HDPE vs carbon steel vs stainless steel – which pipe is right for energy savings?

As budgets get tighter and the expectation to reduce costs continues to rise, all businesses are on the lookout for ways to save.

While some of the more obvious costs are quickly considered, reducing energy usage and the associated costs is a critical item to consider.

While carbon steel and stainless steel have long been the go-to options, high-density polyethylene (HDPE) pressure piping has quickly emerged as a flexible and easy-to-manage alternative, particularly for projects involving water systems and treatment, cooling systems, corrosive liquids and seismic rated construction.

With guidance from Advanced Piping Systems Director, Nathan Craig, we will explore each type of pipe in detail and guide you towards the best option for achieving your energy savings goals.

Friction and scaling

When trying to maximise energy savings, the last thing you want is unnecessary obstacles slowing progress.

Physics tells us that any disruptions in a flow pathway increase friction, leading to additional turbulence and a subsequent decrease in pressure.

HDPE and stainless steel pipes both possess relatively smooth interior surfaces, resulting in lower friction loss and more efficient system performance, particularly in applications where maintaining pressure is vital.

However, carbon steel pipes have a higher surface roughness compared to HDPE and stainless-steel pipes, which can result in more substantial friction loss and an increased loss of pressure, requiring more energy for fluid movement. It may also result in the use of pumps to maintain the flow.

While initially the installation may deliver smooth results, the build up of scaling within the pipes can present a long-term challenge by reducing the internal diameter of the pipe, diminishing flow capacity and increasing energy consumption.

Addressing scaling challenges may involve additional cleaning or the implementation of water treatment methods.

When it comes to scaling, Nathan said HDPE was superior to the other options.

“HDPE is inherently resistant to scaling which offers huge performance benefits,” Nathan said.

“Comparatively, carbon steel pipes are prone to scaling when exposed to hard water or fluids containing minerals, while in some cases, scaling can occur in stainless steel pipes when exposed to certain water conditions or specific fluids.

“The specific friction loss in a given piping system should be calculated using appropriate hydraulic formulas and considering the system’s unique parameters.

“Pipe diameter, flow velocity, fittings, and overall system design will affect the friction loss characteristics.”

Thermal conductivity and insulation

When striving to maximise efficiency, creating an environment that maintains the desired fluid temperature helps to reduce the energy waste caused by excessive heating or cooling to counteract temperature fluctuations.

The thermal conductivity values for the given materials are approximately:
Carbon steel (150NB Schedule 40): approx. 50-60 W/(m·K).
Stainless steel: (150NB Schedule 40): approx. 14-19 W/(m·K)
HDPE PE100 (160mm SDR17): approx. 0.42 W/(m·K)

These values can vary depending on factors such as temperature, pressure, and specific material grades or precise values, and it’s recommended to refer to material specifications or consult technical references specific to the desired grades and conditions.

HDPE’s excellent insulation capabilities provide a natural barrier against heat transfer, effectively reducing heat loss and gain through the pipe walls, which is especially advantageous in applications where precise temperature control is critical, such as in HVAC systems or industrial processes.

“In heating systems, HDPE pipes reduce the heat loss to the surroundings, leading to lower energy requirements for maintaining the desired indoor temperature,” Nathan said.

“Similarly, in chilled water or refrigeration systems, HDPE pipes help to prevent heat gain, reducing the workload on cooling equipment and improving efficiency.”

Installation and maintenance

When handling heavy products which are difficult and expensive to install and replace due to heavy lifting equipment required to make it safe, it is vital to have a quality product which will consistently perform at a high level.

Energy needs and labour costs start long before your pipe is operational, and can include transport to site and the additional equipment required to place it in position, and ongoing maintenance can be costly.

HDPE pipes are lightweight, flexible, and easy to handle, making installation relatively straightforward, and need minimal maintenance due to their corrosion resistance and durability.

They also offer significant benefits due to their lightweight nature, flexibility, and easy handling, which simplifies the installation process.

As an added benefit, their corrosion resistance and durability result in minimal ongoing maintenance requirements.

“Having a product that you depend on, that won’t corrode, and that is easy to install and maintain plays a huge role when you are trying to reduce avoidable waste,” Nathan said.

“HDPE does not corrode or degrade when exposed to moisture, chemicals, or aggressive substances commonly found in industrial environments, making it an ideal choice for applications where corrosion is a concern.

“Prefabrication and the fusion welding process on the joints create a seamless and fully integrated pipeline, eliminating potential leak points, improving quality control and maximising longevity.

“Minimising leaks also helps to maintain the necessary flow rate, which means less energy to pump and maintain the flow rate.

“Likewise, the presence of chromium in the stainless steel alloy provides a high level of protection against corrosion by forming a passive oxide layer that is highly resistant to rust, oxidation, and corrosion in various environments.”

Carbon steel pipes, on the other hand, are relatively heavier, involve more labour-intensive installation and require regular inspections and maintenance to prevent corrosion and scaling

“The weight of your product has an impact on the way it is delivered to site as well as the energy used and safety required by other machines to install it,” Nathan said.

Corrosion makes the pipes more susceptible to leaks, adding another risk.

“Protective coatings or linings can be applied to Carbon Steel pipes to enhance corrosion resistance, prevent leaks and prolong their lifespan, but that could potentially add additional costs to your project when there are such great alternatives available.

“However, each material’s performance in these aspects may vary depending on specific environmental conditions and proper maintenance practices.”

Making the right decision

Nathan believes that, when all of the saving considerations have been studied, HDPE is a stand-out option for new projects looking for more efficient ways to work and encourages engineers to break away from conventional thinking.

“In today’s world, where the need for energy efficiency and streamlined processes is paramount, it’s crucial to explore innovative solutions,” Nathan said.

“While each piping material has its unique applications and pros and cons, HDPE stands out as a game-changer in mechanical applications with its exceptional properties which offer immense potential for revolutionising traditional approaches.

“Embracing new materials is not just about embracing change; it’s about embracing progress and seizing the opportunities that lie ahead.”
Nathan said each project is unique and speaking to an expert is critical to deciding which product is most appropriate to your project.

“It’s important to note that the selection of the most appropriate piping material for a specific application depends on various factors, including the operating conditions, budget, regulatory requirements, and project specifications,” he said.

“Consulting with industry professionals and considering the unique needs of each project is crucial to making an informed decision.”