A Video Guide to Remote Sampling Basics

A Video Guide to Remote Sampling Basics

Jason Fry | Monday, December 26, 2016

Hello, my name is Jason Fry, and I’m one of the instructors with Industrial Scientific’s training team. In this video, we’re going to demonstrate the use of sampling accessories and pump equipment, and also discuss some of the basic guidelines for confined space entry. Remember to consult your regulatory agency for additional information regarding confined space entry in your area. For more information regarding the equipment or accessories used in this video, or additional training, please refer to our website www.indsci.com or contact your local Industrial Scientific representative.


Gas Sampling Basics

Confined space entry is a process that needs to be handled with caution. You should always err on the side of safety. Your life and the lives of others may depend on it. Let’s talk about the approach to the confined space. After you’ve hooked up all of your equipment and you’re sampling the area, you should sample the area as you approach—and you don’t want to approach it directly. For example, you may want to stand upwind or off to the side; you don’t want to be in the direct flow of the gas that could be escaping or evacuating from that space. Once you’ve safely approached your confined space, and you begin to sample, we need to take things like stratification of gases into consideration.

We’re going to sample each of those different levels within that space. Typically we use a four-foot rule—you’re going to sample those levels or intervals every four feet through the entire depth of your space. If your space happens to be less than 12 feet, you could go with a simple top, middle, and bottom entry, and that would cover most of your areas.

Let’s talk about the stratification of gases. In the image on the screen, we see a representation of where some of the common toxic gases would settle. You notice for example H2S settles at the bottom; it’s a heavier-than-air gas. That’s not always a steadfast or absolute rule. We need to take into consideration things like air current or ventilation. You may find H2S at a different level. If you see those readings on your screen, that doesn’t mean that your instrument is incorrect. It could be detecting that gas at a different level. Remember these are general guidelines, and for more specific information concerning confined space entry, consult your regulatory agencies for details.

Let’s take a look at the equipment that we’re going to use for this demonstration or what you might find in your confined space entry. For this demonstration, I’m going to use the Ventis MX4, but this also applies to the Ventis Pro Series, the MX6 iBrid, and even the Ventis slide-on pump. For the sampling accessories, I’ll be using the stainless steel extendable probe, but we also have different lengths and varieties of sampling tubing or even the polycarbonate probe.

Filtration Basics

Let’s talk about filtration. There are filters installed in each of these pumps, and that’s solely to protect the pump—the equipment itself. You’ll also need filtration installed to protect your sampling path. You notice that I have a filter installed on the end of my extendable probe. There’s also a filter installed at the end of my polycarbonate probe, and there are even disc-style filters on the ends of my sampling lines. I can’t stress the importance of filtration enough.

Let’s walk through an example. A worker is in the field and drops a line into a confined space vessel, and it has a filter on the end of it, and that filter pulls in a contaminant—so what do they do in the field? They remove that filter and continue sampling. Next, they contaminate the line. That line becomes contaminated and then ultimately it leads back to the filter in the equipment. So what did they finally do? They removed the filter from the pump and ultimately it causes contamination inside the pump. Filters are cheap, but pumps are expensive. Always use filtration when you are sampling.

Inspecting and Testing the Equipment

Next, we’re going to inspect and test our sampling accessories and our pump. It’s assumed that you’ve already conducted the four steps of safe operation, either using a DSX Docking Station or similar. Or, using your manual calibration and bump testing equipment. Let’s quickly review those four steps.

If we’re using a docking station, the first thing that we would do is dock the instrument. After it ’s finished with its utilities and gives you a green indication on the dock, you would turn on the instrument and check the battery. After that, we would conduct a zero in a clean and safe atmosphere, and finally, we would clear the peaks. If we are conducting it manually, we are going to start with powering on the instrument and checking the battery, then we’re going to zero, conduct our bump test, and finally clear the peaks. Once your four steps of operation are complete and your instruments are ready for use, you can then move on to the inspection and the test.

The first thing I’m going to do is check my instrument and make sure that my filters are in good repair. Unscrew the cap, and verify that the filter is in good condition. The only time I would replace the filter is if it’s either contaminated or damaged. This one is in good condition, so it’s ready for use. Next, I’m going to move on to inspecting the probe that I’m using. Now in this demonstration, this is the extendable probe with the filter installed. I’m going to extend the probe, cap the ends, and collapse it to check to make sure that all of the seals are intact and that I’ve got a good sampling path. After I collapse it and let my finger go, I should hear air escape. If I did, I’ve got a good probe. In the next part of the demonstration, we’re actually going to include the coiled tubing. The probe is going to attach to the tubing, and to the pump. I have to check to make sure that this is also in good condition so I’m going to connect it to the end of the probe and conduct the same test where I collapse the probe again, but this time, I’m going to actually pinch the end of the tubing and then collapse it. I should still hear air escaping, and I do. My sampling path is intact.

In the final test, we’re going to make sure that the pump goes into an overrun condition, and that verifies that if there’s any kind of blockage in my sampling path, it will notify me by shutting the pump off. I’ll attach the pump to the end of my tubing, and when I finally block this, the pump is going to go into an alarm. It’s going to give me an indication showing that the pump motor is blinking, the exclamation point is blinking, and also my alarm indication is going off, and I should see my visual/audible alarms. My instrument went into an alarm as it was expected to. It will wait a few seconds, attempt to clear that blockage, and it will restart. If the alarm condition clears, it shows that my instrument is operational and I can begin my confined space entry.

Rules for Confined Space Sampling

The next part we want to talk about is our two and two rule when it comes to confined space sampling. The two and two rule states that for every foot of tubing, you allow two seconds for the gas to actually pass through that tubing, and then finally the second part is two minutes at each location. Now in this particular example, I’m going to disconnect my sampling probe and just use my tubing. And this tubing, if it’s uncut, is actually 10 feet in length. So given that information, I have to wait approximately 20 seconds for the gas to pass through this sampling tube and get to the front end of the instrument. At that point, the sensors would begin to respond and shortly thereafter you would see those readings once we see those readings beginning we have to give it two minutes at that location to get the full concentration of gas. I’ve got my cylinder here. I’m going to go ahead and attach my sampling path to it, and I’m going to turn on the regulator. After approximately 20 seconds, I should begin to see readings. The readings are beginning to appear. For this demonstration, I’m going to secure the gas, but if this were a confined space entry, once I began to see those readings, I would have to wait two minutes, and that’s the two and to rule.

For additional information regarding confined space entry, refer to Industrial Scientific’s Guide to Detecting Atmospheric Hazards in Confined Spaces part number 17046848. For more information regarding the sampling equipment or the training that was conducted here, refer to our website www.indsci.com.