The pump requires utility air system to operate the priming ejectors. Prior to start up, priming of the suction pipeline is requested. The start/stop of electrical motor is according to demand from process. The ballast pumps are driven by dedicated low voltage water/glycol-cooled submersible electrical motors. Further, the pumps are individually equipped with a priming system preventing the pump from dry running. The ejector system is described in a separate paragraph in this document.
Please note that provisions are to be taken by client to meet the pump minimum continuous stable flow requirements in order to protect the pump from unacceptable operation conditions. Please also note that the pumps should not be operated against closed discharge valve for more than maximum 30 seconds, as this may cause damage to the pumps.
The Ballast pumps with associated electrical motors are individually and equally equipped with instrumentation for protection.
Control/Monitoring parameters for the pumps with motors are as follows:
All temperature monitoring is based on Pt-100 RTD temperature elements of dual type. Using two Pt-100 elements, one active and one spare are included for each sensor.
The motors are equipped with one integrated temperature sensor for monitoring the cooling medium temperature, which will detect excessive motor temperature conditions.
Each motor is equipped with an integrated dry running sensor in the cooling medium loop preventing the motor from starting and running without sufficient cooling medium. (The water/glycol cooling system is a closed loop system). The dry running sensor is connected to a “water level On/Off relay” deriving the signal to an On/Off SAS interface signal.
The priming system consist of an ejector, ejector tank with two level switches one High (H) and one Low (L) level, one solenoid, and one pneumatic actuated on/off valve. Main function of the priming system is to prevent the pump from starting/running when air has entered into the ballast pump system, by evacuating any air pockets from the suction side of the ballast pump system.
The ejector is connected to platform instrument air via the solenoid valve, which opens for air to the pneumatic operated valve on the ejector suction side. Air is evacuated through the pump at pump suction area. The line is joined into the bottom of the ejector tank.
Air intrusion into the line may occur as a consequence of an unwanted event such as vortex formation in the ballast tanks, faulty operation, false air due to movements in the free surface in the ballast tanks, damaged flange gaskets, etc.
Upon given start signal, the ballast priming system will prime the ballast pumps suction line(s) until the ejector tank level switch is activated. In the event that the tank level switch is already indicating High level, priming will not be performed.