Cause of error:

1. Error caused by incorrect installation of test machine

The test machine is not installed horizontally, which will increase the friction between the moving parts and affect the vertical installation, which will cause errors to the test machine.

(1) Valve pressure test bench is not installed horizontally

Friction will be generated between the working piston and the working cylinder, and friction will also be generated between the guide wheel between the working platform of the testing machine and the column on one side. This will cause an error, which is generally shown as a positive difference, and the error will increase with the load While decreasing.

(2) The dynamometer part is not installed horizontally

If the dynamometer is not installed horizontally before and after, it will cause friction between the bearings of the pendulum shaft, and the error will generally be negative.

The combination of the above two factors produces errors that have a large impact on small loads and a small impact on large loads.

2 Errors due to frictional resistance

(1) Friction resistance

The friction resistance of a valve pressure test machine mainly occurs between the working cylinder and the working piston. In addition to the non-horizontal installation, there are dirt in the oil cylinder, and the excessive viscosity of the oil will also increase the friction resistance. In addition, the improper position of the guide wheel of the work platform will also increase the friction with the side column.

Valve Pressure Test Bench

(2) Friction resistance of dynamometer

There are many reasons for the friction resistance of the dynamometer. For example, there is dirt between the force measuring cylinder and the force measuring piston. The viscosity of the oil is too large. The friction force of the driven needle on the indicating device is large. There is oil and dirt on the gear rack. The upper limit piece of the object or rack is pressed too tightly, and the force measuring piston belt is worn and broken.

Error elimination method: For the occurrence of the above errors, first check whether the test machine is installed horizontally, and use a frame-type spirit level on the main machine to level the two directions of the outer circle of the working cylinder. On the front of the dynamometer, adjust the front and rear levels of the dynamometer on the dynamometer, align the edge of the oscillating rod with the inner engraved line, and adjust the left and right levels of the body with a spirit level against the side of the oscillating rod. The oil inside the oil cylinder can be drained and cleaned and the oil with suitable viscosity can be replaced. The dynamometer indicating device has too much friction on the driven needle, the gear rack is too dirty, you can use gasoline to clean and adjust the tightening screw and the upper limit piece of the rack bar, and replace the belt on the force measuring piston, which can eliminate the error. , To make the testing machine qualified.

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