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Specialist Power Plant Valves


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HORA is one of Germany's leading manufacturers of control valves with more than 35 years of experience. This independent company specialises in the design and manufacture of severe service valves in power plants, e.g turbine bypass stations, desuperheaters, pump protection valves and feedwater control valves. The company's minimum flow valves protect centrifugal pumps from potential damage caused by thermal and hydraulic overloads at low load operations. Hora and Powerflo Solutions Pty Ltd offer a whole range of products for use in industry, power plants, as well as electric and pneumatic actuators. 

Power Engineering Technologies for the Highest Demands - Power plant operators and plant manufacturers research and develop new processes and technologies for power plants worldwide with efficiencies of more than 50 percent and steam temperatures of more than 700C. HORA is one of the first manufacturers world-wide to tackle the 700 technology. HORA supplies the control valves for the extreme parameters of 700C and 350 bar in these power plants. For this purpose, new resilient materials which contain high levels of nickel and chromium are researched and applied. In this way, the plant efficiency can be increased above 50 percent, and the CO2 emissions can be reduced simultaneously by a third: Setting the agenda for safe and efficient energy supply across the globe.

Steam Conditioning Valves -Steam conditioning engineering is of considerable importance in the steam generating and steam consuming industries, e.g. power plants, pulp and paper industries, seawater desalination plants, breweries, refineries etc.. As the name already implies, steam conditioning is the simultaneous change of both temperature and pressure - pressure reducing and de-superheating station (PRDS). A steam conditioning valve replaces the separate arrangement of a pressure reducing valve and a de-superheater. It requires less space and is more cost effective. 

Guidelines for Operation of Minimum Flow Control Valves - The design and methods to protect a boiler feed pump is a connection of very complex control systems. The information given here should serve as a basis to avoid mistakes in the selection of the components and of the control systems to be used.

Heavy Duty Control Valve - The Heavy Duty Control Valve is a versatile, modular globe valve designed for severe duties. This type of valve can be utilized to regulate and control the flow of gases, steams or liquids in all industrial applications. It is particularly suitable for the water-steam cycle in high pressure/high temperature power plant applications.

De-Superheater Regulator -A de-superheater is a regulating device for control installations in many fields of industry, providing precise cooling.

Forget Your Problems - This Power Technology Bulletin describes the advantages of the Hora Solution and how problems can be solved by these specialist Power Plant Valves.

HORA Turbine Bypass System - A turbine bypass system permits operation of the boiler independently from the steam turbine during start-up, commissioning, turbine trip (shut down) and load alternations. It gives a higher plant availability and operational flexibility over all different operating conditions. The start-up time under cold, warm and hot conditions is reduced. Keeping the thermal transient in the boiler to a minimum continuous flow through superheater and reheater (maintained tube cooling) must be provided and the pressure during the entire start-up has to be controlled. This article describes how the bypass valve achieves this.


Power Plant Valve Applications

Applications for Specialist Power Valves- This technical bulletin provides some information on the various applications.

Stay Cool when Overheating - Cooling of superheated steam is usually performed by the boiler feed water, which is sprayed directly into the steam pipes by fine nozzles. Sometimes, in the event of extreme condition (excessive temperature), quick transition from high to low temperatures can result in thermal shock at the walls of the cooler. The experts at HORA developed a shock therapy named Cooled Cooler to overcome this problem. It prevents an abrupt cooling process and minimizes the risk of thermal stress at materials and the resulting damage. 

More efficiency at 700 degrees Celsius - Increasing efficiency in power plant engineering is a hot topic. This technologically challenging endeavour of increasing conventional steam temperatures of 600C up to 700C is the requirement and the goal of the project COMTES700. The abbreviation stands for "Component Test Facility for a 700C Power Plant". It is sponsored by the European Union and involves HORA as one of the technology partners: The power of innovation from Schlo Holte-Stukenbrock. Raising steam temperature from 600C to 700C and achieving thermal efficiencies of over 50% is a major step. Increased efficiency of the power plant can be easily explained with physics. The hotter the steam entering the turbine, the more heat energy the turbine blade can transform into rotational energy and feed into the generator. At the same time, it reduces the quantity of coal per kilowatt of generated electricity and the CO2 emissions. At the present time, coal-fired power plants around the world currently emit about eight billion tons into the atmosphere every year.  

Pump Protection with Minimum Flow Control Valves - There are two possible methods to protect a high pressure boiler feed pump from overheating through use of a minimum flow control valve during a low load situation or during starting. They are through on/off control or continuous control. Continuous control is used in case of large power stations that must be often started or stopped, in order to minimize the recirculation of the minimum flow required. This results in a substantial increase in the efficiency and a reduction in operating cost.

Desuperheater - The Desuperheater is a regulating device for control installations in many fields of industry providing precise cooling.

Automatic Pump Recirculation Valve - Automatic pump recirculation valves protect centrifugal pumps from possible damage caused by thermal and hydraulic overloads at low load operations by means of an automatic controlled bypass flow which corresponds with the required minimum flow of the pump.  

Steam Cooling - Two shift operation power plants Power stations that were originally designed for base load applications are now increasingly being asked to operate on a two shift, stop/start regime; this is more commonly known in the industry as dual shifting. The multiple start/stops that these stations are now experiencing is in some instances causing an increase of operational issues due to the to the constantly changing process parameters. For example dual shift stations will experience additional thermal stress in the headers, drums, high temperature piping, valves plus the auxiliary equipment leading to additional wear and tear of their systems and component parts. This is due to the more frequent use of the plant at severe service conditions. The consequences of the change in plant operation cannot be ignored. If the plant is not operated correctly or more importantly modified properly to handle these changes the lifetime of the components within the plant will decrease enormously. The changing operational requirements of the plant require that the steam coolers, de-superheater valves, drains, feed water control valves, main steam isolation valves and the turbine quick closing valves are reviewed. These critical pieces of equipment have to be specifically designed to take the new dual shifting process requirements into consideration, once this has been done the operational performance of the plant can be improved and wear and tear of systems and components can be controlled and significantly reduced. Consequently as these pieces of equipment have been specifically designed for the new operating conditions of the station they are no longer a limiting factor to the start up time of the plant. The following paper highlights some of the more common issues found in dual shifting power stations with special regards to steam control - Another paper on the same subject can be found here 

Pressure Reducing De-Superheater Stations (PRDS) - In the energy markets for example, power stations, paper mills, municipal waste incinerators or any steam raising plants, the control of steam is of crucial importance. The main function of a PRDS is to control both the pressure and temperature of the steam. A de-superheater valve is basically a control valve with an integrated spray water steam cooling facility. Every application is different and requires a custom built solution. A standard off the shelf valve is rarely the answer. HORA can produce all types of steam cooling devices and de-superheater stations. Every HORA valve is designed and optimised for the specific application and duty - from Chase.  

Industry, Power Plants and Process Technology - Pressure Reducing De-Superheater Stations PRDS Installation Guide.


Servicing Power Plant Valves 

Power Plant Valves Servicing - The servicing of these severe service valves requires extensive knowledge of the application along with a highly specialised service and maintenance capability. 


Other Power Plant Valve Links

Steam Converting Valves - The conversion of superheated high pressure steam into steam at lower temperatures and pressures is a common practice in process industries. This technology is also used in power stations to utilize the steam energy leaving the turbine for other purposes (e. g. for heating). Some applications use two different valves for the steam conversion process: the first for the reduction of the steam pressure and the second for the control of the cooling water - from Samson Controls.