Reservoirs Covered in Ch. 5 of Vickers Text

1. ReservoirsCovered in Ch. 5 of Vickers Text Jeremy Lawson Jason Frentzel

2. Overview • Functions of a reservoir • Components of a reservoir • Types of Reservoirs • Modifications to Reservoirs • Sizing of Reservoirs • Heat Exchangers

3. Functions • Holding system fluid • Transfer of waste heat • Allows entrained air to rise and escape • Allows solid contamination to settle on bottom of tank

4. Components • Baffle Plate • Breather Assembly/ Filler Opening • Clean-out Plates • Oil Level Gage • Line Connections and Fittings

5. Baffle Plate • Used to prevent returning fluid from directly entering the pump inlet • Installed lengthwise through the center of the tank • This provides low velocity travel and allows for contamination to settle and for heat dissipation

6. Breather Assembly/Filler Opening • Accommodates the air exchange that results in a constant change in pressure • Must be large enough to handle the airflow requirements to maintain atmospheric pressure whether the tank is empty or full • Filler opening is part of the breather assembly • Filler has a removable screen to keep contaminates out of tank while filling

7. Clean-Out Plates • Usually installed on both ends of tank • The plates should be easily removed and large enough to provide complete access when the interior of the reservoir is being cleaned or painted

8. Oil Level Gauge • Used to check fluid level in reservoir • Either a sight glass or two port holes on the clean-out plate • These allow an easy visual check of fluid limits without the contamination caused by using a dipstick

9. Line Connections and Fittings • Most lines leading to the reservoir terminate below the oil level • Valve drain lines should extend two inches below the fluid level to prevent foaming • Pump return line should be cut at a 45 deg angle directed away from pump inlet to prevent the line from bottoming and cutting off flow

10. Types of Reservoirs • JIC (Joint Industry Conference) • L-Shaped • Overhead Stack • Vertically Mounted

11. JIC Reservoirs • A horizontal tank with extensions that hold it several inches off the floor • Permits air circulation and heat transfer from the bottom and sides • Tanks are usually as deep as they are wide and the length is about twice the width

12. JIC Reservoirs • Made from 9 or 11 gauge pickled and oiled steel • Single bolt clean out plates at each end for cleaning access • Bottom is concave and has a drain plug at its lowest point • Filtered hydraulic fluid is pumped into the reservoir through a filler/breather cap. • A sight gauge is also installed with a thermometer

13. L-Shaped • Vertical tank mounted on one side of a wide base • The other side of the base can hold the rest of the power unit, relief valve, and a heat exchanger • The fluid level in the tank is higher than the pump inlet which reduces the possibility of cavitations

14. L-Shaped • Pressure control and direction valves can be mounted to the side of the tank above the fluid level • If subplate valves are used then nearly all piping can be inserted into the reservoir to reduce losses due to leaks • The interior of the reservoir can be accessed through a hinged top even while operating • This design provides a large surface area for cooling and is also raised off the ground to promote air circulation

15. Overhead Stack • Consists of a standard horizontal tank on top of a modular rack with the rest of the power unit below the tank • This helps prevent cavitations especially for fluids with high density and low viscosity

16. Overhead Stack • For safety reasons, there should be no more than three stacking levels • This system allows for easier draining of the reservoir without the use of pumps • This system also conserves floor space by allowing two or more pump motor assemblies with controls to be incorporated in the rack mounting with a common reservoir

17. Vertically Mounted • Reservoir assemblies are frequently mounted vertically • Generally pump is enclosed inside of reservoir

18. Vertically Mounted • Advantages are: • Reduced floor space • Increased cooling • Fluid acts as a dampener • Fluid creates a pressure head around the pump • Drive force stresses are reduced by gravity • Pump system is kept cleaner in the sealed reservoir • This has a drawback of having to remove the entire pump/motor assembly for maintenance

19. Modifications to Custom Reservoirs • Make sure the reservoir has ample cleanout openings that will be accessible in final position • Make sure walls and sides are strong enough to support equipment • Size should be at least 20% overcapacity of the system to provide a reserve for unexpected problems • Provide a means for filling, draining, and for a fluid level gauge

20. Sizing of Reservoirs • Consider the following factors for sizing: • Fluid expansion caused by high temps. • Change in fluid levels during operation • Exposure of the tank interior to excess condensation • The amount of heat generated in the system

21. Sizing Reservoirs • As a general rule of thumb: • Tank size (gallons)= Pump gpm x2 or x3 • In mobile or aerospace systems, space limitations sacrifice a large reservoir size

22. Heat Exchangers • Heaters • Water Coolers • Air Coolers

23. Heaters • Installed in the reservoir, below the fluid level, and close to the pump inlet • Used for low viscosity fluids

24. Water Coolers • Hydraulic fluid is circulated through the unit and around the tubes containing cool/hot water • Water flow requirements are usually equal to 1/4 and 1/3 of the system oil flow • The water is filtered to prevent the cooler from clogging

25. Air Coolers • Air is used when water is not readily available • The fluid is pumped through tubes that are bonded to fins which transfer heat to the outside air • Air coolers are less efficient than water coolers and tend to be ineffective in areas of high ambient air temperatures

26. Homework • Chapter 5 in Vickers book • Problems 1,3,7,9

27. References • Eaton-Vickers Text, Industrial Hydraulics manual 4th edition 2001 • www.airlinehyd.com • www.vescor.com • www.mazdatrix.com