4 replies to this topic

[JaiEdi]

As part of an olefin plant design, naturally the distillation train operates at cryogenic temperatures resulting in a cold box of multistream HXs and flash drums and 4 refrigerant cycles necessary to provide the cooling duties for the condensers in the columns. 

 

The main hazards I've identified are 

1. Cryogenic temperatures - low temps cause frostbite and burns etc. - Solution adequate PPE 

2. flammability of olefins and refrigerants if they leak - insulate or jacketed vessells, regular pipe inspections, gas detectors? not sure what other safety features I could design or recommend to be implemented to reduce risk of setting alight?

3. Overpressurisation of vessells specifically in condensers and heat exchangers where phase change is occuring- install pressure relief valves to prevent build up of pressure 

4. Cooling water freezing and blocking pipes - insulated the pipes to prevent the CW from freezing? 

 

Are there any other hazards, if you would rank the hazards in order of most signficant based on both severity and likelihood what would you do? 

 

My current thoughts are 

1. flammability and fire due to leak in pipes - feel this is the most dangerous and likely scenario - what safety barriers can I install?

2. overpressurization - Other than relief valves and pressure gauges and their control loops, what else could I recommend to install? 

3. cryogenic temperatures causing col dburns - just easy to 

[Bobby Strain]

There are no systems in an ethylene plant that operate at cryogenic temperature, unless there is a methane system at low pressure. The cryogenic temperature region begins at -150 C. You should check your dictionary to confirm.

 

Bobby

[JaiEdi]

Ok but the hazards identify still stand irrespective of nomenclature do they not? 

 

We do have a methane system at -160 C, but regardless operating at below 0 introduces the risk of cryogenic burns and frostbite does it not? 

There are no systems in an ethylene plant that operate at cryogenic temperature, unless there is a methane system at low pressure. The cryogenic temperature region begins at -150 C. You should check your dictionary to confirm.

 

Bobby

[Pilesar]

Cryogenic burns and frostbite are not much concern compared to high temperatures. Unlike hot surfaces, the cold surfaces are self-limiting. If the insulation is inadequate on a cold process, humidity from the air quickly forms water ice on the surface. So skin contact becomes no more hazardous than with an ice cube from your freezer. You can get frostbite from an ice cube, but only after prolonged skin contact. In contrast, hot surfaces can melt skin almost instantly.

[Pilesar]

Water is not routed to exchange heat with cryogenic processes. Cooling water freezing hazard in an ethylene plant would be due only to low ambient temperatures.