A hydraulic system that is allowed to overheat can cause costly seal deterioration and fluid oxidation or breakdown. This results in corrosion and formation of sludge and varnish, which may in turn clog orifices and accelerate valve wear. High temperatures can also create a safety hazard should high-temperature fluid leak, and operating personnel could be severely burned. High oil temperature can also be caused by metal parts being worn or from the seals being worn, allowing the oil to bypass and cause heat. Ideal system temperatures vary, but the modern trend is toward hotter-running systems. Therefore, heat exchangers are more of a necessity than ever. Heat dissipates from a hydraulic system in two ways: through natural convection and through forced convection. Natural convection takes place as heat moves from the various system components, the reservoir, and the conductors to the surrounding air because of the temperature gradient.