Acid in Diesel Engines

The low sulphur content fuels were meant to lower the emissions of the engine. I do not remember reading of concerns over the damage to the engine from the sulphur content. The oil used will not have any change in the accumulation of acid in the combustion chambers. The only cure for sulphur content would be the fuel consumed. You, as the purchaser would have to set some standard for the fuel you purchase. Good luck.

From the engineers I've talked with, the low sulpher fuel is to reduce emissions and to keep from fouling the new emissions equipment that removes the particulates (soot) from the exhaust. In addition, the LSD fuel engines use a low ash diesel oil for the same reason.

None of the engineers from Ford or GM that I have talked with had any new concerns about acid formation during combustion. They did have the same old concerns about acids in the crankcase from short trips where the engine does not warm up enough to get condensation out of the oil.

As for preventative maintenance, it will depend on the size of the fleet, daily distances driven and the climate driven in. In addition, the quality of the driver and how the vehicle is looked after on a daily basis will also enter into the equation. I'm sure if I sat down to develop such a program there would be another 20 or 30 factors that I could come up with, but you get the idea.

If you get right down to it, low sulpher fuel diesels can run quite well on regular high sulpher fuel as long as you cut all the emissions equipment out, reprogram the computer and pay the EPA a whole bunch of money in fines when you get caught.

This has always been a problem. You may be interested in Lyn,"Combustion Products and Wear in High Speed Compression -ignition Engines, with Particular Reference to Use of Lower Grade Fuels"Proc. Joint Conference on Combustion, Oct,1955, IME, London,1956, Section lV,p.242. (Study of wear and deposits as a function of fuel and oil.)

It is Sulphuric Acid... Some engines (EMD) adopted different cylinders and rings for better longevity with high sulphur fuels.

I believe motor oils are or formulated to neutralize a portion of the sulphuric acid that develop from the combustion blowby by-products in the crankcase and-or absorb excessive humidity in the crankcase, making it unavailable to the sulphuric acid formation process. Preventive maintenance will allow for regular changes of oil, before the neutralization capacity of the oil is reached, as well as regular warming up of the oil in order to remove any accumulated moisture. If the engine is to be left inactive for any significant lenght of time, it is most important that the oil be changed and engine be run with the new oil for it to be dispersed through out the engine, hence spreading this new coat of protective oil (before leaving the motor inactive). Of course this gets even more critical if you are in a moist environment.

The absolute best action would be to specify "low sulphur fuel" to your supplier.

BUT NOT NECESSARILY ULTRA LOW!

Especialy if you are operating in an international and or off-shore enviroment where it is common to recieve most anything that is around at the time.

You need to understand that the sulphur has been added to the fuel for lubricity purposes, but like anything else in life too much of a good thing is a bad thing.

You can provide a sample of your fuel to your company currently taking care of your lube oil samples, they can tell you what your sulphur content is currently.

There is nothing you can do to prevent the formation of the sulphuric acid as such because it is created when the fuel is being burned in the engine. Although a good quality oil would certainly help, there is no substitute for routine oil samples and a good preventative maintenance schedule.

Most all engine manufactures specify recommended fuel and oil grades for there equipment. If you adhere to these as well as there prescribed maintenance schedule you will be fine, as the engineers have most certainly taken the fuel properties into account when preparing the schedule.

If you could provide details such as engine type, load, fuel grade, etc. I could give you a much better answer

Please read the following statement from EMD regarding sulphur content, this should clarify the issue very well.

SERVICE ADVISORY - Ultra Low Sulfur Fuel Position Statement Form CEF-001 Rev A. 4/5//05 Page 1 Copyright  Electro-Motive Diesel, Inc.. All rights reserved. Neither this document, nor any part thereof, may be reproduced or reprinted without the prior written consent of the Electro-Motive Diesel, Inc.. Contact EMD SDO office. Engines Affected:

This Service Advisory (SA) affects all EMD diesel engines.

Purpose:

This SA is issued to provide the EMD Policy Statement regarding ultra low sulfur diesel fuel (ULSD).

Background:

As the on-highway emission rules take effect beginning with the 2007 model year, the petroleum industry will begin supplying ULSD (ultra low sulfur diesel fuel) containing 15 ppm maximum sulfur possibly as early as mid 2006. This low level of sulfur is needed to enable aftertreatment control devices to reduce post-combustion chamber emissions and meet lower limits established by EPA.

ASTM uses the designation S followed by a number representing ppm sulfur. LSD -low sulfur diesel is identified as S500 (0.05%), ULSD - ultra low sulfur diesel will be identified as S15 (0.0015%). The current EPA fuel sulfur rules for locomotive and marine applications require use of S500 (500 ppm) maximum sulfur diesel fuel starting June - 2007. Use of ULSD - S15 (15 ppm) is not slated for locomotive and marine applications until June - 2012. Both of these dates are at the refiners' gate, indicating that a further time delay could occur through the distribution system prior to customers using these fuels on a regular basis.

The concern expressed by rail customers citing the 2006 availability of ULSD S15 fuel is the potential of receiving this fuel in their supply system prior to June 2012 and the impact it may have on their EMD engines. It is recommended that customers talk to their fuel suppliers about availability of off-highway fuel thereby allowing further experience to be gained by the on-highway engine market and to limit exposure to any premium cost for the additional sulfur removal processing. However, it is understood that in some geographic areas, on-highway ULSD may be the only available fuel.

Policy Statement

Based on the information available at the present time, the following comments can be made about ULSD (S15) with respect to EMD engines.

Lubricity

EMD MI 1750 has added a requirement for lubricity at 520 micrometers maximum wear scar using ASTM test D6079 at 60°C. This specification applies regardless of fuel sulfur level. As sulfur is removed from the fuel, additives will be needed to meet the lubricity requirement. The initial lubricity specification was established by the on-highway engine and fuel injection equipment manufacturers to prevent premature SA#: 06-025 REVISION: Release REVISION DATE: N/A ISSUE DATE: 04/7/2006 AUTHOR: John Swanson Customer Engineering • Electro-Motive Diesel, Inc. • 9301 W. 55th Street • LaGrange, IL 60525 SERVICE ADVISORY - Ultra Low Sulfur Fuel Position Statement Form CEF-001 Rev A. 4/5//05 Page 2 Copyright  Electro-Motive Diesel, Inc.. All rights reserved. Neither this document, nor any part thereof, may be reproduced or reprinted without the prior written consent of the Electro-Motive Diesel, Inc.. Contact EMD SDO office.

wear out of rotary pump fuel injection systems used by many in the industry. EMD believes that its fuel injection system, which is not based on a rotary pump design, is more tolerant of lower lubricity fuels but has included the lubricity requirement to assure trouble free operation and to be harmonized with the on-highway lubricity requirement such that fuel treated at the distribution terminals can be used in both markets. EMD is aware of one reported fuel filter plugging incident in an EMD engine associated with the use of a "dimer" type lubricity additive. Its use was subsequently discontinued by the fuel supplier and replaced by a more commonly used additive and no other problems have been reported.

Energy Content

Energy content is directly related to the hydrocarbon composition of the fuel. Heavier (more dense) components provide higher energy content on a per gallon basis. Sulfur in fuel is usually associated with these heavier components. Sulfur removal from fuel can be accomplished by two methods, hydrotreating and hydrocracking. It has been estimated that the resulting ULSD S15 fuel will loose from about 0.7% to as much as 4.5% energy content on a per gallon basis depending on the level and type of processing required at the fuel refinery. The impact to the EMD engines will be shortened racks (or longer pulse width for EUI engines) to make equivalent power. It is believed that the fuel injection system has adequate capacity to make rated power under most environmental conditions. However, in ambient temperatures above 95^o F, there may be noticeable loss of power.

Thermal Stability

The natural thermal stability of diesel fuel is expected to decrease as sulfur is removed during the refining process used to produce these fuels. This could have an adverse impact on long-term storage in wayside tanks and in locomotive fuel tanks. The customer may need to be more vigilant in tank maintenance as the risk from poor stability fuel is one of filter plugging.

Electrical Conductivity

This property is related to the safe handling of diesel fuel to control static electricity build up in the fuel. It has been reported that ULSD may have lower electrical conductivity levels as a consequence of removing sulfur. EMD advises that customers check with their fuel suppliers to determine if ULSD shipments will have adequate electrical conductivity levels to provide for safe handling and establish an internal fuel specification for this property to assure consistent quality from all potential suppliers.

Further Experience

As further experience with ULSD fuels in EMD engines is gained, EMD will revise this position statement as appropriate to address any additional concerns that may arise.

I'm shooting from the hip here, but I think sulfuric acid is a by-product of combustion chemistry and as long as you have sulfur in the fuel, you will generate sulfuric acid. However you do have some control over what happens to the acid after it is formed. If the acid is cooled below about 375 deg.f it will begin to condense and react with whatever it condenses on. If you keep the acid at high temperature, it will remain in vapor form and not condense until it is outside the engine.

Yes it is beneficial to keep the equipment operating at peak load and temps..

However it is difficult to get this through the heads of the actual persons operating the equipment.