BOILER SURVEY

September 30, 2019

9841

Twice in 5 years

Open the boiler vent valve when pressure inside is just above the atm pressure to ensure that there is no vacuum in the boiler
Allow the boiler to cool and then drain
Open all manhole, handhole and mudhole doors and allow boiler to ventilate.
Isolate all feed and steam stop valves as well as the burner control
Ensure another person is standing near the boiler when other person is inside
Plug the blow down pipe to avoid dirt and sludge blocking it.
Post a note to remember that the blowdown is plugged
Thoroughly clean the boiler internally remove any scale and clean the tubes internally and externally prior to inspection.
Gloves, a dust mask and goggles should be worn while working inside the boiler

External inspection:

Inspect boiler externally for any signs of leakage.
Examine the condition of insulating material and replace if necessary
If asbestos then it should be wetted before handling it.
Use gloves and dust mask to avoid inhaling of asbestos
Inspect all mounting flanges and studs for securing and any signs of corrosion, Remove lagging if necessary.
Wastage can occur where there is a leakage of steam or water.
Check for condition of boiler support.

Internal inspection:

Initial condition- colour of surface, scale, sludge
O2 pitting on steam space surface & on water line
Thinning & necking of tube at tube plate
Inspect for signs of cracking, pitting or other corrosion particularly in way of Openings in the shell, around welded connections.
Also check for scale deposits and oil and distortion of heat transfer spaces.
Check for signs of blockage in the way of blowdown pipe and scum and feed distribution pipe

Tubes inspection:
Tubes should be checked for signs of distortion which may be caused by overheating
Smoke tubes must be brushed through
Water tubes to be washed externally with high pressure washer to remove combustion slag.
Joint faces of manhole, handhole, and mudhole doors should be checked to ensure there sealing faces are in good condition
Check the joint faces are in good condition
Ensure clearance is 1.5mm all around
The nut to be re-tightened when boiler is at working pressure.

Spalling
Slagging
Shrinkage cracking
Pitting of tubes due to low temp corrosion.
The sodium and vanadium compounds in the fuel can result in loss of refractory In way of flame
Oil contamination of furnace floor and cracks due to leaky burners
Leakage around boiler tubes at the plate entry due to fatigue corrosion.
Inspect combustion chamber and uptake for any sign of combustion deposits
Check all valves and gauges are not leaking and all cocks are clearly marked to show when open or shut

Overhaul and inspect safety valve

Ensure there are no ridges in the valve lid and seat
Check the valve body drain is clear
Check the easing gear is free to operate.
Check and inspect all wires and pulleys.
Check all the parts are free to move in the valve body
Check the valve spindle for corrosion, ring test the spindle and check for trueness
Check the spring for corrosion and free length
Check valve chest for corrosion and wastage. Also check the condition of flange face
Ensure pipe clamps are secure so that the drain pipe is not exerting and force on the valve body.
Check and measure and note down all the clearances

Check the operation of boiler controls and alarms:

Low fuel temperature.
Low fuel pressure-There may be two settings, ‘alarm’ and ‘shutdown’.
Low air pressure
Atomising steam pressure low.
High steam pressure.
Low steam pressure.
Low water level – Close the feed valve and let the level fall. Check the
alarm sounds.
Extra low water – Reduce the feed water level further until the second
low level alarm activates and the burner locks out
High water – Manually operate the feed valve until the alarm sounds.
Flame failure During the firing sequence remove and cover the
photocell. Test the alarm to ensure it sounds.

Maintenance of steam system also involves checking the valve glands These should be nipped up as leakage will cause deposits around gland as well as soaking the lagging
Glands should never be packed when the system is under pressure. If during pressure testing any valve are removed then it should be blanked off
Feed tanks are Hotwells will require draining and cleaning. Usually during dry dock, Filter towelling should be cleaned and inspected regularly and should be renewed if damaged

Types of corrosion in boiler

Safety valve setting

Open without simmering to full lift at definite set pressure
Remain open until the pressure drops to definite amount called blowdown pressure
Close tightly without chattering
Remain tight when closed.