Stress Relieving / Calibration / Type Testing - Cycling of Pressure Gauges


Pressure Gauge Manufacturing Units can deploy this machine for Manufacturing, Testing, Calibration and Quality Assurance departments. Stress Relieving, Calibration, and Type Testing - Pressure Cycling Test as per ASME B40.2., are carried out. The Personnel Computer (PC) connectivity adds to preserving this valuable data. Printing the test reports, in case of Type Test can be carried out on a Dot-Matrix printer directly interfaced with the machine.

 Stress Relieving: Once the Pressure Gauge is manufactured; it is required to be stress relived before being calibrated. The pressure gauge is subjected to 130% of the range for first time, and is then cycled between greater than 90% and less than 10% of the range for typically 150 – 200 times, depending upon the requirements. Presently implied manual method is quite cumbersome, tedious and tiring. The effective production reduces to 50-60% in the evening, as compared Moring, due to reduced efficiency due to fatigue of a worker.
The deployment of this machine, in production shop, one unskilled worker will stress relieve minimum 5 times as compared to present scheme, thus reducing the work force requirements at least by 4, in total of 5. Similarly one semiskilled worker can calibrate 5 times the normal method, reducing the labour force still further. There is no alternative to this machine for ASME B40.2 type testing.
The operation is quite simple and is as follows:

There can be two Stations connected to one Machine, being used alternately. There will be facility of attaching 5-6 gauges at a time on both the stations. The operational method is very simple; attach the required gauges on the station, blocking the other ones. Set the required Full Scale Pressure range, and Number of Cycles to be completed, on the controller with the help of Keyboard and LCD display. Confirm the data entry and start the machine. Watch the pressure rise and fall, in the Alphanumeric Backlit LCD Digital Display. Adjust the rise and fall timings manually. Generally 90% and 10% are fixed in the software; however please let us know, so as to modify the software as per the requirements. If there is a leakage and pressure dose not rise to required value within 20-25 Seconds, the shrill buzzer will go ON, for attention. Remove the leakage or faulty gauge and start again. Once this station is set, the worker can remove the gauges on the other station, and install the new ones. As the total numbers of cycles are over, a musical buzzer will be ON indicating the completion of the test. The other station is ready for use by now. Worker has to change the station and start the next station operation. The Accuracy of our pressure indication is 0.5% or better, however master gauge can be connected at one of the points for confirmation. The unit of the pressure is generally Kg/Cm2, but can be modified to suit the requirements.

Calibration: The calibration is similar to Stress Relieving. Attach the required gauges on the outlets, blocking all others, or continue this operation after stress relieving is complete. The accuracy of our indication is 0.5%, but can be increased to 0.1%, with use of special transducer. If more accurate with NABL traceability is required, the calibrated Master Gauge can be attached on one outlet for confirmation.
The system works as per the following:

After fixing all the gauges, enter the full-scale range. Pointer setting to ‘0’ and Full-scale is completed using ‘0’ and Full-scale switches alternatively. If external master gauge is used, adjust the pressure by ‘INC’ and ‘DEC’ keys for fine tuning. You may be required to have some iteration for final settings. Now the system is ready for Calibration. Confirm if one needs calibration Upwards or Downwards by setting the same. The calibration will start now. NEXT switch will take the pressure to next calibration point, by increasing or decreasing the pressure. Once this pressure is stable, it will give you a small alarm, where in the operator can either confirm the calibration on PRE PRINTED dials or Mark for the point, on empty dial. External Master Gauge can be used for fine tuning as well. After this point is confirmed, activation of NEXT switch will take the pressure to next position. Follow the same procedure, and complete the calibration. One can calibrate about 5-6 gauges in about 15 Minutes.

Any unskilled labour can be used to remove these gauges, while second station is ready for calibration, by some skilled personnel, increasing the production to the great extent.

Pressure Cycling Test as per ASME B40.2.
This is TYPE TEST required to be carried out on pressure gauges, once. The third party Inspector might ask to perform this test on one or two gauges in a lot.
The test is carried out as follows:

1. All the required parameters like Size, Range, and Serial No of the gauge with Pre selected parameters as Pressure and Number of Cycles is entered through the keyboard. 75% and 25% is calculated by the system software. Once the cycle is STARTED, the internal Real Time Clock will register the Start Time in the Non-volatile memory, and keep the track of Real Time. Now the Pressure will start Oscillating between 75% and 25%. One oscillation should be over in One Second. This rise and fall rate can be adjusted manually to suit the test. It is harmful for the gauge if it oscillates very fast, and the cycle is not counted if it takes more than one second. The system will continue to operate, till all the cycles are over. If one cycle cannot be completed in one second, 5-10 times, a harsh buzzer will blow, indicating either to adjust the FEED or RELEASE manual valves or the system has failed. Once all the preset cycles are completed
successfully, the machine is stopped, giving a Musical buzzer. Now, one has to remove the gauge and test for its accuracy, as per ASME B40.2.

Print-out can be taken any time during the test on a Dot Matrix printer, interfaced with the machine. It is not possible to change the clock during the test is ON. Find attached the typical printout of the cycle.

All the data is stored in the battery backed-up Memory. The system will stop once the power is OFF, but will resume, as the power is restored.

The system consists of the following:

1 Pneumo Pump :
Electromagnetic Pneumo Pump with intensification Ratio of 1:22 or 1:10. All the wetted parts are Brass/SS304. External Pilot operated 5 PORT DCV with 24 Volts DC solenoid coils operates through Solid State Electronic Logic Circuit.

2 Pressure Control :
Pressure Regulator at the entry point, of the Compressed Air Controls the Air Pressure, in turn controls the hydraulic pressure. FRL unit for Air entry and Water Filter at the water entry point is also provided. A pressure accumulator is also provided to avoid frequent operation of the pump.

3 Pressure Transmitter :
100 Kg/cm2 Pressure Transmitter is used to check pressure in the line. This Transmitter will be kept inside the controller so as to get calibration done from any calibrating standard as and when required. The accuracy of this transmitter can be 1%, 0.5% or even better than 0.1% depending upon the accuracy requirements.

4 Microcontroller Unit :
The Micro Controller Unit has
1. 16 Key Keyboard to set all the parameters.
2. 20 x 4 alphanumeric backlit Display, to indicate various parameters and key entry
3. Buzzers to alarm the cycle over, or problem
4. The battery backup RAM with REAL TIME CLOCK to keep the track of real time applications.
5. Throttle Valve to adjust the rate of Pressure Rise.
6. Throttle Valve to adjust the rate of Pressure Drop
7. Interface for Dot-Matrix Printer.

The preset and actual data can be collected on a PC with software as when required.