Control Valves. 1. Inspect both manual and automatic control valves and clean bonnets and stems.
2. Tighten packing glands to assure no leakage, but permit valve stems to operate without galling.
3. Replace packing in valves to retain maximum adjustment after system is complete.
4. Replace packing on any valve which continues to leak.
5. Remove and repair bonnets which leak.
6. Verify that control valve seats are free from foreign material, and are properly positioned for intended service.
Control Valves. (a) Check for valve leakage
(b) Check that valve is secured in open position
(c) Check bracing for damage
Control Valves. Control valves in throttling service will generally be the globe-body cage type with body materials, pressure rating, and valve trims suitable for the service involved. Other style valve bodies (e.g., butterfly, eccentric disk) may also be used when suitable for the intended service. Block valves shall be provided upstream and downstream of all modulating control valves except for the main steam bypass. Bypass valves shall be provided except where bypass valve use is impractical or presents a potential safety hazard, as approved by Purchaser. Control valve actuators shall be the pneumatic-spring diaphragm or piston type. The actuator shall be sized to shut off against at least 110% of the maximum shutoff pressure. Actuators shall be designed to function with instrument air pressure ranging from 60 to 125 psig. All control valves shall be sized such that minimum specified flow results in at least 20% stem lift, normal flow results in 75% stem lift, and maximum flow results in 90% stem lift for equal percentage valves and 85% for linear valves. Parallel, split-range control valves may be necessary to meet this requirement, including the HP drum level and LP drum level applications. The use of a manual bypass valve to meet this requirement is unacceptable. Valves shall be designed to fail in a safe position. Control valve body size shall not be more than two sizes smaller than line size, unless the smaller size is specifically reviewed for stresses in the piping and calculations are provided to Purchaser for record purposes. Where flanged valves are used, minimum flange rating shall be ANSI 300 class. Control valves in 600 class service and below shall be flanged where economical. Critical service valves shall be defined as ANSI 900 class and higher valves in sizes over 2 inches. Severe service valves shall be defined as valves requiring anti-cavitation trim, low noise trim, or flashing service, with differential pressures greater than 100 psig. In general, control valves shall be specified for a noise level no greater than 90 dBA when measured 3 feet downstream and 3 feet away from the pipe surface. Valve actuators shall use positioners and the highest pressure, smallest size actuator. Handwheels shall be furnished only on those valves that can be manually set and controlled during system operation (to maintain Facility operation) and do not have manual bypasses. Control valve accessories, excluding controllers, shall be mounted on the valve actuator unless ...
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. 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. 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.
B. Equip control valves with actuators of proper close-off rating.
C. Modulating control valves shall have equal percentage or linear flow characteristics.
D. Valve bodies shall be 2-way normally open or closed, or 3-way mixing as specified or as required. Valve bodies 2" and smaller shall be bronze, screwed type and 2 ½ " and larger shall be iron, flanged and rated at 240°F 125 psig except where otherwise noted.
E. Valves shall have stainless steel stems and allow for servicing including packing, stem, and disk replacement, or offer a 5 year warranty on parts and labor.
F. Size valves for 50% coil pressure drop (minimum 3', maximum 12' pressure drop).
G. Two-position, two-way control valves shall have quick opening characteristics.
H. Three-way valves shown in mixing application shall have a single, double faced disk.
I. Three-way valves shown in diverting application shall have two separate disks on a common shaft.
J. All steam control valves shall be single seated. No single valve shall be lager than 2-½ ''. Wherever the flow rate is such as to require a valve larger than 2-½”, then multiple valves in parallel shall be used, with one no larger than 2-½ ''. The valves shall operate sequentially. Trim shall be stainless steel for inlet pressures above 15 psig steam.
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. Control valves shall be adjusted as needed to allow proper closing and to eliminate leakage.
