Automated Tube Cleaning Benefits: Save Energy, Cut Downtime

How Automated Tube Cleaning Saves Energy, Cuts Costs, and Extends Heat Exchanger Life

All types of shell and tube facilities regularly face an insidious adversary: fouling. Mineral accumulations, biological development and scaling build up silently within heat exchangers, restricting heat transfer and driving up energy costs month after month. The U.S. Department of Energy estimate fouling related losses in domestic industry at several billion dollars each year.

Automated tube cleaning systems attack the problem at the source – preventing deposit accumulations before they can occur, rather than waiting for a scheduled shutdown to clean tubes. But cleaner tubes are only part of the equation. Lowered power consumption, reduced unforecasted shutdowns and longer equipment life are the ultimately measurable outcomes of these designs. In the paragraphs that follow we detail how these efficiencies are achieved, using data from the industry and direct experience from the BOSHIYA Group’s century and a decade of industrial systems experience.

What Causes Tube Fouling in Heat Exchangers?

Tube fouling is the slow build-up of unwanted material deposits on heat exchanger tube surfaces, creating an insulating blanket that reduces heat transfer performance. Even the most minute deposit – as little as 0.3mm – will produce a 10% reduction in chiller efficiency COP. At 0.6mm the figure is doubled to 20%.

Four Types of Fouling That Attack Your Tubes

Fouling in heat exchangers and condensers can be classified into four categories, each with different underlying causes and different requirements for cleansing:

• Mineral scaling – Calcium carbonate, calcium sulfate and silicate compounds crystallise from cooling water at temperature increases. These crystalline deposits are very resistant to removal and hard to shift with chemical treatment.
• Bio-fouling results from biological materials – and algae, fungi and bacteria in particular – establish themselves on tube surfaces. These cultures produce biofilms that act as insulators. High temperatures and food rich cooling water hasten such growth.
• Particulate fouling occurs when cooling-water supported particles such as rust grime, silt and sand settle out on tube surfaces. Disturbance of the tube shell areas and low flow velocities are conducive conditions for this.
• Corrosive fouling takes place when chemical reactions between tube material and the process stream create deposits of oxide and corrosion products, greatly diminishing heat transfer and general tube strength.

How Automated Tube Cleaning Systems Work

An automatic tube cleaning system prevents fouling during operation by running cleaning cycles continuously — no shutdown required, no loss of output. These systems operate 24 hours a day so that tube surfaces are kept clean whatever the load.

The Cleaning Cycle: Step by Step

1. Nylon brushes or sponge rubber balls – each sized slightly larger than the tube inner diameter – are loaded into a collection basket that is fed by a water flow loop.
2. Using direction reversal by a valve or by a dedicated pump, each ball or brush is propelled through individual tubes. Each cleansing element action cleans the interior surface as it passes through.
3. At the outlet end, a strainer basket to retain the cleaning media. Water flow inversion sends them to the inlet basket for re-circulation.
4. A programmable logic controller initiates cleaning cycles on pre-determined intervals – normally between 15 and 30 minutes in most installations. Each cycle consumes only seconds per tube.

Automatic tube cleaning systems of brush type employ nylon brushes supported in tube-end cages. When water flow is again inverted each brush moves from one end of the tube to the other, physically scrubbing deposits off the tube surface. In ball type systems sponge balls slightly larger than the tube bore deform accordingly during each pass to wipe the surface clear of debris.

“Our Maintenance & Equipment division has maintained tube bundles in refineries, power plants and chemical processing facilities for over a century. Moving from reactive manual cleaning to preventive automated cleaning has been the single largest heat exchanger maintenance efficiency gain we have seen.”

— BOSHIYA Group, Maintenance & Equipment Division

For interim tube bundle cleaning – when exchangers are pulled during turnaround maintenance – BOSH India fabricates automated tube-side bundle cleaning equipment with 5-lance systems capable of 1,500 bars. These recover over 35% less turnaround downtime than manual lance operations, and place operators in a remote cabin to safely manage cleaning operations.

Energy Savings and Heat Transfer Efficiency

Energy savings drive the commercial proposition for automated tube cleaning. Fouling deposits have thermal conductivities ranging 100 to 1,000 times lower than the metal tubes upon which they rest according to U.S. Department of Energy’s Argonne National Laboratory reports. This insulation causes compressors & pumps to operate longer, incurring a proportional electric power penalty.

As tube surfaces stay free of fouling buildup, heat transfer efficiency remains near design value. Your cooling system will not have to add extra water flow or increase compressor load to replace drop in thermal conductivity. Industry data consistently shows facilities using automatic tube cleaning systems attain 10 to 25% reduction in energy bills against facilities dependent on periodic manual cleaning.

One documented example involves a sizeable district cooling installation that deployed an automated tube cleaning system to chiller condensers and realized 7 million kWh reduction in annual energy consumption – cost savings exceeding $480,000 annually. More than 3,500 hours of operation resulted in a sustained 13%+ energy efficiency advantage vs. the fouled baseline – Cooling Best Practices Magazine cites.

Reduced Downtime and Lower Maintenance Costs

Manual tube cleaning involves removing and replacing equipment – generally requiring 8 to 24 hours per operation. An operating chiller or condenser in a continuous process means every shutdown hour results in loss of production, restart energy costs and labor expense. Online cleaning systems remove this need to cycle by cleaning tubes during operation.

Maintenance downtime expenses far surpass cleaning labor. When a chiller is deactivated in a hospital, data center, or manufacturing plant, the impact is felt throughout the facility: cooling loads are transferred to secondary systems (if such exist), product quality impacted, even safety systems are activated. Online tube cleaning systems eliminate these costs by maintaining equipment in service while the cleaning occurs automatically within the tubes.

Based on our industrial plants and oil refineries equipment experience, the leading unplanned shutdown cost pattern presents in facilities that lack a continuous, time-based cleaning schedule. When a condenser fouls faster than predicted, due to seasonal shifts in water quality or upset processes, a gap between maintenance periods emerges that can only be addressed with dedicated automation.

Extended Equipment Lifespan and Fewer Replacements

Fouling not only diminishes thermal efficiency – it also hastens the physical deterioration of tube surfaces. Corrosive deposits accumulate along the tube wall. Biological fouling foments under-deposit corrosion.

Scaling yields localized hot spots responsible for thermal fatigue and deterioration of tube integrity. Each mode of failure shortens the service life of heat exchangers and condensers, leading to increased capital replacement costs.

Preventive tube cleaning keeps fouling from ever reaching the point of surface damage; maintaining tube cleanliness on a continuous basis prevents wet-dry cycling and deposit concentration from aggravating corrosion. Field data from various industrial processes using automated cleaning systems continually demonstrate how automated cleaning protects tube bundles long term – extending equipment lifetime by 15-25% compared to manually maintained units.

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  Continuous deposit prevention decreases wear and tear on tube surfaces
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  Emergency tube replacements from corrosion failures drop sharply
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  Capital expenditure remains lower over the entire 10–20 year equipment lifecycle
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  Tube wall thickness is maintained – no localized thinning from under-deposit attack

Payback calculations become vastly more interesting when replacement costs are added. A single shell and tube heat exchanger replacement at a refinery alone can cost $200,000-$500,000 depending on the metallurgy and size. Just extending the interval between replacements by a year or two generates savings more than amortizes the capital cost of an automatic cleaning system.

Automated vs. Chemical Tube Cleaning Methods

Heat exchanger tube cleaning facilities have to select among chemical cleaning and mechanical options. There are pros and cons to each in terms of effectiveness, environmental friendliness, and the nuisance factor.

Chemical cleans are still the most effective means of removing the most difficult, fully established fouling – particularly the extreme of tough mineral scaling that cannot be mechanically removed. Chemical cleans have environmental and safety issues—spent fluids require neutralization, containment, and disposal following EPA and local requirements. Again, the chemicals have the potential to cause corrosion if the chemical mix concentration or contact duration is not strictly maintained, as Becht Engineering pointed out.

Successful maintenance programs employ all three cleaning types at various steps in the equipment lifecycle. Automated cleaning covers the daily fouling prevention; the chemical cleaning solves the heavy resin buildup in scheduled turnarounds; and the mechanical cleaning puts the tubes back to close to original condition when exchangers are removed for inspection.

Industry Applications: HVAC, Power Plants, and Refineries

Tube cleaning automation operates in all of the larger industry sectors that depend on shell and tube heat exchangers, condensers, and chillers. Fouling issues vary by application, but the principle is unchanged: cost of doing it continuously is less than correcting it periodically.

HVAC and Commercial Cooling

Chiller tube cleaning constitutes the single most widespread use for automated systems. During cooling season, chiller condensers in commercial buildings, hospitals, and data centers run ceaselessly, pulling in biological fouling and mineral scaling through the cooling tower water. HVAC systems with automated tube cleaning keep condenser approach temperatures within 1 F of design spec, resulting in minimal compressor loads and consistent energy charges.

As the majority (~55%) of industrial upsets are due to tube blockages, the business case for condenser tube cleaning automation in HVAC systems is extremely advantageous. Market data corroborates the trend: the global market for HVAC automatic tube cleaning system was valued at $320 million in 2012, growing at a CAGR of 5.2% from 2007 to 2012 – indicating increasing business penetration backed by Progressive Energy Market regulations and soaring electricity prices.

Power Generation

In power plants, condenser fouling has a direct negative impact on Turbine backpressure performance, and on the electrical output. A 1F increase in condenser temperature results in 1-2% loss of power, an important cost at the utility scale. Automated brush systems on power plant condensers prevent fouling and scaling in cooling water circuits, keep vacuum pressure at design levels and MW output constant.

Oil Refining and Petrochemical Processing

Refineries experience some of the most vicious fouling environments: crude deposits, asphaltene buildup, and high-temp scaling make heat exchangers managing hundreds of millions BTU’s/hr the norm. During online automated cleaning the cooling water side is managed and controlled. BOSHIYA’s Maintenance and Equipment division provides high-pressure automated tube bundle cleaning systems for turnaround operations, reducing cleaning time and protecting operators from high-pressure water dangers.

In each of the industries visited, the general trend is similar: those facilities using the automated tube cleaning enjoy energy cost reduction, reduced maintenance expenses and avoided unplanned shutdowns within their first year of operation.

Frequently Asked Questions