Glycol do's and don'ts for chiller operators - Hydratech

Don&#;t use automotive antifreeze

Automotive antifreezes are not formulated for complex mixed metal chillers, or any other low temperature industrial applications. Many automotive antifreezes are not glycol based and contain silicate-based inhibitors (necessary to protect automotive engines), that can cause serious issues for chiller systems, including:

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• Reduction in heat transfer performance
  The silicates coat all metal surfaces in the chiller system, including the heat exchanger surfaces. This coating will reduce the heat transfer efficiency by around 10%. Also, the thickness of the coating increases every time the system is drained and refilled.
• Gel formation
  At certain concentrations and temperatures, silicates can form polymers in heat transfer systems, turning the fluid into a gel. In some cases, the heat transfer fluid can become so thick, that it can no longer be pumped.
• Pump seal failure
  The abrasive nature of silicates can attack pump seals and lead to failure.

Regular drain and refill required
Automotive antifreezes generally have a short lifespan and require more frequent draining and refilling than inhibited glycols. Over the long-term, the cost of draining and refilling a system regularly with auto antifreeze will be far greater than the initial cost of inhibited glycol.

Do use inhibited glycol

Uninhibited glycol/water solutions can be particularly corrosive and potentially more harmful to a chiller system than standard mains water. Inhibitors neutralise the natural tendency of water to corrode, scale and foul pipe-work systems and associated components.

To prevent internal corrosion, scaling and biological fouling all of Hydratech&#;s heat transfer fluids are formulated with multi-metal and multi-function inhibitors, which exceed ASTM D standards.

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Do consider ethylene glycol (MEG/EG) for industrial applications

Ethylene glycol is used in most industrial applications where low toxicity is not required. It offers the best heat transfer rates of all glycols and is often selected ahead of propylene glycol for this reason. The main drawback associated to ethylene glycol is its toxicity to humans and animals, making it unsuitable for the food and beverage industry and frequent user contact.

Hydratech&#;s IGE is an industrial grade secondary refrigerant antifreeze based on ethylene glycol for process cooling & AC systems - with proven corrosion, scale and biological inhibitors.

More information on Coolflow IGE here

Do consider propylene glycol (PG) for food/beverage and user-contact applications

Propylene glycol was developed to replace ethylene glycol for use in food and beverage processing systems or where there is a requirement for a non-toxic classification.

Characteristically, PG has a much lower capacity for efficient heat transfer, compared with ethylene glycol-based mixtures. It is also much more viscous at low temperatures and thus provides more of a challenge to pump.

Hydratech&#;s Coolflow NTP is a non-toxic antifreeze and secondary refrigerant based on propylene glycol for process cooling & AC systems - with proven corrosion, scale and biological inhibitors.

More information on Coolflow NTP here

Do consider Coolflow DTX&#;, a more efficient and cost effective alternative to PG

Coolflow DTX&#; was introduced in as a high performance non-toxic secondary refrigerant, suitable for replacing propylene glycol in food and cold storage cooling systems.

The game-changing fluid combines the thermal efficiency and low viscosity associated to ethylene glycol, with the non-toxic rating of propylene glycol. The list of DTX adopters is now extensive and includes Arla Foods, Mϋller Dairy, Waitrose, Airbus, Siemens and BrewDog.

More information on DTX here

Don&#;t ignore local environmental regulations

It is important to check local environmental rules, as some areas have specific regulations regarding the disposal of working fluids. Your local authority will have all necessary guidelines.

Do use correct water

If using regular tap water in a glycol/water solution, it is vitally important to apply the appropriate multi-metal and multi-function inhibitors. Mains water contains deposits and additives which can damage a chiller system and associated components.

An understanding of the local water&#;s characteristics is also important, as mains water hardness varies from region to region. City or town mains water can be particularly problematic as their water properties can fluctuate.

Using water from a good quality, filtered source will eliminate any uncertainties.

For optimum system protection, Hydratech recommend a filtered water and 25% v/v inhibited glycol mix.

Do use correct dosage of glycol

Selecting the correct type and concentration of glycol is very important. The glycol type should already be known and recorded in the commissioning documents or maintenance logs for your systems.

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Hydratech Services can assist with glycol determination analysis if it is not known &#; it is especially important to verify this for food or beverage process applications.

Too much glycol or too high a % will cause system inefficiencies through reduced heat transfer ability and pumping capacity. Not enough glycol or too low a % can lead to the expensive freeze-ups previously mentioned and can become susceptible to biological fouling.

Typically, external systems susceptible to freezing over winter months will need anti-freeze protection down to the lowest expected ambient temperature, with some margin advised for safety of +10%* (*Lowest temps ever recorded in UK -26.1°C - January ). To prevent internal corrosion, scaling and biological fouling year-round, it is recommended that the glycol is fully inhibited and monitored every 6 months. Hydratech recommend a minimum concentration for their inhibited glycols of 25% v/v &#; this would provide a freeze protection average of -10°C.

Don&#;t overlook the importance of proactive fluid management

Managing chiller working fluids is important if process efficiency is to be optimised and operating costs minimised. It is not uncommon for the maintenance of cooling and heating systems to be overlooked.

Under such circumstances various issues can develop, including; advanced corrosion, biological fouling and sediment formation. All of which will have a direct and negative impact on heat transfer, pumping performance and energy costs.

Often, cooling systems that have been altered or upgraded are topped up with uninhibited water, resulting in a dilution of the antifreeze and inhibitors.

To verify long-term condition of the fluid and system, Hydratech recommend periodic analysis of the heat transfer fluid. Hydratech provide a range of Fluid Management Services&#; to maximise thermal efficiency, minimise downtime and extend component life.

So, you need to upgrade or replace your imaging systems process chiller. If you are like many decision makers, some anxiety about the series of decisions required for such an undertaking is normal. 

Below, I have provided some information that will assist you with your research and decision process. For more detailed information and rating tools to evaluate various process chiller manufacturers, check out the Process Chiller Buyers Guide available at legacychillers.com  

#1: Do I buy a process chiller bundled with my imaging system (OEM supplied) or shop and buy direct?

Let's face it, time is money right? For an owner or manager of a medical imaging center, purchasing a process chiller is most likely not something you will do on a regular basis. For this reason, there is a strong argument to accept your OEM's proposal to bundle the chiller in with the total package.

If the above scenario sounds like a no brainier, and MANY owners go this way, there are pros and cons to a bundled package.  Like many things in business, there are pros and cons to consider as follows:

The PROs:

It's one price that can be budgeted into your financing. One stop shipping can be more time efficient for the initial purchase. 

The CONs:

Since most OEMs sell medical imaging gear all over the world, they generally have pre-engineered process chillers that may or may not be equipped with the correct features (see below on features) for your operating environment. Additionally, you can expect to pay double (or more) for the initial cost of the chiller as well as repair services if the OEM bundles that in as well. 

 Bottom line, if you have time to shop (and ask the right questions) you can usually save significant costs both long and short term. It's also possible to expect less downtime and lower overall operating costs by working direct with a qualified chiller manufacturer that can sell you a properly equipped process chiller specifically designed for your operating environment. On the services side, there are many Independent Service Operators (ISOs) that can provide excellent service on your chiller as well as imaging gear at a lower cost than an OEM. If you are interested in finding an ISO active in your market, please consider reaching out to Legacy. We can generally provide you with several referrals. 

#2: How much can I expect to pay for a process chiller?

Prices can vary a lot depending on the cooling load of your imaging system and your operating environment. Most imaging systems require from 60,000 btuh (5 ton) to 180,000 bthu (15 ton) process chiller capacities.

We have found that cost per ton is the best overall method for budgeting.  Assuming you purchase a chiller specifically designed for mission critical applications, you can expect to pay from $1,400 to  $1,800 per ton. Generally, the more tons you purchase, the lower the cost per ton. Please keep in mind the cost per ton method generally does not include installation or maintenance costs. If you need pricing on system design and/or installation of your next chiller system, consider reaching out to Legacy. We can generally provide you with several referrals. 

#3: What features should my process chiller have?

This subject is probably one of the least understood, yet the most important. I can't tell you how many times we get calls from buyers of other brand chillers in a panic because they just can't get their chiller to work right. Below I have listed the most important process chiller features and when they should be applied:

• Glycol rated evaporator: If your chiller is mounted outside and your outdoor ambient can get to below zero, you MUST run HVAC grade glycol in your process chiller with very few exceptions. If you need to run glycol concentrations higher then 20%, you will need an upgraded evaporator in your chiller. Some manufactures do not offer this feature. If the above conditions apply to your site, please consider asking for this when you get a quote. 
• The right pump: Although your imaging gear will have specific flow and pressure requirements, the distance between your process chiller and the mechanical room can dramatically impact the chillers pumping requirements. If you are buying a replacement chiller, DO NOT fall into the trap of simply matching the pump horsepower of the old chiller. This can lead to some significant and costly problems you don't need.
  
  If your current chiller's pump is running, the best way to go is to get ALL of the information on your pump along with supply and return pressure readings. With that information, the chiller manufacturer should be able to properly specify the right pump for your system's operating environment. 
• Low ambient - Condenser Fan cycle: If your chiller utilizes an air-cooled condenser, is mounted outside and your ambient has the potential to drop below 40F, adding a condenser fan cycle feature is highly recommended.  
• Low ambient - Flooded condenser: If your chiller utilizes an air-cooled condenser, is mounted outside and your ambient has the potential to drop below 20F, adding a flooded condenser feature is highly recommended.  
• Economizer: If your chiller utilizes an air-cooled condenser, is mounted outside and ambient has the potential to drop below 40F, an addition of an Economizer feature can reduce your chiller's energy usage up to 60%.  For more information on process chiller economizers, check out Legacy Chillers Nexus line. 
• Remote alarming: For Mission Critical process chiller applications this is a VERY valuable feature. The ability to connect your chiller to the Internet and send out alerts and other predictive data that can impact the reliability of your system is VERY important.  There is a limited number of process chiller manufacturers that offer this feature. Nonetheless, if it is offered, we highly recommend adding this feature for any mission critical process chiller applications. 

#4: When buying a chiller direct from a manufacturer, who do I call when it needs service?

Since a process chiller is basically a refrigeration system cooling water, very similar to an air conditioning (AC) system that cools air, a qualified journeymen level HVACR technician can provide most services needed on a chiller. A great place to start is with your current HVACR service provider maintaining your facility's air conditioning systems. Many times, they will have technicians on staff that are familiar with process chillers. There are also some potential cost savings advantages of having your process chiller serviced at the same time as your AC. 

#5: How do I keep my chiller downtime to a minimum?

Have a service agreement with a qualified HVACR contractor or ISO in place at all times. Look at repair recommendations and keep on top of routine maintenance schedules. This does represent a little administrative work your your part; however, it provides an excellent return on investment. Following these three items will reduce annual downtime, related to mechanical failures, by 80% or more. 

#5-1/2: How do I know the chiller I am getting is sized properly for my imaging system?

All OEM manufacturers of medical imaging equipment will provide a site preparation (name will vary) document that provides all site cooling (or chiller) requirements. It is highly recommended that you find that data and send it to a qualified process chiller manufacturer. In just a few pages, you can effectively communicate key information assuring the correct sizing of your chiller. Important note, PLEASE make sure the information you are sending is the correct data.

If your are replacing an older chiller, make sure to get all information from your existing chiller's pump, a photo of the chiller nomenclature tag and any other information you may have on it. Send it to a qualified chiller manufacturer and make sure to request the features (above) that your site needs. 

For more Industrial Glycol Chillersinformation, please contact us. We will provide professional answers.