PreventiveMaintenance

Vol. 1

PreventiveMaintenance

Vol. 1

PreventiveMaintenance

Vol. 1

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Base Metal

Chrome Plating

Corrosion in white

Base Metal

Chrome Plating

Melting of CoatMelted Chrome

Base Metal

Chrome Plating

Iron Oxide (Red Rust)Melted Chrome

Base Metal

Chrome Plating

Extrusion of coatInvasion of Rust

Base Metal

Coating

Extrusion of coatInvasion of Rust

In the initial stage, the surface of coating will turn to white (It is visible). This is called "Chrome," and it means the chrom is in initial corrosion.

If the initial corrosion is progressed, the thickness of coating will decrease because the chrome gets melted.

If the corrosion is progressed more, the plating is completely removed, and the base metal will be exposed. Consequently, the base metal gets rusted and turns to red color due to iron oxide (Fe2O3).

Once the red rust is observed, the water and moisture get into the base metal, and the created rust is penetrated through the base metal. The penetrated rust will push the plating up to extrude the coat.

HYDRAULIC CYLINDERSave cylinder rods from corrosion

2. Mechanism how cylinder rod gets rustedHow do you think the cylinder rod get rusted?

1. Rust on Cylinder RodThe cylinder rod which we introduce below is an example of rust exposed to rain and salt wind for a long period. Because the crane owner remained the cylinder extended for the period under the condition, the cylinder gets rusted. If the rod is rusted and if the crane driver

extends or retracts the cylinder, the rusted portion will lead damaging the oil seal which causes oil leakage as seen in the pictures below. In this case, the replacement of oil seal and retreatment of cylinder rod should be performed, and it will cause long down-time of machine.

If red rust is observed on the surface of cylinder rod, it causes damages of sealing for cylinder.Consequently, oil leakage occurs, and the sealing should be replaced. In addition, extrusion of plating seems to be caused by invasion of rust due water, but we can

not identify the exactly portion from which the water or moisture comes. Therefore, in this case, re-coating of cylinder rod, replacement of cylinder rod or cylinder assembly will be required.

Most of mobile cranes have hydraulic cylinders, and they are used for each corresponding functions such as Boom Hoist, Telescopic, Gantry Hoist, Crawler Extension/Retraction and etc. As you know, rods of these cylinders are exposed to rain and wind at most of the time, so the cylinder rods can get rust even if the rods are plated with Hard Chrome. In other words, maintenance of cylinder rod is mandatory.

Location on Cranes Cylinder Rod Without Maintenance for a Long Time Oil Leakage due to defect on seal

Global Service Department740, Yagi, Okubo-cho, Akashi-shi, Hyogo, 674-0063 JAPANTEL: +81-78-936-1408 FAX: +81-78-935-5240

For further information, please contact...

Preventive Maintenance Vol. 1

Hydraulic Mobile Cranes

Where What How

When

Each Hydraulic Cylinder

Exposed Surface of Rod

Best Grease for Cylinder Rods

General Purpose Grease

Every 1 month or every 100 hour

With brush or spray

Sample

3. Cause of corrosion of Chrome and red rustCorrsion is one of the chemical reactions (oxidation) on surface of plating (Chrome) due to environmental factors and/or chemical factors in ambient circumstance. In chemical study, Chrome tends to oxidize much easier than Iron, so you would say, “It is useless to plate the base metal with Chrome.” However, Chrome reacts with oxygen arbitrarily, and the chemical reaction creates “Oxide film” which is very thin. The film prevents the rod

from the rust as well as oil film on the surface of cylinder rod. Because of the oxide film of Chrome, the plating does not get rust easily. However, in the following occasions, the oxide film will get damaged, and the plate of Chrome will also get corrupted.Consequently, the base metal gets rusted to have red rust (iron oxide).

1) When acid element in rain sticks on rod, the acid will melt the plating.2) When chloric element in sea water sticks on rod, the element melts the plating in chemical reaction.3) When chemical in the air such as sulfuric acid sticks on rod, the chemical reaction melts the plating.[jobsite with chemicals such as chemical plant and surroundings]

4. To prevent the corrosion of Chrome and red rust on base metalOn hydraulic cylinder, operation in extension and retraction will create micro oil film on the surface of cylidner rod, so if you leave cylidner rod extended (derricking in and/or tele-out) for a long time, the oil film

will be removed by acid in rain. Consequently, if the acid sticks on the surface of cylinder rod, it causes corrosion of Chrome and red rust on base metal. In this occassion, please follow the operation below.

On machines working near beach, port or cliff, red rust can be observed much earlier than machine wokring in land. If your machine is in those occassions, maintain

the cylinder rods in shorter period than normal in order to extend the service life of hydraulic cylinders.

PMV01_2013-R1

1) In long term storage, retract all the hydraulic cylinders fully.2) If surface of rod is exposed, apply sufficient grease or other oily material to cover the rod.3) Protect the exposed rod with soft cloth including oil.These maintenance job extends the service life of hydraulic cylinders.

Long term storage with boom derricked

Exposed surface of cylinder rod infull retraction