CrazyEngineers Forum - Mechanical & Civil Engineering |
| Posted: 19 Dec 2010 06:04 AM PST Self-Flushing Debris Filter The quality of the cooling water intake and the amount of debris in that water affects the operation and performance of the condenser and therefore the thermal performance of the typical steam plant. Material such as slime, calcium carbonate, calcium sulfate, magnesium dioxide, silt, petroleum products, corrosion products, and the like adhere to the inside of the heat exchanger and condenser tubes. The accumulation and growth of such deposits reduce the overall heat transfer coefficient and will have an adverse effect on the operation of process equipment, plant availability, production, and maintenance cost. Traditionally, plant maintenance teams isolate and open each heat exchanger or condenser unit periodically in order to clean the tubes manually using high-pressure water jets or mechanical scrapers. This process is labor-intensive, costly, and may require process shutdown. Furthermore, when the equipment returns back to operation, the fouling process begins anew. there is an online method to clean the heat exchanger or condenser , it is DEBRIS FILTER Self-Flushing Debris Filter The debris filter is the ultimate protection for condenser tubes, it is designed to automatically separate and remove fibrous and coarse debris from the cooling water during operation of the cooling system. In order to protect the condenser not only from unwanted particles flushed into the cooling system by the cooling water, but also from particles originating from the cooling water intake channel or pipes themselves, the debris filter should be located as close as practical to the CONDENSER INLET . Since the debris filter is the last protection in-line of the screening systems in front of the condenser, particular care has been taken to ensure high reliability, availability and performance as well as low maintenance.    Intake screens are often ineffective in protecting heat exchanger tubes from debris. Many plants designed with through-flow traveling screens located upstream of the condenser still experience heavy debris carryover or are victims of macro fouling via mollusk or crustacean growth within the intake tunnel, which causes many clogged condenser tubes. The normal practice is to clean the tubes manually, but this requires an outage or a period at reduced load, depending on the condenser design. A debris filter or automatic pipe strainers provide the best filtration, ranging from 50 microns to 10 mm. These strainers can be sized to remove the carryover and fine debris that pass through intake screens to prevent buildup inside the condenser or exchanger tubes. The debris filter replaces a section of the cooling water piping. Water and debris enter into the filter housing, and filtered water exits the screen mesh. Debris larger than the mesh size is trapped over the screen area. Based on the desired setpoint for the increased pressure drop above the clean screen, or on a preset time interval, the debris-cleaning rotor travels over the screen mesh to lift and remove debris from the screen surface. The debris-cleaning cycle lasts only a few minutes. The debris is then discharged into the sewer or into the cooling water discharge from the plant using a small quantity of water.  Fixed, semi-spherical shaped filter elements separate the filter area into several independent filter chambers, and consequently no debris can bypass the filter elements. A hood-shaped backwash rotor, located at the raw water side, always covers one filter chamber completely, while a special engineered gear box actuates and rotates the backwash rotor from the clean water side of the filter. The backwash process is automatically initiated by a pressure differential measuring system which monitors debris accumulation permanently. Not only can the backwash process be triggered automatically by the pressure differential measuring system, the backwash sequence can also be started manually from the local control cabinet.  This is the typical TECHNOS Self-Flushing Debris Filter , and its components shown in the figure above , this system is installed at Most of Thermal Power Station , for its ultimate benefits and advantages . The attached files are (*.pdf ) files which describe in detail the debris filter , and TECHNOS Catalog |
| Posted: 19 Dec 2010 06:00 AM PST Vacuum low reasons: 1. Check condenser surface area, make sure it is clean (you can do inspection for one room while the other still in service and you need to reduce load) this is if possible with your business operations 2. Check for leakage around flanges, gaskets, valves etc, near ejector and condenser 3. Check MP steam pressure which drives the ejector (is it according to the required pressure)?? 4. Check ejector drain and steam trap which send the condensate back to condenser (plug-up or not)?? 5. Check if someone has opened chest valve / valve after governor drain, maybe drain valve is open instead of steam trap, because condensate which goes back to condenser should pass steam trap, not through drain. 6. Check your vacuum breaker is not in service 7. Check level of condenser, it should be good, and check temperature of cooling water for condenser, it should be low enough to condenser steam.  |
| Swirling problem at boiler’s start-up Posted: 19 Dec 2010 03:15 AM PST At boiler's start-up, one should take care of water swirling at boiler's Drum, especially when you start at Cold Start Mode. Swirling at cold start, makes water level fluctuates very much at the Drum. Therefore it can trip the boiler with Drum level Hi Hi protection (MFT). Imagine you have some of water in a kettle, and you start boiling the water, the mixture will be water and bubbles. That is what happened at drum but with so many fluctuations. Water swirling takes time until water level stabilize, when a build up pressure at Drum equal to 1 barg. You can notice this from the Drum level indicator. So, how can we eliminate such this problem? 1- Open start up blow off valves ( 2 valves ) 2- Open continuous blow down valve ( 1 valve ) 3- Reduce warm up fuel flow mass ( rate of fuel ) http://science-hamza.blogspot.com/ |
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