Control valves and fail-safe action valves
Control valves 200 series line
Valves in a range from RV 210 to 245 is an important group of products with a large number of executions. They represent a comprehensive range of control and shut-off valves in diameters from DN 15 to 400, the nominal pressure from PN 16, 25 and 40.
Valves RV 21x series, the cast of valve body consists of modern material with favourable foundry and mechanical properties - spheroidal cast iron, are intended to control of media flow in hot water and in steam applications. The field of using includes for example heat exchanger stations, heating circuits and substations, but also the low-pressure steam cycles of fossil fuels power plants, and possibly secondary circuits of nuclear power plants.
Material executions of described valves RV 21x, marked as RV 22x (cast steel valves) and RV 23x (stainless steel valves) extend the use of these products in more demanding applications in power circuits and technology in the chemical industry, petrochemical, gas, cooling circuits, etc. For the most demanding applications in the chemical and petrochemical industry is determined RV 24x series, where the material body chromium-nickel alloys (Monel, Hasteloy) are used.
Valves RV 2xx series are generally of modular design and are manufactured in several versions. The basic solution is RV 2x0, representing a direct two-way valve. Design of direct valve is also known under abbreviation of the English PDTC (Push Down To Close).
Valve body with a streamlined channel was designed with respect to the minimum weight, which greatly simplifies the handling during manufacture, transport, installation and maintenance.
Stainless steel plug is generally cylindrical with cut-outs (V-port), for small diameters with the shaped throttling system. For valves operating under adverse operating conditions (cavitation in liquid or supercritical flow of vapours and gases) can be solved as a perforated plug. Seat of the valve, stainless steel also can be in case of requirement equipped with PTFE ring, ensuring a high and long-term tightness of the close (so-called soft seat sealing). In demanding operating conditions valves can be equipped with seat with hart metal overlay on the sealing surfaces (stellited seat). Sealing is alternatively solved either by packing box with O-rings or PTFE sleeves, expand graphite or bellows for the most demanding applications. In any case, the emphasis is on high reliability and long-term tightness at minimal or no maintenance.
Valves RV 2x1 series are principially of the same design but are intended for using actuators with the reverse function. This valve design is also referred to the English abbreviation PDTO (Push Down To Open).
The two basic designs builds pressure-balanced valve design marked RV 2x2, the reverse design the RV 2x3. The principle of pressure-balanced valve is to create a closed space above the control plug and link this area counterbalance hole channel on the opposite side of plug. This will balance the pressures acting on the plug and it is not loaded by additional forces from the pressure of medium. This solution allows the use of relatively weak actuators for actuating of valves of big diameter, even under high pressure drops. This valve became the basis for the so-called fail-safe action valves, control valves equipped with electric or electro-hydraulic actuators with safety function that ensure in the case of power failure movement of the valve to the required position.
The last type of valves of this series is three-way valves RV 2x4 and RV 2x5, for mixing or diverting of media flow. They differ from each other mainly by the fact that the valves RV 2x4 are able to close tightly both the direct and the angle line (short-circuit), because they can be fitted in both lines of the seat with a PTFE sealing, but by the valves RV 2x5 absence of a torque switch of actuator (this applies particular to electro-hydraulic actuators Siemens) in the bottom position, doesn´t allow to close of a angle line, it should be taken into account in the application (leakage is about 2% Kvs).
All of these types of valves can be supplied fitted plugs with linear or equal percentage flow characteristics, two-way valves in addition to the parabolic (quadratic) characteristics and since year 2000 also with optimized characteristics for applications in heating LDMspline®. Wide range of Kvs values gives to designers and users the ability to accurately design and use the valve without excessive over-or underpowered of power.
The modular design of valves allows easy rebuilding, for example after changing of parameters of equipment (Kvs change or change of characteristics) that may be done usually as on-site service. If necessary, can also be supplied with custom fitting non-standard Kvs value or the flow characteristics.
Smallest supplied Kvs value of LDM valves is 0,01 m3/h-1, achieved with valves RV 210 with micro-throttling trim. These valves were originally developed for use in compact steam heating stations for regulating the power on the condensate side, but are also used in industry and testing for control of very small flow rates.
Valves series RV 2xx are assembled with pneumatic, electromechanical, or electro-hydraulic linear actuators domestic and foreign manufacturers, which allows their actuating from a simple three-point to the unified pneumatic, voltage or current control signal with feedback. Using of direct acting linear actuators ensure particularly in conjunction with a pressure-balanced valve low movement power high precision of regulation and long-term reliability and service life of actuators.
Construction of type numbers of valves, like the other products of company LDM allows precise and unalterable, specification of the valve including of the actuator and theirs later decoding. In the company are stored information on all valves supplied, so as for correct a sufficient knowledge of the user serial number is enough for finding data on the operation of the valve and spare parts or service intervention by authorized company.