What Types of Seals Are Commonly Used in Cranes?

Number of hits：232025-08-18 11:08:40　

Having worked in the sealing industry for over thirty years, I often receive questions from distributors, service companies, and even crane operators about what kind of seals are actually used in cranes. Many people assume seals are just small accessories, but anyone with field experience knows a minor leak in a crane’s hydraulic system can shut down an entire operation. That downtime often costs far more than the price of the seal itself.

From my observations in workshops, ports, and construction sites, I can summarize the main seal types used in cranes and share a few notes about how they are selected, maintained, and supplied.

1. O-Rings

O-rings are the most basic yet essential sealing element in cranes. They appear in hydraulic valves, pipe connections, and sometimes in cylinder assemblies. The material choice is critical:

NBR (nitrile rubber) is commonly used for standard hydraulic oils and moderate pressures.

FKM (fluoroelastomer) performs better in higher temperature conditions, for example in port cranes working under direct sunlight in summer.

PU (polyurethane) is a good choice where impact pressure or wear resistance is a concern, such as in telescopic cylinders.

I have seen many service teams underestimate the role of material selection. Using an NBR O-ring in a high-temperature crane gearbox, for instance, often leads to premature hardening and leakage.

2. Rotary Shaft Oil Seals

Oil seals are heavily used in slewing drives, winch systems, and gearboxes. Their task is twofold: keeping lubrication in and preventing dust, mud, or seawater out. In cranes working near docks, corrosion resistance is a key factor, so FKM or PTFE oil seals are often specified.

One distributor once told me that rotary seals are among their fastest-moving inventory items. This makes sense—gearboxes and winches undergo continuous rotation, and their seals face both thermal and mechanical stress. Replacements are therefore more frequent compared to static seals.

3. Hydraulic Cylinder Seals

The hydraulic cylinder is the “muscle” of the crane, and without reliable sealing, lifting and extending operations cannot be guaranteed. Within a single cylinder, you will find several types:

Rod seals and piston seals to handle high pressure and motion.

U-cups and Glyd rings for dynamic sealing.

Backup rings and wear rings to prevent extrusion and guide movement.

From my perspective, polyurethane remains the workhorse material here, but in certain imported cranes, composite seals are used to reduce friction and energy loss.

4. Wiper Seals (Dust Seals)

Anyone who has worked on a construction site knows the environment is full of dust and abrasive particles. Wiper seals, mounted at the end of hydraulic cylinders, prevent debris from entering the system. I’ve inspected cylinders where the absence of a functioning wiper led to rapid rod scratching and early seal failure. For cranes, polyurethane or rubber-metal wipers are usually the most durable.

How NQKSF Supports Crane Applications

From a supplier’s standpoint, solving crane sealing issues is not only about manufacturing parts. It is about ensuring reliability and helping distributors and service companies deliver solutions quickly. This is where NQKSF has built its reputation.

· Standard parts available for quick delivery: More than 10,000 specifications, including O-rings and oil seals, are kept in stock. Distributors appreciate the ability to source urgently needed parts without long lead times.

· Customized services from start to finish: Some cranes use non-standard or modified seals. NQKSF can assist with material selection, design, prototyping, and testing to provide tailored solutions.

· Technical support based on experience: With over three decades in the field, our team helps optimize sealing systems, reducing downtime and lowering operating costs for crane owners.

NQKSF Seals factory strengths include:

· Fully equipped manufacturing facilities

· Broad range of models that cover most mainstream crane brands

· Products exported to more than 80 countries

· Partnerships with globally recognized brands

· Provincial innovation center recognition and high-tech enterprise certification

· Proven leader in regional sealing industry clusters

Questions from Distributors and Wholesalers

Q1: How often should seals in cranes be replaced?

From my experience, seals should at least be inspected during annual overhauls or after about 2,000 working hours. In harsh environments, shorter intervals are advisable. Stocking common seal kits helps distributors serve customers quickly.

Q2: Can aftermarket seals replace OEM parts?

In many cases, yes. NQKSF maintains a comprehensive database of crane seal dimensions, compatible with leading brands. For unusual cases, we provide custom solutions.

Q3: How can distributors manage inventory risk?

One advantage of working with NQKSF is flexibility. Large-volume orders bring cost benefits, while small-volume orders can be shipped quickly from stock. This approach helps wholesalers reduce tied-up capital.

Q4: How should seal materials be chosen?

The decision depends on the working environment:

High temperature: FKM is preferred.

Low temperature: silicone or low-temp elastomers.

High pressure or shock load: polyurethane.

Continuous rotation: PTFE or FKM oil seals.

In every crane, seals act as the hidden protectors. They may not draw attention until a failure occurs, but their contribution is critical. Selecting the right type, material, and supplier ensures long-term equipment reliability.

For distributors and wholesalers, partnering with a manufacturer that combines broad product coverage, reliable stock, and strong technical support makes all the difference. NQKSF is positioned exactly this way—delivering both standard and customized sealing solutions for cranes, backed by decades of industry expertise and a global service network.

As the crane industry continues to expand into diverse environments—from ports and shipyards to construction and energy projects—the role of seals will only become more vital. With continuous innovation and field-driven support, NQKSF remains committed to being a trusted partner for businesses worldwide.