Simulating Error-Opening of Pressure Relief Valves of a Station on a Continuous Undulating Oil Pipeline with Large Elevation Difference

For oil pipeline in mountain areas,high hydrostatic pressure in the pipeline may cause error-opening of pressure relief valves,and oil is discharged from the pipeline to the pressure relief tanks,bringing spilling-over risk of the pressure relief tanks.Therefore,simulating the error-opening situations of the pressure relief valves and investigating the oil discharge process are necessary for checking the possibility of the spilling-over accident and then proposing measures to improve the pressure relief system.This research focuses on a continuous undulating oil pipeline with large elevation difference and a station along this pipeline,which is named B station in this paper,is studied.By OLGA software,simulation model of the pressure relief system of B station is established,and the accuracy of the model is verified by reconstructing a real accident and making a comparison with the actual accident data.The maximum discharge rate reached 8284 m3/h when the pressure relief valve was opened by mistake in the inlet and outlet of the station.The accumulated filling time of the two pressure relief tanks is 200 s,which is in good agreement with the accident data.On this basis,for error-opening of the pressure relief valves at the inlet and outlet of B station,simulation is performed to investigate variations of the discharge velocity,discharge flow rate,accumulated discharge volume and ventilation volume of the vent valve.The discharge velocity is found to be over the maximum velocity allowed for safety consideration.According to the accumulated discharge volume,it is inferred that spilling over of the pressure relief tanks will be caused once error-opening of the pressure relief valve occurs.Also it is judged that the existing breathing valve can not satisfy the ventilation requirement in case of failure of the pressure relief valves.From these simulation results,it is proposed that increasing the number of vent valves,replacing the manual valves with electrically operated valves,and employing security control interlock protection program are improvement measures to guarantee safe,efficient and reliable operation of the pressure relief system at B station.

High-lift siphon flow velocity in a 4-mm siphon hose

High-lift siphon drainage by 4-mm internal diameter siphon hoses is a real-time, free-power, and long-term approach for slope drainage. The conventional hydraulics formula for pressurized pipe flow is generally used to calculate the single-phase velocity of siphon flow. However, an intensive cavitation phenomenon occurs in the high-lift siphon hose and then a two-phase flow is formed. Research on the velocity of high-lift siphon flow is a prerequisite for the application of siphon drainage with a 4-mm siphon hose. Few investigations of this subject have been carried out. Hence, experiments on the high-lift （8 m〈H0〈10.3 m） siphon drainage in a 4-mm siphon hose were performed. The characteristics of siphon flow under different conditions were ob- served and test data were obtained. Comparisons between test results and calculated results showed that significant errors were given by the hydraulics formula. It is demonstrated that the effect of gas in a siphon hose should be included in the calculation of flow velocity. The findings can be used to determine the number of siphon hoses and layout of siphon drainage holes, and provide valuable information for geotechnical companies.

Role of Salix reinii patches in spatio-temporal patterns of cohabitants on a Japanese volcano

Shrub patches often support the colonizers particularly under stressful and/or disturbed environments.The intensities of stresses and disturbances on mountains are often related to an elevation gradient and are decreased by shrub patches(canopy and litter).We aim to clarify these relationships by using shrub patches at different elevations on a volcano.We monitored all shoots in plots established inside and outside of patches of Salix reinii(Salicaceae)and their related environments,such as temperature,light,moisture and chemistry,at three elevations on Mount Koma(1131 m a.s.l.),northern Japan,from early spring in 2005 to summer in 2006.The patch structures were evaluated by area,branch density and litter thickness.The structures of shrub patches did not differ among the elevations.The patches increased the diversity of rare species,by an overall increase in plant species richness.The moisture,nitrogen and phosphate contents in the patches were higher than outside of patches.The effects of shrub patches on the cohabitants were overall positive,although the effects were negative on seedling abundance,shoot survival and flowering.These results suggest that the growth patterns of shrub patches determine the plant community structures and facilitate plant diversity.