4436678 Hitachi EX2500 / EX2600 Boom Cylinder Aftermarket Replacement

Product Overview

SEIGO’s aftermarket boom cylinder, part number 4436678, is a direct drop-in replacement for the Hitachi EX2500 series mining excavator — a roughly 250-tonne class hydraulic mining shovel used to load ultra-class haul trucks in large open-pit operations. The same cylinder covers the EX2500, EX2500-5 and EX2500-6, and also fits the EX2600-6. It works as part of the front attachment alongside the arm cylinder 4402135 and the bucket cylinder 4402137.

The boom cylinders on a 250-tonne mining excavator are mounted in pairs and carry the full dynamic load of raising the boom, arm, bucket and payload through every dig-and-load cycle, while simultaneously absorbing the reaction forces transmitted back through the front attachment during the dig. On a machine running continuous high-cycle production against a hard-rock or shot-rock face, the boom cylinders endure some of the most severe sustained and fatigue loading of any actuator on the machine — and a boom cylinder failure removes the entire shovel from production until a replacement reaches site.

Because the load here is high and sustained rather than intermittent, the dominant failure modes are rod chrome fatigue and delamination, and gland seal extrusion under continuous pressure. Rod chrome adhesion and gland seal specification are therefore the two variables that most directly determine service life. SEIGO manufactures the 4436678 to address exactly these: a 42CrMo4 induction-hardened, hard-chrome-plated piston rod to HRC 58–62 for resistance to scoring and delamination, an ST52 seamless honed steel barrel, and a genuine NOK (Japan) or Parker (USA) seal kit rated for the EX2500 high-pressure circuit.

Every unit is pressure tested at 1.5× rated working pressure before shipment from our Guangdong factory and is backed by a 12-month or 2,000 operating-hour warranty. Standard lead time is approximately 30 days ex-works, with expedited production available for mine-site downtime. For fleets that also run Hitachi EX1900, EX3600 or EX5500 shovels, SEIGO manufactures boom, arm and bucket cylinders across the full EX mining range.

Product Specifications

* OEM part numbers, brand names and model designations are used for identification and cross-reference purposes only. SEIGO Machinery is an independent aftermarket manufacturer and is not affiliated with Hitachi Construction Machinery.

Hitachi EX2500 / EX2600 Work Equipment Cylinder Cross-Reference

The EX2500 series front attachment uses boom, arm and bucket cylinders. Part 4436678 is the boom cylinder. The main work equipment cylinders are listed below.

The boom cylinders are fitted in pairs. Related work equipment numbers are listed for cross-reference. Confirm your machine serial number and cylinder position before ordering, as backhoe and loading-shovel configurations and build revisions can affect the correct part. SEIGO supplies all work equipment cylinder positions for the EX2500 / EX2600.

Hitachi EX Mining Series — Boom Cylinder Reference

The Hitachi EX mining range spans several size classes, each with its own boom cylinder part number. The EX2500 boom cylinder does not interchange with other classes. SEIGO manufactures boom cylinders across the range.

Each EX mining class uses a different boom cylinder; the numbers above are not interchangeable between classes. If you operate a mixed Hitachi EX fleet, send us the machine model and serial number for each unit and we will supply the correct cylinder for each — boom, arm, bucket and clam positions across the EX750/850, EX1200, EX1900, EX2500, EX3600 and EX5500 range.

Why This Cylinder, Specifically

• Correct class and configuration, verified. Each Hitachi EX mining class uses a different boom cylinder, and backhoe and loading-shovel builds can differ. We confirm the exact number against your machine model and serial number before quoting — a boom cylinder from the wrong class or configuration will not fit.
• Built for sustained lift load. The boom cylinders hold the full weight of the front attachment and payload through most of each cycle. We use a 42CrMo4 rod, deep induction-hardened to HRC 58–62 and hard chrome plated, dimensioned for that sustained load — the failure mode here is chrome delamination and gland seal extrusion, not rod bending.
• Replace in pairs, plan once. The EX2500 runs paired boom cylinders that accumulate identical hours. If one side has reached service limit, the other (4436679) is usually close behind. We supply matched pairs on a single order so the front-attachment work happens in one planned shutdown.
• Whole front attachment on one order. Boom (4436678), arm (4402135) and bucket (4402137) cylinders can be supplied together. For a planned major service, consolidating the front-attachment cylinders on one purchase order coordinates lead times and shipping on these very large components.
• Rods, barrels and seal kits supplied separately. For mine-site rebuild shops, we supply each component individually — typically 40–60% of complete-cylinder cost, and far lower freight on a bare rod than on a 250-tonne-class assembly.
• Full traceability and testing. ISO 9001:2015 manufacturing, 100% pressure tested at 1.5× rated working pressure, shipped in an ISPM-15 fumigated export crate with material certificate and test record.

FAQ

Q1: Which Hitachi machines does 4436678 fit?

A: 4436678 is the boom cylinder for the Hitachi EX2500 series mining excavator, covering the EX2500, EX2500-5 and EX2500-6, and it also fits the EX2600-6. These are roughly 250-tonne class hydraulic mining shovels. Because build configuration (backhoe versus loading shovel) and revision can affect the exact part, confirm your machine model and serial number before ordering. Send us the serial number and we will verify fitment.

Q2: Is 4436678 the boom, arm or bucket cylinder?

A: 4436678 is the boom cylinder. On the EX2500 the arm (stick) cylinder is 4402135 and the backhoe bucket cylinder is 4402137. These are all different parts with different dimensions and are not interchangeable. SEIGO supplies all three positions — specify boom, arm or bucket when you enquire.

Q3: Are the boom cylinders fitted in pairs?

A: Yes. The EX2500 runs two boom cylinders, one on each side of the boom structure, and they accumulate identical operating hours. If one has failed or shows rod chrome scoring or gland leakage, the other is usually close behind. The companion number is 4436679. We recommend replacing both in one planned shutdown, and we supply matched pairs on a single order.

Q4: Do you supply cylinders for other Hitachi EX mining machines?

A: Yes. SEIGO manufactures boom, arm, bucket and clam cylinders across the Hitachi EX mining range, including the EX1200, EX1900, EX3600 and EX5500. Each class uses different part numbers — send us the machine model and serial number for each unit in your fleet and we will supply the correct cylinder for each position.

Q5: Can I buy the rod, barrel or seal kit separately instead of a complete cylinder?

A: Yes. SEIGO manufactures the piston rod, honed barrel, cylinder head, piston and seal kit as individual items and supplies them to hydraulic repair shops and mine-site rebuild facilities. For workshops with in-house honing and assembly capability, sub-component supply typically runs 40–60% of the cost of a complete replacement cylinder, and freight on a bare rod is far lower than on a complete 250-tonne-class assembly. Send us your machine serial number and the component you need for a quotation.

Q6: What is the lead time and how does it ship?

A: Standard production lead time is approximately 30 days ex-works Guangdong, China, with expedited production available for mine-site downtime. Given the size and weight of a 250-tonne-class boom cylinder, sea freight via FOB Shenzhen is standard for planned replacements, packed in an ISPM-15 fumigated wooden export crate. Air freight to major hub airports is available for urgent situations. We support FOB, CIF and DDP Incoterms.

SEIGO Machinery is an independent aftermarket manufacturer. All OEM part numbers, brand names and machine model designations are used for identification and cross-reference purposes only. These aftermarket components are not manufactured by, endorsed by, or affiliated with Hitachi Construction Machinery Co., Ltd.