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O-ring Expansion

O-ring Expansion

O-ring Expansion


Good Day,

i have a problem regarding the O - ring of our Transfer Pump of Spent Caustic unit. the O - ring expanded that caused to break the Mechanical Seal of the said Pump. the o - ring material was EP( Ethylene Propylene) and i checked that the chemical components of the spent caustic is compatible to the said material of the O - Ring. any other factor that may be the caused of o - ring expansion.

thank you and have a nice day.

RE: O-ring Expansion

What was the fluid being pumped?
How long was it in service?
What pressure service?
What temperature service?
What flow rate/pump rpm?
What did the pump seal manufacturer require in HIS bill of material for HIS pump seal?

RE: O-ring Expansion

1. Spent Caustic that contains
Quantity :1800kg/hr (1.8m3/hr)
NaOH: 3.1 wt%
Na2CO3: 0.3wt%
Na2S: 1.43wt%
H2O: 95.08wt%
Mercaptide: 73.48 wt.ppm S
Biological Oxygen Demand (BOD): 402 mg/L
Chemical Oxygen Demand (COD): 36261 mg/L
Oil/Grease (Maximum): 15 mg/L
Phenol (Maximum): 190 mg/L
pH: 12.53
Pressure: 700 kPa(g)
Temperature: 39 C
Density: 1000 kg/m3 (Assumed)
Viscosity: Less than 30 mPas (30 cP) (Assumed)
Higher Heating Value:
Design: 215.2 kJ/kg (51.4 kcal/kg)
Normal: 213.2 kJ/kg (50.9 kcal/kg)

2. RPM of the pump is 3530 RPM (designed)

RE: O-ring Expansion

I don't know the recommended service life for that material under very high pH conditions - EP( Ethylene Propylene) from your original posting - but the pressure and temperature are at least moderate.

But a 12 pH even at only 40 deg C may mean you simply cannot rely on the O-ring for a long time.

RE: O-ring Expansion

Ok sir, Thank You. For now we are looking for the possibility of the error in the temperature either in the product side or barrier side, since all of the O-rings of the pump expanded. Thank You for your information.

Can this amount of Phenol in the fluid may affect the EP O - ring? I read in the internet that Phenol is not compatible with the EP (Ethylene Propylene).

RE: O-ring Expansion

We can't answer the phenol compatibility question; you can.

Go to your local o-ring seller, and buy a few examples of your current material, and of every possible alternative you can speculate, given your newfound knowledge. Size doesn't matter much.

Put a sample of each material in a separate clean beaker.
Fill all the beakers with your spent caustic soup, and wait for something to happen. Given the strong expansion you report, there should be obvious results overnight or sooner.
Proceed accordingly.

In future, please refrain from duplicate posting.
In current time, please Red Flag your duplicate posts.
In the resulting dialog box, ask that the discussion be deleted.

Mike Halloran
Pembroke Pines, FL, USA

RE: O-ring Expansion

The first step would be to verify that the o-ring material is actually what it is advertised to be. Mistakes happen.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: O-ring Expansion

And use the term "swelling" instead of expansion, you will find more information.

RE: O-ring Expansion

Ok Sir, Thank You for your input and advise.

Have a Nice Day.

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