Reciever tank explosion!

[Tassosrr]

Hi to all, i just looking for someone who may have heard/seen something like that...

So....last week i was called from a supermarket for a very big noise like explosion from the basement (where the refrigeration systems are). I didnt know what they meant until i arrived to the store.

(The store has 10 single units with copellant/bitzer compressors from 2 to 4hp)

When i went to the basement i saw this...WP_20160317_13_43_24_Pro.jpgWP_20160317_13_43_46_Pro.jpg.

The reciever tank of a unit was explode!!! The units work with R422D and with no high temperature problems due to high prswsure, and explode only the reciever tank.....no the compressorr, no the tubes, no the condenseur!!

What might have cause that??

Any questions are welcome.

Kind regards, Tassos


P.S....sorry for the language, i dont use offen the english.

[cadwaladr]

There should be a pressure relief valve on the receiver which vents to an empty vessel which is capable of holding a lot more volume than the receiver,that plant is dangerous someone could have been seriously injured if they were close by.

[Tassosrr]

The receiver was not isolated from both sides and the tempertaure in the machine room was good.

Thers was also a pressure relief valve on the receiver, but as you can see it didnt work.

Question : How can it be possible to explode only the receiver tank and not the coper tube that connects the receiver with the condenseur or the condenseur itself?? I have heard that oxygen combined with mixed oils in the instalation can cause explosion...is this correct?

[RANGER1]

It could be a number of reasons, like faulty relief valve, safety cut out setting to high, receiver out of it's design pressure or faulty, hydraulic of vessel.

When did someone work on it last, what did they do?

If pure oxygen in system then expect explosion when it entered, as oil & oxygen cause explosion.
If air or non condensables in system discharge pressure may have been higher than normal

Check if vessel has correct certification stamps for pressure rating & is suitable for that service
Check pressure relief setting & does it operate at correct relief setting with nitrogen, is it correct size valve/
Was outlet of relief valve clear, not capped off or restricted.
Check high pressure trip setpoint, & does it stop compressor is it below pressure relief setting or vessel maximum working pressure.
Have receiver checked by qualified person, they may check other welds on vessel if possible.
Also if correct materials were used.
I would be reluctant to enter this compressor room until basic checks carried out.

Check out other receivers on site, are they correct & relief valves, high pressure safeties correct.

[nike123]

Question : How can it be possible to explode only the receiver tank and not the coper tube that connects the receiver with the condenseur or the condenseur itself?? I have heard that oxygen combined with mixed oils in the instalation can cause explosion...is this correct?

Tubes can withstand much more pressure than vessels. That is one of reasons why vessels need to have pressure release valves.
Bigger diameter mean lower pressure resistance. Also, thinner wall mean lower pressure resistance.
Pressure is force exerted to unit of area. Bigger the area, total force is higher!
In high risk facilities, pressure release valves should be tested and calibrated periodically.
When I was working on oil rig, pressure release valves on receivers has been tested and calibrated once a year.
That mean refrigerant recovery, dismantling of valves, testing and calibration, leak test, vacuum drying, vacuum holding test, charging by weight. Also all other safeties was checked regularly. With accompanying paperwork.

My guess here is relief valve stuck and HP pressurestat not correctly adjusted or bridged with liquid line solenoid faulty .
And, since that is placed in basement, poor air flow!
Therefore, "need" to readjust HP pressurestat to higher value!

[joe-ice]

Possibly dirty oil and air in system, look up diesel effect in r22 refrigeration system on your browser might point you closer to what happened,

[Tassosrr]

It could be a number of reasons, like faulty relief valve, safety cut out setting to high, receiver out of it's design pressure or faulty, hydraulic of vessel.

When did someone work on it last, what did they do? (Almost a month ago for leak trouble. se said he did all things correct, vacum e.t.c)

If pure oxygen in system then expect explosion when it entered, as oil & oxygen cause explosion.
If air or non condensables in system discharge pressure may have been higher than normal

Check if vessel has correct certification stamps for pressure rating & is suitable for that service Yes it was)
Check pressure relief setting & does it operate at correct relief setting with nitrogen, is it correct size valve/ (Now i cant)
Was outlet of relief valve clear, not capped off or restricted. (yes)
Check high pressure trip setpoint, & does it stop compressor is it below pressure relief setting or vessel maximum working pressure. (Yes)
Have receiver checked by qualified person, they may check other welds on vessel if possible.(No)
Also if correct materials were used.
I would be reluctant to enter this compressor room until basic checks carried out.

Check out other receivers on site, are they correct & relief valves, high pressure safeties correct. (Already checked)

[Tassosrr]

My guess here is relief valve stuck and HP pressurestat not correctly adjusted or bridged with liquid line solenoid faulty .(Pressurestet checked and it was working correct, exept if was stak once and cause this blow)
And, since that is placed in basement, poor air flow!(The air flow is very good)
Therefore, "need" to readjust HP pressurestat to higher value!(This is not a solution....if a technician was right in fron of the unit the time it was exploded would be very dangerous if not tragic!!i have to find out the reason first and check all the units in all machine rooms for similar posibilities of the same problem)

[nike123]

This is not a solution....if a technician was right in fron of the unit the time it was exploded would be very dangerous if not tragic!!i have to find out the reason first and check all the units in all machine rooms for similar posibilities of the same problem

I did not said that it is solution. I said that someone else see that as solution for high pressure triping in operation.
And i saw that "solution" too often in my life.
Since two safety devices did not protected that vessel, than it is possible to conclude few scenarios:

1. Vessel was stricturaly weak
2. Both safety devices are faulty or missadjusted
3. One safety (safety relief valve) was faulty and pressure has risen during standstill period of compressor
4.High rate of pressure rise (internal explosion)
Etc...


Please use quote and multiple quote button for quoting texts.

[nike123]

The air flow is very good

I would not said that, looking from pictures! I easily see (imagine) recirculation of hot air.
All that air which is sucked trough battery of condensers (placed at 3 levels with little or no distance between levels) must come from somewhere, and I see wall in front of these condensers. Therefore, lot of air is probably recirculated!
Compare your condenser air entering temperatures at various points at full load, and outdoor air temperature, and you will see by yourself!

These condensers must be at distance from wall at least 1/2 off height of whole pack, and air must come from above, sides and below that pack. I see no space below and at least from one side! And if at opposite side of that wall is not fully open space to outside air, I only can ask myself why that explosion has not happened earlier!

[cadwaladr]

I would not set foot in that plant room with the machines running until I have tested all the safety systems,the pressure switches could be checked with nitrogen quite easily,the mechanical relief valves I would change plus examine all the receivers for corrosion etc,it's got to be cheaper than a funeral .

[Glenn Moore]

Hi Tass
What pressure are the HP switches set to trip, What are the set pressures for the relief valves ?.
Can you send more pictures of the remnants of the liquid receiver, and of the air flow in and out of the plant room. I was Field Support Manager for Danfoss in the UK and any component failure on their componentry is thoroughly investigated as to the root cause of the failure which aids preventing further failures and gives us the ability to learn from situations such as this. I would therefore get the manufacturer of the condensing unit to investigate the cause of the failure in case there are more failures which may occur in the future which could end up with an engineer being seriously injured or worse.
Failures of this nature are very unusual so a thorough investigation must be carried out in conjunction with the component manufacturer and yourself to make sure that the equipment is manufactured to the correct standards applicable to these units and the installation both mechanical and electrical comply with all safety regulations.
Ps keep safe

[Recoilzn]

Ive seen people weld the relief plugs on receivers before, maybe previous technician ignored high temps in room and went to solve leak and welded the relief closed, causing it to explode. The air flow in that plant room looks suspect.

[Rob White]

.

Hello Tassosrr

I have looked at the photos in detail and my poor old eyes can't
quite work out all the details because they are quite dark
but the set up in question, I have seen countless times and
have worked on them for years.

You have a mix and match set of different systems all doing their
own thing and minding their own business, until now............

The units all look standard with no major alterations and the unit
underneath appears to be similar size and make as the one that failed.

Those size systems do not always have pressure reliefs on??

Do you have the remains of the failed receiver? Some good photos of
it would be good.

First thing first, when ever things go wrong I always tell people to go
back to the basics and the basics in this situation is you have a small
plant-room with multiple condensing units and all were doing their own
thing with no major issues until this incident and if that is true what happened
prior to that incident?

You say an engineer worked on the system a month ago, but he claims to have
done a good job? A month ago it was still cool (ambient) but it is warming up
now and whatever the problem is we know pressure and temperature are related.

For it to have failed so catastrophically more than one fault has happened.

Safety switches for over pressurisation failed, why?
Pressure relief (if fitted) failed, why?

Things fail, it's a fact and you might never find the cause. It might be a coincidence
but the guy who worked on it last month did something with the refrigerant and
unfortunately for him I would start there.

Regards

Rob

.

[Magoo]

I would want to have been anywhere near it when it failed.
Looks like a weld failure with dished end still there, this can happenn during normal operation for no obvious reason. I would be getting vessel remains x-rayed to see what and why it failed.
Possible lack of weld fusion and pentration, impurity inclusion in weld, mult possiblities.

[cadwaladr]

I have a great friend long retired,who said problems in fridges are always caused by sh@t as I said before in my earlier post something here was compromised and basic blow off valve failure is rare hp switch could have failed been wrongly set but ,let's face it some people were lucky not to get hurt and some condensing units are supplied without safety valves but it's expected that competent engineers who install also fit the added safety items to prevent such an incident,me I always use the old rule if the liquid line is hot somethings wrong if the receiver is hot the same applys,much of refrigeration trouble shooting initially is done by touch,I would like to know the outcome/investigation into this incident asap.