[Pannalal Chakraborty]

I suppose you either use P5 or P9 tubes for coker. I would like to know the following

1) What is the target skin temp. you use.
2) What is its’ relationship with design pr. of the coker heater ?

Chakra

[Pannalal Chakraborty]

I suppose you are talking of more than one tubes. Does it have only plugs or does it have bends like modern DCU furncaces do ?

Pigging is effective in case of straight tubes but faces difficulties at return bends/headers. We have earlier done turbining (a mechanical turbine operating on compressed air) and switched to steam-air decoking some twenty years back. Only problem with S/A decoking that it makes the un-opened plugs loose as well. At present some Cos. claim to clean any tube with hydrojet blasting operating on principle of hydrokinetics – basically different vibration range for metal tubes & deposits along with high pressure water jet. They claim to clean heater tubes as well along with condensers etc. I do not have any 1st hand experience with their heater cleaning. An net search with hydrokinetics may give you some direction.

‘Hope it helps

Chakra

[Pannalal Chakraborty]

Our standard practice does not allow us to open / enter any system without positive isolation. Basically, a schematic drg showing blinds is maintained along with a master list of blinds. This also helps when you are de-blinding before commissioning.

[Pannalal Chakraborty]

Thanks.

The inlet pr. (SOR) is approx 26 kg/cm2 at convection inlet. At EOR, it becomes approx 30-32 kg/cm2. The inlet pump is designed for 50 kg/cm2 pressure, assuming worst case condition of 3 mm coke deposits in radiatoion tubes – which is never reached. The limiting temp. (as per the original calc which I have seen) has been established by assuming worst combination of pressure & temp. on 7 th tube from outlet (total 34 tubes in a pass) and assuming 22 kg/cm2 pr. in that tube (which is very very high – should have been approx 8-9 kg/cm2, considering outlet pr. -4-4.5 kg/cm2). After that assumption, back -calculation was done to reach the figure of design limit -612 C.
Now, as that design pr. will never be reached, higher op. temp. shoud have been allowed. However, the concerned aquthority is asking for some code/std. or Recomm. Practice reference for changing the op. temp. limits.

‘Hope you can help.

Regards

Chakra

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