Power Boiler Continuous Blowdown Control

I am doing a project to automate our continuous blowdowns on our

115,000 lb/hr power boilers. Presently they have a variable orifice Hancock valve that the operator manually adjusts. I am wondering peoples opinions, on if I should put in a variable orifice automated valve (normal control valve) with PID control, or an open close valve (ball valve) with a restricting orifice and time proportional control.

The control valve would be sized to give me 2% of feedwater flow at

50%, and the flow restrictor for the ball valve would be sized to give me 4% of feedwater flow.

The ball valve with actuator is a cheaper solution, but is it better? The piping is 3/4".

Thanks.

Curtis

Reply to
Curtis
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You are aware of the cost difference. The big question is lifetime and operating reliability. The process certainly does not require that the blow down be a continuous process. Before you can really compare the two methods, you have to think about how few on off cycles per hour are really needed. The lower this number can be, the better the reliability for the ball valve. You may well be able to substitute a two threshold operation for a time proportional control.

Reply to
John Popelish

The control valve in a throttling condition would more prone to plugging with particulate, especially if this is a 600# class boiler with a hot process zeolite softeners or similar equipment.

Are your multiple blowdowns all piped to this po>Curtis wrote:

Reply to
dummy

If you are considering a ball valve with restriction plates downstream take a look at Valvetechnologies

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Reply to
PuNx

We use a normal control valve and a PID controller witch get it´s setpoint from a ratiostation connected to the feedwaterflow. Works fine for us.

"Curtis" skrev i meddelandet news: snipped-for-privacy@posting.google.com...

Reply to
Patrik Johansson

Yeah, I thought about that, and then trimming the ratio station with a Conductivity controller, but I think that might be "over-instrumentating" the control for a little 115,000 pound boiler.

By the way, what type of valve do you use?

Thanks

Curtis

Reply to
Curtis

We use a Neles segment ball valve, DN50 (2") PN100. The ratio between feedwaterflow and blowdown are 4% the lab takes a sample once a day just to make sure everythings ok. "Curtis" skrev i meddelandet news: snipped-for-privacy@posting.google.com...

Reply to
Patrik Johansson

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