Clean and in working order
Side-stream filtration is an effective way of keeping heating and chilled-water systems clean. Keith Wickert of Amazon Filters explains how it works and answers some frequently asked questions.
Building-services managers are responsible for ensuring that buildings and their services meet the needs of the occupants in those buildings. They also manage building maintenance — including the water, heating and air conditioning systems.
Broader efforts to improve organisations’ bottom lines, as well as general and legislative requirements for greater energy efficiency within non-domestic building stock has resulted in changes in the engineering of water systems to improve energy efficiency.
In the case of heating and cooling systems, efforts by maintenance teams to modernise systems have resulted in the use of smaller orifices in control valves and lower flow rates in terminal units. These results in the system being more vulnerable to contamination by suspended solids, contamination which if not managed by improved system design makes systems more prone to partial or full failure.
Closed-loop water circuits used as part of building heating and cooling systems typically become contaminated during fabrication with materials such as millscale, jointing compound and building debris and, on an on-going basis, with suspended solids from corroding pipe-work and bio-films. If these materials are allowed to remain in the system, they are likely to block components and damage control valves and small-bore heat exchangers. Therefore it is critical that maintenance teams have a greater understanding of the systems and the impact on the occupants of the buildings when problems occur.
BSRIA recommends using side-stream filtration systems to overcome these issues
Here are some of the Frequently Asked Questions that come from maintenance teams and building engineers when it comes to side-stream filtration.
What systems is side-stream filtration suitable for?
Low temperature hot water (LTHW), chilled water (CHW) and condenser water. The type of system will influence the choice of filter cartridge that is recommended.
What information needs to be provided for sizing a side-stream filter?
• Which water system is the filter to be used on?
• What flow rate is the primary pump delivering?
• What is the operating temperature?
What fluid is being used in the circuit (water, glycol, other).
• What pressure does the circulating liquid operate at?
• What is the system volume?
• What diameter is the main header pipework?
Having access to this information helps ensure that the correct size is recommended.
Does the system design (provided by architect consultant or other) specify a micron rating (removal efficiency) for the side-stream filter? This will also influence the choice of cartridge
How often should the filters be changed?
Typically every six months
How do I install the system?
General guidance that can be used by a recognised installer such as a mechanical engineering contractor, water-treatment specialist or a maintenance team is provided. Installing a side-stream system into a building plant room is relatively straightforward and requires minimal engineering work. By diverting 5 to 15% of the main water circuit flow through the filter, an effective, gradual removal of suspended solids and the chemically-treated biofilm can be achieved.
What does a typical side-stream system consist of?
A typical system using our equipment would consist of a stainless-steel 61 Series filter housing together with disposable SupaGard filter cartridges. To help ensure the system is easy to operate, the 61 Series housings are typically fitted with pressure gauges and drain valves. Automatic vent valves are also incorporated as part of the filter housing to provide continuous removal of trapped air in the circuit, thus maintaining maximum efficiency. This hidden application works well to reduce maintenance, equipment down-time and repair costs.
SupaGard filters are available with a wide range of micron ratings (removal efficiencies), so finer filters can be used over time so as to achieve a progressive clean-up of the circulating water (i.e. 20 μm rated filter initially, then reduced to 10 μm later and possibly 5 μm after further clean-up is achieved). When blocked, the filters are easily and inexpensively replaced.
An effective side-stream filtration system has the following capabilities.
• Remove suspended solids, thus reducing wear and tear on critical water circuit components.
• Remove chemically treated biofilm and thus minimise degradation of pipework
• Eliminate trapped air from closed-loop systems.
• Minimise time and labour compared with conventional flushing regimes.
• Achieve cleaner systems.
• Reduce maintenance, equipment down-time and repair costs.