Download - Heat Exchanger Stall

©2005 Armstrong International, Inc.

Heat Exchanger Stall

2““Expect many Expect many enjoyable experiencesenjoyable experiences!”!”David M. ArmstrongDavid M. Armstrong

““Expect many Expect many enjoyable experiencesenjoyable experiences!”!”David M. ArmstrongDavid M. Armstrong

Condensate Return

Let’s take a look at a savings analysis...

•Hotter boiler feed water temperatures

•Minimizes the amount of chemicals required to treat boiler feed water

•Eliminates environmental concerns

•Minimizes water usage which is critical in some areas

•Condensate is a tangible item which can be measured in the form of a savings analysis

•Effective return can lower overall costs which can impact profitability



A. Condensate Load A= 2000 lb/hrB. Annual hours of operation B= 5000 hrsC. Total Water Cost = (C1+C2) C1. Untreated water and sewage .002 $/gal C2. Water treatment chemicals .003 $/gal

C= .005 $/galD. Make-up water preheating requirements D1. Condensate return temperature 200 °F D2. Make-up water temperature 60 °F D = (D1-D2) x 1.0 BTU/lb / °F D= 140 BTU/ lb

E. Steam cost E= 5.00 $/1000 lb

F. Savings in water costs(A) x 2000 x (B) 5000 x (C) .005

8.34 lb/gal F= 5,995 $/yr

G. Savings for preheating make-up water *(BTU/lb from direct steam injection)

(A) 2000 x (B) 5000 x (D) 140 x (E) 5.00*1000 x 1000 G= 7,000 $/yr

H. Cost of steam to run Armstrong Pump Trap3 x (A) 2000 x (B) 5000 x (E) 5.00 *1000 x 1000 H= 150 $/yr

I. Total annual savings = (F+G+H) F. Savings in water costs 5,995 $/yr G. Savings for preheating make-up water +7,000 $/yr H. Cost of steam to run Armstrong Pump Trap - 150 $/yr

I= 12,845 $/yrJ. Payback of pump purchase Payback = $5,063 (cost of pump package)

12,845 J= .39 yrs



25 psig Steam 25 psig Steam MainMain

Modulating Modulating Control Valve 0 Control Valve 0 – 25 psig– 25 psig



Effects of “Stall”

• Inadequate condensate drainage

• Water hammer

• Frozen coils

• Corrosion due to Carbonic Acid formation

• Poor temperature control

• Control valve hunting (system cycling)

• Reduction of heat transfer capacity



Factors Contributing to Stall

• Oversized equipment

• Conservative fouling factors

• Excessive safety factors

• Large operating ranges

• Back pressure at steam trap discharge

• Changes in system parameters



25 psig Steam 25 psig Steam MainMain

Modulating Modulating Control Valve 0 Control Valve 0 – 25 psig– 25 psig



What is the “Stall” Solution?

• Use a bigger steam trap ?• Use a vacuum breaker ?• Implement a safety drain ?• Install a Positive-Pressure system ?• Use an electric pump?



Finding “Stall”

Where does Stall occur?

• Air heating coils• Shell & tube heat exchangers• Plate & frame heat exchangers• Absorption chillers• Kettles• Any type of heat transfer equipment that has

Modulating Control



Product Product RangeRange

• Single pump capacities from 350 lb/hr to 73,000 lb/hr

• Flash recovery vessels

• Electric condensate pumps



Rescue Cap™Rescue Cap™

• Fits Spirax Sarco PPC/PPF pumps

• Watson McDaniel

• Spence

• Hoffman PCS

• Gestra FPS23

• Johnson

• Clark Reliance



Armstrong Stainless Steel Sump EjectorArmstrong Stainless Steel Sump Ejector

• Replaces standard electric sump pumps (must have high pressure steam available

• For steam pits, tunnels and enclosed spaces where ground or rain water can accumulate and requires pumping

• Can be used in any application where the water temperature will not exceed 140°F

• Great for locations that run underground steam lines where the drip traps are in tunnels or manholes



Armstrong AFT Vertical Flash VesselsArmstrong AFT Vertical Flash Vessels

• Excellent for providing low velocity flash steam with no water carryover

• ASME Sec. VIII U stamped to 150 PSI (other pressures upon request)



Packaged Packaged SolutionsSolutions

• Standard Packages

• Custom Fabrications

• ASME Packages

• Low Boy Solutions

• Vented Systems

• Closed-loop Systems

• Process Water Packages

and more…Closed-loop Low-Boy Receiver PackageClosed-loop Low-Boy Receiver Package



Common Industry Applications

Modulating Control

• Jacketed KettlesJacketed Kettles

• Process Air HeatingProcess Air Heating

• Tank HeatersTank Heaters

• Shell & Tube ExchangersShell & Tube Exchangers

• Process Media (water, oil, food etc.)Process Media (water, oil, food etc.)

Any steam consuming process heat exchanger Any steam consuming process heat exchanger utilizing…utilizing…