Progressive Helix Mechanism (PHM)

B&W's Diamond Power® Progressive Helix Mechanism (PHM) device is a precision, geared indexing mechanism that shifts the nozzle starting position by a known amount each cycle. With this, hundreds of operating cycles are required before the nozzle repeats the same cleaning path. This allows for a more complete cleaning coverage and significantly reduces tube damage due to erosion.

We recommend installing the PHM device wherever high-performance sootblower nozzles are used, or in any application to improve blower coverage and minimize the potential erosive effects of sootblower cleaning.

Benefits:

• Improves cleaning
• Reduces tube erosion; in many cases eliminating the need for tube shields
• Prolongs lance tube life:
- Combats lance tube sagging
- Reduces lance inside diameter localized corrosion
- Prevents lance outside diameter build-up
- Distributes lance roller-wear over full lance surface

Features:

• Multi-indexing
• Field upgrade/retrofit
• Precise indexing
• Applicable with oscillator cleaning
• Designed for both two-roller and four-roller carriages
• Bolt-in assembly

 

Effectiveness of the Progressive Helix Mechanism device:

The sketches below illustrate the effectiveness of the PHM in providing a precisely-indexed nozzle-cleaning path across the face of a boiler tube bank. Although each lance tube is fitted with two or more nozzles, the path followed by only a single nozzle is shown after 1, 5 and 20 cycles.

The cleaning paths are spread evenly across the cleaning surface with the precise-indexing provided by this geared mechanism.

The lance translates forward without rotation, exactly one gear tooth, each time the sootblower starts a cycle. This even distribution of the indexed-cleaning paths occurs right from the start of, and throughout hundreds of cycles that occur before the nozzle paths repeat themselves exactly.

Note: The cleaning path of the second nozzle (not shown) bisects the helical path of the nozzle shown for each cycle traced on these figures.

1 Complete Cycle

PHM - 1 complete cycle path
Trace path after one complete sootblower cycle; inward and return path represented. (only one of two nozzles with indexing hub shown for clarity)

5 Complete Cycles

PHM - 5 complete cycles path
Trace path of a single nozzle after five (5) complete cycles with PHM

20 Complete Cycles

PHM - 20 complete cycle path
Trace path of a single nozzle after 20 complete cycles with PHM