Flow control Valve (FCV)
Stepping up, the next option is to employ a flow control valve that can be either manually or automatically (via PLC) controlled from surface by means of the surface control system (SCS).
This system allows the user to control the injection pressures and flow
rates to desired levels and alarm when the 
system is at fault.
Typically the system is configured by means of a PLC that will allow the
user to specify the desired injection flowrate provided the injection
pressure remains within a set band of allowable pressures. The valve
will modulate open and closed by way of surface pumps, valves and
controls with the SCS trying to achieve the desired injection flow rate.
If the system falls outside of the desired injection pressures, the
system can be configured to alarm such that the required action can be
taken. Such faults may be:
1. FCV modulated fully open with injection pressures above maximum set
pressure and desired injection flow rate not obtained. This fault would
be caused by a blocked or fouled bore that is not taking the desired
flow rate.
2. Injection pressure falling below minimum set point. This fault
signals a problem with either the FCV or SCS resulting in injection
water possibly cascading into the bore and entraining air which can
result in subsequent air-fouling, bio-fouling or calcite formation.
