Internal Instrument Line Level Measurement Without Tank Leak Paths
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Solution Overview
Problem
Conventional pressure or differential pressure-based level measurement systems require penetrations through the tank or vessel below the fluid surface, which are vulnerable to leaks and not suitable for environments like nuclear power plants, where they can lead to reactor core damage or meltdown.
Innovation Solution
A pressure or differential pressure-based level measurement system using a small-diameter instrument line or tube installed within the tank above the fluid surface, sealed with pressure diaphragm plates, allowing measurement of hydrostatic head without external lines, and featuring a relief valve to equalize pressure in case of failure, preventing fluid drainage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure or differential pressure sensors are used for level measurement, then accurate fluid level data can be obtained, but penetrations through the tank wall below the fluid surface are required which create leak risks
Solution Approach 1:
An internal instrument line acts as an intermediary element, extending from the sensor location at the bottom of the tank up to above the fluid surface. This internal line transmits the hydrostatic pressure from the fluid to the sensor without requiring external penetrations through the tank wall, thereby eliminating the leak risk associated with conventional external instrument lines while maintaining accurate level measurement capability.
2Ease of operation
If penetrations are made below the fluid surface for sensor installation, then level measurement is enabled, but the tank becomes vulnerable to draining in case of leak
Solution Approach 1:
The system incorporates a relief valve positioned at or above the fluid surface level as a preventive safety measure. This relief valve acts as a cushioning protection by providing an alternative pressure equalization path that prevents catastrophic tank draining in case the internal instrument line leaks. The relief valve opens to vent pressure before the fluid level can drop to dangerous levels, thereby cushioning against the harmful effect of tank draining.
3Measurement precision
If conventional pressure-based level measurement is used, then fluid level can be determined, but the sensor must be located near the bottom of the tank which exposes it to harsh conditions
Solution Approach 1:
The measurement system is segmented into distinct functional zones: the sensor and electronics are located in the safe upper region of the tank, while the internal instrument line extends downward to transmit pressure information from the fluid. This segmentation allows the sensor to remain in a benign environment away from harsh conditions (high temperature, radiation, corrosion) at the tank bottom, while still enabling accurate hydrostatic head measurement through the internal pressure transmission line.
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
Enables accurate fluid level measurement without the risk of leakage-induced drainage, allowing for safer operation and maintenance of tanks or vessels, particularly in high-risk environments like small modular reactors, by eliminating the need for penetrations below the fluid surface and protecting against reactor core exposure.
Implementation Method 1
measure the hydrostatic head or weight of the fluid at the bottom of the tank or vessel
Implementation Method 2
a relief valve to equalize pressure in case of failure, preventing fluid drainage
Data Source
AI summary
A fluid level measurement system, including an instrument line configured for installation within a fluid storage tank or vessel, the instrument line having a first end configured to be installed below a fluid level of the storage tank and a second end configured to be installed above the fluid level of the storage tank, the first end including a first pressure diaphragm plate configured to communicate with fluid within the storage tank, a pressure sensor configured to be connected to the second end of the instrument line, and a relief valve configured to open and allow high-pressure gas in the tank to escape through a ventilation port in order to depressurize the tank until tank pressure equalizes with the surrounding atmospheric pressure.