A Brief History

A few applications of immersion tubes in open tanks began to appear around the turn of the century.

1920’s: Applications of immersion firing began to appear in trade journals.

1931: Sellers Engineering applied the principles of immersion firing to steam and hot water generation.

History (Cont’d) 1934: A growing interest in the technology led to

extensive research by the American Gas Association Testing Laboratories.

1944: “Research in Fundamentals of Immersion Tube Heating with gas” was published by the AGA.

During WW II, nearly 10,000 Sellers water heaters were used by the Military.

So what made Sellers the boiler of choice for so many?

The Durable Immersion Shell Design.Backed By a 20 Year Warranty!!

Sellers’ 20 Year Thermal Shock Warranty

Typical Scotch Marine Boilers employ the use of a large diameter combustion tube and several smaller tubes in multiple passes.

The combustion tube is exposed to higher temperatures than the flue tubes, causing an uneven pressure on their common fixed tube sheets.

There is limited thermal expansion room between the attachment of the furnace and tubes to absorb this uneven expansion.

In contrast, the Immersion Boiler tubes are exposed to the same temperature. Adequate thermal expansion room is provided on both tube sheets.

Typical fire tube boilers are warrantied up to 20 degrees F temperature differentials.

Immersion boilers are warrantied to operate with temperature differences exceeding 100 degrees F.

How?

Immersion Boiler Shell Basics

Single Pass Fire TubesCompletely Surrounded

by Water

Single Pass Immersion Tube Pattern Typical 3 Pass tube Pattern

Comparison of Tube Patterns

Scotch Marine Boiler Heating Surface Analysis

1st Pass Radiant is 10-13%

3rd Pass Convection

Tubes 35-45%

2nd Pass Convection

Tubes 30-40%

Scotch Marine Boiler Thermal Analysis

Thermal Stress Points

1st Pass

4th Pass

3rd Pass

2nd Pass

In a Multi-Pass Boiler, the different passes of tubes apply uneven heat to the tube sheet. As a result, tremendous stresses are applied to the tube sheet.

Immersion Boiler Heating Surface Analysis

Immersion Boiler Thermal Stress Analysis

A Sellers Boiler heats both tube sheets evenly with one pass. One inch tube sheet ligaments between tubes allows the tube sheet to flex naturally.

NO THERMAL STRESS POINTS

1st Pass

1st Pass

1st Pass

1st Pass

1st Pass

1st Pass

1st Pass

1st Pass

Scotch Marine Rear Tube Sheets

Immersion Boiler Rear Tube Sheet

History (cont’d) 1970’s - 80’s: Sellers boilers were installed in all

applications across the country and the company prospered.

1990’s - 2014: Sellers struggles to keep up with the boiler market due to on-off firing being the only immersion option. As boiler management systems grew more complex, the opportunities for on-off firing plummeted.

2015: Sellers Manufacturing engineers a fully modulating immersion burner to accompany the highly praised shell design, thus the S-Series is born.

S-Series Modulating Immersion Boiler

Physics 101: Heat Transfer

•Heat is transferred in three ways:

•RADIATION – By infrared electromagnetic waves. The most efficient method of heat transfer. Similar to a microwave.

•CONVECTION – By moving and mixing of masses of molecules. Less efficient than radiation. Similar to an oven.

•CONDUCTION – By the passage of heat from molecule to molecule without the movement of the molecules. Least efficient method. Similar to a boiling pot on a stove.

What causes resistance to heat transfer in boilers?

The insulating effects of:

1. Dead gas film2. Water film

In other words…..Heating Surface!!

How does Immersion firing combat heat transfer resistance?

Air-Gas mixture exits the burner nozzle at a velocity exceeding 80 ft/sec.

When the air/gas is combusted it expands rapidly increasing the velocity of flow scrubbing the dead gas film away from inside the tube.

With less than 3ft of heating surface per BHP, Immersion firing provides much less water & dead gas film area compared to typical Scotch Marine designs.

50% of the total heating surface is radiant! The most efficient method of heat transfer. Typical Scotch Marine boilers have 10-13%.

The Immersion Firing Process

What is Immersion firing?

A method of firing gas in a small diameter tube that is totally immersed in water. Demonstrated below:

The Immersion Burner Assembly

The Firing Tube & Nozzle

Primary Heating Surface (XID) Firing Tube

Secondary Heat Recovery Zone

Sellers “Heat Extractor”

Immersion Modulation

Standard Immersion nozzles were re-engineered with high flame retention technology.

Fixed gas and air intakes are now variable inputs controlled by Siemens servo motors.

Advanced Combustion Technology

• Integrated linkageless PID control.

• User friendly programming with real text annunciation.

• Real time Modbus communication.

• Optional HMI touchscreen interface.

• Optional master control panel for sequencing multiple units.

• Optional Bacnet, Lonworks, Metasys & Modbus RTU communication.

• Optional O2 trim.

Immersion Efficiencies

BOILER

HORSEPOWER

OPERATING TEMPERATURE

180 F 200 F 220 F 240 F

10-200 231 (84.9%) 251 (84.4%) 270 (84.0%) 289 (83.5%)

250-800 211 (85.4%) 230 (84.9%) 249 (84.5%) 267 (84.0%)

BOILER

HORSEPOWER

OPERATING TEMPERATURE

10 PSI 50 PSI 100 PSI 125 PSI

10-200 289 (83.5%) 345 (82.1%) 384 (81.2%) 399 (80.8%)

250-800 267 (84.0%) 321 (82.7%) 359 (81.8%) 373 (81.4%)

Net Stack Temperature and Efficiency Rating for Hot Water Boiler

Net Stack Temperature and Efficiency Rating for Steam Boiler

It’s Guaranteed!!!

Immersion Firing Offers Versatility Steam Boilers from 15 to 300 PSI. Hydronic Heating Boilers – High Temperature Options ASME Sec 1.

&

Chemical Free 15 PSI Steam.

Low NOx emissions 30 & 9 PPM.

Methane Gas Fired Steam or Hot Water.

Outdoor Immersion Boiler Installation with Nema 4 Weatherproof Trim

1. 20 Year Pressure Vessel Warranty – Includes Parts & Labor!

2. Cold Start to Full Capacity Under 20 Minutes. 3. No Refractory. 4. Less than 30 PPM NOx Without FGR.5. Natural Gas, Propane & Methane Gas.6. Heat is Transferred with Greater Uniformity.7. Smallest Fire Tube Boiler Footprint.8. The Most Efficient Use of Heating Surface.

A Few Sellers Customers

918 West Walnut StreetPO Box 48

Danville, KY 40422Ph: 859 236-3181; Fax: 859 236-3184

www.sellersmfg.comwww.sellersmfg.com