Hydraulic Motor Damage Due to Temperature Shock: How Can this Be Prevented?

Blog | December 12th, 2019

If a winch system and crane lock-up because a hydraulic motor is experiencing some form of temperature shock, severe consequences may ensue. All functions lose momentum, then a system failsafe activates to prevent shear pin damage or a serious delay in the winch or boom’s operations. On troubleshooting the hydraulic motor, a temperature shock event is identified as the system-locking culprit. Frustrating and productivity-skewing, the damage causes a nasty worksite hold-up.

Identifying Temperature Shock Problems

The above worst-case scenario temporarily turns a mobile crane into a workplace liability. If it’s not to become an immobile landmark, the service repair person had better dive deep into its hydraulic workings in search of a permanent fix. In no time at all, the fault is diagnosed. A rapid, extremely localized heating effect was experienced by the fluid-based motor. Hot oil affected the motor housing and its inner guts. If that temperature differential is high enough, then an effect referred to as temperature “shock” is induced. Made from different materials and similar materials that are differently sized or shaped, those components were expanding at different rates.

Correcting Localized Hydraulic Motor Expansion

In most equipment layouts, small amounts of component expansion aren’t going to cause an issue. However, hydraulic systems use tight clearance equipment assemblies. During normal operational conditions, moving parts swing by one another at speed. They come within a hair’s breadth of touching. Localized expansion effects, as caused by temperature shock disorders, close this gap. That’s when interference stress happens and frictional contact concerns create a vicious cycle. More heat is created in a hydraulic motor, so the expansion effect worsens. To correct the fault, that vicious cycle must be broken. System designers do this by eliminating the conditions that create the temperature differential in the first place. This is done by continually flushing the motor housing with a small volume of hot oil. Since the goal is to heat up the motor housing, only a negligible amount of hot hydraulic fluid is needed for this purpose.

Just to recap the problem, there are a number of fast-moving parts in hydraulic motors with next to zero clearance between them. If that “hair’s breadth” gap is compromised by temperature shock, by this localized but irregular component expansion effect, they’ll touch and interfere with one another. That’s when hydraulic motors lock-up or hitch as they struggle to compensate against the inner turmoil. Temperature differentials cause the clearance shrinkage, so it’s this thermal difference that has to be corrected. While a cooler fluid stream helps matters, that’s a difficult feature to incorporate. Far better, then, is the addition of an oil injecting mechanism that flushes and warms hydraulic motor housings until the thermal shock shrinks away to nothing.

Mobile Hydraulic Specialties Pty Ltd

Factory 89, 38-40 Popes Road
Keysborough, Victoria, 3173

Phone: (03) 9798-6511

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Contact Us

Mobile Hydraulic Specialties Pty Ltd

Phone: (03) 9798-6511
Address: Factory 89, 38-40 Popes Road, Keysborough, Victoria, 3173