Operation and Maintenance of Electro-Mechanical Equipment of Sabalan Dam M.Rezaifardi & Sh.Partovi Azar Dam department, Ashenab Consulting Engineers Company, Iran ashenab.icold@gmail.com ABSTRACT Dams are important and complex engineering structures with hydro-mechanical equipments and instrumentation. Sabalan dam is an 89m high rock-fill embankment with central clay core constructed in Meshkinshahr city in the northwest of Iran. The electromechanical system of this dam is located in intake tower and valve room. Intake tower comprises of two trash racks, three stop log gates (located at different levels of reservoir), service and emergency slide gates for dewatering and emergency outlet of dam, three needle and butterfly valves, a gate valve, air valves, service and emergency slide gate are located in valve room and are designed to convey water for agriculture and potable usages. Also lifting and measuring systems are designed for these equipments. In this paper, method of maintenance, control and inspection of these equipments in normal and critical conditions such as flooding and large earthquakes are investigated. Keywords: Rock-fill dam; Maintenance; Electro-Mechanical Equipment; Inspection. INTRODUCTION: Dams are important and complicated engineering structures in terms of construction and service time. Due to economical and safety importance of these structures operation and maintenance of them is critical. The subject of dam safety has attracted a great deal of attention in recent years. In United States of America, the national dam safety program, instituted in response to several major dam failures in the early 1970's, focused on the problem nationwide. Under this program the U.S.Army Corps of Engineering and Arkansas soil and water conservation commission worked together to inspect many dams. In recent years the Federal Emergency Management Agency (FEMA) has taken the lead in providing assistance to states in promoting dam safety. The national dam safety program act of 1996 continues to reinforce the commitment by the federal government to dam safety. Substantially society and individuals alike may profit dam operation. Dam ownership, however, is neither justified nor effective if one cannot assure the safety of citizens and property. The cost of dam safety are small in comparison to the consequences following a dam failure particularly in today's litigious society we can directly influence the safety of a dam by developing a safety program witch includes inspection, monitoring through instrumentation maintenance of the structure and proactive emergency planning. In this paper we focus on operation and inspection of Sabalan dam's hydro-mechanical structures. SABALAN DAM: Sabalan dam is a rock-fill dam with central clay core which has been constructed on Ghara Su River in the north west of Iran, some 55 km to the northwest of Ardabil city. The main purpose of this dam is to supply water required for irrigation of 15000 hectares agricultural lands, to provide drinking water and flood control of the region. The capacity of the dam reservoir is 105 10 6 m 3. The construction of the dam body was completed in January 2006 and filling the reservoir began in February 2006. The embankment height from bed rock, height from river bed, crest length and crest width are 89, 77, 304 and 12 meters, respectively.
HYDRO- MECHANICHAL SYSTEM SCHEME: Hydro-mechanical system in a dam is an extremely essential part during operation and life of a dam. As shown on figures 1 to 3 hydro-mechanical system of Sabalan dam consists of Intake tower and Valve room. Intake tower and Valve room structures include intake, bottom outlet and outflow systems. Figure1. Vertical section of intake tower 1. INTAKE & BOTTOM OUTLET STRUCTURES: Sabalan intake structure is a vertical structure, generally referred to as a free-standing intake tower. The vertical tower is usually more economical and easier to layout than the inclined one. Therefore in this type of tower equipments can be well arranged. As shown in figure.1, intake tower includes the following equipments: 1.1.TRASHRAK: In order to prevent trash entrance into the system, there are two trashracks installed in intake tower. One in intake system and the other in bottom outlet system at 1087 and 1079 MASL (Meters Above Sea Level), respectively. The trashrack installed in intake system is mobile and consists of 9 movable 3.5 3m (width height) parts. A lifting beam is utilized to carry up the parts to the top of the intake tower in case of need. Intake trashrack system consists of a body, fixed parts and lifting beam. The 3.7 6.2 m (width height) trashrack installed in bottom outlet is stable. 1.2.FISHING NET: Fishing net is installed behind the intake trashrack to prevent fish and fine trashes entrance to the
system. Size of fishing net and trashrack are the same and fishing net is also mobile. Fishing net again consists of 9 movable 3.5 3m (width height) parts. Lifting beam is used to carry the parts of fishing net as well. Fishing net system includes a body, embedded part and lifting beam. 1.3. STOPLOG GATES: Four stoplog gates (2.4 2.55m (width height)) at 1080, 1086, 1098, 1110 MASL are installed in intake tower to prevent the flow entrance into the intake. There is a by pass system for stoplog gate located at 1086 MASL. The main reason for installing stoplog gates at four levels in the reservoir is to use water at different temperatures. Stoplog gates set include body, embedded parts, link rod and dodging device. Link rod and dogging device are used to lift gates to the top of the tower by a crane. 1.4. SLIDE GATES: Two slide gates (service and emergency) as shown in figure 2 are installed at 1080 MASL in Intake tower. Service gate is used to control and stop the flow from outflow system. Emergency gate is used to stop the flow in repairing time of service gate. Emergency gate can be opened in terms of flow but opening the gate can be operated through upstream head. There is a by pass system for emergency gate to balance the upstream and downstream head. Both gates are operated through a servomotor. The slide gates consist of a body, embedded part casing and servomotor. Figure2. Plan of intake tower 1.5. GATE VALVE: In order to make a by pass between service and emergency gates in intake tower, two 15 inches pipes and four gate valves ( D=15 inches, PN=10) as shown in figure 2 are placed in the system. Gate valves are used to switch the flow.
3 1.6. THE CRANE: At the top of the intake tower a gantry crane with a capacity of 10 tons has installed due to moving the parts of trashrack, fishing net, stop logs,.the main function of this appliance is displacement of load on hoisting, long travel and cross travel motions. This crane is operated from a pendant control station or by a remote control. The crane has made by ADC Company in France. 1.7. STEEL LINING CONDUIT: The conduit assumed for discharge the flow in intake tower has a steel lining coating. The conduits include box, T-branch, box reduction, transition and pipe. 2. OUTFLOW & BOTTOM OUTLET STRUCTURES: As shown in figure 3 outflow and bottom outlet systems are placed in valve room. Figure3. plan of valve room Above mentioned systems include the following parts: 2.1. SLIDE GATES: There are two slide gates placed at 1055 MASL in Sabalan Dam s valve room. Function and dimensions of these gates are same as service and emergency gates in intake tower but these slide gates just regulate the discharge of bottom outlet. 2.2. NEEDLE VALVES (PN 10): Three needle valves are installed in valve room. Two valves (D 1200 mm, PN 10) to regulate and adjust the discharge of agricultural use and one valve (D 500 mm, PN 10) to regulate and adjust the discharge of water right. Aforesaid valves are made by VAG Company in Germany. 2.3. BUTTERFLY VALVES: There are three butterfly valves, two of them with a diameter of 1200 mm and one with a diameter of 500 mm (PN10), accompanying same sized parts which can be disassembled, in valve room. These valves are used to cut the flow during needle valves repairment. Aforesaid valves are manufactured by Mirab Company in Iran.
2.4. STEEL LINING CONDUIT: Conduits to pass flow in valve room have also steel lining. 2.5. GATE VALVES: Two gate valves (D 300mm) are installed on potable water line outlet to switch the flow. Four gate valves (D 200mm) are installed on by pass line of needle and butterfly valves (D 1200mm) and four gate valves (D 100mm) are installed on by pass line of service and emergency gates as well as needle and butterfly valves (D 500mm). 2.6. THE CRANE: In valve room there is an overhead crane with a capacity of 10 tons to displace indoor equipment. MAINTENANCE AND INSPECTION OF EQUIPMENTS Equipments introduced above, require operation, maintenance and periodic controls during the lifetime of the dam which are explained below. INTAKE TRASHRAK AND FISHING NET Parts of trashrack and fishing net are installed with lifting beam. For periodic control and repairmen, these parts will be lifted in the absence of flow. Service: Trashrack and fishing net s body should be repainted every 5 years. In case of maintenance and transportation, prevent their direct contact with the floor via timbers. Trashrack and fishing net s body should be inspected in terms of surface coverage, welded joints, surface distortion and corrosion once a year. Bronze bearings should be controlled for screw connections and corrosion every 6 months as well as indicator rod for proper functioning of bars and rods, welding and corrosion and deformation. STOPLOGS Stoplogs are installed using link rod. Stop logs will be elevated in the absence of flow, in case of periodic inspection and repairment. After closing the flow path for installing or lifting the gates, balance should be established using by pass system of gate placed in 1080 MASL. Service: Gates bodies should be repainted every five years. In case of transportation, prevent their direct contact with the floor via timbers. Gate s body should be inspected in terms of surface coverage, welded joints, surface distortion and corrosion once a year. Indicator rod should be controlled for proper functioning of bars and rods, welded joints, corrosion and deformation every 6 month. By pass system should be controlled in terms of sealing, blockage, corrosion and welding, deformation of rod, proper functioning of spring, trashrack cleanness and no flow obstruction every 6 month. Sealing should be controlled for cracking, tearing, screw joints and surface distortion every 6 month.
LINK ROD Link rods are used to maneuver the gates and should always be placed under tensile force. In case of facing compressive force they will show buckling behavior. Service: Link rod s body should be repainted every 5 years. Injecting grease before each maneuver with a maximum period of three months is required. Main axis should be controlled in terms of welded joints, surface coating and corrosion, longitudinal adjustment links, deformed joints welded joints deformation and rust removal every 6 month. Supports should be controlled for welded joints, corrosion, deformation of the radial plate and surface distortion every 6 month. Pins surfaces should be checked for decay and scratches every 6 month. Sprocket holes should be checked for deformation and distortion, welded joints, rot and pin surface scratches and rust every 6 month. STEEL LINING CONDUIT In order to check the steel lining, depending on the location to be controlled, intake, bottom outlet or outlet should be drained. Conduit shell should be checked in terms of surface coating, welded joints, surface distortion, corrosion and grout caps annually. Manhole should be checked for sealing, welded and bolted joints every 6 month. SERVOMECHANISM OF SLIDE GATES A servomotor is installed on each slide gate to maneuver it. Emergency gate s servomotor opens when pressure is balanced therefore it doesn t bear greater operating pressure. But since Service gate s opening is in unbalanced pressure conditions, the servomotor installed on service gate must tolerate greater operating pressure. Visual check of oil and its operating pressure should be done annually. Visual checking of Oil filters should be done in terms of derbies and dust passage every 100 hours of operation. Color coating of cylinders should be checked for damage in case of scratching every 6 month. Indicator rod should be controlled for proper functioning, deformation, corrosion and welding every 6 month. Pipes and hoses should be checked in terms of presence of nodules, twisting, scratches and swelling every 6 month. The power and speed of the cylinders Speed and frequency of movement in cylinders or engines speed should be checked before each maneuver at least every 6 month. Checking system noises compared with new system in terms of failure of the bushes and guides and pressure controller defects before each maneuver. Sealing should be checked for exhaustion at least every 6 month and during each replacement and opening or closing.
REFERENCES Arkansas soil and water conservation commission, 2002. Inspection and maintenance manual for Arkansas dam owner. Little Rock. Ashenab consulting engineering, 2007. Sabalan dam operation and maintenance instructions. Tabriz. Fannavary Novin Niroo Co., 2008. Sabalan dam s hydromechanical equipment operation and maintenance instructions. Tehran. Texas commission on environmental quality, 2006. Guidance for operation and maintenance of dam in Texas. Texas.