A stuffing box is a sealing device which is used for several applications. The most common use is for pumps and industrial valves. Its main role is to prevent leakage from one medium to another. Therefore, the design of this assembly is very important to maximize the sealing efficiency without impairing the necessary movement in both pump and industrial valves. All the parts in a stuffing box are important, but the packings and the gland are intrinsically linked to the sealing efficiency of the stuffing box. The gland function is to apply and maintain a constant pressure on the stack of packing rings. This axial pressure is then transmitted into every packing contained in the stuffing box which will then transpose it into a lateral contact pressure along the housing and the shaft. Maintaining that contact pressure at both interfaces is the key parameter to maximize the overall sealing efficiency of the stuffing box.
Around 70 years ago, the use of asbestos in the manufacture of valve braids was widespread. Since then, health research has shown that asbestos is carcinogenic, and its use is now prohibited. Therefore, manufacturers and research laboratories had to develop new alternatives. Although research has progressed well, there is still little documentation available to assist engineers in the design of stuffing boxes. The few standards on which engineers can rely on are dedicated to the qualification of valves from a quality control standing point. However, these standards apply for the complete assembly of the stuffing box and do not help in the design of the individual parts of the assembly such as packings.
To extend the documentation available to engineers, past research has focused on studying the mechanical properties of braids as well as the rest of the assembly of the stuffing box. Most of these studies did not consider the effect of high temperatures although this parameter has a major influence on the tightness of a system. The inclusion of temperature in future research is inevitable and necessary to represent the actual behavior of mechanical braids.
The first step of this project is to modify and adjust the measuring instruments of a test bench that reproduce the real behavior of an industrial stuffing box. The measurement of the axial force and displacement of the braids is the most important measurement since it is directly linked to the measurement of the creep behavior. Therefore, this sensor must be as precise as possible. The previous sensors are replaced by two new extensometers and the attachment device has been modified. The second parameter of importance in this project is the heating system. Therefore, the thermal shields of the heater was slightly modified and all thermocouples were replaced to improve the control of the heating. In addition, the position of the control thermocouple is modified to limit the temperature differences inside the oven insure repeatability.
The second step is to collect high temperature creep data of expanded graphite gaskets. A total of 12 tests are performed to collect data at four different temperatures, i.e., 75°F, 200°F, 400°F and 600°F. These tests also make it possible to validate the proper functioning of the test bench and of all the new measuring devices that have been installed.
The data collected during this project is used for two purposes. First, on the MATLAB software, an analytical braid creep model is obtained. This model is interesting since it is the first step before moving on to using computer aided design (CAD) software to study braid mechanical behavior. The other use of the data collected is to revisit observations made in previous research. Degassing is the phenomenon in question; where at high temperature the gaskets would no longer be compressed, but rather would be prone to expanding. However, during this project, no expansion has been observed during the experimental phase.
| Date | 5 Dec 2021 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Hakim A. Bouzid (Supervisor) |
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Maillé, C. (Author),
Bouzid (Supervisor),
5 Dec 2021Student thesis: Master's thesis › Master in Engineering: Mechanical Engineering