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TitleVolume-2. Design and Manufacturing of Hydraulic Cylinders
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Page 27

“Design and Manufacturing of Hydraulic Presses.” ©: Q.S. Khan

Design and Manufacturing of Hydraulic Cylinder

8.4.13 ID of Cylinder as per availability of Seamless Pipe: -

Even if we round off the dimensions of inside diameter of cylinder as per basic series of preferred
number. Then that size may not be available in market. Making a pipe by boring a solid round is not
an easy job, and impossible if length of pipe is more. Hence we should know which standard size
is available in market. Our design and drawing should based on such sizes only, other wise it may
not be economical and possible to manufacture a cylinder shell.
ASTM standards are world famous and recognized, hence good quality pipe made on such stan-
dards are more easily available from local and international companies.
ASTM has defined many standard nominal bore diameters. For each nominal bore sizes they have
defined ten various thicknesses, and named it as Schedule. They have given a number to each
schedule such as10,20,30,40,60,80,100,140, 160. Out of 10 schedules we generally use schedule
80 & 160 in hydraulic application. In Annexure we have given complete detail of pipe as per ASTM
standard.
Indian standard has also defined various nominal bore diameters. And instead of classifying each
nominal bore into ten schedules, they have classified it in to three categories, namely light duty,
medium duty, and heavy duty.
In Annexure we have also described pipes as per Indian standard . If we design and select the inside
diameter of cylinder and its wall thickness as per the standard pipes available in market, and ma-
chine it as per preferred series or advice by ISI Standard, then manufacturing and maintenance of
hydraulic cylinder will be much more convenient and economical.

8.4.14 ID of Cylinder as per Seal: -
Seal are available in standard dimension. Care should be taken that the final dimension of cylinder
is also as per the availability of standard seal. Seals of odd dimension also could be made, but than
keeping spare, and maintenance will be always a problem.

8.4.15 Manufacturing of Cylinder Tube: -
Selection of cylinder tube material depends upon.
1. Constraint about size of cylinder, and its design.
2. Working medium.
If size of cylinder has to be reduced keeping the tonnage (pressing capacity) same. Then working
pressure has to be increased. As working pressure increase corresponding hoop stress also increase.
To cope up with higher stress either wall thickness has to be increased or material with higher
allowable stress has to be selected. To reduce over all size mostly material with higher allowable
stress are selected. Such as plain carbon steel or low or medium alloy steel. But these materials are
difficult to weld.
If working medium of hydraulic cylinder is of corrosive in nature, then brass or stainless steel
seamless pipe are used.
If there is no constraint about size, and working fluid is also not corrosive, then for such standard
working condition seamless pipe of low carbon steel is used, in which carbon percentage is be-
tween 0.15 to 0.35%. Indian standard, and standard of other countries such as ASTM, DIN, BS and
other standards have defined more than 10 various groups of materials for seamless pipe, with
varying percentage of carbon and other element. But most widely used material is ASTM. A106
grade B. For more detail refer chapter "Material used in Hydraulic Presses".

a. Machining: -
For manufacturing of hydraulic cylinder tube, we cut pipe to the length, then machine it by

turning, and boring its inside diameter on lathe machine. Then hone it on honing machine. As per
IS-2709-1965 by honing it is possible to control tolerance limit up to H4 to H5. But the requirement

8-25

Design of Hydraulic Cylinders

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