Bir Su Dağıtım Şebekesinde Su Deposunun Yüksekliğinin ve Konumunun Su Darbesi Üzerinde Etkisi

Öz

Basınçlı boru hatlarında bir vananın aniden kapanması neticesinde oluşan yüksek basınç su darbesi olarak isimlendirilmektedir. Su darbesinin önlenmesi veya etkilerinin sönümlenmesi için kullanılan boru hattı elemanlarının en önemlilerinden biri açık su depolarıdır. Bu depolar, ortaya çıkan yüksek basınçları güvenli sınırlar içinde tutmakta etkilidir. Bir deponun su darbesi tehlikesini bertaraf etmedeki etkinliği, deponun boyutu, taban kotu ve konumu gibi faktörlere bağlıdır. Bu sebeple su darbesi tehlikesine karşı efektif bir şekilde önlem alınabilmesi için açık su depolarının tasarımı önem arz etmektedir. Bu çalışmada açık bir su deposu ilave edilen Tnet1 su dağıtım şebekesinde ani vana kapanması ile su darbesi analizi yapılmıştır. Su darbesi analizi, hem elastik, hem de rijit su sütunu yaklaşımlarına göre hidrolik hesap yapabilen ve EPANET 3’ün açık kaynak uzantısı olan EPANET-CGGA kullanılarak icra edildi. Su deposunun farklı taban kotu ve vanaya olan uzaklığı için toplam 9 adet senaryo oluşturuldu. Bu 9 senaryo neticesinde deponun taban kotunun ve vanaya olan mesafesinin su darbesinin şiddeti üzerinde etkili olduğu tespit edilmiştir. Öyle ki, deponun taban kotunun 100’den 180 m’ye yükseltilmesi, vana menbaındaki maksimum basıncı yaklaşık 20-30 m mertebesinde arttırmakta, mansabındaki basıncı ise yine yaklaşık 20-30 m azaltmaktadır. Depo taban kotu kadar olmasa da, deponun vanaya olan mesafesinin de su darbesi şiddeti üzerinde etkili olduğu görüldü. Depo taban kotu 100 m iken deponun vanaya olan mesafesinin 2000 m’den 2400 m’ye çıkarılması maksimum basıncı 8 m arttırırken, minimum basıncı ise 8 m azaltmaktadır. Depo taban kotu 180 m olduğunda ise mesafe değişiminin basınca herhangi bir etkisi görülmemektedir. Çalışma neticesinde elde edilen sonuçlar, su darbesinin yıkıcı etkilerinin sönümlenebilmesi için açık su depolarının mümkün olduğunca düşük kota ve su darbesinin kaynağı olan vana ve pompa gibi cihazların yakınına yerleştirilmesinin uygun olduğunu göstermiştir.

Anahtar Kelimeler

• Su Darbesi
• Değişken Akım Hidroliği
• EPANET-CGGA
• Su Dağıtım Şebekeleri

Effect of Surge Tank Elevation and Location on Water Hammer in a Water Distribution Network

Öz

The high pressure resulting from the sudden closure of a valve in pressurized pipelines is referred to as a water hammer. Among the pipeline components used to prevent water hammer or dampen its effects, open water reservoirs are among the most important. These reservoirs are effective in maintaining the resulting high pressures within safe limits. The effectiveness of a reservoir in eliminating the danger of water hammer depends on factors such as the size, base elevation, and location of the reservoir. Therefore, the design of open water reservoirs is of great importance for implementing effective measures against the risk of water hammer. In this study, water hammer analysis was performed on the Tnet1 water distribution network to which an open water reservoir was added following the sudden closure of a valve. Water hammer analysis was performed using EPANET-CGGA, an open-source extension of EPANET 3, which is capable of performing hydraulic calculations based on both elastic and rigid water column approaches. Nine scenarios were generated by considering different base elevations of the water reservoir and distances to the valve. The results of these nine scenarios determined that both the base elevation of the tank and its distance to the valve had a significant effect on the severity of the water hammer. Specifically, raising the base elevation of the reservoir from 100 to 180 m increased the maximum pressure at the upstream side of the valve by approximately 20–30 m, whereas it decreased the pressure at the downstream side by approximately 20–30 m. Although not as significant as the base elevation, the distance from the reservoir to the valve was found to influence the severity of the water hammer. When the reservoir base elevation is 100 m, increasing the distance of the reservoir to the valve from 2000 to 2400 m increases the maximum pressure by 8 m and decreases the minimum pressure by 8 m. When the reservoir base elevation was 180 m, changes in distance had no effect on the pressure. The results obtained show that to dampen the destructive effects of the water hammer, it is appropriate to place open water reservoirs at the lowest possible elevation and as close as possible to devices such as valves and pumps that are the source of the water hammer.

Anahtar Kelimeler

• Water Hammer
• Unsteady Flow Hydraulics
• EPANET-CGGA

Kaynakça

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