The manometers with scale in Tons are usually used in hydraulic presses and usually come expressed directly in Force (F) units, Kilograms force or Tons, that the press exerts.
This force is smaller or greater depending on the surface of the piston that exerts that force. The greater the piston (and logically more surface has its piston) the greater the force exerted. This is why there is no standard manometer for all presses, as each press manufacturer builds according to its own criteria.
To be able to manufacture a manometer in Tons for a press, we need to know the force exerted (F) and the size of the piston that exerts that force, that is, the diameter of the piston, in order to calculate its Surface (S).
By means of the following formula we can calculate the Pressure (P) exerted:
P(ressure) = F (force) ÷ S(urface)
To know what is that surface, in case of not knowing it, it can be easely calculated according to the diameter of the piston by means of the following formula: S(surface) = π (pí) x r (adius) ²
Let's see an example:
We know that the diameter of the piston of the press is 7 centimeters, and the force is 40 tons (or what is the same, 40000 kg force).
Then, using the formula to calculate the surface S = π x r²: 3.1416 x (3.5) ² = 3.1416 x 12.25 = 38.48 cm².
Since the pressure is equal to Force divided Surface (P = F ÷ S), we will then divide 40000 Kgf ÷ 38.48 cm² = 1039.50 kg/cm².
Once the pressure known, we can proceed to adjust the manometer with 0-40 Ton scale, adjusting the manometer to 1039.50 kg/cm².
Due to its greater roughness, Abad Controls recommends manometers fully stainless steel made with glycerin filling for this application.