Check with Piston

[jrvakil]

Hi friends,

I am new to this website, I am a spare parts trader from bhavnagar India, we obtain these parts from ship recycling yard called Alang.

Anyway I have one order for 6 pistons of Yanmar GL-ST engine, can anyone advise which things should i check before dispatch to confirm that these pistons are reuseable or not ??

[Big Pete]

Hi jrvakil, welcome to the "DieselDuck",

I assume that these pistons are taken from ships being scrapped.
I think it is very environmentally friendly and potentially profitable to do this.
There is a huge world wide market in so called "Grey Market Spares".
The quality of spare parts available in this Grey Market is hugely variable, and this discourages many reputable companies, and Engineers, from using them, because they do not think these parts will be a as reliable as Original Equipment Maker's spares.
Another consideration, for Marine Spares, is the requirement of the latest MARPOL air pollution regulations which require all critical spare parts to be to Manufacturers Standards and for the ship operator to be able to prove this, with a trail of paperwork, according to the ISM codes.

The simplest option is to just clean up the pistons and sell them as they are to anyone who will buy them, this way you will not carry any risk or require any great expenditure. The downside is that you will get only a very small mark up on the scrap price. This is because the person buying second hand spares from you is taking all the risk that they will be no good.

The next stage would be to get a copy of the engine manufacturers workshop manual and check the pistons against this for suitability for further use, you could then sell them with a guarantee that they comply with the makers requirements for further use. These manuals should be on the ship where the pistons came from, so I would ask the shipyard to send you the engine makers manuals from the ships they break up, you will soon have a large technical library!!!
This would basically involve crack detecting the outside surfaces of the piston, measuring the height of the piston ring grooves at various places around the circumference, checking the diameter of the piston at various positions and examining all the surfaces for damage such as pitting, scuffing, fretting etc. In the case of a water or coil cooled piston a hydraulic pressure/leak test of the cooling space. If there is a bush in the piston for the gudgeon pin, this should also be measured and examined to check its condition.

These checks can be carried out by any competent Mechanic, Fitter or Engineer and the piston sold on. Provide a Certificate issued by your company, detailing all the checks carried out and the measurements taken. If the piston came from a ship it may well be stamped and dated by a Classification Society or have makers numbers stamped on it, details of all these should be recorded on the certificate. You should also include the source of the piston, i.e. Model and serial number of the engine it came from, name of the ship, date it was broken up and name of the breaker's yard. You should get a much better price for a piston like this, because you have reduced the risk to the buyer.
You now have the problem of what to do with the pistons that fail this examination!!!!!!
If you sell these as spares, in the condition that they are, it will damage your reputation, one option would be to sell these pistons through a company with a different name, but you won't get any repeat business!!!!!
In many cases the repair procedures are very simple and you could either set up your own workshop or sub-contract the work, depending on the volume of work you have.

If the piston ring grooves are worn, the most common defect, many engine makers permit them to be machined oversize, in several steps and it is possible to buy oversize piston rings to match, this only requires a lathe big enough to turn the piston and a competent machinist.
When the maximum oversize ring groove is reached, in many cases it is possible to build up the worn face of the groove by welding and then machine the groove back to the original dimensions. However, very precise welding procedures are required, and unless your bussiness grows to a very large size it would not be worth setting up your own workshop to do this.
The Bush in the piston should also be easy to change for a new bush ordered from the makers.

Many other defects could be repaired by specialist engine component repair companies. I know that Unitor set up a workshop in Europe to do this, many years ago. There are also many companies in Holland that specialise in this type of work, but I do not know of any in Asia.
You would obviously have to investigate the cost of sending pistons to such a company for repair against the price you could eventually sell it for.

If you are getting the pistons from the shipyard at a very small mark up, above scrap, it may not be worth carrying out any repairs at all, just sell the reject pistons on as scrap, unless you are unable to meet demand.

I would expect that turnover/ sales volume will be much greater for small diameter pistons than for larger ones, so probably the best business model is to initially concentrate on small bore engines that have been made in large quantities, they will sell faster so your inventory/stock will not cost you as much in interest payments/ opportunity costs as larger, more expensive and slower selling pistons would.
As the volume of business grows and your cash flow improves, you can expand the bussiness into areas of lower demand, (larger and less common engines), obviously you would have to charge a higher mark up for components with a slower turnover.

There also appears to be no reason why you couldn't expand into cylinder heads, fuel injection pumps, & fuel injectors as well, these have similar sales volumes to pistons.
There would also be a market for engine driven pumps, governors, and turbochargers from these scrapped ships, but this would be smaller and more specialised market and assessing the condition of the governors and turbochargers is more specialised work.

Fundamentally your bussiness model is to buy scrap parts at slightly above scrap prices and then YOU take all the risk and expense, of checking and repairing the components, so that you can sell on a guaranteed product that is "Risk Free" to the end user/buyer. The better that you can guarantee the reliability of your end product, the greater the profit margin you will be able to make.
If your turnover is alrge enough, it may be worth having your procedures accredited to a Quality Assurance Standard, and particularly for Marine Spares by a Classification Society.
You are entirely dependant on the confidence that the buyer has in the quality of your product, so you must make every effort to re-assure them, and build there confidence in your procedures.

I hope this helps you, let us know how you get on.

[jrvakil]

Thanks man,

We are supplying all kind of marine machinery and spares.

We are supplying it to many big companies like, Lemissoler, MSC, Mid east ship mgmt, thome ship mgmt, Fleet management. etc.

I found this website so I seeked help to improve my quality.

I really will be very happy to recieve things and checks like this for cyl. heads and all the engine spares.

[Big Pete]

Hi again Jrvaki,

From you first email it sounded as if you were just starting up in this bussiness, but from your second it sounds as if you have more experience than I thought. My apologies if what I said about the basics of the bussiness model were insulting to you.

With regard to cylinder heads, there is a thread on what checks to carry out on a cylinder head, in this fora, just a few posts back.
Maybe I will be buying parts from you some day!!
BP

[JK]

Maybe I will be buying parts from you some day!!

I was thinking the same thing!

[jrvakil]

No friend,

It was really very very important.

Can you please advise what to check in pistons just visually before buying it from scrap yard?? Just to reduce risk ?

[Big Pete]

Hi again Jvraki,

Obvious things to look for are the condition of the piston crown, i.e. if there is a big hole burnt in it it is not a lot of use!!!
If you are looking at lots of pistons you will get a feel for what is normal.
Look for signs of metal burning away or melting in the top part of the piston, above the piston ring grooves.
Look for signs of impact damage on the top of the piston this can be caused if something is left inside the cylinder at overhaul, or if a cylinder head valve sticks or breaks, or a fuel injector nozzle drops of the end of the injector.
Around the sides of the piston, look for signs that the piston has been rubbing against the cylinder liner, causing wear or that metal debris from damage to the cylinder head or a broken piston ring has been rubbing against the side of the piston.
If the piston rings are still fitted to the piston, look at the clearance between the groove and the piston, this should be even all round the piston.
Look at the wear in the piston groove, as new the grooves are Square, more wear occurrs at the outer edges of the groove, so the more worn the grooves become the greater the angle between the upper and lower faces of the groove, if you are familiar with the permitted clearance between the piston ring and the groove, it will only take a feww seconds to check with a feeler gauge. Choose a feeler gauge of the maximum permitted size and if you can get it between any ring and the groove that piston will require repair before use.

Hope that helps.

BP

[jrvakil]

Thank you very much my friend it will help a lot