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Lessons learnt

QUALITY DIVISION - PROPELLANTS & CHEMICALS

QUALITY ASSURANCE & RELIABILITY - PROPELLANTS & CHEMICALS GROUP

SYSTEMS RELIABILITY ENTITY

Dt:10-12-2012

Presentation to PCM & PRSO-SR interface meeting


2/15

Separation within propellant grains/mid web tear observed in

all the three segments of PS0-FM-56 and two segments of

PS0-FM 58 motors

Cause

Lumps of ground Ammonium

Perchlorate (AP) observed at the

time of addition to the mixer

PSOM Segment

Propellant Tear/Separation

Mid Web Tear in PSOM


3/15

Implication of DeviationFrom mission point of view, separation/ tear within propellant is

not allowed. This may cause catastrophic failure of the mission.

All the segments of PSOM-FM-56 and FM-58 got rejected.

Corrective/Preventive Actions

Fine AP is to be added within 2 hrs. of grinding

Fine AP to be added in 3 installments against earlier practice

of 2 installment

Fine AP passed through sieve placed on the kneader during

addition to break the lumps, if any

Scrapping of blades after each addition of AP to the mixer


4/15

Any deviation observed from the standard practice (may bevery minor) to be reported immediately to the supervisor and

wait for the decision before proceeding further.

Visual observation is very important. Carry out visualinspection of the raw materials, mixer, surroundings etc.

Moisture is very harmful for propellant. Take all possible steps

to prevent ingression of moisture during propellant

processing.

Lessons Learnt


5/15

PS0-XL Igniter casting

Issue:

Rejection of Igniter propellant mix during vacuum

casting in the pressure casting vessel


6/15

Cause:

Before propellant casting, the pressure vessel

was covered with a polythene sheet to avoidcontamination which was to be removed prior

to vacuum casting but it was not removed.

As a result, the cast propellant fell on the

Polythene sheet and inside the vacuum

chamber instead of going into the vessel.

Implication:

Mix got rejected.

Vacuum

Chamber

Pressure

casting vessel

Propellant

Polythene

wrapping

Hopper


7/15

Corrective / Preventive action:

Checklist should be available and it is to be filledproperly and authorized by the concerned engineer.

Lessons learnt:

Visual inspection is to be carried out at every step of

operation and logged.


8/15

Issue:

One batch of Adhesive CS2 Part A was rejecteddue to the formation of precipitate during resin

synthesis.

Strain gauge bonding cement, Adhesive CS

2 Part A Synthesis


9/15

CaCl2 guard tube

Conc.H2SO4

To N2 cylinder

Inlet

StirrerConnections got

inter changed

outlet

Reactants

Cause :

During the assembly of the reaction setup, Inlet and outlet

of the moisture trap system [H2SO4 based] got interchanged.

Due to this, the conc. H2SO4 entered the reaction vesselcausing the formation of precipitate during resin synthesis.

Fig: Reaction Set up


10/15

Corrective / Preventive action:

Process document with the reaction setup sketch/drawing is included.

Inlet and outlet were properly labeled.

Training was provided.

Verification of the setup prior to use by the

supervisor.

Lesson learnt: Precautions are to be taken to avoid such human

errors.


11/15

Polarity reversal of

the electrochemical impregnation (EI) bath

Issue:

During the electrochemical impregnation step the nickel

plaques dissolved into the EI bath instead of the nickel

hydroxide active material impregnating into the plaque

matrix.

Nickel hydrogen cells are being used in spacecraft powering systems.

It consists of Nickel and Hydrogen electrodes.

Positive nickel electrode is processed in two steps:

1. Processing of Nickel plaque

2. Impregnation of Nickel hydroxide active material into the plaque.


12/15

Cause:

Due to human error, polarity of the terminals got reversed

during the impregnation operation.

Implication:

The EI bath was rejected.

Corrective action:

Thorough check of the connections prior to the operation.

Lessons Learned:

A Log sheet/ checklist were

incorporated into the system.


13/15

Cause

Lower TBS was due to under curing of Pedcoat liner

Insufficient quantity of curative (TDI) was added during liner

application

During weighing of TDI, empty beaker weight was not tared to

zero. As a result lower quantity of TDI was added to the Pedcoat

premix

TDI Lesser Quantity Weighed

Error in weighingInferior Tensile Bond Strength (TBS) between propellant liner-

insulation in PS0-74 Head Segment


14/15

Implication of weighing error

Due to poor TBS property, the segment PSO-74-HS got rejected.

Corrective/Preventive Actions Weighing balance with printer is to be used.

TDI quantity by volume is also to be verified by putting mark

on the outer surface of the glass beaker

Curing condition of the liner is to be verified on the sample

surface, which is coated along with the main segment.


15/15

A minor error in weighing caused the rejection of a PS0

segment

Ensure the calibration status of the measuring devices

Ensure proper tareing of the container

Re-verify the weighing

Pedcoat Liner Application

Lessons Learnt

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