location of suction/return lines and baffles ????

[territorialmillworks]

About to finish an 11 gallon hydraulic tank but want to confirm where to locate the suction and return lines and how to construct the internal baffles to avoid aeration.  The tank measures 24" long by 16 wide by 12" high.  Thanks in advance for the advice.  

PS  Got lucky in that I leak tested the tank (with water) first....pin holes suck....LOL

[Frosty]

At how many GPM do you expect it to operate? For most presses it's pretty low so things like baffling the tank aren't necessary. Hyd fluid is formulated to NOT foam but if volume is high and return pressure is high it can. Use a return line at least 50% larger than the HP line and it'll be a LOT less likely to foam, even in moderately high volume systems.

A trick I was tipped to to disperse the hot return fluid without stirring the pot was to: First put the tank penetration below the fill line. This prevents it entraining air by falling into the fluid. Second, use a 90* elbow internally to direct the flow straight down. Third, weld a little shelf an inch or so below the return outlet to redirect the return flow horizontally in the tank. This prevents a flow directly to the bottom of the tank to disturb particulates settled out on the bottom. It also allows the fluid a little time to settle out, air foamed oil is lighter and wants to stay at the top this trick gives it more time for the air to escape. It also keeps currents in the tank down so particulates or water foaming can settle out.

I don't know how many times I was told buy the guys at heavy duty there was no reason to use larger than stock fittings. but those guys never had to stand behind the drill all day long listening to the hydraulics screaming through restrictive fittings. So, in spite of professional advice I replaced every I broke with the next size larger, even had to disassemble motors and pumps to drill and tap for larger ports. It took almost a year but our rig was running much more quietly and cooler with crisper response to the controls.

Of course I was still wrong, just ask the mechanics but the drill company's factory rep listened and new drills run much more quietly and cooler. <VBG>

Sorry for the digression, having Hank ask me questions and take notes rather than the pros is a Kodak moment for me. The rules of thumb I offer are, low volume, don't sweat flow rates or special return methods. If it is high volume, use larger than stock return lines, avoid splash on return to tank.

A prime indicator of contamination is foaming, usually water or air and foam is easy to see, the fluid becomes milky. Unfortunately creamy fluid is a visual clue which isn't very typically available in a hydraulic system. However, you can get a flow indicator, which is a little whirlygig in a clear glass bulb. The only safe place to put one is the return line. Unless of course you want to put a sight glass in the tank. I'd go with the sight glass, cheap and easy.

Good thing I took another look at your question before hitting send. Do NOT put the pickup at the bottom of the tank! If it's not a round tank you can tilt it a little so the pickup is at the high end too. It really needs a settling space to prevent running particulates through the pump, valves, cylinders, etc. Of course it doesn't hurt to drop a strong magnet on a string to the bottom a bit in front of the pickup fitting. Sure, most of the wear will not be iron but any particles that are will cut the seals and really grind the system. You can pull the magnet every now and then to check and clean. If you're having to clean it more than once every a couple years or so, the pump is probably wearing out.

Frosty The Lucky.

[Damastang]

I am about to finish a 14 gallon tank. My suction is as close to the bottom as my suction strainer will allow (100 mm dia) with a 15 mm or so gap beneath it. It's also in the centre to allow as much oil to surround it as possible. My return is going to be as far away as possible from my suction but not right at the top, maybe 150 mm or so below the top so that it cannot catch air even if the tank is not completely full. I don't have baffles in mine as being 14 gallons in a 12 GPM system, I doubt the oil is going to heat up and if the return is well under the surface of the oil there is no way it can aerate.

However take what I say with a grain of salt I am by no means experienced haha. This is my first time building a press.

[Frosty]

Yeah, that's a low volume system so it's not going to get very hot. The pump is 12 GPM but that's not what the flow rate will be. Your max flow will be the cylinder's stroke and retract volume per minute x how often you cycle it. A 12 GPM pump will put out way more than that and the excess will escape over the pump's bypass. Unless there is air in the oil just putting it under pressure doesn't cause much heat. Heck, it'll heat more escaping over the pump's bypass than running the press.

Frosty The Lucky.