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excf25088
17-01-2015, 08:34 AM
Hi Everyone,

I was after some advice on a Scraped Surface Heat Exchanger (SSHE) I am in the process of upgrading.

A little about the setup: MSC (Mechanically separated chicken) is fed into a hopper, which is then pumped through the SSHE and out to a three way valve which then either sends it to the packing area if the operator requests it or is fed back in to the top of the hopper and recirculated.

Brine is pumped through a plate heat exchanger off a glycol system. The brine flow feeding the SSHE is controlled with an actuator (once 4-20mA control) now manually turned by the operator.

This once was a automated process but over many years temp sensors, flow sensors, valve controls have broken down/ been removed/ bridged out / etc and it is now a manual process and I have the lucky job of overhauling it.

Previously the brine actuator was controlled by a PLC with a PID instruction which used a PT100 probe on the product outfeed side of the SSHE as the process variable but due to the product being recirculated sometimes the product going into the SSHE may already be near zero degrees and could possibly freeze up in the SSHE after going through a few times.

Would it be better to use another PT100 probe on the Product infeed side as well? Any thoughts?

If I was to do this would it be as simple as using an average of the infeed and out feed temperature sensors as my process variable or would it be a little more complicated?

Thanks in advance for your help.

Magoo
17-01-2015, 11:22 PM
generally operate similar to a continuous ice cream churn barrel, as product freezes the motor current increases on churn drive , which in turn regulates the glycol flow to maintain a constant barrel temperature for optimum product out feed temps and hardness. You will need a PLC to control the inputs and regulation.