Why Fit Side-Stream Filtration to a Process Chilled Water System?

The condition of the water circulating through a process chilled water system has a direct effect on its performance, reliability and operating life.

Even a closed well managed system can gradually accumulate corrosion products, installation debris, scale, jointing materials and other suspended contamination. If these solids remain in circulation, they can restrict strainers, foul heat exchangers, damage pumps and valves, and reduce the system’s ability to transfer heat.

Side-stream filtration provides a practical way to continuously remove this contamination without placing a restrictive filter directly in the main process flow.

What is side-stream filtration?

A side-stream filter is installed on a separate branch connected to the main chilled water circuit.

A controlled proportion of the circulating fluid passes through the filter before being returned to the system. Although the filter only treats part of the system flow at any one time, continuous circulation means the overall system volume is progressively cleaned.

Depending on the application, the filtration equipment may use:

• Bag filters.

• Cartridge filters.

• Magnetic filtration.

• Automatic self-cleaning filters.

• Separators designed for heavier suspended solids.

• A combination of filtration methods.

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The correct arrangement depends on the system volume, fluid type, contamination level and particle size that needs to be removed.

Why does contamination matter?

Suspended debris does not need to cause a complete blockage before it starts creating problems.

Fine particles can settle in areas of lower velocity, including buffer vessels, heat exchangers and final equipment. Corrosion products can accumulate in control valves, pumps and narrow waterways, while deposits on heat-transfer surfaces create an insulating layer between the chilled water and the process.

The possible consequences include:

• Reduced heat-transfer performance.

• Higher pump energy.

• Restricted flow through sensitive equipment.

• Blocked strainers and control valves.

• Increased wear on pump seals and components.

• Unstable process temperatures.

• More frequent alarms and breakdowns.

• Increased cleaning and maintenance requirements.

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A system can therefore appear to be operating normally while its performance and reliability gradually deteriorate.

Protecting the chiller and the process

Modern chiller evaporators and plate heat exchangers can contain relatively narrow waterways. This makes good water quality particularly important.

Contamination passing through the system may become trapped within these waterways, reducing flow and affecting heat transfer. In severe cases, restricted flow can cause low-flow alarms, evaporator freezing or damage to the heat exchanger.

Side-stream filtration continuously reduces the amount of suspended material in circulation.

This helps protect:

• Chiller evaporators.

• Plate heat exchangers.

• Process cooling jackets.

• Pumps and mechanical seals.

• Control and balancing valves.

• Flow meters and temperature sensors.

• Small-bore pipework and terminal equipment.

  
  

It also reduces the amount of debris reaching conventional strainers, helping extend the time between cleaning.

It can often be retrofitted to a live system

One of the major benefits of side-stream filtration is that it can often be added to an existing chilled water system with minimal disruption.

Where suitable valved connections are already available, the filtration package may be installed and commissioned while the main system remains operational. If new connections are required, the installation can still be planned to minimise the shutdown period.

Specialist connection methods may sometimes allow work to be completed on an operational system, but this must be properly assessed and carried out under an appropriate safe system of work. The system pressure, fluid temperature, pipe material, connection method and site operating conditions must all be considered.

This makes side-stream filtration particularly attractive for production facilities where stopping the chilled water system would also stop manufacturing.

Rather than draining and shutting down the entire system for a major cleaning exercise, filtration can be introduced progressively while cooling remains available to the process.

If the filter blocks, the process does not have to stop

A full-flow filter is installed directly in the main circulating water path. If it becomes restricted or blocked, it can reduce the flow available to the process and potentially cause a production interruption.

A correctly designed side-stream filter does not carry the full process flow.

If its filter element becomes blocked, only the flow through the filtration branch is affected. The main chilled water circuit continues to circulate through the process.

The filtration package can be isolated, cleaned and returned to service without shutting down the main cooling system.

For this reason, a good installation should include:

• Isolation valves on the filter inlet and outlet.

• A differential-pressure indicator or gauge.

• A safe drain point.

• Suitable air venting.

• A method of confirming side-stream flow.

• Adequate access for removing filter bags or cartridges.

  
  

A differential-pressure switch can also provide a local or remote warning when the filter needs attention.

The side-stream arrangement should never compromise the chiller’s required minimum flow or the flow available to critical production equipment.

Reduced maintenance downtime

Maintenance on a side-stream filter can normally be completed independently of the primary system.

The filtration branch is isolated, the filter element is cleaned or replaced, and the unit is returned to operation. There is no need to drain the complete chilled water circuit or stop the main pumps.

This provides several operational advantages:

• Shorter maintenance tasks.

• Less disruption to production.

• Reduced loss of treated water or glycol.

• Lower risk of introducing air when refilling the system.

• Less need to re-dose the complete system after maintenance.

• Easier inspection of the material being removed.

  
  

The captured debris can also provide useful evidence about the condition of the system. Heavy corrosion products, unusual solids or repeated rapid blockage may indicate an underlying water-treatment or corrosion problem that requires further investigation.

Why use a stainless-steel filter body?

Stainless-steel filter bodies are suitable for almost all conventional process chilled water and glycol systems.

They offer:

• Good corrosion resistance.

• Compatibility with water and commonly used glycol mixtures.

• A long service life.

• A clean, robust construction.

• Suitability for a wide range of industrial environments.

• Easier inspection and maintenance.

  
  

Material compatibility must still be confirmed for every application. The stainless-steel grade, seals and filter element must be suitable for the glycol type, inhibitor package, operating temperature and any process contaminants present.

For more demanding water chemistry, 316 stainless steel may be preferable to 304 stainless steel. Gaskets and seals should also be selected for the actual fluid rather than assumed to be universally compatible.

With the correct material selection, a stainless-steel side-stream filter can often be used even where the existing system contains a mixture of steel, stainless steel, copper, brass, plastic or other approved pipework materials.

Side-stream filtration doesn't replace water treatment

Filtration removes suspended physical contamination. It does not correct the chemical condition of the water.

A complete water-management strategy may also need to consider:

• Corrosion-inhibitor concentration.

• Glycol concentration and condition.

• PH.

• Bacterial activity.

• Dissolved oxygen.

• Water hardness and conductivity.

• Compatibility between treatment chemicals and system materials.

  
  

Filtration and chemical water treatment perform different but complementary functions.

Chemical treatment helps control corrosion and biological activity. Filtration removes the solid material already circulating through the system.

For best results, the two should be considered together.

Designing the right side-stream filtration system

There is no single filter arrangement suitable for every chilled water system.

The design should consider:

• Total system volume.

• Primary flow rate.

• Available differential pressure.

• Fluid and glycol type.

• Operating temperature and pressure.

• Type and quantity of contamination.

• Required filtration level.

• Acceptable maintenance frequency.

• Available installation space.

• Whether an independent side-stream pump is required.

• How quickly the complete system volume needs to be treated.

Selecting an unnecessarily fine filter at the outset can result in rapid blockage on a heavily contaminated system. It may be better to begin with a coarser element and progressively move to finer filtration as the system becomes cleaner.

The filter should also be sized with enough dirt-holding capacity to provide a practical service interval.

A small addition that can prevent much larger problems

Side-stream filtration is a relatively straightforward addition to many process chilled water systems, but its effect can be significant.

It continuously removes circulating contamination, protects critical equipment and allows the filter to be maintained without stopping the main process.

Most importantly, it offers a way to improve the condition of an existing live system while keeping downtime to a minimum.

For production sites where chilled water reliability is essential, that can make side-stream filtration far more than an optional extra. It becomes part of protecting the process.

Is contamination affecting your chilled water system?

NovaCool Solutions can assess existing process chilled water systems, review water condition and design a side-stream filtration package around the system’s flow, fluid and operating requirements.

Where possible, the installation can be planned around a live system to minimise interruption to production.

To discuss side-stream filtration or an existing chilled water problem, contact NovaCool Solutions now.