PROPANE REFRIGERATION UNIT - Explosive proof components

[kada]

Hello all!

I understand all electrical equipment around propane refrigiration should be explosive proof.
OK, I can imagine I can get/buy explosive-proof fans, however, what about other electrical equipment? Should I follow any best practice for electrical installation/cables? What component is in the highest danger - is it evaporator fan? What about other distances? Could I say component is out of danget if it is let's say 1 meter far away? What about special explosive-proof enclosure - wouldn't it be solution?

Many thanks in advance.
I need something to start with.

Petr

[norseman]

Hi Kada.
The equipment around should normally be that way. I have been many smaller units as ultralow temperature freezers, cold traps and freezedriers using even worse stuff like ethen(ethylen), ethan and your propane. The charge has mostly been less than 500grams. I have never seen any of them "adjusted" for flamable or explosion hazard. Several of the producers does not even make a label out or inside to tell about the hazard. I have seen some US cold traps using R1150 (ethen) and those had a thinly label for flameable. As I know, they was not sold domestic due to some restrictions. Anyway, all components was standard on them. If you are up to some bigger installations, it would be a big risk to be going that way probably. We sell sometimes a normally simple refrigerator type modified for explosion risk enviroments. They are made with some special Ex. compressors and also fanless. Cost a lot of money extra for this application. It is for sure some people out there working on the big ones and have a good knowledge about components.

[NoNickName]

That's not entirely true. The components must be explosion proof, or in better word ATEX certified, only if in case of leakage there is any possibility of reaching the lower flammable limit.
You don't need any special equipment in any case the refrigerant charge is lower than 150g (god knows why), and when the equipment is outdoor and there is no possibility of reaching LFL concentration of flammable refrigerant at any point of the unit and around it.

[Sandro Baptista]

You don't need any special equipment in any case the refrigerant charge is lower than 150g (god knows why), and when the equipment is outdoor and there is no possibility of reaching LFL concentration of flammable refrigerant at any point of the unit and around it.

Don't you want to mean:
You don't need any special equipment in any case the refrigerant charge is lower than 150g (god knows why) OR when the equipment is outdoor and there is no possibility of reaching LFL concentration of flammable refrigerant at any point of the unit and around it.

I mean this because there is domestic fridges with hydrocarbon refrigerants and they are in doors.

[NoNickName]

Of course, thanks Sandro

[kada]

Excellent, guys!

You both agreed on: You don't need any special equipment in any case the refrigerant charge is lower than 150g (god knows why) OR when the equipment is outdoor and there is no possibility of reaching LFL concentration of flammable refrigerant at any point of the unit and around it.

Well, I am above 150g (about 700g). Evaporator fans+motors are in doors (talking about transport refrigeration unit). If all propan 'pours off' into the cooling box (case of crash), then only evaporator fans+motorrs can initiate an explosion, right?
Where did you take your statement from? Any standard or best practice?

[ozzy bill]

Ultra low freezers on ethane (r170) is there a possibility of explostion ? low side leak etc ?

[NoNickName]

Well, I am above 150g (about 700g). Evaporator fans+motors are in doors


Then you need to make sure that when it all pours off, the mixture with air does not reach the lower flammable limit (volume/volume).
Everything can start an explosion, also a light switch. If you are over the LFL, then you need everything esplosion proof (lighting, switches,... everything inside the room basicly).

[lowcool]

mmm static electricity,bang

[kada]

NoNickName wrote:

Then you need to make sure that when it all pours off, the mixture with air does not reach the lower flammable limit (volume/volume).

Is there any simple way how to calculate lower flammable limit (LFL)?
Let's say I've got 0.8 kg of propane R290. All the content can pour-off into 8 m3 box in the case of crash.
Any equation or thumb of rule of thumb?

[kada]

Do you have idea how much is propane leak detector? I'd need robust/reliable one with wired feedback to switch off all risky devices when LFL is reached.

[ice wombat]

In the past I designed a chiller for refrifgeration using propane. I purchased shell&tubes evaporator and air condensers designed especially for propane. The fan blades had rubber tip covers and the pressure switches the double bellow. I do not remember other peculiar requirements but I'll search in my old papers.
I was forgetting to tell you that the chillers were for outdoor installation....

iw

[NoNickName]

Is there any simple way how to calculate lower flammable limit (LFL)?
Let's say I've got 0.8 kg of propane R290. All the content can pour-off into 8 m3 box in the case of crash.
Any equation or thumb of rule of thumb?

The LFL is %, that is vol/vol x 100.
The question is how much volume 800g of Propane takes up at 1 atm.
Specific density of propane @ 1.013mbar and 15°C is 1.91Kg/m3.
0.8/1.91 = 0.418 m3

0.418 / 8 x 100 = 5.22% which is more than 2.1% (LFL) and less than 10% (UFL), therefore it will go kaboom.


Do you have idea how much is propane leak detector? I'd need robust/reliable one with wired feedback to switch off all risky devices when LFL is reached.


It is forbidden by law to rely on electronic equipment for ensuring safety protection.

[kada]

Excellent answers. Thanks.