See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/273316508 ﺔ ﻫﻨﺪ ﺳ ﺔ ن ﻣ ﺪﻧﻴ نﻣﻬﻨﺪﺳــــﻮ إ ﺳﺘﺸــﺎرﻳــــﻮ Article · March 2015 READS 17 1 author: Magdy Bakry Al-Azhar University 51 PUBLICATIONS 0 CITATIONS SEE PROFILE Available from: Magdy Bakry Retrieved on: 08 August 2016 1 Consultants Civil Engineering مهندســــون إستشــاريــــون هندسة مدنية : المشكلة القائمة أثناء تشغيل وحدات أنتاج المياه (التشليرات) الموجودة بدور البدروم لوحظ وجود أهتزازات بأرضية الدور األول باألشارة ألي الموضوع عاليه فأننا نتشرف بتقديم العرضين الفني و المالي األتيين VIBRATION ISOLATION OF CHILLERS (air conditioning compressor) 140-500 Tons (60 Hz), 140-400 Tons (50 Hz) General: Floor vibrations results from high static deflections which can vary from 10 mm to 30+ mm leading to vertical natural frequency ranging from 5 Hz to less than 3 Hz. Possible Solutions The best solution to a vibration problem is to avoid it in the first place. Intelligent design is far more cost effective than building a bad design and having to repair it later. The intelligent Solution to any vibration problem involves the following steps: 1) Characterize the system parameters (mass, stiffness, damping) by experimental methods, - مدينــه ركن حلوان الجديـــدة- ح تقسيــم جمعيـــة النصر4 قطعة المعــــادى- كورنيش النيـــل Mobile : 01014555350 Consultants 2 Consultants Civil Engineering مهندســــون إستشــاريــــون هندسة مدنية Manufacturer’s data, or a combination of both. 2) Model the system dynamics using a simple lumped parameter model a) Identify natural frequencies, look for coincidence with excitation frequencies b) if excitation forces and frequencies are known, system response can be calculated 3) Use the model to assess the effect of changes in system parameters Vibration Solutions - Source 1) Relocate machine – place machine on as rigid a foundation as possible (on grade is best) and as far as possible from potential receivers 2) Replace machine with a higher quality or different type of machine that is quieter (and probably more expensive) 3) Change the operating speed of the unit to avoid coinciding with structural resonances 4) Balance rotating elements, 5) Add a tuned vibration absorber 6) Use active vibration control - مدينــه ركن حلوان الجديـــدة- ح تقسيــم جمعيـــة النصر4 قطعة المعــــادى- كورنيش النيـــل Mobile : 01014555350 Consultants 3 Consultants Civil Engineering مهندســــون إستشــاريــــون هندسة مدنية Vibration Solutions - Path Minimizing the vibration transmission generally involves using isolator springs and/or inertia blocks. The basic principle is to make the natural frequency of the machine on its foundation as far below the excitation frequency as possible. The mathematics for this case, and isolator selection procedures are discussed in the next sections. Vibration Solutions – Receiver 1) Change the natural frequencies of the system to avoid coinciding with excitation frequencies. This can be accomplished by adding stiffeners (which raises the natural frequency) or by adding mass (which lowers the natural frequency) 2) Add structural damping Vibration isolation problems can be divided into two main groups: Firstly, the need to reduce the transmission of vibration from a machine to the structure supporting - مدينــه ركن حلوان الجديـــدة- ح تقسيــم جمعيـــة النصر4 قطعة المعــــادى- كورنيش النيـــل Mobile : 01014555350 Consultants 4 Consultants Civil Engineering مهندســــون إستشــاريــــون هندسة مدنية it, these applications are usually solved fairly simply and with readily available isolation products. The fundamental rule of isolator selection can be stated as follows: ‘The natural frequency of an isolation system is in proportion to the linear deflection of that system from the unloaded state. Reducing Force Transmission from Machine to Structure. The starting point is to determine the lowest forcing frequency of the machine. Usually this is determined by the lowest shaft speed in the machine because of the potential residual unbalance of that component. The second group is the reverse of the above – the need to reduce the transmission of vibration from a vibrating structure to a machine or some equipment supported by it, e.g. isolation of sensitive electrical equipment from excessive building vibrations. The solution of these problems generally requires a lot more careful consideration if a good outcome is to be achieved. Structural vibration generally arises from machinery mounted on the structure that may have forcing frequencies from (typically) 12 to 25 Hz. Isolation may be required for operator comfort, - مدينــه ركن حلوان الجديـــدة- ح تقسيــم جمعيـــة النصر4 قطعة المعــــادى- كورنيش النيـــل Mobile : 01014555350 Consultants 5 Consultants Civil Engineering مهندســــون إستشــاريــــون هندسة مدنية electrical or instrumentation protection or to minimize false brandling of stationary machine bearing. General Remarks A well compacted granular base course is strongly recommended. Base course thickness to be determined in consultation with vibration, structural, and geotechnical engineers Steel framing works well. Reinforced Concrete Framing is preferable especially when Mechanical equipments are close to vibration sensitive tools. Concrete offers advantages over steel: much higher stiffness, more damping, and larger mass, redundancy, less sensitive to short duration temperature fluctuations Mitigating Vibrations from unavoidable sources. - مدينــه ركن حلوان الجديـــدة- ح تقسيــم جمعيـــة النصر4 قطعة المعــــادى- كورنيش النيـــل Mobile : 01014555350 Consultants 6 Consultants Civil Engineering مهندســــون إستشــاريــــون هندسة مدنية Selection of rotating equipment with stringent balancing requirements (e.g. 0.025 in/sec RMS). Spring support for rotating equipment. Inertia bases are generally recommended for supporting fans and pumps with sizable HP motors. There are differing opinions on whether rotating equipments should be rigidly mounted or spring mounted. Place heavy equipment on concrete housekeeping pads, as close as possible to stiff elements (beams and columns). Flow carrying pipe and ducts near connected equipments supported using spring hangers. Use flexible connectors at equipments, to accommodate relative motions and vibration Isolation. Major pumps and fans could be instrumented with accelerometers. When Variable Frequency Drives (VFD) are used, they may need to be programmed to avoid resonance. - مدينــه ركن حلوان الجديـــدة- ح تقسيــم جمعيـــة النصر4 قطعة المعــــادى- كورنيش النيـــل Mobile : 01014555350 Consultants 7 مهندســــون إستشــاريــــون هندسة مدنية Consultants Civil Engineering العرض المالي: -1يشمل العرض المالي أجراء قياسات األهتزازات أن لزم األمر و أجراء التحليل الديناميكي لنتائج القياسات و كذلك أجراء تحليل ديناميكي أنشائئ كامل للتشليرات و قواعدها المرتكزة عليها و أعطاء توصيات كاملة و فعالة لحل مشكلة األهتزازات تماما و األشراف علي تنفيذ الحلول المقترحة في التقرير المفصل الذي سوف يقدم فيما بعد هذا و يجب التنويه ألي أنه من الوارد أجراء بعض األختبارات علي تربة التأسيس أسفل التشليرات نرجوا أن يحوز عرضنا هذا رضاكم الكريم و هللا سبحانه و تعالي ولي التوفيق و تفضلوا بقبول فائق التقدير و األحترام المهندس األستشاري مجدي عبد المحسن 5802\80\80 Consultants قطعة 4ح تقسيــم جمعيـــة النصر -مدينــه ركن حلوان الجديـــدة - كورنيش النيـــل -المعــــادى Mobile : 01014555350
