Blog 137 - When Bellows Rupture and Gas Leaks

Engine Room and Smoke:

Mitsubishi V Type 4 Stroke Engine

Once again, I am repeating an incident from one of my many  “Marine Musings” blog. This was published in Institute of Marine Engineers Newsletter iMelange’ in May 2024.

It goes without saying that this article is meant more for the practising Junior Marine Engineer than those with experience.

I had just joined the ship at Sheerness, UK. 

My first round of the Engine Room was rather disappointing, as I expected more from the Second Engineer, who was my protege’. The Engine Room bulkheads and all machinery, including the Main Engine, were greyish black, giving a rather dismal look to the Engine Room. Although all tube lights were ‘on’, the lighting was poor. It was as if I had entered a dungeon.

Before departure, the aft crane luffing wire parted and the jib came crashing down.

At departure Sheerness, after the Main Engine was started, I saw all the Engine Room staff wearing Ear Protectors - perfectly understandable - and also masks to cover the nose - ????. It sounded an 'alert' within me.

I was told that there would be too much of exhaust gas in the Engine Room with the Main Engine running, even though one of the four Engine Room Blowers was on ‘Exhaust’ mode. I was also told that exhaust gas was leaking from the exhaust pipe banks into which each cylinder was exhausting into.

I said “Show me”.

After we were in the open sea, with the Main Engine running at full, we opened four of the covers (like on the silver painted casing in the image 1 below) to see what was happening. It was hot and we were like cats on a hot tin roof. But unless we pinpoint the location of the leakage of exhaust gas, which can be done only with the Main Engine running, we would not be able to move forward in eliminating the problem.

There were 2 sets of exhaust pipes, leading to 2 turbochargers. Being a V type engine, the layman would think that one bank exhausts into one pipe and the other bank into the second exhaust pipe. But that is not so. Exhausting into the ‘A’ exhaust pipe or ‘B’ exhaust pipe all depended on the firing order and the timing. The two main banks of exhaust pipes are, therefore, side by side but on different planes in order to facilitate maintenance. There were probably 18 or 19 expansion bellows on the exhaust pipes' arrangement, maybe more - I could be wrong.

The leaks were from several ruptured expansion bellows, from which there was steady leakage / flow of exhaust gas. We marked all the ruptured bellows for renewal when possible. 2 of the units’ individual expansion bellows were leaking while 5 of the main line bellows were leaking profusely.

Courtesy dieselduck.net // A 16 cylinder V type Engine (Image 1) Image 1 as referred to in text

Courtesy Youtube // Shows an 18 cylinder engine - ours was 16 cylindered // Image 2 as referred to in text

Along with the Second Engineer, I went through the Maintenance Records. There had been regular changes of cracked exhaust pipe expansion bellows from the time Barber’s took over. Chief Engineer’s report on taking over from the Japanese also indicated they had been plagued with the same problem.

We had more than 16 of these bellows as spare, an unusual excess for this spare part.

The Second Engineer was an excellent, experienced one, my protege’, who, by all rights, should have been on the list for promotion to Chief Engineer. Considerations other than the strictly professional - long hair, gruff attitude, not very articulate and hardly spoke - were all negatively portrayed by successive Chief Engineers - made a  case for him to be left out of the ‘promotion category’ list. I changed that perception in the Office’s mind and, very soon, got him promoted.

As far as this exhaust gas leakage was concerned, he and I started from scratch. I went back to the knowledge I had gained in Sisco - “When there is a recurring problem, go back to first principles.”

I asked the Second how many bellows he had changed by himself after he joined this ship - he said ‘two’, I asked him to think back and tell me, in detail, every stage of the work that he had done when changing the damaged bellows. He gave me a full run down of the procedure he had followed.

Image Courtesy indiamart // Note the stainless steel sleeve in the interior and the corrugated bellows on the outside. // The free, unwelded end of the sleeve is clearly visible, which allows for longitudinal expansion. // This stainless steel sleeve is free at one end (gas outlet end) and welded to the flange at the other end (gas inlet end) // Note both flanges are the same size, same number of bolt holes, so they can be fitted either way. // Note the flat strips welded to each flange. 

The flat strips welded across the two flanges serve two purposes.

One, they prevent the corrugated bellow from getting distorted when in storage.

Two, they keep the bellows marginally compressed in order to allow the bellows to be easily inserted into what would otherwise be a very tight, difficult, fit. There will be no damage to the bellow. Once the bolts are inserted into the bolt holes, the strips are to be gently cut out after installation and before tightening the bolts and nuts.

I asked him to recollect how the bellow was placed, as it could be turned around 180 degrees and still be a perfect fit. He explained that the direction was the same as the one they had removed.

Also, the correct procedure of inserting the new bellow in place, locating it properly, inserting - but not tightening - the bolts, then only cutting away the ‘holding’ strips - which keep the bellows from getting distorted while in storage while, at the same time, keeping the bellows slightly compressed in order for ease of insertion of the bellow into place - was not followed.

If the ‘holding’ strips are not removed prior tightening the bolts, there is likely to be some strain on the corrugations of the bellow, as the tightened bolts are trying to expand the bellow, while the ‘holding’ strip is trying to contract the bellow. This could cause a tear along the corrugation.

Many Engineers fit back items exactly as they found it when opened. Because of this, a recurring problem often gets carried over and, sometimes, is never resolved.

These Expansion Bellows are a marvelous testimony to a near-genius invention that revolutionised engineering and piping systems. Pipes expand not only outwards but also longitudinally, when carrying hot liquids or hot gases. During construction, if no allowance space is given to the pipe line to expand, it will rupture pretty soon at its weakest point, possibly a welded seam. These kinds of Expansion Bellows take up mainly longitudinal expansion. Using the Coefficient of Expansion, different bellows are made to suit different metals. The design of the bellow is where it gets into the realm of inventive genius. Only catch, it has to be installed correctly or it becomes counter productive. Expansion Joints are also installed for liquids at normal temperatures, the design being different from Expansion Bellows for hot products.

In this case, the bellows were made of stainless steel, with a higher percentage of nickel.

(On later ships, I was glad to find that the number of bolt holes on the two flanges were different, with PCD - Pitch Circle Diameter - for the bolt holes also being different, which eliminated the possibility of wrong fitment). On older ships, European built, OEM spares, an arrow is punched on the flange, indicating how it should be fitted.

We went from there to a spare bellow, where I explained to him that the gas flow has to be only one way. I showed him how the interior circular stainless steel sleeve was welded at one end and free / open at the other. The bellows must be fitted so that the gas flow is from the welded side to the free side of the sleeve.

If fitted the other way, exhaust gas will find its way through the gap in the stainless steel sleeve and fill the gap between the sleeve and the - comparatively thin - corrugated / concertinaed bellow. The frequent pulsations in the pressure of the exhaust gas will cause this accumulated gas to flex the bellows at the pressure of every stroke of the engine and soon the bellows will rupture.

I also explained to him the importance of the ‘holding’ strip and the procedure for its removal, once the bellow is positioned in place.

The material of the concertinaed, corrugated bellow is very thin and is meant to gently expand or contract in accordance with rise or fall of gas temperature. It is not meant to pulsate and take up the pressure fluctuations of the exhaust gas.

We were now sure that the damaged bellows were wrongly fitted, direction wise or the fitting procedure was wrong.

In order to prevent wrong fitting of future ones, we drew a large diagram of the exhaust pipes, naming them A and B banks. Then we numbered each bellow in the line as A1, A2 ….. B1, B2 etc., all the while using the Instruction Manual as reference.

Courtesy FEV Group // Note the two Turbochargers at top left, each run by one exhaust bank // For reference only

Gas flow has to be towards the Turbochargers, so the placement of the bellows has to match the flow of exhaust gases. We were certain that a number of them had been wrongly fitted.

As each bellow renewal could take as many as six hours or more (depending on the frozen bolts), we tackled the most damaged one first at the next port, took it out, found it facing the wrong way, changed it to a new one, allowing the gas to flow correctly.

At the same time, in that first port, two others of the engine staff were set the task of easing up each bolt of the others that were going to be changed as time permitted. There were 24 bolts at each end, 48 per bellow, which was the main time consumer. One by one, the bolt was removed, anti-seize compound applied and fitted back. It was a difficult task, especially the bolts underneath, with the work space extremely restricted. With some ingenuity, we fabricated tools to make it easier to reach the bottom 1/3rd of the bolts.

This way, we could change two more bellows in the next port and three in the following port. The seventh was changed in the next port.

All leakages stopped.

The masks came off as there was no more exhaust gas in the Engine Room air.

Two weeks time taken.

The blackened areas of the Main Engine, other machinery and also bulkheads were washed and painted.

By the time we reached Singapore, the Engine Room had transformed itself from a gloomy, dark dungeon to a bright looking machinery space, especially with Bathi Saab changing tube lights and cleaning all the shade casings.

The compactness and design of the V-type engine made it easy to keep not only the Main Engine clean, but also the whole Engine Room, unless we have exhaust gas leakages as seen on this ship. Once we got rid of the leakages and painted the bulkheads and machinery, one could never say she was a 11 year old ship. At best, one would surmise, from looking at the Engine Room, that she was about 1 or two years old.

My Observations on V - Type Engines:

No Engineer’s education is complete without having worked on V type engines. They are a bit complicated to maintain. Overhaul of each unit can be a problem if one does not understand the mechanics of removal and replacement of the cylinder head and piston. Also the cramped space in the crankcase, the recognition of how to fit either the driving (master) connecting rod or the slave connecting rod is dependent on the experience of the engineer. Not all can do it.

The more older, experienced Engineers would also swear by the fact that no Engineer’s education is complete without having worked on Opposed Pistons’ engine.

A. Ranganathan