Boilers

Question 1

How to change a boiler over from MDO to HFO?

Question 2

What is water hammer?

Answer 2

Water hammer conmes in to forms. When steam is introduced into a pipe it travels at high speeds, if there is a build up of condensate, the steam will draw this fluid forward creating ripples. The condensate will form into a slug of fast moving water, when this slug meets a bend or valve it will impact against the surface causing a loud shock and mechanical damage.
The second type is when the steam comes into contact with cold condensate and loses heat. This causes the steam to instantly condense and due to the specific volume of steam being aprroximately 1700x that of water, it creates a small vacuum which draws condensate in at a rapid rate. This condensate then strikes the surface of the pipe with a large amount of energy.

Question 3

How can water hammer by avoided?

Answer 3

Steam lines should use steam traps to remove condensate but keep steam in the system, this will reduce the amount of condensate. When de-isolating a steam line, it is important to drain the condensate from the line and then with the drain open, crack open the steam valve. This will introduce small amounts of steam into the line to prevent thermal shock. Then once the line is open and the small amounts of steam are coming from the drain valve, close the drain valve and slowly open the steam.

Question 4

Boiler Regulations?

Answer 4

Two safety valves
Two Means of monitoring water level, one being gauge glass
Two feed water methods 2 différent lines and pumps
Alarm with flame failure, air supply and fuel pressure
Supervision and control of feed water quality

two independent boiler feed systems

Question 5

What boiler trips are there?

Answer 5

Low low water level
High high water level
Low fuel pressure
High steam pressure
Flame Failure
Low feed water pressure
Low combustion air pressure

Question 6

What boiler water tests do you carry out onboard?

Answer 6

Chloride test - to check if there is a presence of salt water
pH test - should be alkaline 9.5-11
Hydrazine test - Test for dissolved oxygen
P Alkalinity - to test for alkalinity reserve due to carbonates and hydroxides
Conductivity - Dissolved solids
Phosphates - reacts with scale forming salts and to form a non adherent sludge

Question 7

How is the low low level trip tested on a boiler?

Answer 7

Isolate the level sensor from the boiler and drain the sensor.

Question 8

How is the high high level tested on a boiler?

Answer 8

Isolate the steam valve on the level sensor and wait for the water level to rise in the

Question 9

How to test flame failure on a boiler?

Answer 9

Fire boiler and cover flame eye

Question 10

How to test high pressure on the boiler?

Answer 10

With the boiler running, Isolate the pressure sensor and use a hand pump to increase the pressure until the boiler trips

Question 11

What is Caustic cracking?

Answer 11

Caustic cracking or embrittlement occurs due to an excess of NaOH. The NaOH in the water enters microscopic cracks in the metal and the water then evaporates and the NaOH reacts with the steel. This reaction causes the metal to become brittle leading to failure under operating stress.

Question 12

Boiler survey

Answer 12

*Internal inspection

*Safety valves:
- opening with easing gear
-Accumulation test pressurise water side until they lift

*Reviewing of : -Feed water records
-Maintenance records

*Valve overhalls and mountings

*Boiler trip tests