Control Valves: Specifications, Sizing & Technologies

Control Valves: Specifications, Sizing & Technologies David Kandel Application Consultant Belimo david.kandel@us.Belimo.com 720-354-0591

Agenda Control Valves: Specification, Sizing and Technologies Controlling a Coil Ratings and Definitions Hydronic Valve Sizing Steam Valve Sizing Control Valve Technology © Belimo, 2012

Agenda Control Valves: Specification, Sizing and Technologies Controlling a Coil Ratings and Definitions Hydronic Valve Sizing Steam Valve Sizing Control Valve Technology © Belimo, 2012

Understating Coil Behavior Coil Performance Resulting Coil Output Coil Power / Flow ΔT This is how a new coil is controlled by a properly sized PI valve The coil curve relates BTUh to flow (blue) Animation 1: The valve curve relates flow to control signal (orange) Animation 2: By combining these curves, we can relate BTUh to control signal, shown as he resulting coil output (black) The following 3 slides illustrate through the affect of degradation on the performance of the coil. Shown here is the coil as it was manufactured. Blue line = Coil Output Orange line =Valve Flow Green line = Delta T Valve GPM BTUh Flow / Control Signal

Agenda Control Valves: Specification, Sizing and Technologies Controlling a Coil Ratings and Definitions Hydronic Valve Sizing Steam Valve Sizing Control Valve Technology © Belimo, 2012

Pressure/Temperature Ratings Valve Specs Pressure/Temperature Ratings Body Pressure Close-Off Pressure Close-Off Leakage DP Temp Ratings Valve Flow Characterization Curve Rangeability/Turndown Valve Authority Actuation Fail Safe Normally Open/Normally Closed

Body Pressure Pressure Vessel Burst Rating Measured in psi Failure Threshold of the Vessel

Relationship between Pressure and Temperature Body Pressure ANSI Body Rating Relationship between Pressure and Temperature

Close-Off Pressure P1 The maximum pressure that a valve can withstand without leakage while in the fully closed position.

Close-Off Pressure Rule of Thumb 2-way Valve Close-off pressure should at least equal the maximum pressure produced by the circulating pump 3-way Valve Close-off pressure should at least equal the system differential pressure

Close-Off Pressure Close-Off Leakage Bubble Tight is not an ANSI rating. Bubble Tight implies No water leakage.

Pressure Drop P1 P2 The maximum allowable pressure differential that a fully open valve can withstand without damaging the internals of the valve.

Temperature Ratings Media Temperature (hydronic) Acceptable fluid temperature range Media Temperature (steam) Commonly measured in lbs of steam Ambient Temperature Usually an actuator rating

Characterization Curves Equal Percentage Linear Quick Opening Modified Equal Percentage ? Flow Varies based on design Butterfly Valves, others 2 Position control Zone Valves Modulating Control of a Coil CCV, PI-Valves, Globe Valve Modulating Control of Steam Coil or Bypass Applications ePIV, Globe Valves Valve Position

Rangeability & Turndown The ratio of maximum flow to minimum controllable flow of a valve body only under laboratory conditions with a constant differential pressure applied across the valve. Turndown Ratio: The ratio of maximum usable flow to minimum controllable flow of the valve assembly under installed conditions. It is always lower than the rangeability factor.

Agenda Control Valves: Specification, Sizing and Technologies Controlling a Coil Ratings and Definitions Hydronic Valve Sizing Steam Valve Sizing Control Valve Technology © Belimo, 2012

Flow Coefficient FLOW COEFFICIENT (Cv) is the quantity of water in gpm at 60 DegF that flows through an open valve with a pressure drop of 1psi.

Hydronic Valve Sizing Example: Coil Requires 8 GPM Design DP for valve, 4 psi DP of Valve not to exceed 5 psi

Hydronic Valve Sizing Example: Coil Requires 8 GPM Design DP for valve, 4 psi DP of Valve not to exceed 5 psi

Hydronic Valve Sizing Checking DP Example: Coil Requires 8 GPM Design DP for valve, 4 psi DP of Valve not to exceed 5 psi

Hydronic Valve Sizing Checking DP

Hydronic Valve Sizing Checking DP Which should we select? And Why?

Valve Authority Coil Flow (%) Valve Opening (%) Balance Valve First animation: Discuss the formula form Valve Authority as it relates to the branch schematic. Walk through an example of a 20 psi drop on the branch, creating A=0.2 2nd animation: Show the distortions that result from A=0.2

Valve Authority Coil Balance Valve

Valve Authority Distortion 100 90 80 Valve Opening (%) Flow (%) 70 60 Flow / Coil Output (%) 50 40 0.2 30 1 20 1st animation: Explain how EQ% valve curve acts opposite the coil curve and creates a linear 1:1 heat output (in other words, 20% control signal should result in 20% heat output) 2nd animation: When A=0.2, this starts to fall a part 3rd animation: The nice EQ% curve and the linear output are no longer valid (the equal percent curve will fade to make the graph easier to read, the output line will remain dotted, for comparison.) 4th animation: When we combine the new valve curve with the existing coil curve, we get a new out put that is quite fast acting at low flows. Note that at 10% valve opening the original output curve puts out 10%, but the new one puts out 20%. Note that at 20% valve opening the original output curve puts out 20%, but the new one puts out 40%. At low flows, the space is seeing twice the heat output that the is anticipated by the controller. 5th animation: discuss the over flow and underflow caused by riding up and down the much steeper output curve. 10 10 20 30 40 50 60 70 80 90 100 Valve Opening (%)

Should be greater than coil DP Valve Authority > 0.4 Hydronic Valve Sizing Rules of Thumb Differential Pressure Across the Valve Should be greater than coil DP Valve Authority > 0.4 Typically between 3psi - 5psi for modulating Typically about 1 psi for on/off

Pipe Reduction Factor ½" valve in a ½" pipe with a Cv tested at 10 Same ½" valve in a 1" pipe will test at Cv = 6.3

Pipe Reduction Factor

Pipe Reduction Factor Only for Valves with High Cv relative to line size

The control valve shall be no less than ½ the pipe size… Pipe Reduction Factor Rules of Thumb Choosing Valves Smaller than Line size The control valve shall be no less than ½ the pipe size… However, it’s best to keep the valve size reduction no greater than 2 pipe sizes. Large pipe reductions can increase the effects of cavitation

Piping Considerations Which is Correct? And Why is it Correct? Template day month year

Agenda Control Valves: Specification, Sizing and Technologies Controlling a Coil Ratings and Definitions Hydronic Valve Sizing Steam Valve Sizing Control Valve Technology © Belimo, 2012

ΔP = 80% inlet gauge pressure (psig) Steam Valve Sizing Low Pressure Steam (under 15psi) Cv = Flow Coefficient Q = lbs per hour of steam ΔP = Differential Pressure in psig Po = Outlet Pressure in psia (psia = psig + 14.7) ΔP = 80% inlet gauge pressure (psig)

Steam Valve Sizing Low Pressure Steam (under 15psi) Example: Size a modulating control valve for 160 lb/hr with a 5 psig steam supply.

42% absolute inlet pressure (psia) Steam Valve Sizing More than 15psi Cv = Flow Coefficient Q = lbs per hour of steam ΔP = Differential Pressure in psia Po = Outlet Pressure in psia (psia = psig + 14.7) ΔP = 42% absolute inlet pressure (psia)

Steam Valve Sizing More than 15psi Example: Size modulating 1/3-2/3 valves for a heat exchanger with a design flow of 600 lb/hr at 30 psig.

Steam Valve Sizing 1/3rd: 2/3rd: More than 15psi Example: Size modulating 1/3-2/3 valves for a heat exchanger with a design flow of 600 lb/hr at 30 psig. 1/3rd: 2/3rd:

1/3-2/3 Valve Sequencing

Agenda Control Valves: Specification, Sizing and Technologies Controlling a Coil Ratings and Definitions Hydronic Valve Sizing Steam Valve Sizing Control Valve Technology © Belimo, 2012

Control Valve Technologies

Characterized Control Valves CCV Characterized Control Valves Ball Valve (rotary action) Characterizing Disc

CCV

CCV 2-way

CCV 3-way (Mixing or Diverting)

CCV Pros Cons Applications Valve Summary Inexpensive Equal Percentage Characteristic High Close Off Large Range of Cv Cons Hot and Chilled Water with Glycol Only Applications Hot & chilled water coils (for air handling units) Unit ventilators Fan coils VAV units

Globe Valves Globe Valves Linear Action Plug Design

Globe Valves Close-Off Pressure Close-Off Rating Determined by Force Applied to Stem Close-Off is Actuator Dependent Pd Pu

Globe Valves 3-way Mixing

Globe Valves 3-way Mixing

Globe Valves 3-way Diverting

Globe Valves 3-way Diverting

Globe Valves Pros Cons Applications Valve Summary Equal Percentage or Linear Characteristic SS Trim works for Steam Cons Expensive Large 2 Versions of 3-way Close off depends on Actuator Applications Hot & chilled water coils (for air handling units) Chillers

Holes in Plate Balance the Pressure Globe Valves What is a Pressure Compensated Globe Valve? Pu Pd Holes in Plate Balance the Pressure

Globe Valves Pressure Compensated Close-Off Pressures G665 2½” 51 psi Standard Globe Valve Close-Off Ratings AFX24-MFT 2xAFX24-MFT G665 2½” 51 psi 82 psi G680 3” 34 psi 56 psi Pressure Compensated GV Close-Off Ratings AFX24-MFT 2xAFX24-MFT G665C 2½” 150 psi G680C 3” G6100C 4” G6125C 5” G6150C 6” 105 psi

Butterfly Valves Butterfly Valves Rotary Action Flow Characteristic: Modified Equal Percentage Rotating Disc and Resilient Seat

Butterfly Valves

Butterfly Valves 3-Way Butterfly Valves 2 Valves linked on a Tee Mixing or Diverting 1 or 2 Actuators

Butterfly Valves 3-Way Butterfly Valves 2 Valves linked on a Tee Mixing or Diverting 1 or 2 Actuators

Butterfly Valves Sizing a BFV: Velocity 12 ft/sec in Standard BFV 32 ft/sec in High Performance BFV

Butterfly Valves Pros Cons Applications Valve Summary Up to 30” Inexpensive High Close-Off SS and HP Available Cons Modified Eq % High Cv Relative to Size Velocity Limitations Applications Chiller and Cooling Tower Isolation Change Over Systems Large Air Handlers Bypass Controls

V-Ball (Segmented Ball Valve) V-Ball Valves For Extreme Conditions 400F Water 250 PSI Steam 150 PSI Close-off Controls Equal Percent Flow Characteristic 300:1 Rangeability

V-Ball (Segmented Ball Valve) V-Ball Valves Rotatory Valve Single seat Partial Ball reduced torque requirement

V-Ball (Segmented Ball Valve) Valve Summary Pros For extreme applications High Temp Water High Pressure Steam High rangeability Cons Expensive Limited sizes and Cv Large (heavy) Applications Hot & chilled water coils (for air handling units) Chillers

Zone Valves Zone Valves Inexpensive 2 Position Spring Return “Paddle” Design

Zone Valves 2-Way 3-Way Diverting

Zone Valves Pros Cons Applications Valve Summary Cheap Fail Safe 2 Position Only Low Close-Off Applications Baseboards Low Flow needing 2 position, fail safe

Pressure Independent Valves Pressure Independent Control Valves 2-way valve that supplies a specific flow for each value of the control signal – – Regardless of pressure variations in the system PI Valve Pressure Flow

Pressure Independent Technologies Mechanical Regulator Electronic Flow Meter

Pressure Independent Valves Valve Summary Pros Accurate Flow Regardless of Pressure Conditions Increased Water-side DT Reduced Pump Energy Usage Valve Authority = 1.0 Eliminates need of Automatic Balancing Valves Cons Higher Initial Cost Applications Hot & chilled water coils (for air handling units) Unit ventilators Fan coils VAV units

Control Valves: Specifications, Sizing & Technologies Questions?