Ammonia Chiller Explosion

[ssk7899]

Dear Forum

I am a system Integrator , Recently i supplied ammonia rack chiller.
with Bitzer ammonia screw compressors x 3nos.
After Running Successfully for Two Months , Yesterday it had taken a huge Blast.
The blast taken in oil separator, The Oil Separator escaped like a rocket.
It has not happened due to High Pressure , it just happened in fraction of seconds, when it was in running mode.
Only the end cover of the oil separator was separated along with discharge lines also.
Upto my knowledge it may happen due to Air + Ammonia mixture, its my view only.
Can any one help me ,what may be the Reasons?

at that time only one compressor is running.
HP - 190 Psi
LP - 28 Psi
OP - 160 Psi
Cold Room Application - Temperature - 0 Deg.

Thanks

[Segei]

Dear Forum

I am a system Integrator , Recently i supplied ammonia rack chiller.
with Bitzer ammonia screw compressors x 3nos.
After Running Successfully for Two Months , Yesterday it had taken a huge Blast.
The blast taken in oil separator, The Oil Separator escaped like a rocket.
It has not happened due to High Pressure , it just happened in fraction of seconds, when it was in running mode.
Only the end cover of the oil separator was separated along with discharge lines also.
Upto my knowledge it may happen due to Air + Ammonia mixture, its my view only.
Can any one help me ,what may be the Reasons?

at that time only one compressor is running.
HP - 190 Psi
LP - 28 Psi
OP - 160 Psi
Cold Room Application - Temperature - 0 Deg.

Thanks

Defenitely, it is not air+ammonia explosion. No air in operating ammonia compressor. Look at manufacturing defects of the oil separator cover.

[ssk7899]

There are chances for ammonia + air + oil Explosion.
I am searching for any other reasons.
Does any one experienced, on any ammonia explosion.

[Magoo]

More complicated than that. Explore heater failure in sump of separator, should be double isolated in event of electrical failure.

[Segei]

You need 16-25% of air in ammonia to explode. Operating ammonia compressor will never have this concentration.

[ssk7899]

Segei

If At all any external flame is the in the room.
At that time any chances for explosion.
How can a running chiller will explode , its really amazing to everyone.
More over its need a ignition.

[Tesla]

Don't keep us all in suspense give us some pics please.

[ssk7899]

20130408_135029.jpg20130408_135111.jpg20130408_135131.jpg

[ssk7899]

Almost 5 welding joints are broken , four discharge lines and one oil line.
oil separator is not there in its position .
20 feet high it lifted - the weight of oil separator is 500 Kgs
The oil quantity in it is - 180 Ltrs.

[Grizzly]

External electrical fire, which in turn superheated the Ammonia maybe?
There is no way Ammonia vapour even when ignited has the sort of destructive power.
Has Oxygen and not Nitrogen been used to leak check previously?
The evidence so far does not point to an Ammonia explosion.
Spurious chemical compositions maybe?

Sabroe have a video of a dustbin full of Ammonia vapour at explosion concentrations.
When ignited the resultant forces hardly lift the lid.
External heat boiling the chemicals within especially oil. May well help the destructive power?
Grizzly

[ssk7899]

Grizzly & segei

May be as you said it will be one of the reason.
But as per Canadian center for occupational health and safety.
What are fire hazards and extinguishing media for ammonia?

Flammable Properties: FLAMMABLE GAS. High airborne concentrations can be ignited and pose a significant fire and explosion hazard, especially in a confined space. A large and intense energy source is necessary to ignite ammonia gas.

Specific Hazards Arising from the Chemical: Heat from fire can cause a rapid build-up of pressure inside cylinders. Explosive rupture and a sudden release of large amounts of gas may result. Cylinder may rocket. In a fire, the following hazardous materials may be generated: flammable hydrogen

What is your opinion on this

[Sandro Baptista]

Maybe an huge air "leak in" to inside the compressor system (for example shaft seal or other "weak point") if it's working below atmospheric pressure and complemented with a malfunction of the oil separator electric heating coil, so easy could reach about +600% (auto-ignition of the NH3). What do you think?

[mad fridgie]

My best guess.
Ammonia cracking!
Faulty heater control, Nickel plated heater, low oil levels at times.
Hydrogen produced, then element shorted causing a spark

[Sandro Baptista]

Good thinking!

Hidrogen produced because of the high moisture concentration on the oil and NH3 combined with high temperatures?

[NH3LVR]

I have been in rooms where the contents of a NH3 vessel under repair exploded. The force generated by the explosion was nothing near what would be required to do this. It mostly consisted of a dull whoof and a lot of dark brown smoke.
I did hear rumours of such things happening from the oldtimers (back before I became one), but nothing was ever firm on the cause.
Sure someone did not get near this system with a bottle of oxygen?

[Magoo]

Have you checked the sump heater in the oil separator after in landed.? Have you asked Bitzer to comment on failure.? What failed on separator that launched it, a weld or cover plate, was it a certified vessel, did it have a safety releif valve...?
Some piping looks suspect, stab in welds on discharge header, should be forged fittings, vibration and expansion issues. Did any safety controls trip before explosion.? Did ammonia alarm system and extract fans activate prior to explosion.?. Did the alarm system activate remote power isolation to the area.?

[PaulZ]

Very good questions Magoo.
There are no photos of the separator either.
ssk7899 if you want an answer you need to provide a lot more information then you have.
If you can answer all of Magoo's questions then someone may be able to suggest a cause.
Paul

[Peter_1]

The electrical switchboard on picture 3 is also melted.

[ssk7899]

Dear friends

Lots of investigation is going on this , my base doubt is any external flame had occured.
Why because if at all oil separator construction is week.it cant even run for 2 months.
It is running in 180 psi and had a sudden explosion.
If suddenly oil seprator failed in the bottom end then explosion take place.
The majority of the oil will spills at the nearer place of the oil seprator.
But there is no oil at the bottom.the vessel was certifed vessel and it was pressure tested with 500 psi thoroughly.
From past 25 yrs we are in this feild .
This is our first experience , we have seen liquid storage tanks sudden brust or saftey valve realse.
But this is entirely different.

If at all too much liquid is coming from the suction line and the temperature is minus 5 deg
If it meets with oil temperature 90 deg and air in the compressor , at that time what will be the situation.
Are any electrical shot ciruit .

[Magoo]

A flood back would stall the screw compressors, lock rotor fault current should take out overload protection instantaneously, plus the upstream power supply should have tripped and isolated the whole system. Dependent on fault rating of switch board, a flash over could occur in switch board then the fire potential. Where does the oil separator get envolved. If fire was heating the oil separator then HP fault should stop everything. More heat and pressure the safety releif valve should protect the vessel from catastrophic failure. Have you checked the sump heater in separator.

[ssk7899]

Dear magoo

Yesterday we got a information that , there was fire first external to the system and after that a huge sound and explosion take place.
Oil heater is good and the heater pockets also good .

Really so much of confusion.

[Magoo]

Still does not explain why oil separator failed and launched itself into space. If all safety systems worked as per, the releif valves would protect vessel. Of course if vented externally from plant room
Obvious no sprinkler or similar fire protection worked if installed.
From earlier comment about vessel failures, I have never experienced any liquid storage vessels failing if built correctly and safety systems applied.
I am thinking your clients insurance company will have a feild day and decline any risk claims. Hopefully your companies liability risk cover is paid up. Things could get messy and expensive.

[Grizzly]

There was fire first external to the system and after that a huge sound and explosion take place.

I think if you read the above posts. Most of us were saying that or similar!
Almost in that bed Magoo!
Grizzly