02-03-2015 11:33 PM
I agree with the analysis, but I add my news, I have stopped using the method cat registration of the valves, and I returned to the use of the old gauge, I have not broken valves in both the Series A or C, not the registry more cold but only with the engine operating temperature, the jumpers in the old way, but only every 5000 hours, floats are beautiful and practical, bUT oN BOARD wITH IDIESEL VALVES VACUUM BREAKING OFTEN
02-03-2015 02:08 PM
Bridge and Valve lash adjustment is critical! There will always be metallurgy deficiency's that could cause valve stem separation, But generally its bad operator valve train adjustment! CAT procedures for adjusting the bridge is not very accurate, and I have not found a better way to adjust the bridges, but it is indeed not accurate. I noticed this when assembling a spare head, rocker box and valve train in my office to study. When using CAT procedures for adjusting the bridge it does not level or evenly dissipate bridge on the valves 100%. There is a way to preform this adjustment accurately but it would take a very long time when servicing the engine. Valve lash is straight forward and CAT procedures are accurate.
Siloxane buildup on the valve disc seats, generally causes torched or guttered valve discs and generally does not cause collateral damage. Ash from the engine oil can also create valve disc seat failure, again generally no collateral damage occurs.
Galled upper pushrods can contribute to valve stem failure if not addressed. Galled/worn pushrods cause excessive valve lash and can be heard noticeably when the engine is running. Galled upper pushrods fail in two ways, earlier gensets pushrods had a bad surface finish that contributed to excessive wear and was corrected with a new part number. Higher run time units or pushrods fail due to bad splash lubrication for the upper pushrod caused by excessive or abnormal wear on the rocker arm.
Hope this helps
02-02-2015 12:50 PM
Hello We are also experiencing contamination with Siloxane, What about the cylinder head valve & seat, have been using genuine heads or have you found some special valve & seat with different alloy?
I heard that Inconel alloy may work , but not sure if they make valve & seat for 3520
04-29-2014 07:54 AM
Valve stem failure can be contributed to multiple senerios. The most important preventitive practice is to properly adjust the bridges and valve lash. This is critical to valve train durability. Was the bridge screw adjustment nut loose after any or all failures? Was the head noisy before failure? Low hours rule out valve recession and deposit failures. Theres always the potential for metalurgy failure, and i have seen for my own self on the 3520's, BUT the most common and I'd hate to say it is operator failure of not adjusting the valve train properly.
04-25-2014 10:47 AM
We have 6 g3520C landfill 1966kW 50 Hz, and we have same problems like you post.
we are in our first top end overhaul for each engine, can you share pictures of your pistons and liners that you think are ok and what you think need a change.
What system of siloxane removal do you use, we use PPTeck BGAK 5000, 1.7 ug/btu at inlet and 1.4 ug/btu at outlet, we know that it is a high level based on 0.59ug/btu determined by cat, we are looking for a solution i think that the pptek is not working ok. and for the methane level detection we use FAU Landtec to determine concentration and then we set manually the concentration with a 4..20 mA source connected to engines.
03-15-2014 01:30 AM
Steve, it is not true that you are only 8000 hours working with the C series, I have them in the Natural Gas and we are more than 15000 of range, landfills have little caterpillar in Italy, the few work well, recording valves is always been a problem in all engines, but back to the 3500 C series, I'm thinking about a problem related to an incorrect installation of the seats, as being water cooled, it is not so semplicie, without an adjustment and personal
well trained, and even some head reman we checked the external measures do not conform with the data of the service manual, maybe it's here where to look for the solution, greetings also to Marcos
03-13-2014 05:15 AM
How many engine hours have the heads been fitted?
The 3520 valve lash and bridge piece setting is much more critical on this engine than it is on the 3516.
Ash can get trapped under the valve and the seat and this can torch a valve. Usually the engine will trip on temperature of the exhaust.
I would look at the hours of the head and the method used to set the lash and bridge pieces. If it is on LFG then you need to replace at 8000 hours
01-17-2014 02:18 PM
Have you found an explanation of your failures, i'm interested because we had 4 similar failures.
Our dealer say that our 4 failures was because a little particle of siloxane that was deposited over the valve seat and made a little torsion over the stem, and because that happened several times it made a failure in the stem of valve.
01-17-2014 10:52 AM
@ Marcos, CCM control to pc, give to us the PF factory elettrical paralleling, and engine torque controll, now we not go over 98% of full engine mechanical power, this after corects the PF from 95 to 98 in need Et to change on CDVR controlles, kWar are 13% of full electrical power out goin to eletrical networks,
01-17-2014 08:01 AM
The 98 % that you refer, how it is in kW? And when you speak about 95%?
What kind of control of power do you use.
The kW reference is working ok?