L68B1 vs L68B2 vs L68B3: Which Tower Crane Mast Section Grade Do You Actually Need?

If you’ve decided on an L68B mast (the 2.0 m square heavy mast used on most 16–25 t tower cranes in MENA), the next question is which grade to specify — B1, B2 or B3 — and how to stack them up a tall climb without over-specifying or, worse, under-rating the base.

This is the procurement call most often quietly wrong. Either the spec sheet over-budgets heavy sections at the top of the mast (waste), or it under-budgets at the bottom (a problem that doesn’t show up until the structural engineer flags it three weeks before the climb).

Here’s the working framework HOE engineers use when sizing an L68B stack for a UAE or wider MENA project. If you’re trying to make the call quickly, jump to the stacking framework and the grade selector table. For a refresher on what the L68B family is in the first place, the L46A1 vs L68B sizing guide is the prerequisite read.

The L68B family at a glance

All three grades share the same external geometry. What changes is the structural rating — specifically the wall thickness of the corner chords and the diagonal bracing.

The 2.0× bending capacity gap between B1 and B3 is what makes the stacking strategy worth the trouble. Putting B3 at the bottom where it earns its weight, and B1 at the top where loads have already tapered, can cut transport weight by 15–25% on a 60 m mast versus a single-grade stack.

L68B1 — when standard is enough

The standard grade. Adequate for the upper sections of most climbs, and for the entire mast on lighter L68-class cranes that aren’t pushing free-standing height limits.

Best fit:

• Top sections of a tall climb (above the highest tie-in)
• Lighter L68-class cranes (6–12 t) where bending moment never approaches L68B2 territory
• Short cranes (≤30 m free-standing) on benign wind sites

Where B1 fails:

• Base of any climb pushing 50 m+ free-standing
• Anywhere a 16 t crane is operating at maximum radius
• Stowed wind loads exceeding ~30 m/s sustained (rare in the UAE but possible during Khamsin)

The trap with B1 is that it looks identical to B2 unless you measure the chord wall. We have seen sites where a contractor accepted “L68B” sections from a grey-market supplier without verifying the grade — they were all B1, the bottom of the stack was structurally inadequate for the planned climb, and the project lost two weeks while replacement B3 sections were sourced from the OEM. Always check the chord wall thickness, the OEM stamp, and the material certificate before lifting.

L68B2 — the mid-mast workhorse

The default mid-mast grade on most heavy tower crane installations in MENA. Roughly 50% more bending capacity than B1, ~17% heavier, and the sweet spot for the bulk of the mast on most tall climbs.

Best fit:

• Mid-mast (everything between base and the top three sections) on 60–120 m climbs
• Entire mast on 16 t L68-class cranes deployed to ~40–50 m free-standing
• Climbing-cage interface section (the section the cage clamps to during climbs — heavier is better for transient climb loads)

Where B2 isn’t enough:

• Base of cranes free-standing past ~55 m
• Heavy lift envelopes where the crane operates frequently at maximum capacity × max radius
• Coastal sites with sustained high wind exposure

For most Dubai / Abu Dhabi / Sharjah high-rise residential builds running a Yongmao STT293 or Potain MCT 385, the cost-optimal stack uses B2 across the middle two-thirds of the mast.

L68B3 — when you need the heavy

The heaviest L68B variant. Roughly 2× the bending capacity of B1 and ~33% heavier — the section to use at the base of tall free-standing climbs, in seismic regions, on sites with sustained high-wind exposure, and as the base support for internal floor-climbing crane configurations.

Best fit:

• Base 3–5 sections of any climb planned for 55 m+ free-standing height
• All-mast spec for 25 t+ cranes (Yongmao STT423-equivalent, Zoomlion T7530-25, XCMG XGT8039-25)
• Internal floor-climbing cranes where the base sits in a single floor plate — the concentrated load case favours B3 every time
• Cyclone-class wind zones (rare for the UAE; relevant for the Indian Ocean rim and parts of the eastern Mediterranean)

Where B3 is overkill:

• Top of a tall mast (use B1 or B2 — saves weight, reduces base reaction)
• Short cranes (free-standing height under 30 m) — even B1 is plenty
• Inland sites with mild wind exposure on a 12 t L68 crane

B3 is also the only L68B grade we recommend buying second-hand. Used B1/B2 sections often have ambiguous history — were they ever overloaded? Did they sit at the base of a tall stack in a high-wind zone? With B3, the safety margin is generous enough that even a moderately fatigued section retains adequate capacity. (We still inspect every used B3 we sell — corner chord wall measurement at multiple points, weld checks, bolt-hole elongation.)

How to spec the stack

The naive approach: pick one grade and use it for the whole mast. Works on short climbs. Wasteful on tall ones.

The right approach is to layer the grades to match the load gradient up the mast. Bending moment is highest at the base and tapers as you climb — the heavy section earns its weight at the bottom, the light section earns its weight saved at the top.

Here’s the framework:

Step 1 — Compute the base bending moment

You need this from the crane supplier’s load chart for your specific model + jib length + free-standing height + wind region. The number is in kNm. Ballpark figures:

• 12 t crane, 50 m jib, 40 m free-standing, UAE wind: ~3,500–4,500 kNm
• 16 t crane, 60 m jib, 50 m free-standing, UAE wind: ~6,000–7,500 kNm
• 16 t crane, 75 m jib, 55 m free-standing, UAE wind: ~8,000–9,500 kNm
• 25 t crane, 75 m jib, 50 m free-standing, UAE wind: ~10,000–13,000 kNm

Step 2 — Pick the base grade by capacity

• Below ~5,000 kNm: L68B1 is adequate at the base (rare on heavy cranes)
• 5,000–7,500 kNm: L68B2 base
• 7,500 kNm+: L68B3 base
• Above ~12,000 kNm or in cyclone-wind zones: consult the OEM — possibly L69B or all-B3

Step 3 — Compute the load taper

Roughly, bending moment at any point up the mast = base moment × (1 − height/total_height)² for the dead-load contribution, plus a wind contribution that depends on exposure. Your crane supplier provides the full envelope — what you want to know is where in the mast the load drops below the next grade down’s capacity.

Step 4 — Lay out the stack

A typical 60 m stack on a 16 t Yongmao STT293 in Dubai conditions:

This stack uses 24% less steel weight than a pure-B3 alternative, saves on transport (one fewer truck), reduces base anchor reaction by the dead-load difference, and costs ~18% less to lease or buy. Same crane, same lift envelope, same safety margin.

Step 5 — Spec the climbing cage compatibility

The climbing cage interface section needs to be at least one grade heavier than the static load case suggests, because the climb itself is a dynamic load event. If your B2-rated zone includes the climbing cage clamp position, swap that one section to B3. Same logic for the tie-collar interface sections — these carry concentrated horizontal loads from the structure during operation.

(For a deeper look at how the climbing cage interacts with the mast during a climb, see the internal vs external climbing guide. For tie-collar placement strategy, that’s a separate article in this series — coming up next in the spare parts cluster.)

Grade selector

Quick decision table if you’re short on time. For most UAE / GCC tower crane installations:

This is a starting framework, not a final spec. The actual load envelope depends on jib length, hook position duty cycle, tie-collar spacing, base foundation type and the local wind code. Always verify against the crane manufacturer’s load chart and your structural engineer’s sign-off. HOE’s engineering team will run this calculation as part of any quote at no charge — send us the project parameters.

The procurement mistakes we see most

After 20 years and several hundred mast deliveries in MENA, four mistakes come up over and over:

1. Spec’ing a single grade for the whole mast — usually B2 across the board. Safe but ~15–25% over-budget on steel, weight and lease cost for tall climbs.

2. Accepting “L68B” with no grade specified — grey-market suppliers will quote “L68B” and ship B1 (the cheapest). On a tall climb this is a structural problem, not a paperwork problem. Always specify B1 / B2 / B3 by name on the PO, and require the OEM material certificate.

3. Forgetting the climbing cage interface section needs to be the highest grade in the stack — even if the static load case at that height suggests a lower grade. The climb itself is a transient overload event.

4. Buying second-hand B1 or B2 without proper inspection — fatigue history matters, and the cheaper second-hand market is full of sections with ambiguous provenance. We recommend either buying new or only buying second-hand from suppliers who can produce a current third-party inspection report and serial-number traceability.

What it costs

Indicative ballpark, AED per section, ex-Dubai depot (delivery extra):

• L68B1, new, OEM: AED 18,000–28,000 per 3 m section
• L68B2, new, OEM: AED 24,000–34,000 per 3 m section
• L68B3, new, OEM: AED 30,000–42,000 per 3 m section
• L68B (any grade), second-hand, inspected: typically 45–65% of new price

Prices fluctuate with steel costs and OEM lead times. For a current quote on a specific configuration, send us the spec list.

Where to buy in the UAE

HOE keeps L68B1, L68B2 and L68B3 sections in Dubai stock for same-day UAE dispatch and 2–5 days door-to-door to KSA, Qatar, Oman, Bahrain, Kuwait and Egypt. Mast bolts, pin sets, climbing cages and compatible tie collars all available from the same depot.

For a current parts list and 48-hour fixed-price quote: sales +971 50 144 4810 or send a parts list →. For a crane already on site with a section that needs replacing now, that’s the 24/7 breakdown line: +971 4 880 3079.

The full spare-parts hub with all in-stock categories and the rest of the cluster’s articles lives at /spare-parts.