Phosphate Dozing System Problems

Root Cause Analysis (RCA) related to the phosphate dozing system problems.

Article Type:Root Cause Analysis (RCA)
Equipment Type:Miscellaneous Rotating Machine Problems
Author:S. Raghava Chari

Note: This root cause analysis (RCA) is from real-time scenarios that happened in industries during the tenure of two or three decades ago. These articles will help you to improve your troubleshooting skills and knowledge.

Phosphate Dozing

Small quantities of phosphate solution injection called ‘Phosphate Dozing’ into boiler drums (below figure) precipitate the BFW residual salts.

Continuous or periodic small quantities drum water blow down rids of these precipitates and maintains BFW purity.

Phosphate Dozing System


The plant superintendent identified no phosphate dozing to the 100‑bars boiler drum from phosphate feed drum no make ups.

He requested the dozing plunger pump checkup. The field crew unable to solve the problem approached the author.

 Problem Root Cause Identified

The author found the pump discharge pressure 120 against the normal 110 bars.

Hence, he guessed most likely the entire the 150 Nos. 1.5 mm dia holes drilled on the 1” drum length dozing pipe plugged up.

Author Proposed Solution

The author suggested readying a new dispersing pipe with 38 Nos. never choke 3 mm dia holes of near original total flow area.

His pointing out that the drum turbulence would mix the dozed phosphate well won approval

Problem Solved

Crew did find the distributor holes plugged up during the TA. They cut out the old distributor, welded the readied distributor to the stub, and saved TA activity time.

Boiler Phosphate dozing became fit and forget system

Author: S. Raghava Chari

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