Recent developments of electro-hydraulic disc valves at Surrey University have shown that with a careful balance between the hydraulic and magnetic forces, this type of valve can be used as a digital or proportional device. As the valve is simpler in construction and involves very few critical dimension compared with a servo-valve, the sensitivity to contamination is considerably reduced. The dynamic response of the valve is fast due to utilising high electro-magnetic and fluid forces for actuation. The research described in this thesis is an extension of earlier work by Yuksel and Usman to improve electro-hydraulic disc valves by applying closed-loop position or pressure control to the disc. From an investigation of an unbalanced single disc valve, it was found that using position feedback can help to stabilise the disc under varying load conditions. A special differential capacitive transducer to measure the disc position was designed and constructed and was found to perform satisfactorily. As the pressure-flow characteristic of the valve can be varied by controlling the disc position, the function of the valve is similar to an electrically controlled variable orifice. Various modular configurations are proposed to perform more complicated control functions. In the final part of the research, a double disc valve is described for used in an application study to control the damping characteristic of a modified vehicle shock absorber. Initially, the valve was designed for closed-loop position control due to the non-linear hydraulic and magnetic forces. Results show that the valve can be controlled to generate the required range of damping force and has adequate dynamic performance with a response time in the range of 10 to 30 msec. However, tests using direct pressure control were also carried out. Preliminary results indicate that pressure feedback is preferable to position feedback and that by using lead compensation together with a proportional plus integral controller, stable operation is possible.

The work of the gas transmission pipeline system is regulated by the thousands of valveses and other elements of the shut-off valves, located in different places. Information about the current status of each valve, and confidence in its technical serviceability is an important element in the control of pipeline system. There are a number of problems that adversely affect the  valving operation. Principal among them - is the lack of siystematical approach in valving diagnostics. To solve this problem, developed a new approach to the valving diagnostics – multi-level diagnostics. Depending on the level of diagnosis, we get a different amount of information about the object.   The focus is on the 3rd level of diagnosis, which allows to determine the leackages of valves, and identify type of defects quantitatively. This level of diagnosis is regarded as an example of Method «Micropuls». The method «Micropuls» based on the theory of mechanical vibrations and forced with high accuracy to set the time, frequency and spectral characteristics of noise in the details of the valve, and their spatial location and intensity of that in the presence of a system of analysis allows to determine the state of the object, its faults and defects. Micropulse technology is based on the impact on the measured object micropower impulses, records the response and subsequent filtering, decoding and analyzing the data.                    Specially designed calibrated pulses can effectively influence the measured objects (valve) over a wide range of structural dimensions and mounting schemes, regardless of physical location of the valve.

Since the dawn of the computer age, there has been a push to create miniature devices. These devices were initially integrated circuit (IC) devices to perform calculations for computers. As the technology progressed, the scope of the devices diverged to included microelectromechanical (MEMS) devices, meaning that the devices perform mechanical movements via electrical actuation. More recently, a new generation of devices has evolved called microtechnology-based energy and chemical systems (MECS). MECS may employ MEMS technology, however the systems are not designed to produce only mechanical movement. MECS deal with heat and mass transfer, the basic processes used in energy, chemical and biological systems, in the mesoscale realm. Mesoscale devices range from the size of a sugar cube to the size of a human fist. The possibilities of MECS have not been realized. Heating and cooling systems, chemical mixing/distribution, and locking systems are all potential applications. The devices require: 1) revolutionary design, accounting for the scaling effects on device performance; 2) new fabrication technologies for the creation of these designs; and 3) good material properties for mechanical and chemical interactions. Fabrication requirements for MECS are different than for MEMS in that MECS generally require non-silicon metals. Metal microlamination (MML) has been introduced as a general practice for meeting the fabrication requirements for MECS. Prior MML fabrication methods have emphasized the use of diffusion bonding, soldering, or brazing techniques. This thesis will introduce: 1) a novel microflapper valve design fabricated in mild steel using a novel microprojection welding technique; 2) a novel microfloat valve design fabricated in mild steel using a novel capacitive dissociation process for creating free floating geometries. The devices are characterized by comparing actual flow rates to theoretical flow rates of equivalent orifice sizes. Preliminary results show that the microfloat valve achieved an average diodicity (free flow versus leakage rate) ratio of 11.19, while the microflapper valve achieved an average diodicity ratio of 4.08. The theoretical orifice sizes of the microfloat and microflapper valves are 0.629 mm and 0.611 mm respectively. These results suggest that the float valve is the superior design. / Graduation date: 1999

Improving the efficiency of a Pre- Rinse Spray Valve (PRSV) is one of the most cost effective water conservation methods in the Food Services Industry. A significant contributor to this cost efficiency is the reduction in the energy costs required to provide the mandatory hot water. This research paper estimates the potential quantity and dollar value of the water and energy that can be saved annually in Texas A&M University's dining services with the installation of low flow pre-rinse spray valves. The data collection was obtained from four of Texas A&M University's Dining Services facilities. The annual savings were estimated by contrasting the water consumption of the existing T & S Brass B 0107-M PRSVs with the latest and most advanced available low flow T and S Brass B 0107-C PRSV. The annual water consumption of the existing and new PRSVs were predicted by measuring an individual average flow rate for each and observing the number of hours per day the PRSV would be used. The observed and measured values were extrapolated to amount rates to determine cost savings. The dollar value was ascertained using the utility cost data recorded over a semester by the Facilities Coordinator of the Department of Dining Services. The findings of this study show that the water savings from a single PRSV could lead to an estimated annual saving ranging between 46% and 78% of the current operation cost. The T & S Brass B 0107-C PRSV is currently priced between $52- $60 per valve resulting in a payback period ranging between 1.5-6 months per valve. If every valve on campus was replaced, the University could reap a savings in the range of $ 5,400- $22,590 over the 5 year useful life of the valve, having initially invested less than $550.