What's Your Pipe Project Proficiency?

Is there a piping project in your plant’s future? Take heart: It can be done in-house. Get started with these practical tips.
What's Your Pipe Project Proficiency?
When planning a pipe project, start by visualizing the job from start to finish, and consider the viability of positioning heavy pipe segments for assembly.

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When it comes to piping projects, plant managers often consider a contractor, but this type of work can usually be done in-house — at a substantial savings.

Start with an overview. What do you need to do and how are you going to do it? For instance, replacing existing pipe is generally easier because a layout already exists. Take pictures and make careful measurements of every piece before taking anything apart. If your project is an alteration of existing piping or an entirely new construction, careful planning will save you a lot of headaches in the long run.

Physical constraints
Start by visualizing the job from start to finish, and consider the viability of positioning heavy pipe segments for assembly. Lifting equipment requires a footprint, and hoisting requires a suitable overhead attachment point.

Hoisting is serious business, so consult state law to determine if the job requires someone with a hoisting license. Most importantly, consider the weight of items you intend to lift and the capacity of the lifting equipment. Remember that forces exponentially increase on chains and slings when lifting at angles. Select chain, slings and other rigging made specifically for hoisting, which are rated for several times what you intend to lift.

Pipe needs to be permanently supported at regular intervals either by hangers or floor stands, and support spacing will vary depending on pipe type. When using steel pipe in water service, a good rule of thumb is the nominal pipe size plus 10 equals maximum spacing in feet. For example, an 8-inch diameter pipe plus 10 equals 18-foot spacing. Pipe systems for positive displacement pumps, pumps that start and stop often, or systems subject to surges due to valve operation should have thrust blocks, thrust rods or another means to counteract linear forces. Pump volutes cannot be used to support any pipe weight.

If you are replacing pipe, consider why the original pipe failed. If the pipe was in service for 50 years before failing, it was probably well specified. If the pipe you want to replace was installed before the 1970s, PVC might not have been specified and certainly deserves consideration. PVC is easy to work with and can be used in many applications. For chemical applications, make sure you use compatible pipe, and carefully select gasket type.

Start with a basic sketch of your project, including general dimensions. Glued PVC projects are much easier to plan because you can easily cut and fit parts as you go along. With PVC, consider flange joints for high-use valves because they are easier to replace. For projects using flanged or precut threaded pipe, layout planning is much more critical.

Take some time to research various fittings. Get familiar with pipe and fitting nomenclature. Consider using sweeps or a pair of spaced 45s instead of close elbows to cut down on total dynamic head. Also, research your valve choice, which will vary depending on application. Think about including clean-outs and flushing points in your layout. For threaded assemblies allow for twisting the pipes and fittings together — you will probably need to include a union or flanged joint to complete the assembly.

Call your supplier for the dimensions of valves, elbows and any other pieces. If you can, take delivery of these parts first and lay them out to determine the exact length of pipe. Establish fixed points as to where the pipeline starts and ends. Plumb lines, straight edges and levels will help you line things up for measuring. You should also consider buying or renting a laser level because the slightest angular offset will translate to considerable linear inaccuracy.

When making your parts list, measure twice (or more) and order once. Remember to allow for gasket thickness when you measure for pipe length. Also, remember the final assembly will be torqued down tight, so it’s better to spread a flange a bit to get the final gasket installed rather than using flange bolts to draw a gap closed. Threaded pipe has a bit of flexibility, but be careful how much length you allow for insertion into each fitting. Pipes handle enough stress in service; you don’t want them under stress just sitting there.

For glued PVC pipe, dry-fit everything before you cement. Temporarily support partial assemblies with rope or blocks so you can measure for accurate cuts. Remember that a well-cemented PVC joint should be twisted and held fast before it grabs. Plan your final joint accordingly because you can’t twist an elbow once it’s in place.

For flanged pipe, don’t bolt sections together without setting up supports. Bolt everything together loosely to make sure things line up without stress. Tighten flanges gradually and throughout the assembly. Getting the last gasket into place can be tricky. Flange-spreading tools can help, but you can often pull or pry flanges apart enough to get it done.


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