From Billavista's paper:
" 3. Reservoirs
3-1. Reservoirs.
A reservoir stores a liquid that is not being used in a hydraulic system. It has many other important functions too:
* It also allows gases to expel and foreign matter to settle out from a liquid.
* It functions as a cooler
* It functions as a "coarse strainer", providing sedimentation of impurities
* It functions as an air and water separator
* It functions as a foundation for pumps etc.
a. Construction. A properly constructed reservoir should be able to dissipate heat from the oil, separate air from the oil, and settle out contaminates that are in it. Reservoirs range in construction from small steel stampings to large cast or fabricated units. The large tanks should be sandblasted after all the welding is completed and then flushed and steam cleaned.
b. Shape. Design features of a reservoir. It should be high and narrow rather than shallow and broad. The oil level should be as high as possible above the opening to a pump's suction line. This prevents the vacuum at the line opening from causing a vortex or whirlpool effect, which would mean that a system is probably taking in air. Aerated oil will not properly transmit power because air is compressible. Aerated oil has a tendency to break down and lose its lubricating ability. To increase the ability of the tank to separate dirt and water, the bottom must be slightly inclined (deepest end opposite the inlet/outlet end). An ordinary cock (without handle) is fitted so that impurities can easily be drained off. Increased separation of the air that is always present in the oil can be obtained by fitting an inclined coarse metal strainer (approx. 25-50 mesh/ inch) by the return line. Both suction and return pipes must be cut diagonally. The ends of the pipes must be located 2-4 times the pipe diameter above the bottom of the tank, partly to avoid foaming at the return line, and partly to prevent air from being drawn into the suction line, especially when the vehicle/vessel heels over to one side.
c. Size. A reservoir must be large enough so that it has a reserve of oil with all the cylinders in a system fully extended. An oil reserve must be high enough to prevent a vortex at the suction line's opening. A reservoir must have sufficient space to hold all the oil when the cylinders are retracted, as well as allow space for expansion when the oil is hot. A common-size reservoir on a mobile machine is a 20- or 30-gallon tank used with a 100- GPM system. Many 10-GPM systems operate with 2- or 3-gallon tanks because these mobile systems operate intermittently, not constantly. For stationary machinery, a rule of thumb is that a reservoir’s size should be two to three times a pump’s output per minute. A large size tank is highly desirable for cooling. The large surface areas exposed to the outside air transfer heat from the oil. Also, a large tank helps settle out the contaminates and separates the air by reducing recirculation. If the application is mobile, if there is no cooler built into the system, and provided the tank is located where air circulation is good, ideally the size of the tank should be approx. 2-3 times the capacity of the pump per minute.In our 4x4 systems we are unlikely to be able to achieve such large reservoir capacities as this, but the important lesson is that your reservoirs cannot be too big - it is best to use the largest possible reservoir space and weight restrictions allow."
Further down, it states this:
" f. Line Connections. A pump suction and a tank's return lines should be attached by flanges or by welded heavy-duty couplings. Standard couplings usually are not suitable because they spread when welded. If a suction line is connected at the bottom, a coupling should extend well above the bottom, inside the tank; residual dirt will not get in a suction line when a tank or strainer is cleaned.
A return line should discharge near a tank's bottom always below the oil level. A pipe is usually cut at a 45-degree angle and the flow aimed away from a suction line to improve circulation and cooling. A baffle plate is used to separate a suction line from a return line. This causes the return oil to circulate around an outer wall for cooling before it gets to the pump again. A baffle plate should be about two-thirds the height of a tank. The lower corners are cut diagonally to allow circulation. They must be larger in area than a suction line's cross section. Otherwise the oil level between a return and a suction side might be uneven. Baffling also prevents oil from sloshing around when a machine is moving. Many large reservoirs are cross-baffled to provide cooling and prevent sloshing."
From here:
http://www.pirate4x4.com/tech/billav...ng/index1.html
Good luck.
Al