Industry Applications | EICMATION Hydropower Plant Solution Analysis

Hydropower plants are integrated engineering facilities that convert water energy into electrical energy, also known as hydroelectric power plants. They include a series of hydropower plant structures and equipment built to utilize water energy for power generation. These structures concentrate the natural water flow's head drop, collect and regulate the flow rate of natural water flow, and deliver it to the water turbine. Through the combined operation of the water turbine and generator, the concentrated water energy is converted into electrical energy, which is then fed into the power grid via transformers, switch stations, and transmission lines. Some hydropower plants, in addition to the structures required for power generation, often have other structures for comprehensive utilization purposes such as flood control, irrigation, navigation, log transportation, and fish passage. The complex of these structures is called a hydropower hub or water conservancy hub.

01

Types of Hydropower Plants

1. Dam-type hydropower plants: These are hydropower plants that build dams on rivers to raise water levels and create a head for power generation. According to the relative position of the powerhouse and the dam, dam-type hydropower plants can be classified into riverbed type, post-dam type, in-dam type, powerhouse top spillway type, bank type, and underground type.

2. Diversion hydropower plants: These are hydropower plants that use diversion structures to concentrate the natural river head drop to create a head for power generation. According to the hydraulic conditions of the diversion channel, diversion hydropower plants can be divided into pressureless and pressurized types. Pressureless diversion uses open channels or pressureless tunnels for open-flow diversion, suitable for small and medium-sized hydropower plants; pressurized diversion uses pressure tunnels or pressure pipes for diversion, suitable for large and medium-sized hydropower plants.

3. Hybrid hydropower plants: These are hydropower plants that use both water retaining structures and diversion systems to create a head for power generation.

4. Tidal hydropower plants: These generate electricity using the head created by the rising and falling tides.

5. Pumped storage power plants: These are hydropower plants equipped with units that have both pumping and power generation functions. They utilize surplus electricity during periods of low power demand to pump water into the upper reservoir, storing water energy, and then generate electricity from the upper reservoir during peak system load periods.

02

Five Major Systems of a Hydropower Plant

1. Hydraulic system: This refers to the water turbine and its inlet and outlet equipment, including steel pipes, the spiral casing before the water turbine, the water turbine, the tailrace pipe, and the tailrace gates.

2. Current system: This refers to the electrical primary circuit system, including the generator, generator leads, busbars, generator voltage distribution equipment, main transformer, high-voltage switchgear, and distribution equipment.

3. Mechanical control equipment system: This includes the governor of the water turbine, such as the control cabinet, hydraulic system, and relay; the operating control equipment of the butterfly valve; and the operating control equipment of the pressure reducing valve or other gates and trash racks.

4. Electrical control equipment system: This includes the local control panel, excitation equipment system, central control room, various control and operation equipment such as current transformers, meters, relays, control cables, automatic and remote control devices, communication and dispatching equipment.

5. Auxiliary equipment system: This refers to various electrical and mechanical auxiliary equipment necessary for equipment installation, inspection, maintenance, and operation. The auxiliary equipment system also includes the following:

5.1 Plant power system: Plant transformers, plant distribution equipment, DC power system.

5.2 Lifting equipment: Bridge cranes, gantry cranes, gate operating mechanisms inside and outside the powerhouse.

5.3 Oil system: Storage, processing, and circulation equipment for turbine oil and insulating oil.

5.4 Gas system (also known as air system or compressed air system): High and low pressure air compressors, air tanks, air pipes, etc.

5.5 Water system: Technical water supply, domestic water supply, fire water supply, leakage drainage, maintenance drainage, etc.

5.6 Others: Including various electrical and mechanical repair rooms, laboratories, tool rooms, ventilation and heating equipment, etc.

03

Valve Selection for Hydropower Plants

As an important energy production facility, the normal operation of various systems within a hydropower plant relies on various types of valves. Valves in hydropower plants are mainly used in technical water supply, fire water supply, domestic water supply, leakage drainage, maintenance drainage, plant area drainage, oil systems, and compressed air systems. The following describes the types, diameters, and pressure ratings of valves used in each system.

1. Technical Water Supply System

Valve types: Mainly butterfly valves, gate valves, ball valves, and check valves.

Diameter selection: Usually DN50-DN400, depending on the size and flow requirements of the water supply pipeline.

Pressure range: Generally 1.0-2.5MPa, to be determined according to the specific water supply pressure.

2. Fire Water Supply System

Valve types: Commonly used butterfly valves, gate valves, check valves, pressure reducing valves, wet alarm valves, signal butterfly valves, automatic air release valves, etc.

Diameter selection: Usually DN100-DN250, depending on the design flow rate of the fire pipeline.

Pressure range: Generally 1.6-2.5MPa, to meet the requirements of fire codes.

3. Domestic Water Supply System

Valve types: Mainly butterfly valves, gate valves, ball valves, and check valves.

Diameter selection: Usually DN25-DN100, depending on the size and flow rate of the domestic water pipeline.

Pressure range: Generally 0.6-1.6MPa, to ensure the normal supply of domestic water.

4. Leakage Drainage System

Valve types: Commonly used ball valves, gate valves, butterfly valves, and check valves.

Diameter selection: Usually DN50-DN200, depending on the size and drainage volume of the drainage pipeline.

Pressure range: Generally 0.6-1.0MPa, to meet the pressure requirements of the drainage system.

5. Maintenance Drainage System

Valve types: Mainly gate valves, butterfly valves, and check valves.

Caliber Selection: Based on the size and drainage volume of the drainage pipes under inspection, the caliber of DN80-DN250 is usually selected.

Pressure Range: Generally 0.6-1.0MPa, meeting the needs of drainage inspection.

6. Plant Drainage System

Valve Type: Commonly used gate valves, butterfly valves, and check valves, etc.

Caliber Selection: Based on the size and drainage volume of the plant drainage pipes, the caliber of DN100-DN300 is usually selected.

Pressure Range: Generally 0.6-1.0MPa, suitable for the pressure requirements of plant drainage.

7. Oil System

Valve Type: Mainly ball valves, globe valves, and check valves, etc.

Caliber Selection: Based on the size and flow rate of the oil pipeline, the caliber of DN15-DN80 is usually selected.

Pressure Range: Generally 1.6-4.0MPa, needs to be determined according to the pressure requirements of the oil system.

8. Compressed Air System

Valve Type: Commonly used ball valves, globe valves, pressure reducing valves, and safety valves, etc.

Caliber Selection: Based on the size and flow rate of the compressed air pipeline, the caliber of DN15-DN50 is usually selected.

Pressure Range: Generally 0.8-1.6MPa, needs to meet the pressure requirements of the compressed air system.

04

Application of EICMATION Valves in Hydropower Stations

1. Operating Conditions of Valves in Hydropower Stations:

① For a long time, the actual situation is that the river water contains some sediment, and due to the small amount of sediment in the river water, the sealing surface of the on-site soft sealing valve has been damaged, and the sealing surface needs to be wear-resistant and erosion-resistant, and the maintenance work of the underwater unit cannot be carried out normally; ② The technical water supply pipeline will be regularly reversed, and the requirements for two-way sealing are strict. The original on-site ball valve does not move for a long time, resulting in scaling on the ball surface, which leads to the ball valve being unable to open or close normally after a period of use; ③ The service life of some original soft sealing valves on site is not long.

2. EICMATION Solution:

After communication and exchange between the EICMATION professional technical team and the on-site technology, and on-site investigation of the working conditions, the specific idea is to replace and upgrade the existing centerline butterfly valve or ball valve in the technical water supply, using the EICMATION intelligent electric switch type all-metal hard seal three-eccentric flange butterfly valve. Using the structural characteristics of the EICMATION three-eccentric butterfly valve, the above problems are solved in a targeted manner. The sealing surface of the EICMATION all-metal sealed three-eccentric butterfly valve is hard-faced with Stellite alloy, with an effective thickness of more than 1.5mm; the hardness reaches HRC40, rather than the multi-layer sealed metal hard seal on the market, suitable for particles, high-frequency operation, high temperature and high pressure, and low temperature conditions. This three-eccentric butterfly valve has a sealing structure with no mechanical wear and abrasion, small closing torque, good cut-off performance, and good sealing performance. It achieves two-way (full pressure difference) pressure resistance, zero leakage, installation without flow direction restrictions, and long service life. It can completely solve the problem of large water leakage and the regular reversal of the technical water supply pipeline.

Structural Characteristics of EICMATION All-Metal Hard Seal Three-Eccentric Butterfly Valve:

① Three-eccentric sealing structure, no mechanical wear and abrasion, small closing torque, good cut-off performance, good sealing performance, and long service life.

② The torque during valve closure generates valve seat force, acting uniformly and consistently around the entire circumference. The elastic seal bends and is full of vitality, maintaining the shape of the valve seat. The elasticity of the seal allows the valve body valve seat and butterfly plate seal ring to contact or expand, avoiding the danger of blockage due to temperature fluctuations.

③ The valve body valve seat structure is a split valve seat, and the butterfly plate seal ring is also a split type. After removing the retaining ring, the seal ring on the valve plate and the valve seat on the valve body can be removed and replaced with a new valve seat and seal ring. Avoid seal damage causing the entire valve to be scrapped, facilitating maintenance.

④ High platform design: Actuator mounting platform designed according to ISO5211 standard, various actuators can be directly installed.

⑤ It can achieve two-way (full pressure difference) pressure resistance, zero leakage, and installation without flow direction restrictions.

⑥ The sealing surface of our all-metal sealed three-eccentric butterfly valve is hard-faced with Stellite alloy, with an effective thickness of more than 1.5mm; the hardness reaches HRC40, rather than the multi-layer sealed metal hard seal on the market, suitable for particles, high-frequency operation, high temperature and high pressure, and low temperature conditions.

⑦ The valve shaft and actuator are connected by splines, which are closely matched with the actuator, with no idling stroke and no risk of key shearing, minimizing the risk of failure.

⑧ Preload disc springs are set at the bottom of the packing gland and gland bolts. During production and assembly, tightening the gland bolts will compress the disc springs, causing them to deform and store elasticity. When the gland bolts loosen due to valve vibration, pipeline vibration, etc., during use, the disc springs return to their original state, releasing the preload, so that the packing gland can still press the packing, avoiding external leakage.

3. Actual Cases

① The project of replacing and upgrading the centerline butterfly valve or ball valve of technical water supply with the EICMATION all-metal hard seal three-eccentric butterfly valve has very important significance for the maintenance and safe and reliable operation of the hydropower unit after the upgrade and transformation. The Datang Guanyin Rock Hydropower Station renovation achieved the expected goal, and then the Lidi Hydropower Station, Longchuanjiang No. 1 Hydropower Plant, Nalan Hydropower Station, and Nuozhadu Hydropower Station successively learned from and drew lessons from it, cooperating with EICMATION brand valve companies, all using all-metal hard seal three-eccentric butterfly valves to solve problems encountered in hydropower station pipelines.

Photos after on-site upgrading and transformation to all-metal hard seal three-eccentric butterfly valves

② At the same time, relying on its own valve quality, EICMATION has also carried out many upgrading and transformation projects for various system pipelines in many hydropower stations, cooperating with Baihetan Hydropower Station, Jiazha Hydropower Station, Gongguoqiao Hydropower Station, Jinghong Hydropower Plant, Manwan Hydropower Plant, Gelantan Hydropower Station, Longkou Hydropower Station, Huangdeng Dahuaqiao Hydropower Station, etc., and the results have all achieved the expected goals.