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Boiler Water Testing, Treatment & Boiler Reliability

MEO Class 4
UK EOOW
MEO Class 2
Chief Mate

times asked: 27; times asked
questions: 10; questions
last asked: 2026; last asked

The slides, written out

AI-drawn illustration. Simplified to explain the idea, not to scale.

Slide 1 · AN OVERVIEW

AN OVERVIEW OF BOILER WATER MANAGEMENT Why Water Chemistry Determines Boiler Reliability WATER CHEMISTRY PROTECTION & CONTROL EFFICIENCY & RELIABILITY Poor water quality is the leading cause of boiler failures.

Slide 2 · WHY BOILER WATER

WHY BOILER WATER MUST BE CONTROLLED Proper water chemistry prevents damage, improves efficiency and extends boiler life. PREVENTS SCALE FORMATION Hardness salts (Ca & Mg) form scale when heated Scale acts as an insulating layer Causes overheating, metal distortion & tube failures Leads to higher fuel consumption PREVENTS CORROSION Stops oxygen pitting Prevents acidic corrosion Avoids caustic attack and embrittlement Protects boiler metal from chemical attack PREVENTS CARRYOVER & PRIMING Reduces foaming and carryover Ensures dry steam quality Prevents scale & salt deposits in steam lines and turbines Avoids water hammer and line damage ENSURES EFFICIENT OPERATION & BOILER LIFE Better heat transfer Lower maintenance & downtime Fewer tube failures & repairs Longer boiler life Smooth surveys & inspections Scale conducts heat nearly 100 TIMES WORSE than steel. SCALE STEEL

Slide 3 · WHAT HAPPENS WHEN

WHAT HAPPENS WHEN WATER CHEMISTRY FAILS? Poorly maintained boiler water causes scale, corrosion, deposits and failures. SCALE DEPOSITS Hard scale insulates heating surfaces Overheating of tubes and metal Tube bulging, distortion and rupture Higher fuel consumption and reduced efficiency Scale is ~100 times worse conductor of heat than steel. OXYGEN PITTING Dissolved oxygen attacks boiler metal Deep pits form on tubes and drum Pits act as stress raisers Cracks develop and cause leakage or failure Often starts small, but can lead to catastrophic failure. CAUSTIC ATTACK Excess hydroxide concentration leads to caustic embrittlement Intergranular cracking in stressed areas Weakens metal structure silently May cause sudden structural failure One of the most dangerous failures – often undetectable until it's too late. OIL CONTAMINATION Oil coats heating surfaces Carbon deposits form under high temperature Reduces heat transfer efficiency Causes localized overheating and rapid tube failure Oil contamination can cause tube failure faster than scale. Poor water quality = More failures, more downtime, higher costs and shorter boiler life.

Slide 4 · ROUTINE BOILER

ROUTINE BOILER WATER TESTING Regular testing ensures safe, efficient and reliable boiler operation. 4 ESSENTIAL BOILER WATER TESTS 01 ALKALINITY TEST (PHENOLPHTHALEIN ALKALINITY) Purpose Maintains proper corrosion protection and pH control. Ensures the right balance of hydroxide and carbonate alkalinity. Method (Simplified) Sample is titrated with standard acid using phenolphthalein indicator until the pink colour just disappears. Typical Range 100 – 300 ppm as CaCO3 (P-Alkalinity) 02 CHLORIDE TEST Purpose Detects seawater contamination from condenser leaks, gland leaks or other sources. Method (Simplified) Sample is acidified and titrated with silver nitrate using potassium chromate indicator. Endpoint is the first permanent reddish-brown colour. Action / Typical Limit Maintain within limits specified by boiler manufacturer and treatment supplier. Monitor trends closely. 03 SULPHITE TEST (RESIDUAL OXYGEN SCAVENGER) Purpose Verifies that sufficient oxygen scavenger (sodium sulphite) is present to protect boiler metal from oxygen corrosion. Method (Simplified) Sample is acidified and titrated with potassium iodide–iodate solution using starch indicator. Endpoint is the appearance of a blue colour. Typical Range 30 – 60 ppm as Na2SO3 (residual sulphite) 04 PHOSPHATE TEST (RESERVE) Purpose Controls hardness salts and prevents scale formation. Maintains a reserve for continuous protection. Method (Simplified) Filtered sample is mixed with vanadomolybdate reagent. Yellow colour develops and is compared with a standard colour disc. Typical Range 20 – 50 ppm as PO4 (phosphate reserve) Consistent testing. Correct treatment. Zero surprises. The key to long boiler life and safe operations.

In exams

Asked 27 times across 10 different questions, most recently in 2026. Asked most in MEO Class 4 (8), UK EOOW (8), MEO Class 2 (6), Chief Mate (5).

Drafted by SailR from our daily lessons. AI-drawn illustration. Simplified to explain the idea, not to scale. Last updated 19 Oct 2026.

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