Condensate Back-Pressure Problem

Don't quite understand your sketch.

On our condensate return, we have installed a Spence Commander Condensate return pump.

This has been virtually maintenance free.

Is there a steam trap located near the downstream PT?

you mean at PT on condensate line...No, but steam trap assembly exists before PT at steam inlet

Steam traps normally go on the outlets of the heat exchangers they serve. They let condensate drain through, but stop the passage of steam.

If you scroll down there is a page from chiller manual. Within our chiller "condensate cooler" is employed which is a heat recovery stage...what is left afterwards is almost wholly condensate @70-80celsius

And have you installed it in accordance with the manual, Deidre?

How old is your equipment? Do you know?

Do you have the operator's manual? What does it say?

What do the maintenance records, and your maintenance crew, say about it?

Has it been well maintained, or neglected.

My guess is that it is old and poorly maintained, if at all.

I clearly said that it had been recently overhauled...although this chiller is say ~10years old but its performance quite good.

Regarding operational manual...My problem is that these instructions apply if I am using ~7bar steam at the inlet whereas according to our load steam pressure we use never exceed ~1bar (for winter at present). This gives me a chiller outlet temperature of ~8C. I cannot find any correlation that on what load I have to maintain condensate backpressure to what amount?

One can see that no elevation exists in the pipe schematics as given in manual

The gray item in the lower right corner of your sketch shows a steam powered condensate pump such as phoenix911 mentioned in post #1. Does your system have one installed?

I am afraid not, I previously stated that steam is being used as pump itself...

Actually, looking at it closer, I see that it is a condensate collection tank with a pump. But a steam-powered pump could be used. In any case, the 8m vertical rise of piping represents about 10psi of additional pressure that must be overcome. When you use the manual drain, you remove this.

That's why it isn't working properly. If only you'd followed the manual! D'oh!

Is vertical piping insulated?--it should be

@ 1 bar or say 101.321 KPa_gage Absolute is ~202KPa, saturated temperature is ~>121 ⁰C, what's the actual steam temperature again at that point near globe valve? If lower than 121⁰C, steam state at that point is compressed liquid so it will accumulate at the vertical conduit of 8m. Pressure built up for the static height is P=ρgh, say ρ=~1000kg/m³ then, P=1000x9.8x8 (kg/m³xm/s²xm) or Pa, ~78.5KPa irrespective of pressure losses due to pipe, valve and fittings.

It seems senseless to solve, you are in a plant and the company pays you.

Your mechanical engineer knows the computation of this, why not collaborate with him? You are a chemical engineer, yes? Why not tell your manager or owner to get a qualified mechanical engineer. If you are a mechanical engineer, why then you do not know this? You are incapacitated with the job, better quit and study more or consult a professional mechanical engineer.

Thanks to all the feedback, I now know that a Spencer pump will be a good & long life choice, thanks again

Don't use the steam supply to lift condensate. Fit a proper trap on the condensate line and either re-route the condensate pipework so that it falls all the way to the receiver, or install a steam-operated condensate pump to push it there. Doing all of this will prove an attractive investment, Boss.