Common use of Control Valves Clause in Contracts

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. 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. 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 % valves and 85% for linear valves. Parallel, split-range control valves may be necessary to meet this requirement. The use of a manual bypass valve to meet this requirement is unacceptable. Valves shall be used designed to fail in on-off 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 modulating 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 throughout various processes within the facilityand below shall be flanged where economical. Globe Critical service valves shall be used extensively defined as ANSI 900 class and higher valves in water, steam, gas, and oil sizes over 2 inches. Severe 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 defined as type of fluidvalves requiring anti-cavitation trim, static and low noise trim, or flashing service, with differential pressures and temperaturegreater than 100 psig. In general, control valves in water and steam service shall be provided 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 severe vibration is expected. Solenoid valves supplied with hardened stainless steel trim. Modulating the control valves shall have Class H coils. The coil enclosure shall normally be sized a minimum of NEMA 4 but be suitable for the area of installation. Terminations will typically be by pigtail wires. The DCS shall monitor both “Open” and “Closed” position switches for motor-operated valves and pneumatic-operated control valves used for “On-Off” service. Position switches will not typically be provided for control valves used for “throttling” service. Where required, automatic combined recirculation flow control and check valves or orifices (provided by the pump manufacturer) shall be used for pump minimum flow recirculation control. Modulating or two-position automatic recirculation valves or restriction orifices shall be used as applicable. Body material and rating shall conform to pass design flow at 80 to 85 percent of piping specifications as a minimum. In no case shall be valve capacity. Multiple service conditions should body minimum rating 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 controlthat permitted by piping specifications. Minimum control Control valve body size shall be not less than 50 percent of the upstream pipe size1-inch minimum. When a calculated Cv requires a smaller valve, consideration should be given to the use of reduced trim in order to maintain the Sizes such as 5-inch body size requirement. Reduced trim shall not be less used. Body sizes smaller than 40 percent of valve capacity1 inch may be used for special applications with 3/4-inch-and-under line size, and for pressure regulator services. Pneumatic actuators Reduced ports shall be used as required. Body size shall not be more than two pipe sizes smaller than the line. Valves for on-off service shall normally be line size. Valve type and size shall be selected taking into account such factors as cost, operating and design conditions, fluid being handled, rangeability-required allowable leakage, noise, and any other special requirements. For general services, the following types shall be considered: Cage Guided Globe Valves with balanced or unbalanced type trim. Single seated globe valves may be either top and bottom or top guided. Eccentric Rotating Plug Valves of the diaphragm throttling type. Ball Valves of the throttling type. Butterfly Valves with either conventional or piston/cylinder type shaped discs. Special Body Types may be considered for special applications such as slurry handling, highly erosive or viscous streams, and noise control. Characteristics of the inner valve shall be provided for all determined by the following system characteristics: Equal Percentage Characteristics shall normally be used on loops that have large variations in valve pressure drops, fast pressure control valves. Careful consideration should be given to the fail-safe position of loops, and most flow control valves. Where practicable, actuators with integral springs will be specifiedloops. In generalprocesses where no guidelines are available, control valves design to fail closed shall have ANSI class IV leakage ratings. Control valves equal percentages shall be designed to operate used. Linear Characteristics shall normally be used for most level control, slow pressure control loops, and loops where the measurement is linear and the variation in the pressure drop across the control valve is small. Linear characteristics shall be used for three-way valves and for two-way valves used in three-way service. Quick Opening Characteristics shall normally be used for off-on service and for direct connected regulators using low lift. Valve trim shall be stainless steel minimum, hardened for erosive service. Severe service conditions may dictate consideration of other materials. Guide bushings shall be of corrosion-resistant material. It is preferred that the guide material be a minimum of 125 Brinell harder than the trim. Packing glands shall be equipped with a control signal range of 3flange-15 psistyle gland followers, secured by two bolts. Each control A lubricator with steel isolating valve shall be provided where packing lubrication is required. Packing shall be Teflon below 450°F and Graphoil for temperatures of 450°F and higher. No asbestos is permissible. Extension bonnets shall be provided on throttling services above 450°F and below 0°F, or in accordance with accessories such as handwheelsthe manufacturer's recommendation. On-off control valves shall use high temperature packing in lieu of extension bonnets when practicable. Piston actuators shall be furnished with pneumatic trip valve, filter regulatorsvolume tank, solenoid pilot piping, and necessary components to lock-in supply air pressure on loss of supply air pressure to actuator to ensure proper failure position. Split ranging of control valves shall be done electronically using independent DCS outputs. Pneumatic split ranging is not allowed. Positioners may be electric/pneumatic or smart type. Electric/pneumatic positioners shall have two gauges and limit switches as applicablea smart type one. A control system failure philosophy will be developed with Owner participationValve leakage class shall conform to ANSI B l6.104, “Control Valve Seat Leakage.”

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 used designed to fail in on-off 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 modulating 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 throughout various processes within the facilityand below shall be flanged where economical. Globe Critical service valves shall be used extensively defined as ANSI 900 class and higher valves in water, steam, gas, and oil sizes over 2 inches. Severe 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 defined as type of fluidvalves requiring anti-cavitation trim, static and low noise trim, or flashing service, with differential pressures and temperaturegreater than 100 psig. In general, control valves in water and steam service shall be provided 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 severe vibration is expected. Solenoid valves supplied with hardened stainless steel trim. Modulating the control valves shall have Class H coils. The coil enclosure shall normally be sized to pass design a minimum of NEMA 4 but be suitable for the area of installation. Terminations will typically be by pigtail wires. The DCS shall monitor both “Open” and “Closed” position switches for motor-operated valves and pneumatic-operated control valves used for “On-Off” service. Position switches will not typically be provided for control valves used for “throttling” service. Where required, automatic combined recirculation flow at 80 to 85 percent of valve capacitycontrol and check valves or orifices (provided by the pump manufacturer) shall be used for pump minimum flow recirculation control. Multiple service conditions should Modulating or two-position automatic recirculation valves or restriction orifices shall be specified when a used as applicable. For the boiler feedwater pump, modulating automatic recirculation control valve is expected or combined recirculation/check valve shall be used. Body material and rating shall conform to operate over piping specifications as a wide range of travel, i.e., feedwater flow and deaerator level control valvesminimum. When In no case shall the calculated Cv is valve body minimum rating be less than the manufacturer's recommended minimum Cv, consideration should be given to providing two valves with split range controlthat permitted by piping specifications. Minimum control Control valve body size shall be not less than 50 percent of the upstream pipe size1-inch minimum. When a calculated Cv requires a smaller valve, consideration should be given to the use of reduced trim in order to maintain the Sizes such as 5-inch body size requirement. Reduced trim shall not be less used. Body sizes smaller than 40 percent of valve capacity1 inch may be used for special applications with 3/4-inch-and-under line size, and for pressure regulator services. Pneumatic actuators Reduced ports shall be used as required. Body size shall not be more than two pipe sizes smaller than the line. Valves for on-off service shall normally be line size. Valve type and size shall be selected taking into account such factors as cost, operating and design conditions, fluid being handled, rangeability-required allowable leakage, noise, and any other special requirements. For general services, the following types shall be considered: Cage Guided Globe Valves with balanced or unbalanced type trim. Single seated globe valves may be either top and bottom or top guided. Eccentric Rotating Plug Valves of the diaphragm throttling type. Ball Valves of the throttling type. Butterfly Valves with either conventional or piston/cylinder type shaped discs. Special Body Types may be considered for special applications such as slurry handling, highly erosive or viscous streams, and noise control. Characteristics of the inner valve shall be provided for all determined by the following system characteristics: Equal Percentage Characteristics shall normally be used on loops that have large variations in valve pressure drops, fast pressure control valves. Careful consideration should be given to the fail-safe position of loops, and most flow control valves. Where practicable, actuators with integral springs will be specifiedloops. In generalprocesses where no guidelines are available, control valves design to fail closed shall have ANSI class IV leakage ratings. Control valves equal percentages shall be designed to operate used. Linear Characteristics shall normally be used for most level control, slow pressure control loops, and loops where the measurement is linear and the variation in the pressure drop across the control valve is small. Linear characteristics shall be used for three-way valves and for two-way valves used in three-way service. Quick Opening Characteristics shall normally be used for off-on service and for direct connected regulators using low lift. Valve trim shall be stainless steel minimum, hardened for erosive service. Severe service conditions may dictate consideration of other materials. Guide bushings shall be of corrosion-resistant material. It is preferred that the guide material be a minimum of 125 Brinell harder than the trim. Packing glands shall be equipped with a control signal range of 3flange-15 psistyle gland followers, secured by two bolts. Each control A lubricator with steel isolating valve shall be provided where packing lubrication is required. Packing shall be Teflon below 450°F and Graphoil for temperatures of 450°F and higher. No asbestos is permissible. Extension bonnets shall be provided on throttling services above 450°F and below 0°F, or in accordance with accessories such as handwheelsthe manufacturer's recommendation. On-off control valves shall use high temperature packing in lieu of extension bonnets when practicable. Piston actuators shall be furnished with pneumatic trip valve, filter regulatorsvolume tank, solenoid pilot piping, and necessary components to lock-in supply air pressure on loss of supply air pressure to actuator to ensure proper failure position. Split ranging of control valves shall be done electronically using independent DCS outputs. Pneumatic split ranging is not allowed. Positioners may be electric/pneumatic or smart type. Electric/pneumatic positioners shall have two gauges and limit switches as applicablea smart type one. A control system failure philosophy will be developed with Owner participationValve leakage class shall conform to ANSI B l6.104, “Control Valve Seat Leakage.”