Why do hydraulic systems overheat?

Heating of hydraulic fluid in operation is due to inefficiency. The inefficiency of the loss of input power, which is converted into heat. A hydraulic system load thermal energy is equal to the sum of all power lost (PL) by inefficiency and can be expressed as follows:

PLtotal = PLpump + PLvalves + PLplumbing + PLactuators

If the total amount of heat lost power is greater than the heat, the hydraulic system to overheat more. Installed cooling capacity ranges usually between 25 and 40 per cent of electricity consumption, according to the nature of hydraulics.

Temperature of hydraulic fluid
What temperature is too hot? Hydraulic fluid temperatures above 180 ° C (82 ° C) damage to sealants and accelerate oil degradation. During operation of the hydraulic system at temperatures above 180 ° C should be avoided, fluid temperature too high when viscosity is less than the optimum value for the hydraulic system components. This can occur even below 180 ° C as the viscosity of the liquid class.

Maintain stable temperature of fluid
To achieve a stable temperature environment, the ability of a hydraulic system to dissipate heat, must exceed the heat load. For example, a system needs input power of 100 kilowatts continuous and can disperse an efficiency of 80 percent to a heat load of 20 kilowatts. Assuming that the system is designed cooling capacity of 25 kilowatts, all growing, underlining the heat above 25 kilowatts or reduced cooling capacity below 25 kW, the system will lead to overheating.

Consider an example. I was recently asked to investigate and solve an overheating problem in a mobile application. The hydraulic system consists of a motor unit diesel-hydraulic, which is currently used to power a pipe cutting saw. The saw was designed for the under-utilization of the sea and was connected to the hydraulic unit on the surface of a 710-foot cord. The conditions for the operation of the saw were 24 GPM at 3000 PSI.

The hydropower plant has a continuous power of 37 kW and was fitted with a heat exchanger air furnaces. The interchange has been dispersed to 10 kilowatts of heat at room temperature or 27 percent of the available input power (10/37 x 100 = 27) Can. The performance of all components of the cooling system were monitored and their activity within the design.

In this passage, it was clear that the overheating problem was caused by the heat load is excessive. Concerned about the length of the umbilical cord, so I thought the pressure drop. The theoretical pressure drop over 710 feet of pipe ¾ inch pressure is 800 psi at 24 L / min. The pressure drop over the same length of 1-inch return pipe is 200 PSI. The theoretical heat load produced by the pressure drop through the umbilical cord is 1000 PSI (800 + 200 = 1000) was 10.35 kilowatts. This meant that heat stress is the navel of 0.35 kilowatts more than the capacity of heat dissipation of the heat exchanger of the hydraulic system. That’s when they load with the normal heat system (inefficiency caused) in connection with the hydraulic system to overheat.

Beat the Heat

Besides improving chip control and tool life, directing a jet with accuracy at high speed cooling may increase the overall productivity. One of the potential beneficiaries of this approach to liquid cooling is the multitasking turning center. Most of these machines offer the supply of liquid cooling option with a pressure between 70 and 100 bar. In fact, Sandvik Coromant has developed accessories for high pressure coolant specifically for use with such machines, the amount of pressure.

For multitasking machines in particular, inefficient chip removal hinder the ability to make changes effective tools. Sandvik CoroTurn HP system reacts to this riddle. In this system, each tool carrier fitted with two or three nozzles replaceable stainless steel from which coolant is circulated at high pressure. Sandvik said spray heads are mounted near the edge of the temperature in the heat-affected zone (HAZ) below. They are correctly positioned and oriented at an angle, depending on the type of tools and application.

Getting the positioning right is just one of the keys to the effectiveness of this cooling technology delivery. The system pushes the chip and provides localized cooling of the insert point without thermal shock. It does this by producing a precise laminar flow – that is to flow with the energy flows is based on work instead of drawn by turbulence.