1 Failure Analysis & Overhauling Report-Sodium Bicarbonate Plant DG

Equipment Specification

Equipment Designation Make

Bicarb DG Cummins

Assembly UK (Daventry Engine Plant) Manufacturing Date 12/92 Rated power (KVA) 750 KVA Model Engine Type

KTA-38-G2 V-12

Problem Reported

On the morning of 03rd May 2012, it was reported that

the DG during operation had shut down (tripped) and the low engine oil pressure warning LED had come

on.

Initial Observation

The initial observations made were;

- The Dip Stick for Oil level in the Engine was thrown out

- The Engine Oil mixed with water (Grayish White Fluid) was oozing out of the Dip stick opening as

well as the blow by/breather pipe.

- The Radiator was found empty, i.e. the water had flown into the Engine Sump.

Initial Troubleshooting

The initial troubleshooting was done by taking the following steps;

- The Radiator was filled with water but it was found that the water was flowing into the Engine

Oil sump and it was overflowing out of the Dip Stick opening and the blow by/breather pipe.

- The Oil in the sump was drained.

- The inspection plates on the sides of the Engine Block were opened and it was found that the

bottom of the sump was full of pieces of metal that seemed like parts of Piston & Engine Liner.

2 Failure Analysis & Overhauling Report-Sodium Bicarbonate Plant DG

- Based on the above observation, it was decided to disassemble the single head over the very

place where those pieces of metal were found.

- On disassembling the Head, i.e. the one right above the damaged area observations taken are

shown in the pictures below;

Damaged Tip of the Fuel Injector Damaged Valve Guide

Damaged Liner Area in the Block Missing Liner and Piston

3 Failure Analysis & Overhauling Report-Sodium Bicarbonate Plant DG

Damaged Valve Seat Deformed Valves

After the above observations were recorded, it was decided to call in the OEM for Cummins Power

Generation Products, i.e. Orient Energy Systems to give an expert view on the accident and to proceed

for the repair of the Engine.

OEM’s View

The OEM’s personnel paid a visit to the site on 04th May, 2012 and their response is given below.

“Reference to our service team visit at your site regarding inspection of Generator set please note said

engine block is damage and could not repair at site therefore its major overhauling will be perform and

after complete dismantling of engine its block will repair.”

As per the discussion with the OEM’s personnel, it was found that there can be two reasons for an

engine going into an accident of the type that occurred.

- One case can be when Fuel Injectors go out of calibration due to working for longer durations

without calibration. This causes excess fuel to be injected onto the Piston Heads, a phenomenon

called Fuel Beating. This causes the pistons to expand/overheat and damage the liner as well as

the piston itself. The symptoms that fuel beating shows are usually signs of overheating on the

piston heads along with pitting.

- The other reason can be if in any case the lubrication becomes insufficient the Piston can

overheat and can over expand, in that case damages the liner and the engine block. That often

occurs when the Oil spraying nozzles in the engine block that spray oil on the inside of the

Cylinder liner stop to spray oil for some reason. In our case, this seemed to be the more

probable reason.

One of the pictures showing damaged Spraying Nozzle (Valve Piston Cooling) is shown below.

4 Failure Analysis & Overhauling Report-Sodium Bicarbonate Plant DG

Damaged Piston Cooling Valve Damaged Piston Cooling Valve

Repair

The Engine was disassembled off the Skid and brought to the in house workshop for Major Overhauling

as per the OEM’s Recommendation.

The OEM recommendation on the repair of the damaged portion of the Engine Block was obtained and

the preparations for the repair accordingly were made.

As per the OEM the Cylinder had to be bored within the limits as to not puncture the Oil & Water

Galleries in the engine block. The OEM consulted its principle and found that the scratched area in the

engine block was the one that seals the water end against the oil end of the liner, hence can be bored to

an extent and can be safely done.

Hence the cylinder was bored and an oversized sleeve and a liner seal set were put in.

Observations on Major Disassembling

The DG was disassembled completely, i.e. all the 12 Heads, pistons & Connecting rods were

disassembled and the engine block was cleaned using Kerosene Oil and compressed air so as to ensure

all the Oil galleries are flushed and no debris is left in the Engine Block.

The major observations taken on the Engine are as follows;

- Two Pistons, i.e. 4th Cylinder on both Left and Right Bank were severely damaged.

- Two Connecting rods, i.e. 4th Cylinder on both Left and Right Bank were deformed.

- Two Cylinder Liners i.e. 4th Cylinder on both Left and Right Bank were severely damaged.

- Two pistons were found cracked when DPT was carried out, 1st Right Bank & 5 Left Bank.

- Two Cylinder Liners were found Scratched when minutely observed, 1st Right Bank & 5 Left

Bank.

5 Failure Analysis & Overhauling Report-Sodium Bicarbonate Plant DG

Parts Replaced, Overhauled & Calibrated

The flowing parts were replaced during the major overhauling.

Part Description Part Number Quantity

Kit, Liner 300752 5

Insert, Liner 301188 4

Injector 305312 2

Valve, Exhaust 3035110 4

Valve, Intake 207241 4

Guide, Valve Stem 3202210 8

Insert, Valve 205093 4

Insert, Valve 3026926 4

Bearing, Connecting Rod 3047390 24

Kit, Piston Engine AR-12313 2

Pin, Piston 205200 2

Gasket, Lower Engine 3804301 1

Rod, Push 3057139 4

Gasket, Single Head 3015239 12

Valve, Piston Cooling 3179664 3

Valve, Collette 205091 16

Ring, Retaining 205269 4

Set, Piston Ring AR-10680 12

Rod, Push 3017961 2

Insert, Valve 205093 2

Bushing 3043909 12

The flowing parts were overhauled/ calibrated during the major overhauling.

Part Description Status

Fuel Injectors Overhauled/Calibrated

Fuel Pump Overhauled

Thermostat Valves Calibrated

Oil Pump Overhauled

Heads Overhauled

6 Failure Analysis & Overhauling Report-Sodium Bicarbonate Plant DG

Cause of Failure

Impurity in Engine Oil

- Ingression of Impurities can be caused at several stages during handling of Oil hence

recommendations below have to be followed.

Recommendations & Status

- Ensure that

o New Oil is used every time engine oil replacement takes place. (In Place)

o Oil Filters are replaced at every Oil Change. (In Place)

o All containers are checked for cleanliness before being used. (In Place)

o Oil Levels/Quantities have to be ensured as per recommendations in the Manual. (In

Place)

o Since the DG stays un-operational for extended periods of time, hence a regime to be

set to start on regular interval for a specific period of time. (Not In Place)

o Engine Oil Analysis to be carried out every 200 hrs. (Not in Place)