In a distribution network of low-pressure gas pipelines, the situation of gas leak can be further aggravated when groundwater enters the pipeline through leaks and eventually blocks the gas flow. This will have critical implications on the gas supply to the customers. This is termed as 'water ingress', which typically happens only in low-pressure distribution networks, and not in high-pressure transmission networks. In order to find the location of water ingress, distributed temperature sensing (DTS) system has been used experimentally. The results show significant temperature change immediately after the onset of water ingress, and with data post-processing based on temporal difference, location information of the leak can be obtained. With a selected time window of interest, the inclination of gas pipeline is also indicated by the differenced temperature profiles. The DTS system is still capable of identifying the position, even if the location of water ingress is changed.
The purpose of this study is to evaluate hemodynamic responses to acute volume expansion in chronically instrumented, conscious Dahl salt-sensitive (Dahl-S) and Dahl salt-resistant (Dahl-R) rats that have been maintained on either 0.45% NaCl, 1% NaCl, or 7% NaCl (5 days) intakes. Total peripheral resistance (TPR), but not arterial pressure, was increased by 5 days of 7% NaCl in Dahl-S (P less than 0.05) but not in Dahl-R. In Dahl-S, but not in Dahl-R, right atrial pressure increased with increasing dietary NaCl (P less than 0.05). On the 0.45% NaCl intake, atrial pressure did not differ in the two strains, whereas on both the 1 and 7% NaCl diets atrial pressure was higher in Dahl-S than in Dahl-R (P less than 0.05). In response to acute extracellular fluid volume expansion, arterial pressure did not change, and cardiac output increased in Dahl-S and in Dahl-R. On the 0.45% NaCl intake, TPR decreased (P less than 0.01) similarly in response to volume expansion in both strains; however, on the 1% NaCl intake TPR decreased in Dahl-R (P less than 0.05) but not in Dahl-S. In contrast, in animals fed 7% NaCl for 5 days, TPR decreased acutely in Dahl-S (P less than 0.01) but not in Dahl-R. These observations suggest that cardiopulmonary baroreflex activity is impaired in Dahl-S on a 1% NaCl intake, possibly as a consequence of elevated right atrial pressure. This alteration of the cardiopulmonary baroreflex may contribute to increased TPR in Dahl-S on a high-NaCl intake.
In underground low-pressure gas distribution pipelines, ground water enters the pipeline through cracks. This is known as the water ingress problem, and it occurs predominantly in the monsoon season when the water table is high. This issue is currently detected based on complaints from the users. In order to arrive at an efficient and reliable processing technique, experimental results of pressure and flow on an existing low-pressure gas pipeline are reported in the present paper. Several experiments for leak location, severity of the leak, water ingression with various volumes of water followed by removal of water are conducted. Healthy network loading data collected over a 24 hr period is used to verify the robustness of the derived parameters for water ingression detection. The present technique can detect leaks easily with a leak valve opening of 30 o . Robust detection of water ingression with more than 10% of pipe volume is possible.
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