2000 Hook-up Book

Multi-Coil Heaters

Single Section

1.0

SYSTEM DESIGN

0.9

0.8

0.7

Single Section t s

Two Section

0.6

∆ t o

Outlet Temp. t o

Temp.

0.5

Three Section

∆ t i

0.4

Four Section Five Section

t i 2

Proportion of Load on First Section

0.3

Inlet Temp. t i

0.2

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

0.9

Ratio ∆ t o/ ∆ t i

Figure 49 Temperature Distribution in Multi-Coil Heater

Figure 50 Load on First Section of Multi-Coil Heater

Case in Action: Air Make-Up Coil Drainage

Solution Mill Engineers, working with the local Spirax Sarco Representative, developed a long-range plan to redesign and retrofit the entire Air Make-Up System. Over the last two years, approximately 20 Pressure Powered Pump ™ /float & thermostatic trap closed-loop packages have been installed. The project will continue until the entire system is retrofitted. They have similarly retrofitted several shell and tube heat exchangers, improving water heating efficiency. Benefits • Energy savings are achieved through installation of pressurized closed-loop packages. There is no loss to flash. • Chemical savings are achieved because of the pressur ized packages. Chemicals are not lost out the vent. • Desired air heating efficiency has been achieved. All retrofitted coils have operated properly and continuous ly since installation. Flooding has been eliminated. • Maintenance costs dropped dramatically with elimina tion of condensate flooding, water-hammer and freezing. • Personnel safety has improved as steam/condensate leaks have been reduced.

Paper Mills require a huge volume of air exchange. This means that a great deal of air heating is necessary, partic ularly during winter months. Air Make-Up systems are split between two general applications: a. Machine or Process Air Make-Up is supplied to t he immediate area around the machine and, more specifi cally, to certain areas within the machine for higher temperature heating (i.e. Pocket Ventilation or PV coils). b. Mill Air Make-Up, which is distributed across the mill for HVAC comfort. Either application may be accomplished with single banks of coils or double-preheat/reheat coils, depending on heating requirements. The mill experienced a chronic problem of frozen Air Make-Up coils, typically associated with condensate flood ing and waterhammer. The 50/150 psig steam coils ballooned and ruptured routinely, creating costly mainte nance headaches and safety hazards. Several coils were removed from service, requiring extensive repair.

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