Greetings! In this article I recommend that you familiarize yourself with the main safety devices of auxiliary boiler on a ship that inspectors like to check. It does not matter which inspector came to the ship (PSC, flag, annual surveyor, etc.), usually the checks are not much different.
.JPG "Boiler safety devices. A quick check for the surveyor")
Surveyors mainly look at how critical protections work (selectively), i.e. those protections that stop the boiler (shutdown protection). They are not very concerned with auxiliary signals (alarms). But it is necessary to be prepared for everything, i.e. for the fact that the inspector can check the auxiliary alarms of the boiler.
For example, the inspector can look at the boiler control panel and request to check any alarm that is visible to him on the panel.
.JPG "Miura boiler alarm panel")
"Make this light so that it glows red!"
We will consider boiler protections and the procedure for checking them using the Miura, Volcano, Aalborg (Alfa Laval) and Kangrim boilers as examples. In fact, the boiler models are not particularly important here, everything is pretty much the same everywhere. It is very important to be able to correctly demonstrate a particular protection (or alarm), without opening the manual.
Deficiency. During the PSC (port state control) boiler check, the crew hesitated and started looking at the instructions. As a result, the vessel received a remark (deficiency) that the engineers do not know how to check the boiler (not familiarized). It would seem that there is nothing special about looking at the manuals, but the inspector did not like it and slapped a deficiency. Everyone shrugs their shoulders, the company too, but take measures to ensure that this does not happen again!
What does it mean to demonstrate boiler safety devices correctly?
The concept of "correctly" should include two main points. First - when checking, do not open the manuals, second - do not open the boiler control panel, pull out the relay or short-circuit the contacts with a screwdriver :) All this can be done only if the inspector is not standing nearby, but it is better not to do this, otherwise there will be deficiency.
.JPG "Miura boiler control panel")
.JPG "Miura boiler control panel")
In this article I will consider some cases when it was necessary to do the above actions, but it was not in the presence of an inspector and it was necessary, otherwise deficiency :)
Boiler protections
So, first, let's consider the protections that inspectors most often check. And only after that we will deal with the secondary boiler alarms.
.JPG "General view of the Miura boiler")
.JPG "Pressure switches, transmitters and controllers of the Miura boiler")
In the table, which is published below, you can find all the protections that the Miura boiler has. In the Burner Trip column you can see which protections (marked with a circle) stop the boiler (make a shutdown).
1. Miss fire and Flame failure - flame failure (absence of flame). Occurs if the photocell (Flame Eye, or "Eye") does not see the flame in the boiler firebox. That is, ignition does not occur or it fails. It is very easy to demonstrate Flame failure, just start the boiler, take the photocell out of its socket and cover it with your palm. In this case, the boiler should stop (shutdown) and issue a "Flame failure" alarm.
.JPG "Flame Eye, or \"Eye\" of the boiler")
There are also accompanying alarms and shutdowns "Abnormal Fire" and "Flame Eye Abnormal". Abnormal Fire is a protection that characterizes the flame quality more, i.e. if the the flame will be irregular, ragged, then this alarm will occur. This protection is very well described in the article "Abnormal Fire. The boiler does not start. Troubleshooting".
Flame Eye Abnormal indicates some problem with the "eye", for example, there was a break in its circuit or the relay failed.
On the Miura GK-1628-800/700 boiler, there is a special button "Abnormal Fire Alarm Test" in the boiler control panel. When you press it, the photocell is closed by a special damper, the boiler slows down and the Flame failure alarm comes out, you can also simulate Abnormal Fire by briefly pressing the button. This is the case when you can open the panel to simulate protection.
.jpg "AMS Terasaki issues alarms for Aalborg boiler")
But, as a rule, it is better to demonstrate the protection directly to the inspector on the photocell. Otherwise, he will think that we installed this button ourselves, we will have to get the diagram and show what is what. Therefore, the simpler the better. By the way, there is no such button in the control panel on the Miura GK-2230-1400 boiler.
.JPG "Abnormal Fire Alarm Test")
2. Low water level and Low low water level - low level and the lowest water level in the boiler. Checked on the steam-water column. To do this, drain the water from the measuring column. Close the valves on the column, open the drain and drain the water.
.jpg "Low low water level on the Aalborg boiler (Alfa Laval)")
In this case, the feed pumps must be in the OFF position. The electrodes inside the column will change their resistance and the Low water level alarm will appear, and then the Low low water level alarm will stop the boiler.
In addition to electrodes, floats on reed switches can also be used. For example, a special glass with a float is installed on the Kangrim boiler, which stops the boiler according to the "Low low water level" alarm. And there are boilers where only reed switches are used instead of electrodes. But the principle of checking is the same everywhere, it is necessary to stop the feed pumps and drain the water from the column (it does not matter what level sensors are used, floats or electrodes).
.JPG "Column with electrodes")
.JPG "Column with electrodes")
High water level - high water level in the boiler. As a rule, inspectors are not interested in this alarm, because it does not shutdown the boiler. To check it, it is necessary to re-feed the boiler by starting the feed pumps in manual mode. In automatic mode, these pumps operate either by water levels in the columns (electrodes or reed switches), or by a differential pressure transmitter (Differential Pressure Transmitter).
In China, an inspector wanted to be shown the High water level on the boiler. He was in the ECR and waited for the alarm to appear on the AMS alarm panel. After re-feeding the boiler and reaching the required level on the column, the alarm did not appear (taking into account the time delay). The electrician had to remove the relay from the control circuit so that the protection would work. Of course, the inspector did not see this, but the boiler passed the test. As a result, it was discovered that the electrodes on the column were very dirty, which is why the alarm did not appear.
Important! Different boiler models have different control circuits. Somewhere you need to pull out the relay, somewhere activate the contact, somewhere disconnect the wire, and somewhere put a jumper. Everything is individual and there is no one magical way to simulate an alarm that suits all boilers. Read the electrical circuits!
And attention! I do not recommend doing all this, I am simply describing the test options. You need to check all protections in fact and not use any bypass methods!
Video of checking Low low water level and High water level on Aalborg boiler (Alfa Laval) is available on ETO ENGINEER TikTok channel.
3. Safety Steam valves - steam safety valves. Should work if steam pressure in the boiler exceeds 6.5 - 6.7 kg (Miura). To check these valves, it is necessary to either activate them manually using special levers, or fill the steam pressure in the boiler to the set limit.
.JPG "Safety Steam valves")
.JPG "Safety Steam valves")
Here you need to agree with the inspector how exactly he wants to check these valves (using manual activation or high steam pressure in the boiler). To build up the pressure to the upper limits, it is necessary to close the steam flow to consumers and start the boiler in manual mode. If a pressure switch is used that stops the boiler by steam pressure in manual mode, then it must be bypassed.
Usually, it is enough for inspectors to activate the valves in manual mode, but there are exceptions.
By the way, there is usually no alarm for high steam pressure in the boiler, but there is an alarm (aka boiler shutdown) Steam Pressure Abnormal for a high temperature of 190°C. There is also an alarm for Low Steam Pressure in the boiler, which is usually set at 4 kg. But these alarms are not of particular interest to inspectors.
The above three protections are the main alarms (shutdowns) of the boiler that inspectors like to check. With rare exceptions, they check something else. In my practice, there were different checks in addition to the main protections, below we will consider some of them.
Boiler Exhaust Gas Temperature High - protection for a high temperature of 450°C in the boiler exhaust system. Usually, it is enough to turn the thermostat below the current temperature value, an alarm and a boiler shutdown occur. I have yet to come across an inspector who forces you to do this with a temperature calibrator. Although you need to be prepared for anything.
.JPG "Thermostat Exhaust Gas Temperature High")
Fuel Oil Pressure Low - low fuel pressure, set at about 14 kg (Miura). This protection stops the boiler due to low fuel pressure, a pressure switch is used. By the way, the article "Pressure switch. The fuel pressure switch on the boiler has failed" describes the problem with this pressure switch and what it can ultimately lead to.
.JPG "Low fuel pressure switch")
To check this protection, it is enough to close the fuel valve on the pressure switch (on the heater) and drain the fuel from the heater into the drain.
I will not repeat myself everywhere about calibrators. Usually the check is simple, it is enough to demonstrate that the protection works and it does not matter at what setting of the thermostat or pressure switch. But if this does not suit the inspector, then it is necessary to take a calibrator and demonstrate on it.
In the video above, you can see how thermostats and pressure switches are checked on a calibrator. In our case, you need to do the same thing only on site, without removing the sensor. For example, on a fuel pressure switch, you need to remove the fuel pipe, connect the press pliers (calibrator) and fill (bleed) the pressure to the desired mark.
By the way, usually on such pressure switches (thermostats) there is a special TEST contact group for checking the circuit (open or close the contact). This is in case the sensor doesn't work, assuming the surveyor can't see.
Fuel Oil Temperature High and Fuel Oil Temperature Low - high and low fuel temperature, these alarms usually occur when the boiler is switched from DO to HFO fuel or vice versa. Surveyors do not check such alarms.
You can check them on the temperature controller, by lowering or raising the temperature setpoint, or on the thermostats, if they are installed. Fuel Oil Temperature Low protection should stop the boiler.
.JPG "Fuel Heater Temperature Controllers")
Fan Abnormal Stop - another uninteresting protection for fan malfunction. You can check it using the thermal relay (press the TEST button) of the fan electric motor. This protection stops the boiler. This is the case when you need to open the control panel and press the TEST button.
.JPG "Fan thermal relay (TEST button)")
That's probably all. I recommend that you study the electrical diagrams and manuals of the boiler upon arrival on the vessel to know what protections it has, and also periodically check everything according to the checklist and pass any checks without deficiencies!
What did I not tell you about in the article?
It will not be possible to tell everything about all the boilers in one article, no matter how hard I try. I will still forget something, and somewhere I have not encountered something. Nevertheless, I believe that this article provides a good basis for what exactly you need to pay attention to when checking the boiler protections.
Boiler emergency stop. Each boiler has emergency stop buttons. They are usually located directly on the control panel, as well as in the ECR (engine control room) of the vessel's engine room.
Limit switches on nozzles (burners). Aalborg or Kangrim boilers (Weishaupt Monarch oil burner) have end switches or inductive sensors that stop the boiler if an attempt is made to open a nozzle (burner) during boiler operation (operator protection). By the way, the same protection can be found on incinerators (on the firebox doors), this will be described in a separate article.
.jpg "Aalborg boiler (Alfa Laval)")
Salinity sensors and cascade tanks float switches. Also on Miura and Aalborg boilers there are cascade tank salinity sensors, which can shutdown the boiler. And the cascade tank float switches of the Aalborg boiler are involved in the boiler feed circuit.
.jpg "Reed switches on the cascade tank")
Standby feed and fuel pumps. Boilers should also have standby modes for feed water and fuel pumps.
As you can see, the boiler has many protections and alarms, since the auxiliary boiler on a ship is a very responsible and dangerous mechanism that requires increased attention. All protections must function well so that working with the boiler is as safe as possible.
What other boiler protections do you know? If you have experience checking boiler protections or have had any interesting cases during inspections, then share them in the comments to this article!
By the way, if you need manuals for the boilers discussed in this article (or for others, for example, Saacke, DAEWOO MITSUBISHI), then all this can be found in our closed telegram channel Marine Engineering Manuals.
Thank you for your attention! I hope this article was useful for you!
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