Measuring Control Valve Noise

By:

Nathan Kotz, Sean Newton and Jimmy Greco

11/30/10

Executive Summary: We are designing a system to measure the pressure, temperature and vibration in a sealed control valve. Our final design will have an accelerometer being held on by a powerful magnet and the temperature and pressure gages will be screwed into the pipe. The final system will meet all of these requirements but we will have to keep the pressure in the pipe below 500 psi in order for our pressure sensor to read properly. We must also keep the frequency in the pipe below 10000 Hertz otherwise our accelerometer will not read correctly. Overall our goals are met but if we are going to deal with higher frequencies we would need to go with the other accelerometers to measure up to and over 20000 Hertz.

Objectives:
Our group is trying to measure the sound created by the flow through a control valve in an extremely noise sensitive environment. The line we are testing is being used for air flow and we are asked to measure a few different quantities. First we have to measure the internal static pressure upstream and downstream of the valve, second we must find the pipe wall vibration at two different locations upstream and downstream of the valve and lastly our group has to take the temperature downstream of the valve. The static and dynamic pressures need to be measured inside the pipe and the specifications that need to be met are shown in table 1 and figure 1A.
Figure 1A.

Measurement System Design: Our group first started looking for pressure sensors that were in the 0-400 psi range and we were unable to find any that would meet our resolution requirement. So we decided to go with the PCB Piezotronics Model PX309. This made the most sense because it had the closest range to our specified values and the resolution was the lowest. It was the second most expensive pressure sensor that our group researched but it wasn’t much more expensive than the 119B model. The next items that our group researched were the temperature gages that had to be able to measure between -20 and 100 degrees Celsius. The gages also needed to have a resolution of 0.1 degrees Celsius. All of the gages met the range specification but the best model was the omega TH-44007-40-T because of its low cost. This model met all the specs and was cheaper than the other two. Lastly our group looked at a couple of accelerometers to measure the vibration in the pipe wall. We found two one dimensional sensors that fit the range and resolution but we would need three of them to measure in all 3 dimensions. Omega