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Air-Oil Tanks


Nopak air-oil tanks are used as a simple economical method to supply a make up source of oil to any hydraulic circuit. Mounting the tank in a vertical position above the circuit that is being supplied, automatically bleeds the entire circuit system. The air supply to the air over oil tank is supplied by the same shop air source that provides low pressure power to the booster. In addition, air-oil tanks offer a means of smooth hydraulic speed control.

Design Features:

  • Baffles on either end of the tank to reduce turbulence caused by rapid intake of air and discharge of oil causing aeration, whirlpooling and foaming.
  • Replaceable sight gauge mounted in heads on the tank side. The transparent plastic sight tube clearly shows oil levels in the tank and is compatible with most hydraulic fluids.
  • Large pipe ports enable the quick filling or draining of the tank. Aluminum heads are standard for tank diameters of 31/4 dia. thru 8" diameter. Otherwise steel class 6 inventoried stock of 31/4" dia. thru 14" diameters modified for added ports plus aluminum tubes are standard stock.


Tanks are also available with glass wound filament fiberglass tubing. Because it is translucent, it provides a visual oil level indication. This eliminates the use of a sight gauge. Fiberglass tubing has the highest strength to weight ratio commercially avail-able. It has a higher resistance for high impact and dents than brass or aluminum tubing. Corrosion resistant to a wide range of chemicals, acids, high moisture and other severe conditions make for a trouble-free operation in most environments. Nopak can economically supply you with either tank depending on your choice preference or specification.

How to select the correct sized air-oil tank.

1.Determine the bore diameter and stroke of the work cylinder.
2.Calculate the cubic inch oil displacement of work cylinder by multiplying the piston square inch area times the stroke in inches. (Use Catalog 106, Page 35, Table B, Blind End Dis¬placement for piston square inch area for ready reference.) Your determination will result in the cubic inch displacement volume requirement needed to select an air-oil tank.

Air-Oil TanksExample: Work cylinder has a 4 inch diameter bore with 15 inch long stroke.
From Cat. 106 P. 35
12.56 sq. in. area 4" bore x 15 Stroke
Length 188.4 Cubic inch displacement volume needed.

See the tank selector chart below to select proper choice. Select a bore-height combination that has a capacity closest to, but larger than 188.4 cu.". Your options are the 4 inch diameter bore with a 21 inch long tank length or the 5 inch bore with a 14 inch tank length or a 6 inch bore with an 11 inch tank length.

Economics recommends that your selection be the smaller 4 inch diameter bore with the 21 inch long tank length. This of course is predicated on available space. The smaller bore tanks are gener¬ally less costly than larger bores. Exceptions to this are the booster-tank combination which then makes your selection to be that the tank diameter be the same diameter as the booster. Next selection would be the type of mount applicable to your require¬ments. See the chart on opposite page for selection and dimen-sions. Nopak offers Models H, S, T, TB, and AP as a standard. However other mounting styles can be selected from Catalog 106. When boosters and air-oil tanks are ordered, specify whether air- oil tanks should be separate or integral. It is assumed that air-oil tanks are to be separate unless specified.

Please consult the Nopak Safes office or your nearest Nopak representative for additional information.


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