Guidelines
for
the
construction and operation
of marine steam plants.
With 20 psi / 140 kPa on the steam gauge, prove
the gauge glasses clear and then ease the safety
valve to ensure air is removed and the valve is
mechanically free to function.
INTRODUCTION
Constant attention to the water gauge and
handing???, to blow through the cocks to
confirm water levels, will avoid misleading
indication.
The following information is offered to ensure
that you enjoy trouble free steaming and to
present your pride and joy in public or for formal
inspection, with confidence.
Your boiler is a pressure vessel, which imposes a
statutory obligation on the OWNER or
MANAGER, the responsibility of compliance
with all statutary regulations currently in force in
your State.
There is a duty of care to comply with
Occupational Health and Welfare Regulations
when operating in the public domain.
To design, build, operate or repair a boiler
outside these parameters will not only alienate
you from a dedicated world of enthusiasts and
jeopardize their hard won status, but, may have
your friends buying you flowers.
Compliance, on the other hand, is a ticket to a
unique community of priceless advice and
enjoyment.
The annual inspection fee is good value for your
peace of mind and cheaper than a dental check.
(don't tell him that!)
GETTING UP STEAM
Protecting your boiler from thermal stress by
uneven or sudden heating or cooling will
guarantee its long and trouble free service.
For small boilers without circulating pumps, the
gradual raising of temperature and pressure is
important. (30 minutes per foot of boiler
diameter)
First fill the boiler to the manufacturer's
recommended level.
Secondly, prove the accuracy of the water gauge
glass by opening the gauge glass lower cock and
watching the water level return.
To heat the lower parts of the boiler (particularly
Scotch type) blow-down to the working water
level at about 8-10 psi.
Do not force the fire with blast pipe while
raising steam.
Marking the working water level and also the
furnace crown level on the boiler casing near the
glass is a good idea.
Be aware of the boat trim, for bad indication.
Low Water Alert
When the water level fails to give any reading on
the gauge glass, you have not kept tabs on
proceedings. Shut off steam to engine, blower
and auxiliaries. Open the firebox door. Remove
the fire.
Allow the boiler to cool.
Present the boiler for inspection.
In an extreme case where the furnace crown is
exposed, cool the fire rapidly.
Open the fire door for cooling air and close the
damper.
Do not release the safety valve or run the engine
as this can impose added stress to a possibly red
hot crown. Allow the boiler to cool naturally,
before inspection.
DO NOT ADD FEEDWATER TO A HOT DRY
BOILER
Feed water can be 200 F difference. Preheating
minimizes thermal shock and hand pumping cold
water into a boiler will induce stresses and kill
performance in particular.
Be aware that ball valves will not lift if feed
water gets beyond 601 C.
Maintaining Furnace
To get the best performance from your boiler and
fuel, do not have too deep a bed of coal that
airflow is choked, or too thin, that cool air
bypasses the fuel through grate bars.
Keep the fire door closed. A few holes through
the door, behind a heat shield will provide
secondary air to aid complete combustion.
Air, preheated prior to introduction below grate
will also enhance thermal efficiency.
or exposed to the bilge water causing rapid
corrosion. The shell should be kept well painted.
EXERNAL CORROSION Cause and Cure
Attention to Shell and Ash-pan
The greatest enemy of steam boilers is pitting or
corrosion, pitting being a localized form of the
latter. Boilers set in brickwork, insulated with
lagging and with refractory cement are especially
liable to external corrosion due to dampness
penetrating these materials in places where it is
difficult to find.
The combination of condensation, leaks, rain or
just damp air, combining with ash rich in sulphur
and other chemicals is a bad recipe.
Vertical Boilers
The vertical boiler is prone to abuse, due to its
installation in all kinds of cramped situations where reasonable access is difficult.
Ash must not be allowed to accumulate round
the inside of the ash pan and under the firebox.
Keep tops of cross-tubes, or top of the tube plate,
free from soot and moisture, especially when
boiler is idle.
Periodically remove the bars, clean all the scale
off the plates below the fire-bar bearers and give
a coat of fireproof or graphite paint to the whole
interior of the firebox and around the bottom of
the shell on the outside of the boiler.
It is pointless to paint over any corrosion present.
It must be chipped off with a scaling hammer.
Carefully check for any reduction of the plate
thickness and if uncertain, seek advice from a
boiler inspector.
DO NOT attempt welding or repairs. (AS 378801 applies)
Leakage
Where white furry deposit is seen around mudhole doors or fittings, leakage and therefore
corrosion can take place. The plate surrounding
these points should be kept well painted, holding
corrosion at bay until proper remedial action can
occur.
All boilers, particularly verticals, should have a
Cowl (Chinaman's Hat) to cover the funnel to
prevent rain getting into the boiler or smoke-box.
Expansion Mounting and Plumbing
Protecting Uptake Tube
With cross tube boilers, the length of the uptake
tube above the water level can overheat. If
protected with a cast iron sleeve, it should be
withdrawn to check if it has burned away.
Vertical multi-tube boilers can suffer the same
problem although the smaller tubes are less
prone to overheating. Varying the water level
will minimize localized damage.
Do not over-fire with less than 3/4 gauge glass.
For those boilers raised on a brick ring under the
foundation flange, corrosion of the firebox and
the shell, by damp ash, will be rapid.
Direct Tube-Scotch Boiler
In marine boilers, like the Scotch type, the
bottom of the shell dips under the stokehold floor
Check holding down bolts and brackets for
corrosion, they usually reside in the hot and
moist environment of the bilge and may look in
good condition, but remember, the damage is
generally within joints, where you can't see it.
Also inspect blow-off pipes and keel condensers.
Some installations are rigidly set cement or
through hull fittings where corrosion is invisible
or even worse the inability to expand has
fractured the fittings.
Boiler fittings, steam pipes and inspection
openings in the shell, should be checked for
leaks or ash accumulation where rusting can
initiate.
Channel Corrosion
Condensate laying in steam pipes, absorbs gases
from the atmosphere, to form acidic solutions.
An example is the keel condenser. By mounting
the outlet below the hot-well surface, the
concentrated solution will not occur.
To Sum Up
(1) External corrosion is the chief enemy to the
life of boilers, more are scrapped due to this
effect than any other.
(2) Repairs by welding must be performed by a
qualified pressure vessel welder and only if
approved by a certified engineering boiler
inspector.
(AS 3788-01 applies) (is this
the correct AS?)
INTERNAL CORROSION
minimized by preheating the feed or neutralizing
the acids they form.
Oil in feed water
Allowing oil into a boiler, even in minute
quantities, is not recommended and must be
avoided.
Oil combines with other suspended matter,
coating heating surfaces, and at best, causes
priming, and at worst, its long term effects of
corrosion and insulation of heated surfaces can
lead to boiler failure.
It can be prevented with absorption filters in the
hotwell but is to be avoided at all cost. The
Naval limit was 1 part per million.
Cleaning
Incrustation
The incrustation or ‘furring up' by hard water
impurities, is one of the most common problems.
In large plants, it is usually processed in water
treatment plants before entering the boiler.
Using soft water, a boiler in regular service
should be opened for cleaning every 500 hours.
Boilers of traction or ploughing engines and
steam boats, which have to pick up water where
available, suffer from internal corrosion and
therefore need close attention to feed water
chemical treatment.
Using hard water, a boiler should be opened for
cleaning every 100 hours.
The loss is in evaporating efficiency, due to scale
build up, (equally soot deposit on heating
surfaces) and therefore, use of fuel, is shown on
the following table:Scale thickness
Loss of Fuel
The water should be blown down an inch or so,
of the glass, daily to remove sludge.
The water should be blown down daily when the
pressure is low to remove sludge.
Blowing down is usually an intermittent process,
but can be continuous, usually through a scum
pan just below the operating level of the boiler
and the flow regulated via a metering valve. The
heat is recovered to the boiler by a coil through
the feed tank.
1/16”
(1.5mm)
1/8”
(3mm)
*18%
1/4”
(6mm)
38%
Small boilers at low pressures
½”
(12mm)
60%
The object of internal treatment is to convert
scale forming impurities into a dispersed sludge,
which can be removed by blowing down.
9%
*TIME FOR SCALE REMOVAL
Secondly, and far more serious, is the danger due
to poor conduction, of overheating of plates and
tubes with their consequent collapse.
The lower tubes in water tube boilers are
particularly prone.
Scale can coat fusible plugs to a point where, if
the tin melts out, the scale can still bridge and
block the passage of water.
Air in feed water
Dissolved oxygen and other gases in the feed
water are a cause of internal corrosion and can be
BOILER WATER TREATMENT
The chief compound is calcium sulphate,
because of its inverted solubility, it can be
converted to calcium carbonates or phosphates,
by adding sodium carbonate or sodium
phosphate.
(below 150-250 psi --- 1.05-1.75Mpa.)
Alkalinity
can
controlled with:
be
Mono-sodium
phosphate .........
Acid
corrosive to condensers, gaskets, 'O' rings and
fittings and may lead to embrittlement of steel.
Di-sodium
..............
phosphate
Neutral
The principal danger of internal treatment with
chemicals is over or under dosing.
Tri-sodium
............
phosphate
Alkaline
Unless you have an accurate water analysis, they
can become harmful.
Testing
Analysis is the first step to identify which
treatment is applicable. This is an exacting
process and impractical for small boilers,
however, there are some simple tests, which can
give a reasonable guide to minimize ill effects.
All tests must be performed in a clean container,
as contamination with salt or oil will give
incorrect results.
The rule is to BLOWDOWN REGULARLY, but
be aware that you lose some of your compounds.
WATER TREATMENT PROCESSES
A. Fresh water from natural earth catchment:
1 .Filter to crystal clear condition (to remove
undissolved solids)
2.
Pass
through
water
(to remove temporary hardness)
Hardness
3.
Keep a soap solution of Castile soap in distilled
water for test purposes.
Heat
water
to
(to remove dissolved gasses)
4.
A few drops of HARD WATER in a small
quantity of test solution will go cloudy, and not
hold a lather for 5 minutes.
Add
chemical
treatment.
and
precipitate permanent hardness, removed by
blowdown.
B Rainwater:
Alternatively, a few drops of the soap dissolved
in alcohol, will cloud HARD WATER.
Acidity
Litmus papers, should be carried and used to test
a (clean) sample of boiler water drawn from the
gauge glass or hot-well. Maintain PH 10.5 – 11
(look at Tandex data)
A slightly alkaline water will neutralise acidic
corrosion from dissolved oxygen and carbon or
sulphur dioxide.
Dissolved Solids
Dissolved solids should be below 1500 ppm,
ideally by chemical water treatment and
blowdown.
softener.
950
C.
1. Use crystal clear water only
2. Add Tannin to give ‘weak tea’ colour.
3. For small boilers 2-4 seconds blowdown every
hour.
C. Salt water:
1. Distil the water in an evaporator.
2. Add alkali to neutralize all acidity.
3.
Treat
as
received.
N.B. High pressure feed above 450 psi (3.1
Mpa) must not have, even moderately
accepted levels of total dissolved solids, as the
high speed of water leads to erosion of the
tubes, in watertube boilers.
Suspended Solids
By allowing a water sample to stand overnight
the precipitation of solids can be gauged.
Tannins are a safe option, in that they are
alkaline, they inhibit foaming by precipitating
suspended solids and inaccurate application will
do no harm.
Caustic Soda should be avoided for acidic
neutralising countermeasure as it can be
LAYING-UP A BOILER
It is often necessary to lay up a boiler for an
extended period and unless proper precautions
are taken, damage may be done both internally
and externally.
Drain Boiler
Draw the fire and blow the boiler right down
once the pressure has dropped to a few pounds.
The heat -will dry it out. Man hole and mud hole
doors are removed to allow circulation of air.
The efficient and safe working of a steam boiler
depends on the state of the controlling fittings
If all moisture- has not evaporated, a small fire
may be lit with a few sticks but beware of
overheating -the fusible plug.
Safety Valves
Leaving, Boiler Filled
The other method is to leave the boiler quite
filled with all openings closed, but water should.
be non-acidic and gases driven off by steaming
before closure.
A boiler preserved in this way is not
recommended for long term storage, say for
more than a month.
It must be free from frost, as freezing will
expand the water and destroy the boiler.
All exposed parts and smoke-box should be well
painted to prevent rusting.
The firebars should be taken out, the, tubes
swept and all ash removed.
Leave flue and fire doors open to prevent
condensation.
Drain the pressure gauge siphon or it may be
damaged if there is a risk of freezing.
THE CARE OF STEAM FITTINGS
Larger boilers normally have two safety valves.
Leakage of the valve seat may be caused by wear
or foreign matter on the seating face.
Should a valve fail to seat after blow-off, a quick
release or tap on the lever will often clear it.
Should this fail, the seat should be inspected for
scale and cleaned when the boiler is cold. A
damaged seat must be reground and bedded.
(AS 3788-01 applies)
Springs should be checked for corrosion or
softening.
Remember, the release pressure is only as
accurate as your pressure gauge.
STEAM FITTINGS
Water Gauges
Water Gauges should be given special care and
protection from cold air or water.
The consequences of a broken glass can be
serious. Check alignment of fittings and renew
packing, which can harden and weld to the glass.
The Klinger type with flat plate glass and ribbed
for better visualization is a safer option.
Type A for low pressure work
Type B for medium pressures, employs glands at
the handle ends.
SPRING LOADED
-POP' OR QUICK
LIFT
SAFETY
VALVE
The passages may become choked with scale,
which can be cleared by carefully passing a rod
or drill through the cock body and passage into
the boiler. The lower cock which is opened each
time the level is tested, gets far more use than
others and the effects of sediments will lead to
leakage which may go unnoticed down the waste
pipe.
If the plug is grooved, grinding in may not be
successful and replacement the best remedy.
All cocks should be checked periodically, as they
can "set" and cases have been known where
handles have sheared without the cocks being
closed.
Stop Valves
Valves should be checked for effective seals and
packing on spindles renewed periodically as
compaction over a long period can harden and
score the shaft.
GAUGE
Stopping leakage by undue force on the handle is
dangerous, causing further damage or even
fracturing the valve body.
As there is no flow through the siphon, it can
become choked with sediment and scale after
long working, and should be cleaned annually.
Worn seats can be resurfaced but replacement is
a good policy.
It must be refilled with water before replacing
the gauge, although the first steaming will
produce sufficient condensate.
A perfectly tight valve tested under hydraulic
pressure may leak under steam.
Check Valves
These are the hardest workers, against boiler
pressure in unison with the feed pump, they are
subject to shock and considerable wear.
The maximum lift must not exceed 1/4 of its
diameter.
If the boiler will not sustain pressure when
closed, then this item would be a good candidate
for attention.
Pressure Gauges
Only cold water must enter the gauge. If steam is
allowed to get into the curved tube the heat can
damage it with consequent reading inaccuracy.
Generally they require little attention other than
care to avoid water entry into the casing and a
periodic test against a gauge of known accuracy.
Cleaning the Siphon
Terry Lance’s suggestions
GENERAL MACHINERY

(not to intrude into companionways)
PIPING

(lagged to prevent burns)
BLOWDOWN (piping to drain away from crew)
MAIN ENGINES, AUXILLIARIES
(Rotating parts, hot oil etc)
PROPELLER SHAFTING (covered or guarded)
FIRST AID KIT (Burn treatment incl)
EMERGENCIES
Broken Gauge glass
Fire on Board
MOB
Emergency Procedures to be provided to crew
(verbal on boarding)
The Master is LAW at sea.
Peter Cowie’s suggestions






Boilers must have a gauge glass to
indicate the level of water in the
boiler… elaborate on position,
construction etc
Fittings exposed to full boiler pressure
must not be made with soft solder or
constructed from brass… elaborate
on reasons why
Gauge glasses should have devices
fitted that protect individuals from
injury should the gauge glass fail.
Boiler pressure gauges must be
protected by a pigtail.
At least two methods of boiler feed
must be provided
At least one safety valve must be
fitted with direct, unimpeded access
to the steam space and properly
vented in a way that its operation
does not direct steam at passengers.
The boiler and funnel and engine
should be adequately secured to
prevent movement in rough
conditions
A start-up, general operation,
emergency and shutdown checklist
should be developed for each boat
with the input of other members