Forklift Propane Tanks: Sizes, Steel vs Aluminum, Exchange and Storage

Forklift propane tank sizes

A forklift propane tank is a DOT cylinder sized by the pounds of propane it holds. Manchester Tank and Worthington both list 20 lb, 33.5 lb and 43.5 lb forklift cylinders in steel and in aluminum, and Worthington adds a 28 lb aluminum size. The figures below come from the two manufacturers' spec sheets, which describe them as approximate; check the sheet for the exact model you are offered.

Nominal size	Propane capacity	Steel, empty	Aluminum, empty	Height
20 lb	4.6 to 4.7 gal	26.5 to 27 lb	17 to 19.3 lb	19.2 to 20.4 in
33.5 lb	7.7 to 7.9 gal	34.5 to 36 lb	22.9 to 24 lb	26.9 to 28 in
43.5 lb	10 to 10.3 gal	40 to 44 lb	25 to 27 lb	32.8 to 34 in

All three sizes share roughly the same 12.2 to 12.3 inch diameter, so the choice is mostly about height and weight. A taller cylinder runs longer between changes, but it has to fit the truck's bracket and still be lifted safely, so check with your forklift dealer or manual which sizes the truck accepts.

To estimate a full cylinder's weight, add the propane to the empty (tare) weight marked on the cylinder. A full 33.5 lb steel cylinder comes to roughly 68 to 70 lb and an aluminum one to roughly 56 to 58 lb.

Steel vs aluminum forklift cylinders

Both materials meet the same federal rule for lift-truck fuel. OSHA requires industrial truck fuel containers to be DOT containers with a minimum service pressure of 240 psig, or a qualifying ASME container. Worthington's sheets show its steel forklift cylinders built to DOT-4BA240 and its aluminum ones to DOT-4E240. The practical differences are weight and corrosion.

• Weight. At the 33.5 lb size, Manchester lists 36 lb empty for steel and 24 lb for aluminum, and Worthington lists 34.5 lb and 22.9 lb. That is about 11 to 12 lb less to lift at every change, which adds up over a shift.
• Corrosion. Aluminum does not rust. Worthington's spec sheet marks the aluminum withdrawal tubes and valves "non-rusting", and Manchester's aluminum cylinders are shot blasted to a textured finish. Steel cylinders depend on their powder-coat paint, so chips and rust spots deserve attention at every inspection.
• Ready to fill. Manchester states that its aluminum cylinders are vacuum purged and ready for filling.
• Cost. In an exchange program the supplier chooses the material. If you are buying, ask your supplier to quote both; this guide does not quote cylinder prices.

Use only cylinders built for forklift service. Manchester's catalog lists its forklift cylinders as liquid cylinders and its buffer cylinders as vapor cylinders, so a cylinder that looks the same size is not necessarily interchangeable.

Cylinder exchange vs owning your cylinders

There are two common ways to keep propane forklifts fueled. In an exchange program, the propane supplier owns a pool of cylinders, drops off full ones and collects empties on a schedule. If you own your cylinders, they are refilled by your supplier or at a dispensing station and stay yours.

What exchange does well. No money tied up in cylinders, no requalification dates for you to track, and a fixed routine for your drivers. For many fleets that simplicity is a real advantage. Get in writing who inspects, requalifies and replaces damaged cylinders, and how often deliveries come.

What owning does well. You choose the material, you know every cylinder's history, and you are not tied to one supplier's cylinder pool. The trade-off is responsibility. DOT cylinders must be requalified when they come due, and a DOT 4-series cylinder that shows a leak, corrosion, denting or bulging, or has lost 5 percent or more of its tare weight, must be requalified before it is refilled. Manchester Tank summarizes the DOT retest schedule as 12 years after manufacture and then every 5 years. The federal rule allows several methods with different intervals, so go by the date marked on each cylinder and ask a requalification facility.

Either way, compare cost per cylinder, delivery frequency, how many full spares and waiting empties you must hold, and who handles damaged cylinders. The same reasoning applies to stationary tanks; see buying vs leasing a propane tank. For how DOT cylinders differ from ASME tanks, see ASME vs DOT propane tanks.

Forklift cylinder storage requirements

Storing spare forklift cylinders is regulated. OSHA's rule at 29 CFR 1910.110(f) covers portable containers of up to 1,000 lb water capacity stored at the user's location and not connected for use, which takes in a 33.5 lb forklift cylinder (about 80 lb water capacity). OSHA's powered industrial truck standard also points to NFPA 58 for cylinder storage. In practice, your state or local fire code adopts a specific edition of NFPA 58, and the fire marshal or other authority having jurisdiction has the final word. The points below are what the sources say, not a substitute for that sign-off.

What OSHA 1910.110 says

• Locate stored cylinders to minimize exposure to excessive temperature rise, physical damage and tampering.
• Indoors, keep them away from exits, stairways and areas used for safe exit.
• Keep cylinder outlet valves closed in storage.
• Count empty cylinders stored inside as full when working out quantity limits.
• In buildings not frequented by the public, such as industrial buildings, store no more than 300 lb of LP-gas outside a special storage room. That is eight full 33.5 lb cylinders, not nine.
• Outdoors, OSHA's distance table requires no separation from the nearest important building for 500 lb or less. From 501 to 2,500 lb, cylinders must be at least 10 ft from any building on adjoining property, any sidewalk and busy thoroughfares.
• Outdoor storage must be in a suitable enclosure or otherwise protected against tampering.
• Provide at least one approved portable fire extinguisher with a minimum 8-B:C rating at cylinder storage locations (separate supply depots aside).

On the truck itself, OSHA allows LP-gas trucks to be used in buildings, limits each truck to two fuel containers, and says trucks must not be parked and left unattended near excessive heat or ignition sources.

What NFPA 58 says

NFPA 58 has a full chapter on storage of cylinders awaiting use, resale or exchange. NFPA's own fact sheet, written for the 2017 edition, sums up the indoor limits: buildings frequented by the public are limited to 1 lb cylinders and 200 lb in total, while buildings not frequented by the public are limited to 300 lb, with cylinder size not restricted. Later editions and local amendments can differ, which is another reason to confirm with your fire inspector.

Industry handling guidance

Guidance written by the Propane Education & Research Council for forklift fleets is to keep cylinders in a secure rack or cage, stored horizontally with the pressure relief valves in the uppermost position, at a safe distance from heat and ignition sources, protected from the elements and away from stairwells and high-traffic areas.

Choosing a forklift cylinder cage

A lockable, ventilated cage is the usual way to meet the enclosure and tamper points above outdoors. Size it by cylinders, not trucks: at any moment you hold full spares and empties waiting for collection, and both need a slot.

• 12-Hold Steel 33.5# Forklift Cage, $745.00: powder-coated steel, 44 x 68 x 30 in, twelve 33.5 lb cylinders.
• 12-Hold Aluminum 33.5# Forklift Cage, $720.00: aluminum, 44 x 65 x 30 in, the same twelve cylinders, for coastal or uncovered sites where rust is a concern.

Twelve full 33.5 lb cylinders hold 402 lb of propane, inside the 500 lb band of OSHA's outdoor table. A second cage beside it takes the site to 804 lb, which brings in OSHA's 10 ft separation from sidewalks, busy thoroughfares and buildings on adjoining property. The NFPA 58 edition and local code that apply to you may set other distances, including from doorways and building openings, so settle the location with the fire inspector before the slab is poured. Neither cage includes cylinders or a padlock; see shipping and delivery for how freight arrives. The full range, including cages for 20 lb grill cylinders, is under forklift and BBQ cylinder cages.

Safety: who does what

• Only trained operators should change cylinders, following the truck maker's procedure and PERC's checklist: valve closed before connecting, cylinder seated so the pin enters the locating hole in the collar, relief valve roughly 180 degrees from the locating pin, brackets tightened, then a leak check with leak-detection solution.
• Inspect cylinders before use for rust, dents, gouges and leaks. Take damaged or leaking cylinders out of service even if they are within their requalification date.
• Leave filling to your propane supplier or trained dispensing staff, and never try to repair a cylinder or its valves on site.
• Close the service valve when the truck is not in use.

If you also run stationary tanks, see the propane tank size chart. For cage questions, contact us.