Black iron pipes are steel pipes that are cut to length, threaded, and used in applications such as gas lines and water supply lines. They are primarily used for natural or propane gas lines, so when you have to work on your gas line, it's essential that you know how to deal with black iron piping. Because of the specific nature of such piping and a large variety of fittings that black iron pipes come in, projects or repairs involving this steel pipe can potentially be demanding and expensive.
Before you begin any work on your gas line, you need to be sure you've turned off your gas main. Even the smallest spark or the smallest leak could cause an explosion.
Also be sure to check with your local authorities when installing a gas pipe, as there may be local codes in place that you must obey for both legal and safety purposes.
Step 1 - Cut and Thread the Pipe
Installation is work intensive but straightforward. You start by measuring the run length and cutting the black iron pipe accordingly.
Hold the pipe in a pipe vise on a stand and cut with a pipe cutter with rotary cutting blades. It is recommended that you use a high-quality cutting oil to help protect the pipe cutter.
Once the pipe is cut to length, deburr or shave down the cut end to remove the sharp ridge that will be present when the pipe is finished being cut. Use a lot of cutting oil to prevent damage to the cutter and the threads. A large piece of cardboard or plywood under your cutting and threading area will save you a lot of cleaning later. Alternatively, use a bucket with a large screen strainer under your cutting area to catch excess oil, which will allow you to re-use it later on.
The pipe must be threaded to make the proper connection. If you're lucky, you may find pipe in the required length at a plumbing outlet or hardware store. Threading is accomplished with a pipe threader. Use the proper die for the size of the pipe. Fit the die over the end of the pipe, and turn the handle a half turn at a time to cut the thread. Use a good quality cutting oil to protect the die. Continue threading until the thread is the thickness of the die. The thread will be cut on a taper when finished, providing a better seal. Stand the pipe on end when done to dislodge any pipe cuttings. Wipe the threads with a rag. Be careful here - the pipe threads are sharp.
Step 2 - Attach Pipe Fittings
Black iron pipes are joined using fittings and connectors. In a typical gas line installation, Teflon tape or pipe joint compound should always be used on the threads to insure there are no leaks.
If using a pipe thread sealant tape, wrap it around the threads and insert into the fitting. Make sure you wrap the Teflon tape in the correct direction; facing the end of the pipe, you wrap in a clockwise direction. You should wrap the tape around the threading at least four times, but no more than six or seven times.
Alternatively, you could use pipe joint compound, also known as pipe dope, as an adhesive on the threading to ensure a tight connection. Pipe dope is applied with a brush, small piece of wood, or a rag. It is applied on the threaded end of the pipe and inside of connection fittings before the two pieces are attached to each other. The adhesive dries over time and slightly expands to create an airtight seal between the pipe and the connection fitting where the compound has been applied.
Hand tighten the pipe, then using two pipe wrenches - one on the pipe and the other on the fitting - tighten the connector. If you're finding the pipe is too loose, you may have to re-cut it.
Step 3 - Test for Leaks
Once everything is in place, it is a good idea to test the pipes for leaks before adding supports and hangers. To do so, use an air compressor at the main line to run air through the lines. Brush water mixed with common dish soap on the joints. If there are any bubbles, it means you are leaking gas and should tighten the connection further. On gas pipe, even a small leak is not OK and needs to be fixed.
Note: You do not want to test a gas line by turning on the main supply. This is dangerous for a number of reasons: one being inhaling pure gas, and the other being the increased potential for explosion if too much gas leaks from the lines.
Step 4 - Support the Pipes
Black iron pipe is heavy and requires a good deal of support, especially for longevity. Secure the pipe at every joint, fitting it to floor joists or other structural members with pipe strapping. A good rule of thumb for supports is to secure the pipe every 6-8 feet on horizontal piping.