Operations
Start-Up (cont’d)
Start-up of New Plant or an Empty System
The machinery must always be started in an order reverse to the run of the process.
(Downstream equipment is started first.) This will ensure the unobstructed flow of the
pulp in the process by having the downstream equipment running and thus ready to
receive the incoming pulp.
Frequently equipment have interlocking by-pass switches which will allow the starting
of the machines even if the receiving part of the process is not running. This is done
by initiating a by-pass switch in the instrumentation, or having electrical/computer
support people disable certain interlocks without evidence of this from the operator’s
console.
Should interlock bypasses be used for any reason, take adequate steps to prevent
personal injury or equipment damage.
Instrumentation Note:
Some interlocking systems will adequately STOP the system in a fail safe mode, but
cause unnecessary problems when restarting, if controllers are left in automatic.
For example:
While running a flow control (FC) valve in automatic mode, an interlock condition is
not satisfied (loss of interlock permissive), causing the valve to automatically close.
The last (or normal) valve position is stored in the computer’s memory. When the
interlock condition has been satisfied (permissive condition has been corrected), the
valve returns to the opening stored in memory. This opening may be too large while
normal operation is being established.
OperationsStart-Up (cont’d)Start-up of New Plant or an Empty SystemThe machinery must always be started in an order reverse to the run of the process.(Downstream equipment is started first.) This will ensure the unobstructed flow of thepulp in the process by having the downstream equipment running and thus ready toreceive the incoming pulp.Frequently equipment have interlocking by-pass switches which will allow the startingof the machines even if the receiving part of the process is not running. This is doneby initiating a by-pass switch in the instrumentation, or having electrical/computersupport people disable certain interlocks without evidence of this from the operator’sconsole.Should interlock bypasses be used for any reason, take adequate steps to preventpersonal injury or equipment damage.Instrumentation Note:Some interlocking systems will adequately STOP the system in a fail safe mode, butcause unnecessary problems when restarting, if controllers are left in automatic.For example:While running a flow control (FC) valve in automatic mode, an interlock condition isnot satisfied (loss of interlock permissive), causing the valve to automatically close.The last (or normal) valve position is stored in the computer’s memory. When theinterlock condition has been satisfied (permissive condition has been corrected), thevalve returns to the opening stored in memory. This opening may be too large whilenormal operation is being established.
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