# Technical Learning – Ram Gauges

A gauge that measures force on a press. Using the diameter of the ram in a calculation, ITI are able to rescale a standard pressure gauge to read in ton.

“I have a 14 tonne press with a 0.809” diameter ram.

What range pressure gauge would be correct and how to work out the dial markings?”

Pressure = Force / Area

14 tonnes = 30864.7 lbs

Ram diameter D = 0.809”

Area of a circle is    = π r2 where r is the radius          π = 3.14159

or                                = π D2 / 4 where D is the diameter

so,       Area               = π x D2 / 4 = 0.5139 in2

So,      Pressure        =          Force / Area

=          30864.7 / 0.5139

=          60,059 lbs/in2 (PSI)

You need a 0 / 60,000 PSI Pressure Gauge

Scaled 0 / 14 tonnes where 1 tonne = 60059 / 14 = 4289.9 PSI

MOST IMPORTANT

Keep the units the same.  If you work in PSI then force must be calculated in lbs and work out the area of the ram or piston using inches.

Another example:

“What are the calculations for a 20ton hydraulic system with a 2.5 inch diameter piston / ram?”

Pressure = Force / Area

20 tons = 44800 lbs                       (1 ton = 2240 lbs)

Ram diameter D = 2.5”

Area of a circle is    = π r2 where r is the radius          π = 3.14159

or                                = π D2 / 4 where D is the diameter

so,       Area               = π x D2 / 4 = 4.909 in2

So,      Pressure        =          Force / Area

=          44800 / 4.909

=          9,126 lbs/in2 (PSI)

or                                =          629.3 bar      (1 bar = 14.5 PSI)

You need a 0 / 10,000 PSI Pressure Gauge

Scaled 0 / 20 tons where 1 ton = 629.3 / 20 = 456.3 PSI