Thief Hatch Force Sensor for VOC Leak Detection
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Solution Overview
Problem
Thief hatches in storage tanks, used for inspecting and sampling liquids containing volatile organic compounds (VOCs), often leak due to improper closure and maintenance issues, leading to unchecked VOC emissions into the atmosphere, as existing sensors cannot accurately distinguish between a closed and latched state, and there is a lack of monitoring for the mechanical condition of the pressure seal.
Innovation Solution
A force sensor is positioned between the upper and lower sealing rings of the hatch, detecting the force applied across the pressure gasket to differentiate between open, closed, and closed-latched states, and is coupled with a monitoring unit to communicate force readings and alert operators of insecure hatch conditions, allowing for real-time monitoring and proactive maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing sensors are used to monitor hatch closure, then the monitoring system is simple, but the sensors cannot accurately distinguish between closed and latched states leading to VOC leakage
Solution Approach 1:
The monitoring system is segmented into multiple independent force sensors positioned at different locations (center and perimeter) of the hatch cover. Each sensor independently monitors local closure conditions, allowing the system to distinguish between partially closed and fully latched states with high precision while maintaining relatively simple individual sensor components.
Solution Approach 2:
Force sensors serve as intermediary devices between the hatch mechanical structure and the monitoring system. These sensors translate mechanical closure states into electrical signals that can be processed by the control system, enabling accurate detection of closure and latched states without requiring complex mechanical linkages or modifications to the hatch structure.
2Ease of operation
If thief hatches are left open or unlatched for operational access, then ease of operation is improved, but VOC emissions increase due to improper closure
Solution Approach 1:
The monitoring system provides real-time feedback to operators about the hatch closure state through alarms and notifications. When the hatch is opened for inspection or sampling, the system detects the change in force readings and alerts operators. Upon closure, the system verifies that sufficient force is applied to achieve proper sealing, providing feedback that confirms VOC containment before allowing operations to resume.
Solution Approach 2:
The system prevents harmful VOC emissions by requiring proper latching action before normal operations can continue. The force sensors detect insufficient closure force and trigger alarms that prevent operations until the hatch is properly sealed, thereby preemptively blocking the pathway for VOC leakage rather than merely detecting it after the fact.
3Reliability
If pressure gasket hardness is reduced to improve sealing, then the seal effectiveness is improved, but the gasket wears faster due to maintenance issues
Solution Approach 1:
The force sensors are installed and calibrated before the pressure gasket fails, establishing baseline closure force requirements. The monitoring system continuously compares actual closure forces against these baselines, enabling early detection of degradation trends. This preliminary monitoring allows maintenance to be scheduled before the gasket wears out completely, extending its effective service life through proactive replacement.
Solution Approach 2:
The monitoring system provides continuous feedback on closure force magnitudes, allowing operators to verify that sufficient force is applied during each closure cycle. This feedback ensures that the soft pressure gasket is consistently compressed to its optimal sealing state, maximizing its sealing effectiveness and service life by preventing improper closure that would accelerate wear.
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 reduces VOC emissions by ensuring accurate detection of hatch closure states and monitoring the condition of the pressure seal, preventing leaks and enabling timely maintenance, thus complying with environmental regulations.
Implementation Method 1
A force sensor is positioned between the upper sealing ring of the hatch lid and the lower sealing ring of the flange, adjacent to the pressure gasket
Data Source
AI summary
The present invention is directed to a device and system for monitoring the closure state of a hatch. A pressure sensor is positioned between the upper sealing ring of the hatch lid and the lower sealing ring of the flange, adjacent to or within the pressure gasket. In the open position, force sensor detects little force between the upper and lower sealing rings, in the closed position, the sensors detects an increase in force, but in the closed and latched position, the force sensor detects much higher force between the upper and lower sealing rings. The force sensor is electrically coupled to a monitor unit that communicates the force readings (either as raw or processed data) to remote locations such as data/processing remote centers, clouds, or portable devices. Cry-out alarms may be employed to alert operators when a hatch is open or not securely latched.