Storage Tank Pump Speed Control for Vacuum Prevention
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Solution Overview
Problem
Storage tanks used for well fluids, such as oil and water, face issues where gas flashing off into the atmosphere leads to pressure differentials, causing relief valves to open and admit atmospheric air, which is detrimental to downstream gas processing equipment due to oxygen introduction and corrosion concerns.
Innovation Solution
A well fluid storage system with a storage tank equipped with a gas pressure relief valve and a controller system that adjusts the pump speed to maintain gas pressure above a vacuum threshold, preventing atmospheric air from entering the tank, and includes sensors for liquid levels and flow rates to manage the discharge process effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If liquid is removed quickly from the storage tank to increase productivity, then the discharge rate improves, but the gas pressure decreases too much causing the relief valve to open and atmospheric air enters the tank
Solution Approach 1:
The pump speed is made variable rather than fixed. The controller dynamically adjusts the pump speed based on real-time gas pressure measurements from the gas cap, allowing the system to optimize discharge rate while preventing pressure from dropping below the vacuum threshold that would open the relief valve
Solution Approach 2:
A feedback control loop is implemented where the gas pressure sensor continuously monitors the gas cap pressure and feeds this information to the controller. The controller then adjusts the pump speed accordingly, creating a closed-loop system that maintains gas pressure within safe limits while maximizing discharge efficiency
2Extent of automation
If a pump is used to automatically discharge liquids from the storage tank, then the discharge process becomes automated and efficient, but the risk of excessive pressure drop and air admission increases
Solution Approach 1:
The automated discharge system incorporates a feedback mechanism where gas pressure sensors monitor the gas cap pressure and provide real-time data to the controller. This feedback loop ensures that the pump operates within safe pressure parameters, maintaining reliability while achieving automation
Solution Approach 2:
The system replaces manual discharge operations with an automated pump-controlled system. The mechanical pump is supplemented with electronic controls and sensors that automatically adjust operation based on pressure conditions, transitioning from purely mechanical to an integrated electromechanical system with improved reliability
3Strength
If the gas pressure relief valve is installed to prevent tank collapse, then the tank structural integrity is protected, but downstream gas processing equipment is exposed to oxygen and corrosion risks
Solution Approach 1:
The system takes preliminary action by monitoring gas pressure and controlling pump operation to prevent the pressure from dropping to levels that would open the relief valve. This proactive approach stops the harmful effect (air admission) before it occurs, protecting downstream equipment from oxygen exposure while maintaining tank structural safety
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively maintains gas pressure within the tank, preventing the introduction of atmospheric air and minimizing corrosion and safety risks in downstream equipment, while ensuring accurate and controlled discharge of well fluids.
Implementation Method 1
a gas pressure sensor in communication with the gas cap in the storage tank
Implementation Method 2
A pump is connected to the liquid outlet. A controller operates the drive to slow the pump speed as the pressure in the gap cap decreases toward the vacuum threshold pressure
Implementation Method 3
If the pressure of the gas falls too much, a relief valve on the tank opens to admit atmospheric air into the tank. This is done to prevent the walls and exterior shell of the storage tank from collapsing due to a pressure differential between the outside and inside
Data Source
AI summary
A system and method removes well fluids, which include gas and liquids, from a storage tank. The storage tank has a gas relief valve that opens to admit atmospheric air into the storage tank when the pressure of a gas cap decreases below a vacuum threshold pressure. Well fluids flow into the storage tank and the level of liquid is monitored. When the level reaches a first level, a pump is operated by a controller to remove liquid from the storage tank. The pressure in the gas cap is monitored while the pump is operating. The speed of the pump is adjusted to maintain the gas cap pressure above the predetermined pressure and avoid the introduction of atmospheric air into the gas cap.