Cylinder liner honing

[wr180561]

I understand that honing of cylinder liner is not a routine work. Can someone tell me when it is necessary to hone a cylinder liner? And what is the correct procedure for honing a cylinder liner? Regards - wr

 

[SMOKEY44211]

Honing a cylinder liner accomplishes the same tasks as it would if you were honing a cylinder in an engine block that doesn't use one. Honing produces a round hole and the suface finished to be compatible with intended ring material. The OEM's that use them do so to provide the rings to ride on a wear resitant alloy without incurring the additional cost of casting the whole block out of it.-------Phil

 

[incandescent]

When bores are out of round, slightly out of size, or if the bore surface has left its optimum profile for oil retention as matched to ring type and material. Or any combination of these.

Procedures for honing can be found all over the internet or buy a book. Honing procedure varies with material and desired surface finish which all depends on application.

 

[tbuelna]

WR180561,

Most ductile iron or hardend steel (nitrided) liners are honed with a "plateau" honing technique. They are first honed with a relatively coarse stone to true-up the bore. The coarse stone leaves microscopic 'peaks" and "valleys" in the liner surface. The bore is then finish honed with a relatively smooth stone, which knocks off the "peaks" but leaves "plateaus" and shallow "valleys".

The theory is that the rings will glide against the "plateaus", while the "valleys" will provide little lubricant reservoirs. Nikasil/aluminum liners supposedly work in the same manner.

Regards,
Terry

 

[gbent]

Cylinder bores are usually honed any time new rings are installed. If the existing bore geometry is acceptable, this may be only a "touch hone" to roughen the surface for the new rings (origional size) to seal. If the bore geometry is worn enough, the bore is oversized to the next available size and honed for the new piston/ring package.

You used the term "liner". If this indicates a replaceable liner (sleeve), such as that used in a heavy duty diesel, they are not commonly honed. When the engine is torn down, new liners and pistons are installed.

The correct procedure for honing should be obtained from the ring supplier, and executed as well as possible, given the equipment available. Factory hone quality can be closely approximated in a good automotive machine shop.

 

[wr180561]

Dear all,

Thanks for your responses. Yes, it is a liner that is replaceable in a medium speed diesel engine. The liner is still within the wear limits but new piston rings will be installed, is it necessary to hone the liner in this case using a honing brush ? Regards WR

 

[GTM2U]

>I understand that honing of cylinder liner is not a routine work. Can someone tell me when it is necessary to hone a cylinder liner? And what is the correct procedure for honing a cylinder liner? Regards - wr >
.................

I'm not sure what you are asking and why, it depends what car and what year you are working on/talking about. If you are doing a nominal overhaul perhaps using original pistons and new (first rebuild rings) which should be about .002" oversize you would use a "bead hone" to de glaze and adjust for minor taper. A more precise honing can be achieved using a rigid cylinder hone and can substitute for the bead hone which is mostly used for de-glazing as mentioned above. If the cylrs have been bored the rigid cylinder hone will be used with successive finer grits.

The bead hone labor process is included when giving quote for a minor overhaul as is the rigid cylinder honing if it's just use to de-glaze the cylinders; however; if things are worn beyond specifications and require more time then there may be an additional charge. Machine shops will usually include the honing process if they give a quote for boring. Like all things, it depends on the skill of the mechanic who knows how to do the best possible job.

As mentioned above it's very important to know the year and design of the engine in question for metallurgy has changed in the last 15 years. The piston and ring fitting clearances have changed dramatically and without consulting a professional it should not be undertaken until you know what you are doing if this is to be a home repair / rebuild.

Cheers,
GTM2U

 

[wr180561]

Gentlemen,

Let me give you some more information about this engine; it used for power generation, it’s output power is 3.85 MW, arranged with 16 V- type cylinders, rotating at 720 rpm and having bore diameter of 280 mm. As mentioned above, all liners are replaceable and therefore, neither machine shop nor boring would be required because if a liner is out of wear limits it would simply be replaced for a new one. The situation now is that all liners are still within wear limits and therefore would not be replaced but all piston rings will be replaced for new ones. Now, would the liners require manual honing before installing the pistons and piston rings as a routine work? or are there some measures / indications that determine the necessity of such honing. Please note that we mean by manual honing is that type of honing carried out at site using a honing brush driven by electric drill. Regards WR

 

[WGJ]

In a smaller bore engine, the ideal way to get over the problem is with a flexi-hone. In case you haven't seen one, it's like a toilet brush with balls of abrasive stuck on the ends of the bristles. The stem goes into an electric drill at slow speed and the brush end is moved up and down the bore with a little kerosine lubrication. This takes any glaze off the bore and provides a surface for the new rings to bed into.
Sorry - I couldn't find the name of a manufacturer but I bet a rebuild shop would know. I don't know wheter a 280mm dia tool exists.
A colleague did a lot of durability work with a few engines some years ago with limited funding. Re-ringing following flexi-honing did a good job and oil consumption tended to improve.

 

[harrisj]

WGJ is right - but the product is called flex-hone not flexi-hone. And, yes, they make them in sizes up to about 1000mm bore. They do a really good job but the engine will need some running-in (breaking-in) while the bore is being polished by the new rings. Recommended!

John

 

[ctmtwilliams]

Flex-hones should be thought of more as "glaze brakers" than hones. And yes, when you are going to re-ring is the proper aplication of the device.

 

[harrisj]

Correct - conventional honing with rigid abrasive slippers will correct minor imperfections in the bore but flex-hones will just produce a cross-hatched finish on whatever profile already exists. So you need to be sure that the cylinders are within tolerance at about a dozen positions (or more)in each bore to ensure that ovality, taper and localised wear haven't taken place. Also beware of a top ridge where the top ring has travelled to - it has a tendency to break the new compression rings unless they are 'stepped' so that they don't go quite so far up the bore as the old ones.

Sounds like a serious engine you're rebuilding! Is it a marine or rail unit? What were the symptoms that led you to inspect the cylinders and re-ring? Let us know how it goes.

 

[Rob45]

One more point:
Conventional honing does not correct any out-of-round condition in the cylinder bore. It is used purely to provide the proper surface finish to achieve good ring seating.
When re-ringing, it is done to de-glaze the cylinder, again to permit good ring seating.

 

[incandescent]

Rob, can you expound on conventional honing not correcting any out-of-round condition? I have always thought that an aggressive enough hone job would work the imperfections out of the cylinder.

 

[pko]

My experience with marine propulsion engines (medium speed diesels driving either generators or coupled to reduction gears), is that we typically limit ourselves to deglazing the liner and remove soot/carbon deposits in the headspace mechanically using honing brush on non-chromed liners. However for hard chromed liners, no honing tools are permitted, instead chemical cleaning/deglazing and use of 'soft' scrapers are used to remove the carbon ridge.

 

[patprimmer]

On a race engine, that was prepared correctly in the first place (ie a head plate torqued down on a similar gasket with similar fasteners at operating temperature), for a freshen up, I simply use a bubble hone to help the rings seat. I believe that if no real wear is measurable, then the rings will have worn only, or at least, mostly the high spots in the engine under actual operating conditions, and will correct any minor errors that result from honing under the best simulated conditions.

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Lou Scannon]

For an engine of the value you describe I would recommend keeping guesswork out of it. There should be a manufacturer's overhaul manual which will specify wear and inspection limits for components such as the piston rings, and the correct procedure for overhaul if they are found to be out of spec. In your region there should be a distributor for the engine that can provide that information as well as locations of approved service outlets nearest you.

 

[dwedel]

WR,

I work in a maintenance section of a Natural Gas Pipeline in the US and we use 2000Hp (1.4MW) natural gas engines and smaller for compression. My experience is that we use the flex-hones (beri-brush) on cast liners to create a "hatch" surface to break in the rings on our 4-stroke spark ignited engines. On our 2-stroke engines, some are cromed liners which are too hard for honing, the rest have oil injection systems in the power cylinder bores which seem to reduce the need for the initial break in procedures that a 4-stroke needs. Again, as our engines are spark ignited I'm not sure how this compares to your diesel. With your higher compression and sealing loads, you may be back to needing the break-in surface, that our four strokes need.

This information is what has been handed down from the older guys here, so acuracy should be checked. I have been meaning to contact some of our piston, ring, and liner vendors as well as the OEM's and get some more up to date information. Does your ring vendor have an opinion? A person should be careful, but our vendors and OEMs have been my best source of information. If they give me good information, I keep buying from them.

What is the make and model of your engine? Where in the world is it located? Is this an in-frame overhaul? Is this a emergancy, peaking, or base-load, genset.

Just to give the auto guys some scale, these are 11" pistons on a 5100 Hp genset.

 

[optimum]

If the liners are in spec, you are just trying to achieve an acceptable surface for the new rings to seat. The service manual should provide a spec on surface and angle of the cross-hatch pattern the rings require for proper oil control
Tim

 

[Tmoose]

spring loaded "glaze breakers" pretty much just change the finish.

http://jcsonlinetoolshed.com/product.php/6340/295//6c4b67b1e5e53c28f84fc2b3ba52f95c

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"rigid" hones like these at Sunnen can correct out-of-round, taper etc. (Or, if impropely used, introduce taper or bell-mouth or barrel).

http://www.sunnen.com/product_detail.jsp?id=38&prod=Sunnen+Portable+Hones&catId=65&lnk=