Diesel Fuel and Injector Failure - Part 2

Diesel Fuel Cleanliness Standards

The awareness of fuel cleanliness in diesel engines is not new – in fact, it was first documented as early as 1931 with the introduction of the Caterpillar Diesel Sixty Tractor. The fuel injection pressure developed by the engine was only 1,250 psi, yet the caption from a Manual of the time tells a powerful story and it should be reflected on in respect to today’s engines.

Caterpillar Manual

In today’s world, measuring how clean or dirty fuel may be is critically important, and as such, fuel cleanliness levels are now measured and reported according to the ISO Cleanliness Code 4406:1999. The International Organization for Standardization (ISO) created the cleanliness code ISO4406:1999 to quantify particulate contamination levels per millilitre of fluid at three sizes: 4μ, 6μ, 14μ.

Scale Number

Particles per ml. More Than

Particles per ml. Less or Equal

22

20,000

40,000

21

10,000

20,000

20

5,000

10,000

19

2,500

5,000

18

1,300

2,500

17

640

1,300

16

320

640

15

160

320

14

80

160

13

40

80

12

20

40

11

10

20

10

5

10

9

2.5

5

8

1.3

2.5

7

.64

1.3

6

.32

.64

Fuel Cleanliness Vs. Engine Technology

Fuel cleanliness levels using the ISO4406:1999 method were officially documented as a global standard in 1998 with the development of the Worldwide Fuels Charter (WWFC). Since its inception, the charter has established a minimum cleanliness level for each of the diesel fuels under various available categories around the world.

WWFC Diesel Category Fuel Cleanliness Standards

Diesel Category

Cleanliness Level

1

10 mg/kg

2

ISO 18/16/13

3

ISO 18/16/13

4

ISO 18/16/13

Most mainstream engine OEM’s now subscribe to these standards. Interestingly, however, and somewhat troubling to note, is that fuel cleanliness levels for each Diesel Category being specified by engine OEM’s and the WWFC have not changed since their inception in 1998. Despite the enormous advances in fuel injection technology, and the demands under which HPCR Fuel Injection systems operate, increasing the fuel cleanliness requirements is needed to assure optimal performance and longevity of system components. The following table shows how the characteristics of the more advanced HPCR systems have changed.

Diesel Fuel Injection – Advancing Technologies & Cleanliness Levels

Injection

Pressure

Viscosity

Clearances

Cleanliness

EUI

16,000 psi

1-4 cSt

5-8μm

18/16/13

HPCR

36,000 psi

1-4 cSt

1-4μm

18/16/13

This table shows that fuel injector critical clearances have halved and fuel pressures have doubled yet the level of fuel cleanliness being specified has not been altered in accordance with such advancements. In fact, the same cleanliness levels specified in 2000 are still being used today despite these magnificent technological advancements.

Leading fuel injector manufacturers around the world have clearly identified and communicated that their systems require Ultra Clean Diesel (UCD) fuels with fuel cleanliness levels as low as ISO 12/9/6 to maintain ultimate performance and reliability while fuel being provided is ISO 18/16/13. It is here where we see an enormous mismatch in what the fuel injection OEM desires as a fuel cleanliness level, to what the engine OEM’s and the WWFC are advising the industry. The following table identifies the discrepancies in fuel cleanliness levels.

Diesel Cleanliness Levels

Company

Specified ISO Cleanliness Level

World Wide Fuel Charter

18/16/13

Engine OEM’s

18/16/13

Fuel Injector OEM

12/9/6

Owners and operators of diesel engines should take note that the cleanliness levels required by the fuel injector OEM’s are 64x cleaner than what the industry is being advised as an acceptable standard of fuel for engines. This is a critical point when considering contamination control solutions for diesel fuel systems.

Fuel Cleanliness – Deciphering the Code

When referring to the ISO4406:1999 cleanliness code, it can sometimes be difficult to comprehend how much contamination the codes actually represent in a real world operating system. To help clarify this, we can use a real world scenario that is more meaningful. The example used to demonstrate this is as follows:

Model:

Cummins DQKB Diesel Generator

Engine:

QSK60-G3

Duty:

Continuous

Rating:

1450kW (1813kVA)

Cycle:

60Hz

Load:

100% Peek Load

Run Time:

5000 hrs/year

Fuel:

74.8 US GPH (283 L/hr)

The following table provides an indication of how much contamination is being presented to the above engine’s fuel system each year under this example.

Volume of Contamination

Fuel Cleanliness

Volume of Contamination

ISO 23/21/18

26.4 lb/year

ISO 18/16/13

0.8 lb/year

ISO 12/9/6

0.10 lb/year

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