1 Dampers for Centrifugal Fans Inlet and Outlet commercial & industrial Applications November 2007. $FOUSJGVHBM 'BO %BNQFST. Greenheck CENTRIFUGAL FANS WITH DAMPERS FOR. commercial AND industrial APPLICATIONS ARE AN. UNBEATABLE COMBINATION. Dampers used in conjunction with centrifugal fans provide a simple, reliable and cost effective means for controlling air systems. Complimenting its centrifugal fan line, Greenheck has an extensive offering of control and isolation dampers for commercial and industrial applications. t &BDI DFOUSJGVHBM GBO NPEFM IBT B EBNQFS UIBU JT TJ[FE UP IBOEMF . the maximum air velocity. t /P HVFTTXPSL JO USZJOH UP NBUDI B GBO T QFSGPSNBODF MFWFM XJUI B . EBNQFS T DBQBCJMJUZ . t %BNQFS EFTJHOT XJUI DFOUSJGVHBM GBOT IBWF CFFO PQUJNJ[FE UP.]]
2 Reduce system effect losses. t 8 JEF WBSJFUZ PG UZQFT BOE DPOTUSVDUJPO PQUJPOT BWBJMBCMF . means versatility and exibility in being able to select the best combination for system requirements. t %BNQFST BSF GBDUPSZ UFTUFE BOE JOTQFDUFE CFGPSF TIJQQJOH 'JOF . tuning counter balances; adjustments for linkage and blade operation; setting actuator limits. t $FOUSJGVHBM GBOT BOE EBNQFST BSF TIJQQFE UPHFUIFS BT POF . unit so there is no eld mounting required. The Greenheck Total Centrifugal Fan Package . Dampers are just one component of the Greenheck centrifugal fan package. Completely assembled fan and option packages are available including your DIPJDF PG UIF GPMMPXJOH . t 4 USVDUVSBM #BTFT *TPMBUPST.
3 T .PUPST %SJWFT. t %BNQFST. t 1 SPUFDUJWF $PBUJOHT. t %JTDPOOFDU 4 XJUDIFT. t 4 BGFUZ (VBSET 8 FBUIFSIPPET. t 'MPX .POJUPSJOH 4 UBUJPOT. (Sure-Aire ). The package includes long life bearings and a Outlet Volume Control Dampers are commonly used in variable air volume complete vibration analysis. systems. Blades are mounted perpendicular to fan shaft for even force loading on the blades and to reduce pressure losses. 2. Backdraft Dampers prevent reverse air ow through the system. Recommended to be used on fan Classes I, II, III only. Inlet Box Dampers are used when applications require Inlet boxes. Inlet box dampers have performance characteristics similar to Inlet vane dampers. Nested Inlet Vane Dampers External Inlet Vane Dampers have linkages incorporated into the housing are mounted in the airstream or directly to the of the fan.)
4 Used in variable air volume fan housing leaving linkages accessible for applications with space constraints. maintenance. Often used for variable air volume retro t applications. 3. Outlet Dampers Outlet DAMPERS. &JUIFS CBDLESBGU PS PVUMFU WPMVNF DPOUSPM EBNQFST BSF BWBJMBCMF 5IF UZQF PS BNPVOU PG DPOUSPM SFRVJSFE BMPOH XJUI . the need for actuators differentiates these models. BACKDRAFT DAMPERS Outlet VOLUME. allow air to pass in one direction CONTROL DAMPERS. and restrict ow in the opposite regulate the air ow by direction. The dampers have modulating the damper blades. gravity actuation with a counter Actuators may be manual, weight and linkage assembly. electric or pneumatic and are This is an inexpensive means of mounted out of the airstream.
5 Keeping air from owing back Control dampers are specially through a system. Initial and designed so blades are all required maintenance costs perpendicular to the fan are low. TIBGU 5 IJT GFBUVSF NJOJNJ[FT . pressure losses and distributes the stresses associated with velocity pressures evenly. Both parallel and opposed blade styles are available. HOW Outlet DAMPERS AFFECT. FAN PERFORMANCE. 8 IFSF PVUMFU WPMVNF DPOUSPM EBNQFST BSF VTFE UIF GBO . Fan Curve (Ps). static pressure changes with the resistance produced by modulating or closing the damper blades. B. The gure to the right illustrates the performance characteristics of a centrifugal fan with different damper blade positions. Point A shows the performance when the A.]
6 Damper is in an open position. Point B illustrates the shift JO UIF PQFSBUJOH QPJOU BT UIF EBNQFS TUBSUT UP DMPTF 'PS . each blade position there will be a new system curve and operating point. The original static pressure (Ps) and brake Bhp Curve horsepower (Bhp) curves remain unchanged. PARALLEL OR OPPOSED? Control dampers are offered with either parallel PS PQQPTFE CMBEFT &BDI TUZMF IBT EJTUJOHVJTIJOH System Curves DIBSBDUFSJTUJDT JO SFHBSET UP DPOUSPM PG UIF GBO T . performance plus a change in air velocity pro le. t 1 BSBMMFM CMBEF EBNQFST IBWF FYDFMMFOU DPOUSPM PWFS UIF . range of 75% to 100% wide open volume due to the Volumetric Flow (CFM). amount of control arm swing required to modulate the blades.
7 Parallel blades are used when greater control is Centrifugal Fan with Outlet Damper required near the top end of the volume operating range or for systems requiring two position (fully open or fully closed) operation. Parallel blades should not be used upstream of critical components due to uneven air ow. t 0 QQPTFE CMBEF EBNQFST PGGFS UIF CFTU DPOUSPM PWFS . the entire operating range. Opposed blades are used for applications where it is necessary to maintain even distribution of air downstream from the damper. This style of blade is the best selection for ducted outlets. Parallel Blade Opposed Blade Top View of Blade Action Styles 4. Inlet Dampers Inlet DAMPERS. Inlet dampers include nested Inlet vane, external Inlet vane and Inlet box dampers.
8 These models save power by reducing Bhp requirements and should be considered when the fan operates for long periods at reduced capacities. NESTED Inlet VANE EXTERNAL Inlet VANE Inlet BOX DAMPERS. DAMPERS DAMPERS are used in clean air are primarily used in non-ducted are intended for ducted applications where an Inlet box applications with space applications and those with JT VUJMJ[FE 5 IFTF EBNQFST BSF . constraints. The vanes and higher pressures and velocities. supplied with parallel blades linkages are located inside These dampers are mounted in for performance characteristics the fan housing with the the airstream or directly to the similar to Inlet vane dampers. actuator mounted outside. fan housing.]
9 Advantages are Actuators are mounted outside Recommended for clean air accessibility to the linkages for of the airstream. applications only. maintenance and exibility in mounting location. HOW Inlet DAMPERS IMPACT. FAN PERFORMANCE. Inlet dampers start a pre-spin on air entering into the fan. Fan Curves (Ps). The pre-spin placed on the entering air ow will be in the same direction as the wheel rotation. This does not allow the wheel to develop its full performance pro le, limiting the amount of air owing through the fan. This pre-spin also reduces the energy requirements of the fan and the Ps/Bhp overall effect is very similar to reducing the speed on an undampered fan. C. Centrifugal fans with Inlet vane dampers have different Bhp Curves operating points depending on the blade position of the damper.
10 As an Inlet damper actuates, open or closed, D. new operating points are found on the system curve. See the gure to the right. Different operating points are SFQSFTFOUFE CZ $ % BOE & XJUI $ UIF NPTU XJEF PQFO . E. BOE & UIF MFBTU &BDI QPJOU IBT B VOJRVF TUBUJD QSFTTVSF System Curves and brake horsepower curve. These points show that by closing an Inlet damper, air ow is reduced and less energy is required by the fan. Volumetric Flow (CFM). Centrifugal Fan with Inlet Damper 5. Damper Selection Inlet VANE DAMPER. 8 IFO TFMFDUJOH B OFTUFE PS FYUFSOBM JOMFU WBOF EBNQFS UIF EJSFDUJPO PG UIF BJS T QSF SPUBUJPO JT DSJUJDBM GPS QSPQFS . functioning of the damper and fan combination. Damper rotations are viewed from the air Inlet side of the fan, and DBO CF FJUIFS DMPDLXJTF DX.