Conversion of water into steam is the primary function of a utility boiler.The steam pressure is used to turn a steam turbine thus, generating electricity.Within the boiler drum there exists a steam/water interface.Boiler steam drum water level is one of the important parameters of power plant that must be measured and controlled.For safe and efficient boiler operation, a constant level of water in the boiler drum is required to be maintained.Too low water level may cause damage boiler tube by overheating.On the other hand too high drum water level leads to improper function of separators, difficulty in temperature controlling and damage in superheater tubes.Turbine may also be damaged by moisture or water treatment chemicals carryover.The amount of water entering the boiler drum must be balanced with the amounts of steam leaving to accomplish the constant water level in the drum.Therefore it is extremely important to have the knowledge of the operating principles, installation requirements, strength and weaknesses of drum water level control system.Ignoring these considerations can result in misapplication, frequent maintenance, unsafe operation and poor instrument as well as system performance.In this paper design aspects and installation requirements of boiler drum level control are discussed for safe and economic operation.
In today's world we are faced with different types of emergencies in the environment predicting the risks such as sudden raise in atmospheric temperatures. Response to such emergencies is critical in order to protect various natural resources. Therefore, we need an emergency response system which is easy to deploy and can report these emergencies to the users or local communities in various ways, such as pop-ups on a computer screen, SMS to their cell phones and so on. During the last few years, significant advances in embedded hardware and software technologies are driving down rapidly the cost of wireless sensor networks (WSN) and allow large scale WSN deployments for various applications to become viable. The present study elaborates the use of 6LoWPAN based WSN to monitor the changes in room and human body temperature and suggests that the same can be deployed to detect the sudden changes in temperature in inaccessible areas.
We study the H NMR line shapes of a sample of a-Si:H under several conditions: 1) as grown, 2) light-soaked for 600 hours, and 3) light-soaked followed by annealing at different temperatures. At T = 7 K, the NMR line shape of the sample after light soaking exhibits an additional doublet compared to that of the sample as-grown. This doublet is an indication of a closely separated hydrogen pair. The distance between the two hydrogen atoms is estimated to be about (2.3 ± 0.2) Å. The concentration of these hydrogen sites is estimated to be between 1017 and 1018 cm-3 consistent with ESR measurements of the defect density after light soaking. This doublet disappears after the sample is annealed at 200°C for 4 hours.
Majority of commercial silicon solar cell technology around the world is based on screen print technology with or without a single or combined layer of titanium dioxide, silicon dioxide or recently PECVD silicon nitride. Most of the reported work on dual layer anti-reflection coating is based on two different materials. Less work has been done on dual layer silicon nitride for this purpose. In this work, a simple approach is presented to utilize dual layer silicon nitride. An improvement in weighted average reflectance has been achieved compared to single layer silicon nitride layer by this approach.
