Common Resource
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A resource that can provide services to more than one requester.

NOTE - Common resources are identified as either exclusive-use resources or shared-use resources

If more than one unit can acquire or request the services of a single resource, the resource is designated as a common resource.  Common resources are often present with complex batch processes.  Common resources are often implemented as either equipment modules or control modules.  A common resource may be either exclusive-use or shared-use.

If the resource is designated as exclusive-use, only one unit may use the resource at a time.  A  shared weigh tank in a  batch plant  might be an example of an exclusive-use resource.  It can be used by only one reactor at a time.  The schedule or some other basis for allocation must take this exclusive-use resource into consideration.  If a reactor is waiting for the use of the weigh tank while another is using it, the waiting reactor is idle and is not making product, which has a negative effect on equipment utilization.

If the common resource is designated as shared, several units may use the resource at the same time.  Some  shared-use resources in a batch plant might be a process heater serving multiple units at the same time or a raw material distribution system which is capable of delivering material to more than one unit at a time.  If the capabilities of a shared-use resource are limited, then it is possible that the requests for service might exceed the capacity of the resource.  In that case some of the same concerns about allocation which apply to exclusive-use resources also apply to shared-use resources.  Care must also be taken so that one unit does not improperly shut off or deactivate a resource while other units are using it.

Specification notes

Typically Common resources are much like Units, being made from equipment modules, Control modules etc.

Often they are used for utilities

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