Choosing the Right Piping Option for Your Industrial Project
By Brent Amelon
You want your industrial piping systems to last as long as possible, operate efficiently, resist corrosion and abrasion, and prevent leaks. That’s a pretty tall order for a pipe – especially when there are several different piping options for industrial applications.
How can you determine which is the best type of pipe for your industrial project? There are several factors to consider:
- Maximum pressure conditions
- Soil conditions, soil chemistry, and the water table
- Connections to existing piping systems
- The types of chemicals in the pipe and in the soil around the pipe
- Unique loading that the pipe might be subjected to
- Thermal expansion and contraction
- Staff availability and knowledge level to maintain the system
Here, we’ll outline four common types of industrial pipe, along with their differences and where they work best.
Ductile Iron Pipe
Often the standard piping material used to transport water and sewage in industrial applications, ductile iron pipe is stronger than thermoplastic pipes, but it’s also more expensive and is susceptible to corrosion.
There are many layers of corrosion protection for ductile iron pipe. Starting with the interior surface, it is typical to have cement lining. This helps prevent tuberculation and maintains a smooth pipe wall for more efficient flow. Epoxy linings are also available for applications with special chemical resistances requirements.
The exterior of the pipe should be protected with a polyethylene wrap. This is the most effective and economical means of preventing corrosion in aggressive soils. Special polyethylene wraps are also available that contain biocide which prevents anaerobic bacteria from corroding the pipe. Cathodic protection can also be utilized to protect ductile iron pipes. This can be effective as long is the cathodic protection system is maintained. Ductile iron pipe may also be coated in zinc. The zinc coating acts as a sacrificial anode that can be used to protect the ductile iron pipe.
Direct buried ductile iron pipe typically comes in 18’ or 20’ sections and come with a bell and spigot ends. The joints can be restrained or unrestrained. Pressurized systems should be restrained within the joints or with the use of thrust blocks at bends, tees, fittings, and valves. Gasket materials at the joint should be selected based on the environment that it will be installed in. Gasket material includes standard rubber, nitrile or fluorocarbon.
Known for its strength, durability, and light weight, high-density polyethylene (HDPE) pipe is often used in water main, storm sewer, telecomm, and electrical pathway applications. The pipe can be color coded to indicate what type of utility the pipe is used for. Its flexibility makes it a great option when considering trenchless installations. HDPE has thicker walls than ductile iron and PVC pipes. The thickness of the pipe wall should be based on the pipe operating pressures and the installation techniques.
Because of its material, HDPE piping systems are inherently corrosion resistant. When installed above ground, or placed outdoors for long periods of time during a below-grade installation, strength can be impacted by exposure to UV rays. Piping that will see extended exposure to sun should be black pipe. Black HDPE pipe contains carbon black that protects the pipe from UV rays. HDPE pipe is also susceptible to hydrocarbons. Hydrocarbons can permeate through the pipe walls and contaminate the utility system. HDPE is sensitive to temperature changes. When installed below grade the temperature remains relatively constant so there is little change. When installed above grade there can be significant thermal expansion and contraction of the pipe in the winter and summer months. The above grade pipe must be properly anchored, guided and supported to accommodate the pipe expansion and contraction.
In most applications, HDPE pipes are welded together with butt fusion or electro fusion welds. When welded together, the fused joints of an HDPE pipe won’t leak – so there is no need for gaskets. Joining the pipe with these methods requires special equipment and training to ensure that the pipe is installed properly. If installed properly the joint will be stronger than the pipe itself. Mechanical joints may also be used on HDPE pipe but it is more prone to failure. Mechanical joints are more commonly used for repairs on the pipe.
PVC pipe is lightweight, strong, and cost efficient. It can be used for above-ground and below-ground piping applications. Similar to HDPE pipe but it differs in that it is a stronger, but more brittle.
Based on the type of industrial application, there are a few PVC choices:
- PVC truss is a double-wall pipe with inner and outer walls that are braced by a truss structure so it can stand up to variable loads and maintain its shape
- Corrugated PVC features a corrugated exterior that offers increased structural strength
- Closed-profile PVC utilizes honeycomb or I-beam internal construction
The material is naturally corrosion resistant; it doesn’t react with air or water like metal. Similar to HDPE, PVC is susceptible to hydrocarbons and UV degradation. Being more brittle than ductile iron pipe or HDPE pipe, the pipe is more susceptible to damage such as an excavator digging around the pipe.
PVC pipe is bell and spigot. Like ductile iron pipe the joints may be restrained or unrestrained and special consideration should go into controlling the thrust force on pressurized systems. Fusible PVC pipe is available as well, which is a gasket-free.
Reinforced concrete pipe (RCP) is known for its strength and ability to retain shape in order to maintain maximum flow. Its most common applications are for sanitary or storm sewer.
RCP offers good corrosion resistance, but coating the RCP pipe improves performance even more by improving resistance to hydrogen sulfide common in sanitary sewer systems. In sanitary applications, an interior lining – such as coal-tar epoxy – can be added to an RCP pipe to protect the pipe walls
This type of pipe is heavy, and manufactured in short lengths due to its weight – which means that more joints are necessary. These joints are typically tongue-and-groove and should be gasketed when used in sanitary sewer applications.
Installation Best Practices for All Types of Pipe
No matter what type of piping system you ultimately choose, following these recommended installation best practices can ensure that the pipes will perform as expected for as long as possible:
- Properly size and slope trenches to facilitate compaction efforts and reducing loading on the pipes
- Remove unsuitable soils before installation
- Ensure that there is proper pipe bedding and compaction to fully support the pipe
- Properly place and compact the backfill in the appropriate lifts
- Apply warning tape to prevent pipe damage during future projects
- Introduce geogrid below paving to minimize differential settlement between the disturbed and undisturbed for soil
- Let concrete structures cure before backfilling
- Make sure to conduct appropriate tests throughout installation: compaction testing, pressure testing, leakage testing, and mandrel testing (for PVC and HDPE pipes)
Once you’ve determined how your piping will be used, we can work with you to select a piping material that will last as long as possible, operate efficiently, resist corrosion and abrasion, and prevent leaks.
After the material has been selected, we’ll ensure that the best practices listed above are followed so that the pipes perform as expected for decades to come.