Nihon Koso

  • Booth: O29


Koso is a leading global manufacturer of Valves & Controls

Nihon Koso is a global manufacturer of General and Severe Service valves, actuators & accessories for the Power & Process industries since 1965. Koso has large manufacturing factories in Asia, Europe and USA, including high quality castings from our own foundries. Superior custom-engineered valves.

Brands: Koso, Nihon Koso, KKI, KentIntrol, Rexa, Yoneki, KIPL, Vector, Severe Service


 Products

  • Koso Vector Control Valve
    Koso Vector Severe Service Control Valves for extreme pressure drop applications. Power water cycle: Feedwater Regulator, Boiler Feedpump Recirculation, HP Spraywater Control, Deaerator Level Control....

  • Severe Service control valves perform the most critical functions in a plant’s pipeline flow control system. They are the valves that regulate high energy feedwater and steam, and their failure to perform correctly will degrade a unit’s efficiency & reliability. A malfunction can cause a plant’s unscheduled shutdown or allow damage to major capital equipment such as turbines and condensers. 

    The most common severe service operating condition is high pressure drop, where the valve outlet pressure is less than 50 percent of the valve inlet pressure. Fluid pressure is lowered by reducing the size of the flow path, causing high fluid velocities and high friction energy transfer from the fluid into the metal surfaces of the valve.

    High pressure drops with high fluid velocities and high drag friction, cause destructive shear stress and erosion inside the valve. The excessive fluid velocity also causes noise, vibration and turbulence.

    Advanced Severe Service valve design follows the ISA™ (International Society of Automation) specification, in its publication: Control Valves: Practical Guides for Measurement and Control. The acceptance criteria for control valve sizing is fluid velocity control at the valve trim exit; for liquids the maximum speed is 30 meters per second, and for compressible fluids the maximum kinetic energy (velocity + density) is 480 kilopascals (4.8 bar). Valve designs that allow higher fluid velocities will suffer damage and cause fluid control problems.

    ISA™-compliant valve designs divide the pressure reduction into a series of discrete pressure reduction stages, where no single stage endures excessive velocities. The control element may need to have 10, 20, 30, 40, or more separate pressure drop stages, to maintain fluid velocities below 30 mps, or 4.8 bar.

    The more simple type multi-cage valve designs can be well-suited for non-severe pressure drop conditions, where the outlet pressure is 70 to 80 percent of the valve inlet pressure. But these multi-cage designs are limited to 6 or 8 maximum pressure reduction stages, and are not suitable for severe service pressure drop conditions in excess of 50 percent of upstream pressure, due to their high internal fluid velocities in violation of ISA’s specification.

    The Koso Vector™ control valve, with a proprietary disk stack control element, delivers high rangeability max-min flow control, always with the required number of pressure-reducing stages to comply with ISA™ velocity limits.

    Nihon Koso Co. Ltd. is a leading global manufacturer of standard and custom-engineered severe service control valves, fully in compliance with ISA™ fluid velocity specifications. Water-cycle and steam-cycle severe applications, such as: Turbine Bypass, Feedwater Regulator, Boiler Feedpump Recirculation and Deaerator Level Control.

    Koso today has large manufacturing factories in Asia, Europe and USA. Koso also features the highest quality valve castings from our own foundries. Superior custom-engineered valves for the most extreme operating conditions. Bring us your worst flow control problems … we can solve them.

  • Koso Turbine Bypass Control Valve
    Koso Vector™ Turbine Bypass Control Valves are designed for extreme steam pressure drop applications in subcritical, supercritical and ultra-supercritical power plants, with ISA™-compliant velocity control disk stack technology....

  • Thermal Power plant designs utilize water & steam under extreme pressures and temperatures, to transfer energy from a fossil fuel (coal, oil, gas) to the electric generator; kilojoules become kilowatts.

    Pumping high pressure water into a boiler, adding high heat content for phase change to steam, then directing it through spinning steam turbines, and finally exhaust it into a condenser, to begin the cycle again, exerts massive drag friction and shear stress forces against the surface of the pipes, valves & other pressure-retaining components.

    Protection of the steam turbine during startup and trip events is a critical function of the Turbine Bypass Control Valves (TBV); steam is re-routed away from the turbine into the Bypass valve. In milliseconds, this valve must replicate the same large drop in fluid pressure & temperature energy, as occurs when the steam flows through the turbine chambers. But the valve has no rotating parts like in a turbine, which is designed to transfer away the energy down the shaft to the generator. So the fluid energy reduction process is achieved by transfer of its energy into the internal metal surfaces of the valve via high fluid velocity drag friction, causing erosive shear stress forces against the inner valve surfaces. The high fluid velocity also causes noise, vibration and turbulence.

    Advanced Turbine Bypass valve design follows the ISA™ (International Society of Automation) specification, in its publication: Control Valves: Practical Guides for Measurement and Control. The acceptance criteria for Turbine Bypass control valve sizing a maximum kinetic energy (velocity + density) of 480 kilopascals (4.8 bar) at the seat/trim exit. Valve designs that allow higher fluid velocities will suffer damage and cause steam control problems.

    ISA™-compliant Turbine Bypass valve designs divide the pressure reduction into a series of discrete pressure reduction stages, where no single stage endures excessive velocities. The control element may need to have 10, 20, 30, 40, or more separate pressure drop stages, to maintain fluid velocities below 30 mps, or 4.8 bar.

    The more simple type multi-cage valve designs can be well-suited for non-severe pressure drop conditions, where the outlet pressure is 70 to 90 percent of the valve inlet pressure. But these multi-cage designs are limited to 6 or 8 maximum pressure reduction stages, and are not suitable for severe service pressure drop conditions in excess of 50 percent of upstream pressure, due to their high internal fluid velocities in violation of ISA’s specification.

    The Koso Vector™ Turbine Bypass control valve, with a proprietary disk stack control element, delivers high rangeability max-min flow control, always with the required number of pressure-reducing stages to comply with ISA™ velocity limits.

  • Koso Desuperheating Systems
    Koso offers the most advanced Desuperheating system technology, for precise steam conditioning in all applications. Our expertise extends from dry super-heated steam for Power turbines, to highly saturated steam for efficient Process heat transfer....

  • Desuperheating, also called steam conditioning, sprays water into steam pipelines to lower temperature. The process requires a ‘system’, consisting of 1) pressure control valve, 2) desuperheater device with spray nozzle, 3) spraywater control valve, 4) pressure & temperature sensors.

    Desuperheating application requirements have a wide range of operating conditions, and the most common cause of desuperheating problems is due to mis-application of designs intended for less critical service, into more extreme services which have much greater levels of severity.

    ‘Rangeability’ is the first consideration: what is the variation of range between maximum & minimum steam flow rates? Services with small variation of steam flows usually are suitable for fixed-area spray nozzles & cage-type spraywater control valve with system rangeability of 5-to-1. But when steam flow volumes (and temperatures) have higher variations, it requires more advanced variable-area nozzles with severe service spraywater control valve for system rangeability of 20-to-one or even 40-to-one.

    Rapid vaporization of the injected water is another major consideration. Precise control of the spraywater volume to the nozzles is always needed from the spraywater control valve. Primary atomization by the nozzles into droplets of less than 250 microns is always required; larger size droplets extend the ‘dwell time’ and delay spraywater vaporization, causing erratic steam/water mixing and thus poor conditioning.

    Extending/delaying the spraywater vaporization will result in erratic process control decisions because the temperature sensor feedback will give false readings in a zone where the fluid is a mixture of hot steam and unevaporated water droplets.

    Spraywater evaporation delay allows higher incidence of water droplets impinging on downstream pipe walls, causing thermal shock and structural pipe damage. Power plant desuperheating applications such as Turbine Bypass or Dump To Condenser, normally require one-third of the conditioned steam volume to come from the injected spraywater. Process applications, such as heat transfer into downstream processes, normally require at least 20 percent of the conditioned steam volume to come from the injected spraywater. These are huge volumes of water being injected into steam pipelines. Failure to rapidly vaporize will cause significant process control and piping component damage.  

    ‘Penetration’ control is a mandatory requirement. The nozzle’s spray pattern of the injected water must maintain a distance of 15 percent from the ID of the pipe wall, to prevent water droplets from contacting the wall, which will cause thermal stresses & pipe cracking. The design of the nozzles (probe type, ring type, fixed or variable, number of nozzles, etc.) is a complex analysis, to ensure the outer diameter of the water spray pattern is safely away from the pipe wall.

    Dry versus saturated steam is another major challenge for Desuperheating systems. Steam turbines in power stations require dry superheated steam; process steam for heat transfer in downstream industrial facilities require highly saturated steam. Delivering such different qualities of steam, and considering the large volumes of water injected, places radically different demands on the Desuperheating system components. Great care must be taken by the product engineering specialist, to select the correct design equipment, to achieve the correct result.

    A common mistake in lower pressure Process steam conditioning is to assume that a more basic Desuperheater system is good enough for use. This is not a safe assumption. This Desuperheater must deliver fully saturated steam to the downstream process, for efficient heat transfer. Condensate is one-third as efficient, and dry steam is less than one-tenth as efficient at transfer of heat. Maintaining steam right at the maximum saturation point is extremely difficult for a Desuperheater system to achieve; the closer to saturation, the more ‘severe’ it is.

    Koso’s broad range of Desuperheating products is the world’s leading technology source for solving all existing Desuperheater problems, and engineering the best system design for new installations.

    Koso’s Desuperheating product range summary is:

    Nozzle Type

    Series

    Description

    Rangeability

    Pipe Size

    Fixed Area Nozzle

    DV1

    Venturi

     5:1

     2" - 6"

    DVL

    Venturi Low-Loss

     5:1

     2" - 6"

    DVR

    Venturi Ring

     10:1

     2" - 6"

    DPF

    Probe

     4:1

     6" - 24"

    DSR

    Spray Ring

     10:1

     6" - 24"

    Variable Area Nozzle

    DPS

    Probe type with Spring-loaded nozzle

     20:1

     < 16"

    DPW

    Whirl type nozzle

     40:1

     6" - 24"

    DMR

    Multi-nozzle Ring with Spring-loaded nozzles

     20:1

     > 8"

    Steam-Assist Nozzle

    DAS

    Steam-Assist nozzle

     40:1

     6" - 24"


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