Control Valves. 1. Inspect both manual and automatic control valves and clean bonnets and stems.
Control Valves. (a) Check for valve leakage
Control Valves. Control Valves shall be used in on-off and modulating service throughout various processes within the facility. Globe valves shall be used extensively in water, steam, gas, and oil service with butterfly and ball valves used in limited applications, typically low pressure and temperature water service. Valtek valves will not be allowed. Pressure retaining component and valve trim materials shall be selected based on process conditions such as type of fluid, static and differential pressures and temperature. In general, control valves in water and steam service shall be provided with hardened stainless steel trim. Modulating control valves shall be sized to pass design flow at 80 to 85 percent of valve capacity. Multiple service conditions should be specified when a control valve is expected to operate over a wide range of travel, i.e., feedwater flow and deaerator level control valves. When the calculated Cv is less than the manufacturer's recommended minimum Cv, consideration should be given to providing two valves with split range control. Minimum control valve body size shall be not less than 50 percent of the upstream pipe size. When a calculated Cv requires a smaller valve, consideration should be given to the use of reduced trim in order to maintain the body size requirement. Reduced trim shall not be less than 40 percent of valve capacity. Pneumatic actuators of the diaphragm or piston/cylinder type shall be provided for all control valves. Careful consideration should be given to the fail-safe position of control valves. Where practicable, actuators with integral springs will be specified. In general, control valves design to fail closed shall have ANSI class IV leakage ratings. Control valves shall be designed to operate with a control signal range of 3-15 psi. Each control valve shall be provided with accessories such as handwheels, filter regulators, solenoid pilot valves and limit switches as applicable. A control system failure philosophy will be developed with Owner participation.
Control Valves. EPC - Exhibit B -------------------- TENASKA GEORGIA GENERATION PROJECT Page 127 of 132 -------------------------------------------------------------------------------- The entire operating load range of the plant shall be fully considered when developing the control valve specification sheets. Control valve body sizes shall not be more than one pipe size smaller than the nominal pipeline size up to eight (8) inches. For nominal line sizes greater than eight (8) inches, control valve body sizes shall not be more than 2 pipe sizes smaller than the nominal pipeline size. Valve travel shall not exceed 80 percent at the maximum operating condition. Valve noise (excluding steam conditioning valves) shall not exceed 95 dBA @ three (3) feet. Control valve sizing and detailed requirements shall be the responsibility of the Contractor. ISA Format Data Sheets shall be used to specify the valves. Control valves shall conform to the requirements of ANSI B31.1, Code for Power Piping and be suitable for use under the specific operating conditions. Handwheels shall be provided on all air-operated valves. The control valve body shall be no more than two nominal sizes smaller than the line in which the valve is installed. Body fluid velocities shall be limited to 40 fps as liquid and 0.3 mach as vapor or gas. Trim sizes may be reduced to 0.4 factor trim minimum when pipe size or velocities are limiting. Valves shall be capable of passing 125 percent of the normal capacity. If the maximum capacity is listed, the valve shall be capable of passing 105 percent of that figure. Globe and angle type valves will have cage, top and bottom, or top guiding (no skirt guiding). Bonnets shall be flanged or of integral construction. The packing gland shall be the bolted type. Under the normal range of operating conditions the sound level at any point 3 ft radially from the surface of the downstream pipe at a distance of 3 ft downstream of the valve outlet should not exceed 90 dBA (excluding steam conditioning valves). Valve materials shall be ASTM or ASME type carbon steel, chrome moly, or stainless steel, as required by the service conditions. All trim materials shall be stainless steel, as a minimum, with hardened 400 Series stainless steel or Stellite hard surfaced trim where pressure drops exceed 100 psi or wear is expected from erosion. -------------------------------------------------------------------------------- EPC - Exhibit B -------------------- TENASKA GEORGIA GENERATION PRO...
Control Valves. Automatic temperature control valves for HVAC equipment shall be furnished by the ATC Contractor and installed by the HVAC system installer.
Control Valves. Depending on the heat load design, normally, one motorized control valve is installed for smaller installations with service lines under three inch. For three inch and larger service it is advisable to use two valves operating in a one-third and two-thirds sequence for the total capacity. Care should be taken to size control valves correctly; oversized valves will shorten valve service life and cause temperature variations in the secondary system. Hot Water District Heating System pressure varies depending on the location/elevation of the customer's building. The DES has the information on the minimum and maximum pressure anticipated. This information will be essential in the proper selection of control valves for heat exchangers. The correct size of valve should be designed for each system for proper building system control and to minimize the noise, cavitation, and general wear on valves. The motorized control valve shall be designed for a maximum pressure of 150 psi and a maximum temperature of 220° F. Materials shall consist of a cast iron, bronze, or steel with screwed or flanged connections. The valve shall be equal percentage type with a spring-loaded Teflon V-ring packing. Motorized control valve for heat exchangers shall have a minimum rangeability of 100:1. Control equipment should be electronic. Electric control valve actuators shall be fail safe and configured as Normally Closed (signal to open) / Fail Closed so that there is full shutoff with a loss of actuator power and reposition automatically without intervention. The actuator shall be equipped with a manual override in the event of a loss of control signal. The operation mode should be proportional-integrating (PI), i.e., dictated by temperature accuracy and response time. Close temperature control is desirable for low energy consumption. Design pressure losses for the control valves can be determined by subtracting pressure losses through the heat exchanger, energy meter, strainer, and pipes from the value of the minimum pressure difference between the supply and return lines at the design outdoor temperature. Control valves are installed in the return line for two primary reasons: return water has a lower temperature, which increases the life of the valve glands and actuators, and improved control by reduced valve cycling. Note: the supply line temperature sensor in the secondary system must be located as close as possible to the point where supply pipes emerge from the heat exchangers.
Control Valves. The most important criteria for choosing a control valve at the OEC system is the pressure drop across the valves. In order to minimize the valve pressure drop most valves are High Performance butterfly valves with double or triple Eccentric construction. On/Off valves equipped with piston actuator, 24 VDC solenoid valve and some with quick exhaust device for fast action in emergency for close or open. Modulating control valves equipped with diaphragm or piston actuator and Electro Pneumatic positioner. All Positioner have 90(degree) opening with input signal. Of 4-20 mA and are classified for Class I Zone 2 Group IIA.
Control Valves. 6.3 PURCHASER will be responsible for the final earth dike installation, permanent roads, permanent drainage, and spill containment basins and pumping.
Control Valves. A. Provide control valves of the type, body material and pressure class as determined by manufacturer, based on operating requirements and maximum pressure and temperature in the piping system.
Control Valves. Control valves shall be adjusted as needed to allow proper closing and to eliminate leakage.
