynamic forces that shift the centre of gravity. [2] OSHA's eTool adds that an off-centre, badly distributed or oversized load may exceed capacity, and that tilting the load forward increases the load distance and makes it less stable. [3]

Editorial calculation: in metric terms, a truck rated 2,500 kg at an assumed 500 mm load centre has a load moment of 2,500 × 0.5 = 1,250 kg·m; a load whose centre of gravity sits 700 mm from the fork face may then weigh about 1,250 / 0.7 ≈ 1,786 kg; also check the capacity plate for your mast height and attachments. Rating and load centre are assumed examples; use the truck's capacity plate.

Give the supplier the heaviest load and its dimensions and centre of gravity, required load centre, maximum lift height and lowered height, aisle width and turning space, floor and ground conditions, grades, indoor or outdoor use, power source and charging or refuelling arrangements, hazardous-area classification, attachments (side shift, fork positioner, clamps), shifts per day, and the safety and certification rules that apply where it will be used.

02

Match the truck, attachments and power to the site

29 CFR 1910.178 requires new trucks to meet the design and construction requirements of ANSI B56.1-1969 (incorporated by reference), forbids modifications and additions that affect capacity and safe operation without the manufacturer's prior written approval, with capacity and instruction plates changed to suit, and asks users of non-factory front-end attachments to have the truck marked with the attachment and the approximate combined weight at maximum elevation with the load laterally centred. It defines eleven designations by power source and safeguards: D, DS, DY, E, ES, EE, EX, G, GS, LP and LPS. [1]

The same standard requires that only loads within rated capacity are handled, that trucks with attachments are operated as partially loaded when empty, that loaded trucks ascend or descend grades over 10 percent with the load upgrade, and that each operator is trained and evaluated before operating. [1] Appendix A defines grade as the rise or fall in feet over a 100-foot horizontal distance, expressed as a percent. [2]

Editorial calculation: a 10 percent grade rises 10 units in 100, an angle of about 5.7°. Ask the supplier for the truck's rated gradeability loaded and unloaded and compare it with your steepest ramp.

03

Ask for the ISO safety and stability standards outside the US

The OSHA rules this page cites call on ANSI B56.1 for design and construction [1]. ISO also publishes standards for these trucks: ISO 3691-1:2011, which "gives safety requirements and the means for their verification" for self-propelled industrial trucks as defined in ISO 5053 — including counterbalanced trucks, rough-terrain counterbalanced trucks and trucks powered by battery, diesel, gasoline or LPG — and ISO 22915-2:2018, which "specifies the tests for verifying the stability of counterbalanced trucks with masts, equipped with fork arms or with load handling attachments", excluding trucks for freight containers, which ISO 22915-9 covers. [4] [5]

OSHA's Appendix A explains stability by load and vehicle moments around the front wheels [2]; ISO 22915-2 is the test a manufacturer uses to verify that stability for a counterbalanced truck, including with load handling attachments [5]. If a truck will be fitted with a side-shifter, clamp or rotator, ask the supplier for stability verification with that attachment and for the revised capacity plate, which OSHA also requires when attachments change capacity [1].

For trucks bought outside the US, ask which edition of ISO 3691-1 the truck is declared to, including the 2020 amendment, and whether a rough-terrain model is declared under the rough-terrain provisions [4]. OSHA's eTool on load handling gives the operating practices that sit on top of these design standards [3].

Editorial calculation: ISO 3691-1 covers tractors with a drawbar pull up to 20 000 N, about 2,039 kgf (20,000 ÷ 9.81); ISO 22915-2:2018 replaced an edition ten years older. [4] [5]

Values are from the Standard Norge catalogue pages for ISO 3691-1:2011 and ISO 22915-2:2018; the full standards were not reviewed.

04

Counterbalanced, rough-terrain and driverless trucks on the listed sites

Listings include electric counterbalanced forklifts, diesel and electric forklifts with telescopic handlers and side loaders, rough-terrain four-wheel-drive forklifts, and autonomous forklift trucks. Ask each for the capacity plate data at your load centre and lift height, power source designation and attachments.

05

Mast, counterweight, steer axle and plates in OSHA's terms

Counterweight and steer axle matter here because Appendix A builds its stability triangle from them; the plate row is where any attachment change has to show up.

06

What the capacity plate and spec sheet must show for your loads

Capacity means nothing without its load centre and lift height, as OSHA's moment example shows. Speeds, tyres, battery and truck weight are not given in these OSHA and ISO sources and must come from the maker.

07

Send the load, site and power data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Load: [weight; dimensions; load centre]
Lift: [maximum height; lowered height]
Site: [aisles; floor; grades; indoor or outdoor]
Power: [electric, diesel, LPG; designation; charging]
Attachments: [side shift; positioner; clamp]
Duty: [shifts; hours; operators]

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