Introduction

Buying an overhead crane is not like buying a forklift off a lot. You cannot test-drive it, return it, or trade it in next year. Once it is installed, it becomes part of your building — a fixed asset that shapes how your facility works for the next 20 to 30 years. Choose well and it quietly earns its keep every shift. Choose poorly and you inherit a crane that is too small for the loads you grow into, too slow for your cycle rate, or too costly to keep running.

The problem is that most buying decisions get made under pressure. A production line needs lifting capacity, a budget window opens, and the specification gets rushed. Corners get cut on the parts nobody sees at purchase time — the duty class, the supplier’s engineering support, the true cost of running the crane over its life. Those corners come back as downtime, early wear, and repair bills that dwarf whatever the shortcut saved.

This guide walks you through the specification and purchasing process from a procurement manager’s point of view. You will learn the real difference between single and double girder cranes, when to choose top-running over underhung, the specification factors that drive every quote, why total cost of ownership matters more than the sticker price, how to separate a strong supplier from a weak one, and the buying mistakes that cost facilities the most. By the end, you will be able to write a tight specification, read a quote critically, and buy a crane that fits your facility and your future.

This is article 2 of 3 in the Weiyuan Crane overhead crane series. Where article 1 covered OSHA safety compliance, this one covers how to buy the right crane in the first place.

---

Single Girder vs Double Girder Overhead Cranes

The first structural decision you face is how many bridge girders the crane needs. This single choice ripples through your capacity, your headroom, your cost, and how much of your building the crane can actually use.

Single Girder Cranes

A single girder crane uses one bridge beam spanning the runway, with the hoist and trolley usually running underneath it (an underhung trolley on the bottom flange). It is the lighter, simpler, more economical design.

Capacity range: commonly up to around 20 tonnes, with most single girder cranes sitting in the 1 to 10 tonne band.

Span range: practical up to roughly 20 to 30 metres, though longer spans push toward double girder territory as beam deflection grows.

Strengths: lower purchase price, lighter dead weight (so less demanding on the building structure), simpler installation, and a compact profile that suits light to moderate duty.

Best for: general manufacturing, workshops, assembly, warehousing, and maintenance bays where loads are moderate and lift height is not pushed to the limit.

Double Girder Cranes

A double girder crane uses two bridge beams, with the hoist and trolley riding on top of them (a top-running trolley on rails fixed to the girders). The twin-beam design carries heavier loads, spans wider bays, and — critically — lifts higher.

Capacity range: from around 5 tonnes to several hundred tonnes, covering all heavy-duty industrial lifting.

Span range: comfortably beyond 30 metres with the right girder design.

Strengths: higher capacity, longer spans, greater rigidity, and better hook height. Because the trolley sits on top of the girders rather than below them, the hook can be raised much closer to the underside of the roof — a decisive advantage in tight buildings. Double girder designs also carry walkways, larger hoists, and higher travel speeds more easily.

Best for: steel fabrication, heavy machining, foundries, paper mills, power plants, and any bay demanding heavy loads, wide spans, or maximum lift height.

How to Choose Between Them

The decision usually comes down to four questions:

• How heavy? Loads comfortably under 10 to 20 tonnes lean single girder. Heavier loads point to double girder.
• How high? If you need maximum hook height in a fixed building, double girder’s top-running trolley recovers lift height a single girder underhung design gives away.
• How wide? Wide spans deflect a single beam too much; a double girder carries the span with less sag.
• How hard? High duty cycles and high speeds favor the rigidity and durability of a double girder.

Takeaway: single girder wins on cost and simplicity for light-to-moderate duty; double girder wins on capacity, span, hook height, and heavy-duty durability. Do not pay for double girder capacity you will never use — but do not starve a heavy bay of the hook height and rigidity it needs.

---

Top-Running vs Underhung Configurations

Beyond girder count, you must decide how the crane sits on its runway. This is the top-running versus underhung question, and it changes what the crane demands from your building.

Top-Running Cranes

A top-running crane rides on rails mounted on top of the runway beams, which in turn sit on columns or brackets. The crane’s wheels run along the top of the rail.

Capacity: the standard for medium and heavy loads — from a few tonnes up to several hundred tonnes.

Strengths: carries the highest capacities, spans the widest bays, and gives the best hook height and coverage. The load path runs straight down through the runway beams into columns, which is structurally efficient for heavy loads.

Trade-off: requires a runway supported by columns or robust brackets, and the runway beams and their supports must be engineered for the crane loads.

Best for: most double girder cranes and any heavy-duty top-running single girder installation.

Underhung Cranes

An underhung crane hangs from the bottom flange of the runway beams, which are usually suspended from the building roof structure. The crane’s wheels run along the underside of the runway beam flanges.

Capacity: typically light to moderate — commonly up to around 10 tonnes.

Strengths: excellent coverage because the crane can run very close to walls and columns, no floor columns required (the load hangs from the roof), and multiple underhung cranes can share interlocking runways or transfer between bays. It maximizes use of the building’s width.

Trade-off: the roof structure must carry the crane and its load, which caps capacity and demands a structural check of the building. Hook height is reduced because the crane hangs below the runway.

Best for: lighter loads, facilities where floor columns are undesirable, and layouts needing edge-to-edge coverage or crane-to-crane transfer.

Making the Call

Top-running is the default for heavy loads, wide spans, and maximum hook height, provided you can support a column-mounted runway. Underhung suits lighter loads where you want maximum floor space, wall-to-wall coverage, or the flexibility to transfer loads between runways — and where the roof can carry the weight.

Takeaway: top-running carries the heavy work and gives the best hook height; underhung frees the floor and maximizes coverage for lighter loads. Your building structure often decides which is even possible.

---

The Key Specification Factors

Every quote you receive is built from a handful of specification inputs. Get these right and the quotes you compare are accurate and comparable. Get them wrong and you are comparing cranes that will never perform the same way.

1. Rated Capacity

Start with your heaviest single lift, then add the weight of any lifting device — spreader beam, lifting frame, magnet, grab, or below-the-hook tooling — plus a safety margin. This total, not the bare load, is your required rated capacity. If your loads may grow, size up now; adding capacity later usually means a new crane.

2. Span

The span is the distance between the runway rails — effectively the width of the area the crane covers. Measure it from the actual building or runway centres, not a rough estimate. Span drives the girder size and design: a wider span needs a deeper, stronger girder to control deflection, which affects both cost and headroom.

3. Duty Class (CMAA Classification)

This is the single most under-appreciated factor in the whole specification. The CMAA classification (Class A through F) defines how hard the crane works — how many lifts per hour, how close to capacity, over how many years.

• Class A to B: standby or light service — infrequent lifting, rarely near capacity.
• Class C: moderate service — general manufacturing.
• Class D: heavy service — high-volume production, frequent cycling.
• Class E to F: severe to continuous service — near-constant operation, often near capacity.

Two cranes with identical capacity and span can cost very differently because one is built for Class C and the other for Class E. Specify the class from your real duty cycle. Under-classify and the crane wears out years early; over-classify and you pay for durability you never use.

4. Hook Height (Lift Height)

Hook height is how far the hook travels vertically — from its lowest to its highest point. It is set by your building’s clear height minus the space the crane structure, trolley, and hoist occupy. This is exactly where the girder and configuration choices pay off: top-running double girder designs recover hook height that underhung single girder designs give away. Specify the hook height you actually need, and confirm it against the real building dimensions.

5. Building Structure

An overhead crane imposes real loads on your building. A top-running crane loads its columns and foundations; an underhung crane loads the roof structure. Before you finalize anything, confirm the building can carry the crane’s dead weight plus the rated load plus dynamic forces. Where the existing structure cannot, you either reinforce it or specify a freestanding crane support structure — and that cost belongs in the buying decision, not as a surprise at installation.

6. Speeds and Controls

Hoist, trolley, and bridge travel speeds shape your cycle time. Faster is not always better — higher speeds add cost and, without smooth control, cause load swing. Variable frequency drive (VFD) control on the motions delivers soft starts and stops, slow-speed positioning, and reduced wear, and is worth specifying on any crane where accuracy or cycle rate matters.

Takeaway: capacity, span, duty class, hook height, building structure, and speeds are the six inputs behind every quote. Nail them down before you ask for pricing, and every quote you receive becomes genuinely comparable.

---

Total Cost of Ownership vs Purchase Price

The most expensive crane mistake is buying on the sticker price alone. The purchase price is only the first — and often the smallest — part of what a crane costs you over its life.

What the Purchase Price Hides

A cheap crane is easy to sell and easy to buy. What the low number often hides is a lighter duty class than your work demands, thinner engineering support, generic components that are hard to source spares for, and no real after-sales presence. Every one of those gaps becomes a cost later.

The Full Cost Picture

Total cost of ownership (TCO) adds up everything the crane costs across its service life:

• Purchase and installation: the crane, plus delivery, erection, commissioning, and any building reinforcement.
• Energy: motors running many hours a day for decades. Efficient drives and right-sized motors save real money over 20 years.
• Maintenance and spares: routine service, wear parts (wheels, brakes, rope, contactors), and the availability and price of replacement components.
• Downtime: the biggest hidden cost. When a crane stops, the production that depends on it stops too. A reliable, well-classified crane that rarely fails is worth far more than its price difference over a cheap one that faults regularly.
• Service life: a correctly specified crane runs for decades; an under-specified one may need major rebuilding or replacement in a fraction of that time.

The Real Comparison

The right comparison is not “which crane is cheaper to buy” but “which crane is cheaper to own.” A crane that costs 15% more up front but is correctly classified, well supported, and built from serviceable components almost always wins over 20 years — because it avoids the downtime and early replacement that quietly drain the budget.

Takeaway: buy on total cost of ownership, not purchase price. The cheapest crane to buy is rarely the cheapest to own, and downtime is the cost that dwarfs all the others.

---

How to Evaluate Overhead Crane Suppliers

Two suppliers can quote the same specification and deliver wildly different value. The crane is only as good as the company behind it — before, during, and long after the sale. Here is how to tell a strong supplier from a weak one.

Certifications and Standards Compliance

A credible supplier designs and builds to recognized standards. Look for compliance with CMAA classification and design guidance, ASME B30.2 for overhead crane safety, and appropriate quality management certification such as ISO 9001. For international suppliers, confirm the design meets the standards that apply in your country. Certifications are not marketing badges — they are evidence the supplier engineers to a defined, verifiable practice.

Engineering Support

The best value shows up before you buy. A strong supplier assigns engineers who assess your loads, duty cycle, span, hook height, and building structure, then design the crane around your facility rather than pushing a catalog model. Ask whether they provide structural calculations, whether they will verify your building’s capacity, and whether they can engineer a custom solution when a standard one does not fit. Thin engineering support at the quote stage predicts thin support later.

After-Sales and Spare Parts

A crane lives for decades, and it will need service and spares across that whole life. Evaluate:

• Availability of spare parts and how quickly they ship.
• Technical support for troubleshooting and maintenance.
• Installation and commissioning support, whether direct or through a partner.
• Warranty terms and what they actually cover.
• Service reach in your region — a supplier with no presence near you is slow help when a crane is down.

Track Record and References

Ask for references in your industry and for cranes of similar duty and capacity. A supplier who has delivered heavy Class E cranes to steel plants understands demands a light-duty workshop supplier does not. Proven experience with your kind of application is worth more than a lower price from an untested source.

Takeaway: judge a supplier on certifications, upfront engineering, after-sales reach, and a relevant track record — not on price alone. The company behind the crane determines whether it stays reliable for 20 years.

---

Common Overhead Crane Buying Mistakes

Even experienced buyers repeat a handful of costly errors. Knowing them upfront is the cheapest insurance in this whole process.

Mistake 1: Specifying Capacity on Load Alone

Buyers size the crane to the bare load and forget the rigging. The spreader beam, slings, and shackles all count against capacity, so the crane ends up quietly overloaded on every lift.

Prevention: size to the heaviest load plus all below-the-hook tooling plus a safety margin.

Mistake 2: Ignoring Duty Class

The most expensive specification shortcut. A crane sized correctly for capacity but under-classified for its real cycle rate overheats, wears its brakes and motors, and fails years early.

Prevention: specify the CMAA class from your true duty cycle, not a hopeful estimate. Match durability to how hard the crane actually works.

Mistake 3: Overlooking Hook Height Until Installation

Buyers focus on capacity and span and discover too late that the crane’s own structure eats the lift height they needed. Fixing it after installation is expensive or impossible.

Prevention: calculate hook height early from real building dimensions and the actual crane, trolley, and hoist heights. Choose the girder and configuration that protect the lift height you need.

Mistake 4: Skipping the Building Structure Check

The crane is ordered before anyone confirms the building can carry it. Then installation reveals the columns, foundations, or roof need reinforcement — a large, unbudgeted surprise.

Prevention: commission a structural assessment as part of the buying process, and put any reinforcement cost into the decision from the start.

Mistake 5: Buying on Price Alone

The lowest quote wins, and the hidden gaps — light duty class, thin support, hard-to-source spares — surface as downtime and early failure.

Prevention: evaluate on total cost of ownership and supplier strength, not the sticker price.

Mistake 6: Writing a Vague Specification

An incomplete or ambiguous specification produces quotes that cannot be compared, because each supplier fills the gaps differently.

Prevention: write a complete specification — capacity, span, duty class, hook height, speeds, controls, and environment — so every quote answers the same question.

Takeaway: almost every buying mistake traces back to an incomplete specification, an ignored duty class, or a price-first decision. Close those three gaps and you avoid the errors that cost the most.

---

Frequently Asked Questions

Q: What is the difference between a single girder and double girder overhead crane?

A single girder crane uses one bridge beam with the hoist usually running underneath it, making it lighter, cheaper, and ideal for loads up to around 20 tonnes and moderate spans. A double girder crane uses two bridge beams with the hoist running on top, allowing higher capacities (well into hundreds of tonnes), wider spans, greater rigidity, and — importantly — more hook height. Choose single girder for light-to-moderate duty on cost grounds, and double girder for heavy loads, wide spans, high duty cycles, or maximum lift height.

Q: Should I choose a top-running or underhung overhead crane?

Top-running cranes ride on rails atop column-supported runway beams and handle the heaviest loads, widest spans, and best hook heights — the default for medium and heavy duty. Underhung cranes hang from the roof structure, handle lighter loads (typically up to around 10 tonnes), and excel at maximizing floor space and wall-to-wall coverage, with the option to transfer between runways. Your load, required hook height, and — crucially — whether your building can support a column runway or must carry the crane from the roof all drive the choice.

Q: What is CMAA duty class and why does it matter when buying a crane?

CMAA duty class (A through F) defines how hard a crane works — the number of lifts per hour, how close to capacity, and over how many years. It matters because two cranes with the same capacity and span can be built very differently and cost very differently depending on their class. Specifying the class from your real duty cycle is critical: under-classifying causes early wear and failure, while over-classifying means paying for durability you will not use. It is the most commonly overlooked specification factor.

Q: How do I determine the right crane capacity?

Start with your heaviest single lift, then add the weight of any below-the-hook equipment — spreader beam, lifting frame, magnet, grab, or slings — plus a safety margin. That total is your required rated capacity, not the bare load. If your loads are likely to grow, size up at purchase, because adding capacity to an installed crane usually means replacing it. Never specify capacity on the load alone; forgotten rigging weight quietly overloads the crane on every lift.

Q: Why is total cost of ownership more important than purchase price?

Because the purchase price is often the smallest part of what a crane costs over 20 to 30 years. Total cost of ownership adds installation, energy, maintenance, spare parts, and — above all — downtime, which is the biggest hidden cost when a crane stops the production that depends on it. A correctly specified, well-supported crane that costs more up front usually wins over its life by avoiding the failures and early replacement that plague a cheap, under-specified unit.

Q: How do I evaluate an overhead crane supplier?

Look at four things beyond price. First, certifications and standards compliance — CMAA and ASME B30.2 design, plus ISO 9001 quality management. Second, upfront engineering support — do they design around your facility and verify your building structure, or push a catalog model? Third, after-sales strength — spare parts availability, technical support, installation, warranty, and service reach in your region. Fourth, a relevant track record with cranes of similar duty and capacity. The company behind the crane determines whether it stays reliable for decades.

Q: How long does an overhead crane last?

A correctly specified and well-maintained overhead crane commonly serves 20 to 30 years or more. The key words are “correctly specified” and “well-maintained.” A crane matched to its real duty class, supported by available spares, and serviced on schedule reaches the top of that range. An under-classified crane run beyond its design duty, or one starved of maintenance, can need major rebuilding or replacement in a fraction of that time — which is exactly why the buying decision matters so much.

Q: Do I need to reinforce my building for an overhead crane?

Possibly — it depends on the crane and the building. A top-running crane loads its columns and foundations, while an underhung crane loads the roof structure. Before ordering, confirm the building can carry the crane’s dead weight plus rated load plus dynamic forces through a structural assessment. Where it cannot, you either reinforce the structure or specify a freestanding crane support system. Either way, that cost belongs in the buying decision from the start, not as a surprise at installation.