Sniffing Leak Detector Orifice Pressure Stabilization
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Solution Overview
Problem
Sniffing leak detectors face reduced detection sensitivity due to fluctuations in the suction capacity of the vacuum pump, which affect the total pressure at the distribution point, leading to unstable measurement signals.
Innovation Solution
A circular orifice is used as the throttle between the sniffing line and the vacuum pump, ensuring a pressure drop greater than P2/2, making the gas flow independent of the pump pressure, thus maintaining constant pressure at the inlet of the vacuum pump and stabilizing the detection sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a vacuum pump is used to maintain pressure at the distribution point, then gas flow can be controlled, but the suction capacity of the pump fluctuates causing total pressure instability
Solution Approach 1:
A capillary tube is introduced as an intermediary element between the vacuum pump and the distribution point. This capillary tube acts as a flow resistance element that decouples the pump's suction capacity fluctuations from the distribution point pressure, allowing the distribution point to maintain stable total pressure while the pump continues to provide gas flow control.
2Speed
If the suction capacity of the vacuum pump increases, then gas flow improves, but the total pressure at the distribution point becomes unstable
Solution Approach 1:
The capillary tube serves as a buffer that absorbs the dynamic variations in pump suction capacity. By providing fixed flow resistance, it ensures that changes in pump speed do not directly translate to pressure fluctuations at the distribution point, thereby maintaining reliable operating conditions.
3Ease of operation
If a throttle is used to control gas flow, then flow regulation is achieved, but pressure fluctuations from the pump affect detection sensitivity
Solution Approach 1:
The capillary tube is positioned downstream of the distribution point to provide flow resistance that isolates the detection system from pump-induced pressure fluctuations. This allows the throttle to maintain flow regulation capability while the capillary tube protects the detection sensitivity from pressure instability.
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
This configuration ensures that the detection sensitivity of the sniffing leak detector remains unaffected by fluctuations in the vacuum pump's suction capacity, providing consistent signal stability and sensitivity regardless of pump pressure variations.
Implementation Method 1
the throttle provided between the sniffing line and the vacuum pump behind the distribution point is a circular orifice having such a conductance value that the pressure drop at the orifice is larger than P2/2
Implementation Method 2
In a blocked flow, the flow is independent from the low pressure on the outlet side of the orifice
Data Source
AI summary
The invention relates to a sniffing leak detector comprising a sniffing line (11) and a feed line (33) that leads to a vacuum pump (16). A distribution point (24) from which a branch line (25) leads to a test gas sensor (15) is provided on the feed line (33). In order for the intermediate pressure (P2) at the distribution point (24) to be independent of feed fluctuations of the vacuum pump (16), a throttle (D2) comprising a supercritically operated orifice (20) is provided between the distribution point (24) and the vacuum pump (16). The pressure drop at the orifice (20) is greater than half the intermediate pressure (P2) at the distribution point (24). The flow at the orifice (20) is thus blocked, wherein the flow (Q) remains constant regardless of changes of the pump pressure (P3). Changes of the intermediate pressure (P2) are thus prevented so that the sensitivity and signal stability of the test gas sensor (15) is unaffected by changes of the pump pressure.