Yüksek sıcaklık altında çalışacak küresel vananın optimum tasarımı, dayanım analizi, imalatı ve maliyetinin incelenmesi
Ball valve working in high temperature, optimum design, resistance analyse, manufacturing and cost study
Yazar: KADİR AKCAN
Danışman: DOÇ. DR. VEDAT ZİYA DOĞAN
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Uçak ve Uzay Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 2013
Konu: Makine Mühendisliği = Mechanical Engineering ; Mühendislik Bilimleri = Engineering Sciences ; Uçak Mühendisliği = Aircraft Engineering
Dizin: Akış analizi = Flow analysis ; Akış denetimi = Flow control ; Akış modellemeleri = Flow modellings ; Akış modelleri = Flow models ; Tasarım bileşenleri = Design components ; Tasarım optimizasyonu = Design optimization ; Tasarım süreci = Design process ; Valf =

Özet:
İçerisinden +1oC ve 230oC arası akışkan geçen küresel vanalarda sızdırmazlık elemanı olarak PTFE (teflon) malzeme kulanılmaktadır. İçerisinden 230oC üzerinde akışkan geçen küresel vanalarda ise sızdırmazlık elemanı olarak  metal  malzeme ve grafit kullanılır. Bu iki malzemenin birlikte kullanılmasıyla sızdırmazlık sağlanmaktadır. 
İhtiyaç duyulan düşük sıcaklıkta çalışan küresel vanalar, birçok farklı imalatçı tarafından Türkiye?de üretilebilmekteyken, yüksek sıcaklıkta çalışan vanalar yurtdışından ihraç edilerek getirtilmektedir. Yurtdışından yapılan bu alımı azaltmak ve Türkiye?de bu tip vanaların imal edilebilme durumu, tasarım ve analiz sonuçları ile, üretildiği taktirde, pazarda maliyet açısından yer edinebilirliğini araştırmak hedeflenmiştir. 
Bunun için, model alınan bir tesiste, 400oC ve 14 barlık basınç altında çalışacak küresel vananın, bu sınıfa göre gerekli standartlara uyularak, Solidworks programı ile, ana tasarımı yapıldı. Tasarımda vana parçalarının kolay montajlanabilmesi ve standartlara uygunluğu belirtildi. 
Amaç, maliyet açısından uygun, yüksek sıcaklıkta çalışabilen küresel vana imalatı olduğundan, diğer imalatçıların standart boyda ürettiği, kullanıcının elini ya da vananın kontrol edilmesini sağlayan eyleyiciye zarar vermemesi için, içerisinden geçecek akışkana göre döndürme miline optimum uzatma yapabilmek için, tasarlanan vana, Solidworks Flow Simulation programına aktarıldı ve burada, farklı kullanım sıcaklıklarında, gerekli optimum kontrol mili mesafesi saptandı. Elde edilen bu verilerle, giriş sıcaklığına bağlı üstel denklem elde edildi. 
Mekanik analizde ise, vananın çalışacağı maksimum ve minumum  çalışma sıcaklıklarındaki uzama mesafeleri hesaplandı, vananın yüksek basınçlarda dayanımı incelenerek, et kalınlıklarında azaltma yapılabilecek yerler belirlendi ve bu sayede maliyette azaltmaya gidildi. Ağırlıkta yapılan azaltma, bu çalışmada oransal olarak az görünse de; büyük çapta üretilecek olan vanalarda aynı sistemin kullanılması ile yüksek ağırlık farklılıkları elde edilecektir. 
Parçaların imalatı, imalat türleri, parçaların tedarik edilebileceği yerli ve yabancı firmalar belirlendi ve  ilgili firmalardan, gerekli parçalarının teklifleri alınarak, tasarımı ve optimizasyonu yapılan küresel vananın, toplam üretim maliyeti hesaplandı. Aynı tip bir vananın yurtdışındaki firmalardan alınması ile yerli olarak Türkiye?de üretilmesi durumundaki maliyet farkı incelendi.

Abstract:
While inlet temperature of ball valve under the 230oC,  PTFE is used as seal in order to prevent water leak,  if it is over the 230oC, metal seat have to be used as seal because of melting of seal parts.
Ball valves are bought from foreign companies if it is over 230oC fluents. It will be manufatured in Turkey by Turkish companies if costs and manufacturing has enough advantages. 
Ball valves whether using in high temperature or using low temperatures, they have some common parts which are body, flange (cover), shaft, disc spring, nuts, rings, screws and also actuator.
 If valve using in high temperature process, its parts are differ from low temperature ball valve parts such as; metal surface sealing, ball which is actually common for high and low temperatures ball valves but in high temperature process, ball must be hardened because of metal sealing will demage its surface, graphite, graphite protecter and also disc spring.
Study steps are; ball valve design which is resistance high temperature, analyse the design, optimisation, manufacturing and cost analyse.
First step ball wall whose working pressure class and diameter was determined, will work in 400oC, DN 50 and 14 bar pressure in a model heater plant. According to determined working status and also the standarts, a ball valve was designed by Solidworks program. 
In this stage, firstly investigating the ball valve standarts which are; face to face dimension standart which is EN 558. It includes lots of standarts different from country or using area such as; DIN 3201/F1, DIN 3201/F32, DIN 3201/F33, DIN 3201/F4, DIN 3201/F5, DIN3202, ANSI B16.10, BS 2080, BS 5154, API609, BS 5156, BS 2080, API 600, API 609. Suitable standart was choosen for design ball valve. 
Flange standarts was investigated which is EN 1092. It has different dimensions for different pressure class and different inlet diameter for ball valves. So suitable standart was choosen for DN 50, PN 14 ball valve. 
Actuator joint standart was investigated which is ISO 5211, ISO 5210 and DIN 3210. ISO 5211 for single way actuator joint dimensions, ISO 5210 is for double way actuator joint dimension and DIN3210 electrical actuator joint dimension standarts. Suitable dimension was chosen from ISO 5211 for DN 50 PN 16 ball valve design which is resistance for 400oC.
Flange joint standart was chosen in DIN2633 standart and it was added standarts list for DN 50 PN 16 ball valve design. 
After determining suitable standarts, general design was scratched, it has not detail informations. Some dimensions can?t find from standarts, so they scratched but analayse and making optimisation in next subject. 
Ball dimension has not any standarts, it is differ form company to company. This dimension was taken from ball manufacturer company in order to produce prototype cheaper.
After general design parts were created as 3D solid model. Firstly main body and flange were generated in Solidworks program and than the other parts which are body, flange (cover), shaft, disc spring, nuts, rings, screws, actuator metal surface sealing, ball graphite, and also graphite protecter. Parts are assembled and the ball was ready for analyse.
Before analysing, different companies designs were shown because of proofing it has lots of different method for ball valve design. Especially Pekos, Valbart and also Neles products are shown.
In analyse step; first aim is that determining optimum extended stem dimension  whic is used to prevent demage of pneumatic or electirical actuator or human hand, equation was created for minimum manufacturing cost by Solidworks Flow Simulation Program which calculates flow and thermal problems. Not only to determine the stem dimension for 400oC inlet temperature situation but also determining  from 200 oC to 700 oC in order to not calculate again for different orders in future dor DN 50 PN16 ball valves. 
In last step for flow analyse, creating an equation in order to find required stem dimension for different inlet temperature. It advantage for companies because they manufacture their products with constant stem dimension, so customer will use that valve different temperature but if use not so high temperature like 300 oC, it causes cost excess.
The other analyse step is mechanical analyse via Solidworks Simulation program. Firstly joint the ball valve from its hole and enter required datas for analyse. First condition was 700 oC and 16 bar pressure resistance study. 
After prooving design is enough for that working condition, changing the design in order to get cost reduction, so changing wall thickness from 17.5 mm to 4 mm and working the program again with 700 oC and 16 bar pressure but results show that it is not enough thickness for ball valve. And changing the wall thickness from 4 mm to 8 mm, and it showed that it is enough in working conditions.
 As a last study for valve body in mechanical and thermal analyse, 700 oC and 25 bar pressure durable condition was investigated in order to be sure it is really durable for pressure walves in working conditions. 
The flange screws forces, and valve extension diameters and also disc spring extansion diameter was calculated. 
The other mechanical durable analyse is that twisted analyse for control shaft, Experimental necessary turning moment was given the companies catalouges so 85Nm was used as turning moment force and investigated the resistance situation for shaft. 
All analyses provides to manufacture ball valve lighter, cheaper and also more effective. Maybe it not have big costs and weight advantege but it is a model, so it will provide more contribute for bigger dimensions. 
The next step is supplying parts from companies and manufacturing system. In this part, AISI 316 metarial mechanical, thermal and general using properties was given because lots of parts of valves will be manufactured with this meterial. And the hardening process information was given for some parts of valve must be send to hardening company to Holland. And graphite properties and the last one disck spring information was given in this section. 
In cost analyse step, firstly investigating manufacturing to metal parts.  This parts will be manufactured with two option which is casting or machining. Both costs are taken from manufacturer and compared with each other. 
Order was taken for hardening process from Bodycote company which is in Holland and also transportion costs, all of them were added to cost matrix. 
Inconel disc springs quotation was taken from Gökşen makine which is located in Bursa and costs was added to cost matrix too. 
The sum of the parts? costs was acquired. And seen that it is possible to manufacture the high temperature resistance ball valve in Turkey. It is not required great technological developments. But selling these valves is required to have all qulity certificate, it is long term for a company. 
In last step, two quotation was taken from companies which are high temperature ball valve manufacturer. One is Ava armaturen and the other one is Metso. They give their quotation more expensive than the study design. And also their delivert date is 14-15 weeks. 
If manufacturing these valves in Turkey, companies will have lots of advantage and earnings. They will delivery their products shorted time and also customer will prefered them because of cost advantage. 
But big problem is not have any certificate if company is new. So it is possible to manufacture these high temperature resistance ball valves by valves companies because of their working area and human power will simplify the first step.  
This study will help for next studies such as; low temperature ball valves which are working approzimately -200 oC are not manufactured in Turkey and also nucleer power plant ball valves are not manufactured in Turkey.