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Preparing your hydraulic systems for winter with the right fluids

Hydraulic System

With winter on the horizon, hydraulic system operators must consider the impact of incoming lower temperatures.

Fluid systems aren’t immune to the cold, and those using hydraulics need to adapt and ensure they employ the right fluids suited to winter. To prepare you for the colder season ahead, we’re taking a deep dive into fluid power systems in wintertime, and the hydraulic fluids needed to manage and maintain them effectively.

The consequences of the cold on hydraulic systems

When faced with low temperatures, issues occur in hydraulic fluid power systems. This typically begins with increased fluid viscosity and the formation of vapour-filled cavities (cavitation).

These alterations to hydraulic oils and fluids lower their operational effectiveness and can lead to inefficient mechanical process and damage, which heightens the risk of a complete system failure overall.

To counter this unwanted outcome, operators must winterise the hydraulic system in their care by selecting the right type of fluid for low temperature use, performing fluid checks and adhering to consistent processes.

Winterising systems is critical to maintaining hydraulic systems and helps mitigate many issues. These include increases in fluid viscosity, cavitation and poor lubrication, as well as moisture trapped in pipework, build-up of ice and loss of functionality in key components, like motors and hydraulic pumps.

Preparing for winter also helps prevent damage to other parts like hydraulic hoses, mountings, fittings and seals.

Understanding low temperature thresholds

The freezing point for hydraulic oil is -23°C. At this point, it gels and becomes completely useless. However, a lower threshold of 0°C can still alter the viscosity of a fluid, and cause serious performance issues for motors and pumps using hydraulics.

How to select the right hydraulic fluid for winter system use

When choosing the right hydraulic fluid for your system in winter, viscosity is the primary concern. Employing a fluid with the correct viscosity for cold temperature applications will help to protect your equipment against threats like abrasion, friction and adhesive wear.

However, using a fluid with the wrong viscosity has an opposite effect. When oils have higher levels of viscosity, it can cause cavitation and a lack of sufficient lubrication due to pumps starved of fluid.

At lower temperatures, the viscosity of hydraulic fluid starts to increase. As a result, operators ordering fluid must pay attention to the viscosity index (VI) of products, but also their pour point and grade.

Most parts in hydraulic systems are manufactured from iron, and iron alloys like steel, and might not be impacted by a fall in temperature. However, wear and friction, especially on seal materials, can happen because of fluids becoming more viscous at colder operating conditions.

To get hydraulic fluid systems ready for winter, always pick hydraulic fluids that have a low viscosity, as they are thinner and will flow more easily when they encounter a drop in temperature. In simple terms, the higher a fluid’s viscosity index, the greater its resistance to alterations in viscosity.

When ordering hydraulic fluid, you will find a wide range of products available, and many designed specifically for use in low temperatures. As a rule, synthetic hydraulic oils and fluids that have a higher quality base oil will perform better at lower temperatures than other products.

Hydraulic oils for cold weather use also feature additives that imbue them with properties that are beneficial in winter, like antifreeze and pour point depressants (PPDs). These chemical inclusions effectively lower the lubricant’s pour point temperature. The term “pour point” refers to the lowest temperature that a lubricant can flow at. PPDs are helpful in cold climates, ensuring fluids perform dependably at lower temperatures.

Hydraulic fluid checks can help you prepare. Before starting, check the fluid levels and VI requirements in your hydraulic system. If you observe that the fluid is too thick and can’t drip off the dipstick you test with, it is far too viscous to work properly, particularly in cold temperatures.

Preparing hydraulic equipment for winter and storing fluids

As well as ensuring you are using a fluid with the right viscosity to meet anticipated winter temperatures, it is also vital to warm-up equipment properly to prepare the hydraulic systems for the cold.

For optimum low temperature performance, before operation either run the system’s hydraulic pump or utilise a hydraulic tank heater. To guarantee correct lubrication in the system, make certain that the temperature of the hydraulic oil reads 65.5°C before running. Hydraulic fluids should be stored indoors during winter and not subject to temperatures that result in lower viscosity and cavitation.

For high-quality hydraulic fluids suited to winter use, explore our range of products from leading lubrication manufacturers at Oil Store today.

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