ACS Gas Training - Gas Pipe Sizing 

How to size gas pipe work BS6891
ACS Gas Training. Gas pipe sizing. My name's Allen Hart, and today, I'm a Viva Training Academy, and I'm with Russ, the expert trainer. Russ is going to go through pipe sizing. We've got a few charts. This is a question that I get asked quite a lot. When I do my sizing, and I say, "We're only allowed one mb drop over the installation," on GAS pipe sizing, and people question that and say, "Well, manufacturer instructions say we can go down to 15 mb. People are misreading the installation instructions.
In this video today, Russ is going to go through pipe sizing. Some charts on there. There are also some charts here with the different sizes for different pipes. Russ is going to go through all these. Also, when you've got elbows and you've got Ts, how they affect your pipe sizing. This is going to be a very, very detailed video. It's going to go through the pipe sizing from start to finish really. If you do have any questions about pipe sizing, then obviously, please ask them in the comments below.
Yeah, I think that's it. So let's go over to Russ. This video is for gas safe registered and trainee gas engineers under supervision. Please comply with the current regulations of the time.
Thanks, Allen, for that. Today we're going to look a pipe sizing. Domestic pipe sizing, we'll call it on your SES up to the maximum 35 mil. All I want to do today is give you the principles of pipe sizing and show you some simple, straightforward exercises and practises. There are many, many different ways of pipe sizing. Different publications will show you different methods. I am slightly of the old-school, as you may imagine. I've done it one way for a long time, but there's a new method out there, which I'm going to show you today that I'm quite impressed with, and I've adopted myself. Different publications of this way show you different ways. This one we're using from our training manuals at VIVA training. We use logic, but you'll get the same information out of other publications, example, British Standards BS6891, that type of thing. They'll have the same systems in them. Hopefully by the end of this, and I am trying to keep this simple and break it down as much as I can, you'll understand where we're coming from, and why we pipe size, and of course, a simple method of how to pipe size.
Pipe sizing, as I hope you know by now, is a very vital part of gas pipe work. We need to supply the volume of gas required for the appliance, but we also need to maintain a tolerance within the pressure range. I'm going to give you round figures so you'll understand where I'm coming from, so we don't mess too much on that one. If we have 21 millibars coming out of our metre, on a low pressure system, we should have no more than one millibar drop across the system, therefore no less than 20 millibars going into the appliance.
We're going to do a couple of simple examples of pipe sizing. Remember what we're saying, we're looking to maintain pressure, but we're also looking to maintain that pressure with a volume of gas over a distance. Now the two examples I'm going to show you first are very simplistic, but will show you the difference in how to use the chart initially and how a different pipe size can completely change the pressure loss across that system.
We've got two different systems here. Very simple, very straightforward. In fact, it's all straightforward. You haven't even got any bends. It's a straight piece of pipe just to show you, initially, the example of that. First of all is 10 metres, 10 metres of pipe, up to 15 kilowatts of load. In other words, that boiler is going to use 15 kilowatts of gas per hour. That's the idea behind that. You can convert that to metres cubed, but in this particular case, you actually don't need to. You just work off the . It's one of those situations.
Same with this one. Shorter distance, but now a bigger appliance just to show what different it makes. What you must do on something like this is use a little bit of professional knowledge, if you like, or experience, which I know you don't have a lot at the moment if you're in the process, but it will come in time. You get a feel for what size pipe you need to put in. Now, remember, ideally ... Not ideally, exactly. If you've got 21 millibar coming out of there, you must have no more than one millibar pressure drop across the system. So you should have no less than 20 millibar to the inlet to the appliance, and still supplying sufficient gas to provide 15 kilowatts.