What is a Yokohama Fender?

A Yokohama-type fender, more precisely a floating pneumatic rubber fender, is an air-filled marine fender that absorbs berthing and mooring energy between a vessel and a jetty, or between two vessels during ship-to-ship transfers. The name is used loosely across the industry, so understanding what it refers to, and what drives its performance, matters more to a buyer than the label. This article covers what the fender is, how it works, how it compares with solid and foam fenders, and how to size and verify one. It does not cover mooring-line design, jetty structural loading, or installation rigging; each of those depends on the specific berth and should be engineered separately.

What a Yokohama Fender Is ?

A Yokohama-type fender and a floating pneumatic rubber fender describe the same air-filled design, whose performance depends on internal pressure and size rather than on a solid rubber body. The type was first developed by the Yokohama Rubber Company of Japan, and the history of Yokohama fenders traces the name’s spread from there into general use. The term is widely used in procurement conversations, but the technically precise name is floating pneumatic rubber fender or Yokohama-type pneumatic fender. Strictly speaking, Yokohama is also a company and brand name, so a buyer should confirm the actual manufacturer and the ISO documentation rather than infer origin from the label.

The most common avoidable error in procurement is treating a Yokohama fender as one fixed product rather than a class defined by size and pressure. When the initial pressure (P50 versus P80) is assumed rather than matched to the berthing energy, a fender can arrive correctly marked and still be wrong for the berth. The naming clears up one frequent question; it leaves the sizing question open, and that one depends on the vessel and the berth.

How a Yokohama Fender Works: Air-Filled Construction and Energy Absorption

A Yokohama-type fender absorbs impact by compressing the air sealed inside a multi-layer rubber body, so the energy it can take up depends directly on its diameter, length, and initial internal pressure. The body combines an inner rubber layer that seals the air, one or more synthetic cord-reinforced layers that carry the load, and an abrasion-resistant outer rubber layer, all vulcanized together. End flanges close each end and carry the inflation valve. Under ISO 17357-1:2014, fenders of 2,500 mm diameter and larger must carry a safety valve that releases excess pressure under accidental over-compression; smaller fenders may carry one if required.

Because the working medium is air, the fender deflects and conforms to the hull as it compresses, spreading the load so that hull pressure and reaction force stay comparatively low. Low, even hull pressure is the goal: it protects thin-plated hulls and the quay face alike. The angle is what makes this matter in ship-to-ship contact, where two vessels meet obliquely. A pneumatic body holds much of its energy absorption under inclined compression, commonly cited up to around 15 degrees, whereas a solid block loses performance as the angle increases and can behave like a rigid lump under overload.

The variable to confirm is the initial pressure rating, and the right Yokohama fender pressure is matched to the berth rather than assumed. P50 (50 kPa) suits standard berthing and P80 (80 kPa) higher-energy duty such as large tankers, but P80 is not simply an upgrade. For the same nominal size it raises energy absorption and raises reaction force and hull pressure with it, so the berth structure’s capacity and the vessel’s allowable hull pressure must be checked together before selecting it. Choosing the higher pressure by default can return more force into the hull than the structure is meant to take.

Where Yokohama Fenders Outperform Solid and Foam Fenders

Yokohama-type fenders suit large vessels and oblique, ship-to-ship contact better than solid or foam fenders, but whether they are the right choice depends on fender size, budget, and the maintenance access a site can offer. Their strengths are low and even hull pressure, self-buoyancy, and the ability to be deflated and relocated. Their main vulnerability is the air itself: if the rubber skin is breached the fender deflates and loses function, so it needs periodic pressure checks that a sealed foam fender does not.

These are general tendencies, not fixed rules, and the full difference between pneumatic and foam fenders comes down to the duty at a given berth. For smaller fenders, foam often performs comparably and avoids pressure maintenance, and the cost gap narrows. For large fenders and ship-to-ship work, the pneumatic design usually wins on both cost and hull conformance; industry comparisons commonly note that, at large sizes, an equivalent foam unit can cost several times more. Which one fits should be decided against vessel size, exposure, and inspection access rather than on a single line in a spec sheet.

Sizing and Pressure: Matching a Yokohama Fender to the Vessel and Berth

Selecting a Yokohama-type fender comes down to matching its diameter, length, and initial pressure to the vessel’s displacement, berthing velocity, and the berth’s exposure. Yokohama fender sizes run from diameters of roughly 0.5 m up to about 4.5 m and lengths up to around 9 m, depending on the manufacturer and the standard applied. ISO 17357-1 sizes fenders by guaranteed energy absorption, which at its most basic level is a function of vessel mass and approach velocity, so berthing velocity, not diameter alone, drives the choice. The variables that govern the selection:

• Diameter and length — set the energy the fender can absorb; larger vessels and higher approach energy call for larger bodies.
• Initial pressure (P50 vs P80) — matched to berthing energy and checked against reaction force and hull pressure, not chosen as a default upgrade.
• Berthing velocity and contact angle — the velocity at first contact is the dominant driver of berthing energy; oblique contact favours the conforming pneumatic body.
• Hull pressure limit and allowable reaction force — the berth structure and the hull set the upper bounds the fender must stay within.
• Fitting type — net type (chain, wire, or fibre net) for fixed positions, or sling type for lighter handling and frequent redeployment.
• Tidal range and exposure — wide water-level changes and open exposure favour the floating, self-adjusting design.

In practice the selection starts from these berthing-energy inputs and only then compares candidate sizes. The P50-versus-P80 decision is settled by checking reaction force and hull pressure against the berth, not by taking the higher pressure as better. Because berthing energy is specific to each vessel and berth, the final size and pressure should be confirmed against a berthing-energy calculation rather than carried over from a previous job. For project quotations, Zhonghaihang confirms size, pressure, fitting type, and ISO documentation together rather than quoting by diameter alone.

Verifying Compliance: ISO 17357 and What to Check on Delivery

A Yokohama-type fender’s compliance rests on ISO 17357-1:2014, the current standard for high-pressure floating pneumatic rubber fenders, which sets the construction, testing, and marking requirements a buyer should confirm before the fender enters service. The standard remains current; it was reviewed and confirmed in 2024, and it is the high-pressure half of a two-part set, with Part 2 covering low-pressure fenders. It defines the rubber-layer properties, the air-pressure and hydrostatic tests, and the markings each fender should carry; PIANC’s guidelines for fender systems provide the wider berthing-energy and reaction-force context behind selection. References to other standards or years, a frequent source of confusion in product listings, should be checked against the current ISO text rather than taken at face value.

On delivery, the end fittings and the valve seat are usually the first areas worth re-checking, because folded shipping and handling can disturb the seal before the fender ever reaches the water. A short receiving check is faster than diagnosing a soft fender after it has been rigged:

• ISO 17357-1:2014 conformity, with the standard and year marked on the fender body.
• Prototype and commercial inspection or test certificates, including air-pressure and hydrostatic test records.
• Marked nominal size, P50/P80 pressure rating, and serial number, checked against the order.
• Safety-valve setting where the diameter is 2,500 mm or more.
• End fittings, valve seat, shackles, swivels, and chain or tyre net condition.
• A major classification society’s evaluation where the project requires one.

What “compliant” means in practice still depends on the duty, so the certificate is best read alongside the berthing conditions the fender will work in.

Common Marine Applications for Yokohama Fenders

Yokohama-type fenders are used wherever vessels make contact under movement: in ship-to-ship transfers, at ship-to-jetty berths, and around offshore and floating structures, with the suitable size and pressure depending on the vessel and exposure. In ship-to-ship operations they hold two moving hulls apart while cargo transfers, where buoyancy and conformance handle the oblique contact. At commercial, oil, gas, and LNG berths they protect both hull and quay during berthing and mooring. At offshore platforms and floating docks they cushion supply and crew-transfer contact in open water. The constant across all of these is that the application sets the exposure, and the exposure sets the size and pressure, not the other way around.

Conclusion

Choosing a Yokohama-type fender returns to three variables: size, initial pressure, and fitting type, each tied to the vessel and the berth rather than to the product name. The naming question is easy; the sizing question, and especially the P50-versus-P80 decision, is where most choices are won or lost.

At Zhonghaihang we design and build pneumatic fenders around these project variables, and we treat the berthing-energy check and the ISO 17357 documentation as part of the specification, not an afterthought. In our experience the fenders that cause problems are rarely the ones that fail in service; they are the ones specified without confirming berthing velocity, contact angle, and hull pressure limit against the actual berth. Where a value depends on the berth, we confirm it at project level rather than carrying over a figure from another job.

If you are specifying fenders for a berth or a ship-to-ship operation, the useful next step is to gather the vessel size, berthing velocity at first contact, contact angle, and tidal range. Send us those parameters and we can review the size and pressure against your berthing conditions and the applicable standard.