Electro-Motion Devices - Essay Example

Electro-motion Devices Electro-Motion devices are evolving in a number of applications. In many environments, devices operated by electric power have been developed. This is the case with the petrochemical and process industries as well. The process industries work by suitably controlling the temperatures, pressures and flow of the chemicals through their pipes and ducts. This flow is continuously and closely controlled by valves. Ball valve based control is very critical in most of the process industry application. Therefore, this novel electro-motion device has been developed to operate as a ball valve. The Electro-Motion Ball Valve makes use an electric field that would rotate the ball valve by 90 degrees keeping the valve open. This novel electro-motion device has been explained in the paper below. Introduction The common electro-motion devices comprise of the normal rotary machines running on both AC and DC power supply. In addition to these, electro-motion devices also produce linear motion, controlled rotary and linear motions. On most of the occasions, the linear motion in an electro motion device is produced using rotary equipment. For long traveling devices, motors are used with appropriate capacity. Stepper motors and servo controlled motors are normally used for small and incremental movements needed out of electro motion devices. These motors are normally rotating devices. They are not directly producing linear movement. However, there are devices which produce controlled linear movement. Uncontrolled linear devices are used in high speed trains typically, the bullet trains. In some special applications, rotating devices need to be controlled to an accurate angle. This kind of controlled movement becomes a tough implementation because of the motor's speed and the reduction that might be required. These are normally used for controlling the movement of telescopes and antennas in radar systems. Design of the Device The electro motion device for rotation control is a common requirement. This is found as indicated in telescopes and in antennas for radar systems. But implementing them in an effective way at a reduced cost makes it all the more challenging. The application is a ball valve electro motion device that would open or close a pipe line carrying chemicals. The ball valve is normally operated using either a mechanical lever or a rotating member or it could be a pneumatically operated valve. The ball valves are used to control the flow rate and could be placed in any of the angles to control the flow. In order to realize this, an electro motion device is used more comfortably rather than use one of the indicated methods. The design consists of a large gear wheel connected to a standard AC motor. This motor to gear ratio is predetermined in such a way that the motor has to rotate about 100 times to realize one complete rotation of the gear wheel. One rotation of the gear wheel will, in turn, open the valve fully. If the gear wheel is to be rotated only through half of the rotation, then the valve will be open ninety degrees. The design of the gear wheel has to take into consideration the size of the motor drive gear. The ratio between them has to be one hundred ensuring that the motor rotates one hundred times to open the valve fully. By controlling the motor and the number of times it could rotate, the opening of the valve could be controlled. The percentage opening obtained is exactly proportion to the number of rotations that the motor has performed. If it has rotated twenty times, then the valve is open for twenty percent. The same logic is maintained for one hundred percent opening too. The working of the device varies with the options that are required. In the process industries where such devices are put to use, the electro motion ball valve can be used in any of the following applications: 1. Steam handling 2. Non Corrosive liquid handling 3. Corrosive liquid handling 4. Gas handling 5. Sludge or semi solid handling Depending on the viscosity of the fluid that is flowing through it the design would get suitably altered. The body of the ball valve will also be altered depending on the nature of corrosiveness of the fluid flowing through it. For highly corrosive fluids, the ball is lined with rubber or such other corrosion resistant material. The inner body and the pipe linings till the flange are normally lined with rubber lining to resist corrosion. Apart from this, the size of the valve is designed based on the amount of fluid that has to flow through it. Appropriate fluid flow is assumed or computed and designed accordingly. Once the size of the ball valve, the material of the valve and the nature of lining are all designed, this would help in identifying the overall load in the valve including the weight of the fluid when it has to open or close. Taking this into consideration, the amount of force that has to be applied on the valve to open or close is computed. A rotating motor of required capacity to meet the load conditions has to be selected to drive the valve. According to the rotational speed of the motor, a suitable gear ratio is selected between the valve gear wheel and the motor gear wheel. Ideally, this can be taken to be 100 so that for every 100 rotations of the motor the valve will open once. Operation of the Device The electro motion device will be operated using a normal electric motor control system. In this case, the motor that is connected to the valve over a gear, is operated for a fixed number depending upon the opening that is required. In most cases since ball valves are made for accurate opening and closing a control circuitry is designed to rotate the valve accordingly. This control circuitry is operated by the operator by suitably providing it with a percentage opening needed. This can be any number between zero and one hundred inclusive of the extremes. If it is one hundred it is fully open and if it is zero it is fully closed. Most of these valves are threaded to the pipe or flanged couplings are provided. In either case an appropriate sealant will be required to ensure that there is good coupling between the stationary parts of the valve and the pipeline it is serving. In case of the valve motor, a suitable braking mechanism is used in order to ensure that the valve rotates accurately to the required angle and stops without disturbing the entire working process. A valve rotation and braking mechanism is normally designed to ensure that the exact rotation angle is obtained during the operation of the system. The valves are also designed to operate within the specified temperature range. If the range exceeds then the operation of the valve might not be in line with the expectations of the operator. The material of construction of the valve is also critical and is chosen based on the needs of the application. The actuation is electrical and therefore it is an electro motion device. Electro motion devices are better than pneumatic or the manual systems as well for the following reasons. 1. Pneumatic systems have a slow response time once the request for open or close is received. Whereas, in the case of electrical devices the response time is normally fast and the valve opens or closes immediately. 2. Pneumatic systems would expect additional process equipments to be in operation and to be maintained in appropriate pressure in order to function properly. This kind of additional requirement is not there in case of electro motion devices. They work independent of the other devices. 3. Of course, manual operations in a number of cases are not advisable particularly in cases like acid handling and sludge handling where the normal manual valves could be difficult and unsafe to operate. In these cases, if electro motion devices are employed, they will be safe as well as can be made to work against the load required. This will ensure better operating environment for the workers. All these would make the operation of a ball valve much more easier and safer if it is an electro motion device. Issues faced Some of the typical issues faced by the manufacturers and operators are as follows. The solution for the same is also listed alongside. 1. Ball valves made out of cast iron or such other material is normally heavy and therefore requires a large motor to operate the valve particularly when working against fluids of high viscosity. 2. In order to counter this problem, it is normal to find valves with plastic or PVC balls. These are used in those cases where they can withstand the load on them from the fluid. There are also fiber balls that are made to withstand higher loads at the same time being light. This would ensure that the motor employed is not large and would help in reducing the size of the motor. 3. The response time of the ball valves could be sluggish. This would become specifically an issue under emergency conditions. 4. Ball valves are sluggish as they grow larger in their size. This is particularly true in those cases where they are manually operated. In those cases where they are operated using electro motion devices, the ball valves have lot faster response and are more dependable than otherwise. This makes them all the more safer and easier under emergency conditions. 5. The electro motion ball valves might get locked up while handling slurry or such other sludges. 6. This can be set right only by suitably selecting the drive behind the ball valve. In the case of ball valves, the load has to be calculated with the size of the valve and the density of the fluid flowing throw it and the rate of flow should also be taken into account. This has to determine the size of the valve and the nature of the valve used. Based on this, the material of the ball can also be modified. Bronze is also used in addition to brass sometimes. Aluminum and other metals are also used for this purpose to make the balls for the electro motion ball valve. 7. They are expected to be accurate in controlling the flow. This is not properly maintained in some of the cases. 8. This issue is normally faced when the ball valve controlling motor rotation speed and the valve movement is not properly synchronized. This can also happen when the valve design does not match with the choice of the drive. Therefore, it is essential for the valve design speed to match with the rotational speed of the motor drive. This issue would come up if such a matching is not fairly done. This issue can also arise if the gear wheel design is not done appropriately and results in a mismatch. 9. Corrosion resistance in drives in corrosive atmosphere is a must. Some of the devices are made to operate in corrosive environment internally but does not stand it externally. This primarily happens when the motor is selected separately and the device is separately selected without appropriate design parameters getting fixed. The motor should also be suitably rated to operate in corrosive environments. Similar Systems A number of similar systems exist which are also electro motion devices that would help in opening or closing of the valves. Some of the different types of valves that employ electro motion actuators would include the following: 1. Gate valves: These are normally not flow control valves. Instead they are only open and close valves. They are used to either keep the line open or keep it closed. These gate valves themselves have either a swivel that would turn around and allow the fluid to flow through. In other cases, there are also slide gate valves that would slide in and out to make the pipe open or close. In both the cases, electro motion is used. In cases of rotating members, a similar structure as that used in the case of ball valves is made use of. This will have the gear arrangements that connect to the motor and operate. In case of slide gate valves, the rotary movement of the motor is converted into a linear movement by using appropriate crank shafts with the needed stroke lengths matching the linear movement required. 2. Butterfly valves: The butterfly valves are normally hinged at the centre and they open or close using this hinge. It is also possible to control this valve with the same mechanism that was adopted for the ball valve since this is also rotary. The movement of the valve will be controlled using a gear wheel connected to the servo motor that would rotate for the exact number of turns required and the valve will be opened accordingly. 3. Globe valves: These valves also are rotary. They can also be controlled using a similar method as adopted in the case of ball valves. The electro motion device is made use of to control and rotate the globe valve opening up as desired. These devices are used mostly in process industries. 4. The actuators employed for the electro motion devices are normally motors in case of rotary applications. These actuators also come in varied sizes and designs to work under different pressures. Undersea actuators are common for under sea applications where these valves may be put through. Similar corrosive environments, cold or tropical or temperate environments will also have other modifiers added to the actuators. Actuators also operate in icy locations like Antarctica or in hot conditions in space. In either of the cases, the actuators need to work flawlessly. Therefore, they are designed to suit the needs of the environment. In dusty environments, IP 55, IP 65 or such other Ingress Protection specifications will help if adopted. Electro motion devices are employed for varied purposes in every industry. In process industries and in engineering industries automation has become the major player. Therefore, it is found that the electro motion devices employed are also in line with the needs of the industry. The operational mechanisms and design would change depending on the specifications worked out for these equipments. Conclusion The electro motion devices are mostly electro mechanical in nature. They are employed to convert the electrical energy into kinetic. Either a linear or a rotary motion is normally obtained. However, there are also cases where linear movement is directly created by the electro motion devices as in the case of actuators found in vertically operated valves. While these are used in few places, mostly rotary converters are easy to build and operate. Wherever the linear movement becomes a need, in those places, a rotary to linear mechanical converter is employed. This makes the implementation more robust and easy to maintain. Using electro motion devices in process industries is very common. Controlling signals are electrical and therefore, to use them to move the devices and to monitor their motion makes it easier. This marks the success of electro motion devices in the process industries. References 1. US patent (2001) Electro motion ball valve available at: http://www.freepatentsonline.com/20010035510.html 2. Global Spec (2006) Electrically Actuated Ball valve Specifications. Available at: http://flow-control.globalspec.com/SpecSearch/PartSpecsPartId={F716540D-E36A-4249-86E2-75F43ACCA49E}&VID=149884&Comp=854&OemId=2450 3. Tyco International (2007) Actuators. Tyco Flow Control Systems, available at: http://www.tycoflowcontrol-as.com/products_results.aspSelection=Actuators&m=2 Read More