Design Of Penstocks Research Articles

Fatigue design in penstocks – comparison of the nominal stress and structural stress method for common details

AbstractPenstocks in hydro power plants have a very long working life. They can have high pressure variations during service life, especially in pumped storage power plants caused by the dynamic pressure. Therefore, the fatigue design can be a dominating factor in the design of penstocks. In this paper, two common used construction details in penstocks are investigated with the nominal stress and the structural hot‐spot stress method for fatigue verification. The investigated construction details are: i) a wall thickness transition of the penstock with a weld along the circumference and ii) a ring stiffener welded to the penstock. The results of the different methods for fatigue verification for these two construction details are compared with each other, with variation of different geometric parameters. Also an analytical solution for the stresses in the hot‐spot for the two construction details, based on the semi‐membrane theory of cylindrical shells, was developed. Based on that stresses, stress concentration factors kHS are calculated and are available for practical applications in form of presented Tables in this paper. With the calculated stresses by the semi‐membrane theory in the hot‐spot it can be shown, that they are nearly equal to the hot‐spot stresses of a Finite‐Element‐Analysis, based on the IIW recommendation. Finally, a recommendation for fatigue verification of the two common details in penstocks is given.

Sizing optimization of exposed steel penstocks supported by ring girders using the combined ANN-GA technique

The design of penstock is a major concern in the implementation of large hydropower plants, where penstock is a large-scale structure. A design procedure incorporating the combined ANN-GA approach was developed for optimizing the exposed penstock supported by ring girders. The objective function considered is the total mass of the penstock to be minimized under the strength requirements. For this purpose, a numerical finite element analysis (FEA) model of a steel exposed penstock supported by ring girders was used to evaluate the equivalent and local stresses on the penstock shell. Parametric analysis was conducted to examine the influence of penstock thickness, ring girders spacing, and sectional size of the T-shaped ring girders on the weight of the penstock and the maximum equivalent stress. Subsequently, an artificial neural network (ANN) was developed by collecting data from the FEA numerical results, before being combined with a genetic algorithm to provide the optimal design of the penstock. The results of the FEA give a detailed distribution of local stresses in the penstock shell. The performance of the trained ANN was illustrated, and its prediction results show good agreement with the FEA numerical results. The results obtained by the ANN-GA approach proved the efficiency of the proposed process in optimizing the exposed penstock supported by ring girders. This process should be a valuable aid for the design of large penstocks.

The Development of Civil Components of a Small Hydropower System

This study aims at developing design charts for sizing of the water channelling system of SHP, using both theoretical and empirical relations. The focus is to make the design of SHP civil features quick, devoid of under or over design, and to minimize capital cost without compromising safety. A low head range of 0-20 m and channel flow velocities of 1.2 m/s, 1.3 m/s and 1.4 m/s will be utilised. The range of flowrate considered for both orifice and headrace channel is 0-1.5 m/s2. Linear relations were used to make the design and evaluation of SHP components for water transportation to the turbine station at certain flowrates simple. The study observed that it would be more economical to use the theoretical relations than the empirical ones in the design of penstocks and other water channelling components. However, the components perform less in terms of safety and lifetime to those designed with empirical relations.

Modification of the shell type trifurcation shape for penstock design in a hydraulic plant by numerical simulations

The branching of pipes is commonly used for fluid distribution in penstock of hydro-power plants to reduce construction cost. A trifurcation allows flow of water to provide three turbines operating at the same time, and it is usually designed for uniform distribution of discharge rate and minimum hydraulic loss. A symmetric trifurcation not considered fluid dynamics occasionally may make unequal power production of each hydro turbine and its severe fluctuation. The paper focuses on the cause of fluctuating power production and suggests a solution for stable operation by numerical simulations. The discharge rate distribution for existing and modified shapes of the trifurcation has been investigated by steady state computations, and quasi-steady state calculations have been carried out in order to find the cause of the flow fluctuations in the penstock for rated plant discharge (Qt = 153.66 m3/s). In addition, the time dependent flow structures and the head losses in the penstock have been compared for the existing and modified trifurcation shapes, and it is also verified that the fluctuating power production can be reduced significantly with modified trifurcation.

Desain Pembangkit Listrik Tenaga Mikrohidro di Air Terjun Kedung Kayang

Kedung Kayang waterfall is located on the border of Magelang and Boyolali regency of Central Java. The waterfall is 38 meters high, so it has the potential to be used as a micro hydro power plant (MHP). In designing the MHP, it requires some studies including hydrology, civil, mechanical, and electrical. The purpose of this research is to predict the water discharge, determine the potential of hydro power, selection of MHP sites, design of hydro turbine and electric generator. This research uses Penman Modification method to calculate evapotranspiration, Mock method to calculate water discharge, geographical mapping for MHP sites selection and cross-flow turbine design calculation. This paper presents the results of MHP design consist of MHP capacity, selection of MHP sites, penstock design, cross-flow turbine design and electric generator selection. The result showed that dependable water discharge is 0.143 m3 / sec, effective head is 19.5 meters, hydro potential is 27.33 kW, and electric power that can be produced is 18 kW, length and diameter penstock are 81,74 m and 26,77 m, hydro turbine used cross flow type with outer diameter of the runner is 17,17 cm, inner diameter is 11,45 cm and width is 59,16 cm. MHP site is located in Klakah village, Selo Sub-district, Boyolali District.

Optimum Design of Penstock for Hydro Projects

Penstock, a closed conduit, is an important component of hydropower projects. Various methods are available for optimum design of penstock. These methods are either based on empirical relations or derived analytically by optimizing the friction loss in the penstock. These formulae produce different values of penstock diameter for same site. In this study, formulae available for penstock design have been compared to review their suitability. A new method has been developed for the optimum design of penstock based on minimizing the total head loss comprising of friction and other losses. By using new developed method, diameter and annual cost of penstocks for few Hydro Electric plants of varying capacity have been worked out and reduction in annual cost of penstocks have been found in comparison to penstock cost for these projects.

To Confirm Structural Coefficient for Design of Penstocks in Hydropower Stations by Partial Factors-Based Method

When confirming the partial factors in design formulas by the probability-based limit states design method (PLSDM), the structural coefficient can determined by two methods. On one hand, the structural coefficient is determined by the engineering experience calibration method, which is calculated by decomposition of the safety coefficient in the former specifications SD144-85. On the other hand, it can be determined by the probability analysis method and optimization calculation based on the target reliability index resulted from reliability calibration analysis. The appropriate value is finally determined by synthesizing results of the two methods.

Influence of the penstock design on the operation of the inlet spherical valves

Spherical valves are supplied for high-head turbines. The drive of spherical valves designed and manufactured by Power Machines/LMZ provides opening by means of servomotors, and closing under the action of the moment created by counterweights.Selection of parameters for the spherical valve and its design are based on the assumption continuity of the water flow entering the turbine through the penstock. In case, when two or more hydro-units are installed at the HPP, the penstocks usually have pipe bifurcations (Fig.1). The design of the penstock should provide a uniform supply of water to all units without spin, rupture of continuity and pulsation. Given in the paper is an example of the HPP with two (2) hydro-units equipped with inlet spherical valves. In the course of operation valve rotor oscillations with different periods in time (T ≈ 15 sec.) were detected. When analyzing, no faults in the valve design and its mechanism of operation were detected.In the course of the tests, vibration parameters of the spherical valves were determined in the following operating conditions: each of the hydro-units running separately and both of them running simultaneously for different power output values. Based on the test results, operating conditions with maximum vibration of were located. The reasons of surging of perturbing forces acting on the rotor of the spherical valve were detected in the course of analysis of the penstock design. Possibility of accumulation of air at the penstock pipe bifurcations was found. When the air transported by the water achieved its critical value, this air appeared to be the cause of instability in the valve operation. The attention was drawn to necessity of taking into account this circumstance when designing penstock pipe bifurcations.

Analysis of Stiffened Penstock External Pressure Stability Based on Immune Algorithm and Neural Network

The critical external pressure stability calculation of stiffened penstock in the hydroelectric power station is very important work for penstock design. At present, different assumptions and boundary simplification are adopted by different calculation methods which sometimes cause huge differences too. In this paper, we present an immune based artificial neural network model via the model and stability theory of elastic ring, we study effects of some factors (such as pipe diameter, pipe wall thickness, sectional size of stiffening ring, and spacing between stiffening rings) on penstock critical external pressure during huge thin-wall procedure of penstock. The results reveal that the variation of diameter and wall thickness can lead to sharp variation of penstock external pressure bearing capacity and then give the change interval of it. This paper presents an optimizing design method to optimize sectional size and spacing of stiffening rings and to determine penstock bearing capacity coordinate with the bearing capacity of stiffening rings and penstock external pressure stability coordinate with its strength safety. As a practical example, the simulation results illustrate that the method presented in this paper is available and can efficiently overcome inherent defects of BP neural network.

Analysis on Dynamic Response and its Optimized Design of Penstock and Expansion Joint Structure in Hydropower Station

During electricity generation in the power station, the dynamic pulsating loads bring about vibration on penstock and expansion joint structure and lead to fatigue damage. This essay is mainly about doing research on flow-induced vibration response of power station expansion joint structure, putting the flow pulsating pressure load of expansion joint tested into numerical model to calculate, and making evaluations about its engineering safety. With regard to the problems existing in this engineering project, we bring forward the corresponding design proposal of optimization. The results of calculation indicate that the optimization program has a significant effect on controlling the decreasing amplitude of the max displacement and stress, which makes sure of the safety of generating system.

Design of penstocks of pumped-storage stations

When designing the penstocks of pumped-storage stations (PSSs) it is necessary to solve a wide range of new engineering problems. They include first of all the selection of the route of the penstocks with consideration of the engineering-geologic conditions and general layout of the station. As a rule, for the PSSs examined in this article the route of the penstocksruns along a slope composed~soil rather than rock. Traces of landslide phenomena are often found already during surveys. Therefore, when designing penstocks it is necessary to assess the stability of the slope and to develop engineering measures to increase it. Such measures include primarily flattening of the slope, control of the levels and drainage of groundwaters, and grading and stabilizing the slope with construction of a surface water drainage system. The general and decisive conditions for selecting the design of a penstock for the investigated type of PSS are: location of the open route of the penstocks on slopes composed of soils; averageslope of the route of the penstocks 1:6-1:10; the relatively small design head (90-120 m) for PSSs, which for units with an individual capacity of about 20OMWpredetermines the turbine discharge of up to 250 mS/sec and penstock diameter from 6.5 to 8 m. Here it is timely to examine the problem of the reliability of the designs of metal penstocks, on the one hand, and of reinforced-concrete and concrete-encased penstocks, on the other. Despite the fact that among construction materials metal is distinguished by a high homogeneity and stability of mechanical properties, metal structural elements of a penstock can have defects, which in individual cases cause its rupture. The occurrence of cracks in the penstock lead to its avalanche failure under a load, since in the design of a metal penstock there are no elements restraining the development of cracks. For this reason hydrotechnical construction practice and the construction regulations (SNIP 11-50-74) specify the need to take appropriate measures to protect the powerhouse from the consequence of failure of the penstock. Such measures include either a muta! arrangement of the station and route of the penstocks which provides diversion of the failure flow away from the powerhouse or the construction of a special structure deflecting the failure flow. It is obvious in this case that the failure flow also should not cause erosion along the route of the penstocks, reducing to naught the measures on deflecting the flow. In layouts with reservoir powerhouses

Intake and penstock design at Agua Vermelha : Besker, M Int Water Power Dam Constr, V30, N10, Oct 1978, P46–50

Intake and penstock design at Agua Vermelha : Besker, M Int Water Power Dam Constr, V30, N10, Oct 1978, P46–50

Unsteady processes in reversible hydraulic machines and consideration of their special characteristics in the design of penstocks for pumped-storage plants

1. The unsteady phenomena which occur in the internal passages of reversible hydraulic machines and whose intensity is unusually high are stable and propagate, with only a small attenuation along the penstock, to a considerable distance. 2. The complex form of the action of unsteady processes caused by large pressure fluctuations in penstocks does not make it possible at the present time to obtain a theoretical solution of the problem of determination of the loads acting on the penstock shells along their entire length. 3. The experimental investigations carried out at the factories on reversible hydraulic machines are not sufficiently adequate, since they do not reproduce the operating conditions of the penstock or the effect of the latter upon the pressure pulsations in the scroll case. 4. The unsteady phenomena which occur in the internal passages of reversible hydraulic machines, the distribution of the pressure fluctuations along the penstocks, and the regulation regimes of reversible units can be simulated by using for the penstock model a material having a considerably lower modulus of elasticity than that of the prototype material.

Steel Penstock Design for Tims Ford Dam

The design and construction of an embedded steel penstock is discussed. A straight line trench, from intake to powerhouse, cut into the rock under the left side of the dam reduced construction time. The concrete encasement is designed to carry the dead load of the rockfill dam and shell. Shell and stiffeners made of A 516, grade 60 are designed for internal head of 235 ft and an external head of 153 ft. Allowable working stress of 60% of yield strength gave a safety factor of three. Hydrostatic tests of the penstock in place along with 100% radiographing of all shell welds was required.

Penstock Codes—U.S. and Foreign Practice

Penstock design and construction in the United States have been guided to a large extent by the ASME Code for Unfired Pressure Vessels. At the same time, the penstock practice often deviates from the latter, particularly in the critical area of the allowable working stresses. As a result, safety standards in penstock design in the United States are far from being uniform. A study of three foreign penstock codes brings out certain advantages of separate design standards for this specialized field. It also suggests the use of higher allowable working stresses in penstocks than those permitted by the ASME Code. The contents of the foreign codes are listed and their more important aspects reviewed. Action by the ASCE toward creation of a uniform set of recommended rules for design and construction of penstocks in the United States is proposed.

Design Features of Glen Canyon Dam

Dam under construction is principal structure of Colorado River Storage Project in Upper Colorado River Basin; various design features described; topics included are geology of foundation, stress studies of dam, structural behavior instrumentation, foundation treatment, temperature control of mass concrete, design of penstocks, river outlets, and spillway, and diversion and care of river.

Design Features of Glen Canyon Dam

Dam under construction is principal structure of Colorado River Storage Project in Upper Colorado River Basin; various design features described; topics included are geology of foundation, stress studies of dam, structural behavior instrumentation, foundation treatment, temperature control of mass concrete, design of penstocks, river outlets, and spillway, and diversion and care of river.

Foreword

At the June 1957 ASCE Convention in Buffalo, N. Y., the Power Division presented a series of papers on the subjects of penstock design, construction, and operating experiences. Subsequent to the meeting, nine of the papers were published in the Journal of the Power Division and these nine papers were reprinted in March 1961 as Proceedings Symposium Series Number 4, “Symposium on Penstocks.”

Closure to “Penstock Design and Construction”

Closure to “Penstock Design and Construction”

Discussion of “Penstock Design and Construction”

Discussion of “Penstock Design and Construction”