Use a Swagelok Regulator to Speed up Analytical Systems
by Katie Reid, on Fri, Nov 18, 2016 @ 12:11 PM
The lower the pressure of a gas, the shorter the time delay to the analyzer
In an ideal world, you would be able to get a fluid sample instantly from the process line to the analyzer. The real world, alas, it is far from ideal. So it's important to learn a bit about time delays and how do minimize them.
First, realize that a delay may occur in any of the major parts of an analytical instrumentation system: the process line, the tap and probe, the field station, the transport line, the sample conditioning system, the stream switching system, and the analyzer itself. A small delay at each stage will add up.
One way to minimize the delay is with a pressure regulator. In gas systems with a controlled flow rate, the lower the pressure, the faster the gas moves, which means the shorter the time delay.
Start at the tap
Ideally you want to tap the process line as close to the analyzer as possible. But you also want to stay upstream of drums, tanks, dead legs, stagnant lines, or other sources of delay. Because of that, you may have to make do with a location that's less than ideal. If the tap is a long distance from the analyzer, a fast loop is a good means of quickly delivering fluid to the analyzer and returning the unused portion to the process.
Another typical source of time delay is the probe. The larger the probe's volume, the greater the delay. Minimize the delay by choosing a low-volume probe.
At the field station
For an analyzer that requires a liquid sample it is better not to use a regulator. High pressure will help prevent the formation of bubbles. But with a gas sample, a field station is one of the means of reducing pressure in the transport lines. Time delay decreases in direct proportion to absolute pressure. At half the pressure, you will get half the time delay. The sooner the pressure is dropped, the better, so put the field station as close to the tap as possible.
There are a few different ways to configure the regulator. With a drop in pressure, almost all gasses lose heat. If the gas is close to its dew point, the result from this cooling is condensation. In some cases, the loss of heat may be great enough to cause the regulator to freeze up. In those cases, a heated regulator may solve the problem. If you don't expect condensation, a standard regulator will probably do. Read more about Pressure Regualators and how to read a flow curve here.
If a liquid must become a gas before it can be analyzed by a gas chromatograph or other analyzer, it's time for a vapourizing regulator.
Another means of attaining a faster response is to move the regulator closer to the analyzer with the aid of a second fast loop.
There's a lot more to these tips than simply plugging in a component. Vapourizing regulators, in particular, require extra care because the volume of a sample can increase greatly as it changes from liquid to gas. Done incorrectly, the addition of a vapourizing regulator can actually increase the time delay to the analyzer.
Fortunately for you, Edmonton Valve & Fitting loves to discuss regulators, analyzer systems and all things dealing with fluid systems. Tell us about your analyzer system and let's get started finding the right configuration.