2 replies to this topic

[Jome128]

Sorry to bother the expert this trivial.

The waste water is transferred from reaeration tank to the clarifier which incorporated gear box and conveyor.

 

The wastewater concentrated with sludge to be carried outside and picked up by sludge return pump transfer to

two destination (1).back to aeration basin.(Main route) (2). Sludge storage tank (accumulated sludge reach to amount to be discharge).

 

The control scheme is confused to me. (Scheme is attached). There are two trains of clarifiers, and two trains are running at the same time.

Each train has the 2 clarifiers / 2 sludge returns pump (1 primary/1 backup).

The pump is VSD type. Upon failure of the primary pump in train 1, (automatic case):

The primary pump is taken out of service (thus becoming the backup one), and backup pump is placed into service(becoming the primary pump), Selection of the primary and backup is alternated on daily basis via the scheduling function of a time clock. (Manual case) :the primary pump and backup pump is alternated through  selector switch which is inside the MCC. The maintenance personnel can manually flip the switch periodically.

 

I am not sure how to put this control scheme in P&ID(I means that the signal from vsd to mcc or interlock first ?).

 

The other question bothers me is,

 

1. Why is the VSD control signal always transfer to MCC first instead of interlock ?

2. What is the difference between MCC and interlock? Is possible to just replace MCC function with Interlock function and

no more MCC to participate in this P&ID scheme.

 

 

Greatly appreciated your kindly help and comment.  question conveyor control.png   62.03KB   33 downloads

Edited by Jome128, 26 April 2013 - 07:32 AM.

[thorium90]

Is your attached file correct?

 

By MCC, you mean motor control centre right? As the name implies, the signals for starting or stopping the pump motor go to the MCC first. MCC is where one finds the switchgear, breakers, motor feeders.. Interlocks dont control the motor, they provide permissive.

Edited by thorium90, 25 April 2013 - 10:22 AM.

[Jome128]

thorium90

 

Your are correct. Thank you for your reminding. The attached was attached.