Overheating Ranks No

APEX PUMPS LIMITED (AN ISO9001:2000 COMPANY) G-228,RIICO INDUSTRIAL AREA, SITAPURA, JAIPUR-302022. [email protected] DELHI OFFICE- 14A/90, W.E.A., Karol Bagh, New Delhi- 110005. Mobile-9810461516

Generally, the system should not allow the oil to get more than 15°C over that of the surrounding (35°C) air. HTMA recommends a heat dissipation capacity of at Overheating ranks No.-2 least 5 KW for 40 lpm Circuit. Using any ISO32 oil, In the list of most common problems with hydraulic based on 55°C, every 8°C increase in oil temperature equipment. Unlike leaks, which rank No.1, the causes reduces the life of the oil by 50%. of overheating and its remedies are often not well understood by maintenance personnel. Why do hydraulic systems overheat? Heating of hydraulic fluid Why use an air-cooled heat Exchanger/cooler in operation is caused by inefficiencies. Inefficiencies result in losses of input power, which are converted to Air-cooled heat exchangers are generally used where a heat. process system generates heat which must be removed. Most of the heat must be dissipated Concerns about Hydraulic System Overheating somehow. One of the simplest ways is to use the ambient air. Air-cooled heat exchangers (often simply called air-coolers) do not require any cooling water When hydraulic systems overheat several things can from a cooling tower. occur that can damage the system. (1) Breakdown of the hydraulic oil producing “sludge”, (2) Deterioration of hose lining releasing rubber APEX particles into the system, Air-cooler are usually used when the outlet (3) o-rings and seals become less pliable and begin to temperature is more than about 4-6 deg. C above the leak, and maximum expected ambient air temperature. They can (4) Increased formation of acids that can begin to be used with closer approach temperatures, and often corrode components. become inexpensive compared to a combination of a If you are experiencing hydraulic system overheating, cooling tower and a water-cooled exchanger. be sure the hydraulic oil viscosity is correct for the ambient conditions. Correct any overheat problems as Maintaining the correct system temperature is soon as possible. important to ensure optimum oil viscosity in a hydraulic system. In many hydraulic systems only 50% The major causes of heat in a hydraulic circuit are: of the consumed energy is left to do its designated The inside diameter of the hydraulic “return” hose is work. The remaining 50% is lost by friction, pressure too small. drops and lost due to interruptions in flow conditions.    Hydraulic “pressure” and “return” hoses are too Lost energy results in temperature unacceptably high long. for the oil as well as for the hydraulic system Hydraulic reservoir is too small. components. The vital physical characteristics and the Hydraulic oil reservoir is low on oil. lubricity of the oil are considerably reduced.    Internal parts in the tool / cylinder are worn beyond part tolerance creating oil bypass. The Air cooled oil cooler provides reliable No oil Cooler. temperature control    Hydraulic power source exceeding system relief pressure. The Air cooled oil cooler reduces the difference Inefficient designs, poor plumbing practices and the between consumed and input energy providing reliable overriding idea to make it a cheap as possible will temperature control of oils and a wide range of other produce 8 out of 10 hydraulic systems with a heat highly viscous fluids. The correct type of cooler and oil problem. means a system that operates properly with maintained oil viscosity. Hydraulic fluid temperature - How hot is too hot? Inherent advantages of oil cooler Most hydraulic systems should operate between 48°C and 57°C under normal operations. This temperature is the average temperature taken at the oil reservoir, and • Hydraulic system life extended by 3-5 times. higher temperatures can be seen at other locations in • Long lasting oil durability. the circuit. Oil temperatures above 75° C damage most seal compounds and accelerate degradation of the • Reduced internal potential for leaks. hydraulic fluid. The fluid temperature is too high when the fluid viscosity falls below the optimum value for the • Prolonged lubricating qualities. hydraulic fluid system components. This can occur well below 75° C, depending on the fluids • Maintained hydraulic efficiency for the entire working cycle. 1 The negative aspect of a cooling tower DON’T – Use heavy oils such as 30W or 10W30 engine The cooling water is directly open to the environment. oils. These will cause high losses in lines and add to Airborne particulate contaminants are washed back pressure and heat. out of the air by the water flowing over the tower. The water also absorbs oxygen and other gases, DON’T – Run return oil through control valves or other including products of air pollution. series circuits. DO the following to reduce heat generation The evaporation process causes the minerals that were initially dissolved in the water to be left behind as 1. DO - Operate pumps at moderate speed – gear fine, highly abrasive particles. It also causes the pumps usually generate less heat (and mineral concentration of the remaining water to Are less prone to cavitations) at speeds of 1,000-2,000 increase. As a result, cooling tower water quickly rpm. If this speed range can be used, pick a pump size becomes highly contaminated water that causes to supply desired flow in this speed range. Power take- fouling, scaling, corrosion and erosion of heat offs are available at various speed ranges. transfer surfaces. These detrimental effects can 2. DO - Use generous line sizes – Especially on pump increase maintenance costs as well as incur suction and return from tool to tank. unscheduled equipment and process downtime and loss of productivity 3. DO - Use oils in 150-200 SSU range, with high viscosity index if a range of weathe Conditions are The negative aspect of Shell & tube type heat encountered. exchangers Provide good cooling for hydraulic oil -Laminar flow of water in the tubes results in falling of heat transfer surface. A hard layer gets deposited -Use an air-to-oil cooler of maximum size for inside the tubes narrowing passage. This layer of space available. deposits acts as insulter and does not allow the heat to be transferred from oil to water. -For oil pulsing type application, use off line air to oil cooler -When water passes through the tube the highest velocity is at the cavitations. The velocity near the walls of the tube is reduced to almost zero; this creates a stagnant water film near heat transfer area which is a Disclaimer bad conductor of heat. While these recommendations for AIR COOLED OIL COOLER requirements are technically -When leakage starts in shell & tube type heat sound, it exchanger water mixes with oil of hydraulic system is not intended that they be considered the resulting in further damage to the system. only method for OIL COOLING. Neither should these recommendations be interpreted as The negative aspect of air cooled oil cooler superior to or standard that would necessarily be preferred in lieu of an engineer’s design for aparticular - In aggressive environments ambient air may contain application or system. dust particles that will increase air fin clogging These recommendations originate from the coefficient. collective experience of leading technical personnel in the hydraulic tool industry, but - Operating coolers at high altitudes will reduce heat must, due to the nature of the responsibilities dissipation. involved, be presented only as a guide for the use of a qualified designer or engineer. Thus, - Oil temperature is more than about 4-6 deg. C above the APEX PUMPS LIMITED the maximum expected ambient air temperature. disclaims any responsibility for damages arising out of the use,application, or reliance Basic DON’TS for cool oil control on the recommendations and information DON’T – Rely on a large tank to control oil heating contained herein by designers, engineers, or by users of hydraulic tools and systems. DON’T – Set relief pressure too low. For oil pulsing type application pressure peaks may run up to 350 PSI over gauge pressure, popping the relief and causing heat as well as low performance. APEX PUMPS LIMITED DON’T – Pump more oil than the application should (AN ISO9001:2000 COMPANY) use. Avoid flow controls if possible. It is best to size G-228,RIICO INDUSTRIAL AREA, the pump for desired flow volume. SITAPURA, JAIPUR-302022. 2 [email protected]