Deadweight Tester Parts Description
Dual Volume Hand Pump
The lever action hand pump, which is supplied with both the type T & R hydraulic Deadweight Testers, incorporates a dual volume control valve. This allows the pump to deliver a high volume in order to rapidly fill systems and build pressure. The low volume permits easy pumping at high pressures and a more gradual approach to the point of pressure calibration. A venier adjustment is provided for fine adjustment to the desired pressure.
Within the re-entrant piston and cylinder design, the test fluid is applied to a chamber on the outside of the cylinder as well as to the inside of the cylinder.
The area of the outside of the cylinder is larger than the inside giving a reduced clearance between the piston and the cylinder at higher pressures. This design reduces the rate of fluid leakage, thus increasing the time available for calibration of instruments prior to pumping to restore fluid loss.
Overhung Weight Carriers
Overhung weight carriers The weights are placed on a weight tube that is suspended from the piston assembly. Suspended weights have a lower center of gravity that minimizes side thrust on the measuring piston and cylinder assembly resulting in improved measurement accuracy, and minimized wear on the piston and cylinder assembly.
DW – Floating Ball
Principle of operation
AMETEK pneumatic testers are self-regulating, primary type pressure standards. An accurate calibrating pressure is produced by bringing into equilibrium the pneumatic pressure on the underside of a ball of known area by weights of known mass on the top. The precision ceramic ball is floated within a tapered stainless steel nozzle. A flow regulator introduces pressure under the ball, lifting it in the tapered annulus until equilibrium is reached. At this point the ball is floating and the vented flow is equal to the fixed flow from the supply regulator. The pressure, which is also the output pressure, is proportional to the weight load. During operation the ball is centered by a dynamic film of air, eliminating physical contact between the ball and the nozzle.
Source by: Ametek