Calcium Chloride versus Glycol

On an indirect refrigeration system a choice must be made between the type of secondary coolant that you select. Both Calcium Chloride and glycol have been successfully used over the years and there are applications where both secondary coolants have an advantage. To a much lesser degree other heat transfer mediums such as methyl alcohol have also been utilized in the ice rink industry.

In regards to energy efficiency, Calcium Chloride is the better choice. Its heat transfer coefficient is much better than glycol. This fact equates to smaller, less expensive chillers for the same heat transfer. The heat transfer in the floor piping system is also better. Due to the superior heat transfer characteristics, the brine pump can be smaller and the required pump horsepower and corresponding energy consumption is reduced with calcium chloride.

Calcium chloride is highly corrosive when not maintained properly. With proper system design and operation it is still the best choice for most ice rink applications. The system components must be selected specifically for the Calcium Chloride. Typically chillers are made out of carbon steel or cuper-nickle. Brine pump shafts and butterfly valve stems should be made out of stainless steel.

With a system utilizing Calcium Chloride, it is imperative that the system is kept full at all times and no air is allowed to come in contact with the internal components. A high-grade environmentally friendly rust inhibitor must be used to ensure equipment longevity. It is good practice to carry out routine in house brine tests to monitor brine strength and pH on a semi annual basis and to request a lab report once a year.

In systems that are occasionally emptied and filled such as a portable system, glycol can be a very good choice. Glycol will reduce the effects of corrosion in systems that are occasionally opened to the air. It is still important to use good quality inhibited glycol such as Dow SR-1 and to ensure that annual lab samples are taken to verify the integrity of the solution.

Comparison of 1" pipe in cement versus ½" mat style system

On floors with end headers, the 1" pipe permits higher glycol flow rates at lower pressure drops. This results in reduced temperature drops across the grid, faster temperature recovery, and superior temperature control. Better ice surface conditions are maintained during varying conditions. Equivalent flow rates can be achieved with the ½" mat style system if side headers are installed but this will result in over 400% more mechanical joints and the corresponding potential for leaks.

The lower pressure drops in the large pipe system will result in reduced horsepower requirements per gallon of pumped glycol.

When the 1" pipes are imbedded in the cement floor this design provides a very large thermal mass, which keeps temperature swings to a minimum further improving ice consistency.

The larger 1" pipes are less susceptible to fouling or blockage by foreign objects and have less than ½ the mechanical connections reducing the chance of leaks.

The 1" pipes when imbedded in cement require no further handling and do not deteriorate as rapidly as the ½" pipes that are rolled and unrolled over the years.

In order to provide sufficient pipe protection for the mat style system it is normal to operate with a thicker ice surface than is required with a cement floor.

A cement floor is easier to monitor ice thickness by drilling tap holes on a weekly basis. Consistent ice thickness means consistent ice temperature and reduced operating costs.

Set up and take down time is eliminated with the cement floor versus the mat style system that must be rolled up and put away if the ice is removed.

Sand Floor versus Cement Floor

There are good reasons for installing both sand floors and cement floors in an ice skating facility. Hopefully the following should make your decision easier.

Sand floors are utilized to reduce the initial cost of an ice surface. A sand floor is generally used in a year round ice facility but can be installed in a seasonal facility with some precautions to prevent unwanted traffic on the piping system during the off season.

A sand floor reduces the flexibility of the facility in that no off-season activities can be held directly on top of the sand. An ice covering can be used to facilitate light activities on top of the ice, but there is not enough support for rodeos, tractor pulls etc. If for some reason the building must be sold, a sand floor will reduce the buildings usefulness and resale value.

A cement floor for an NHL size ice rink will cost between $50,000.00 and $125,000.00 more than a sand floor depending on the floor strength, proximity of material, and a good super-flat contractor. A cement floor increases the flexibility of the facility in that dances, bingo's, and trade shows can be held in the off season. With a properly engineered floor, a circus or other heavy event can be held as well. As with a sand floor, the ice surface can be covered for non-ice events while the ice is in place.

In order to prevent puncturing the cooling pipes, additional care and attention is required during the initial stages of ice making with a sand floor. Before applying the first water, you must ensure that all of the pipes are in their chairs and the sand has been dressed out to its normal operating level.

In order to maintain a crisp, clean, efficient ice surface all arenas should have the ice periodically removed to purge the buildup of solids and old paint that is deposited over time. On a sand floor the residue tends to cake on the sand surface and can only removed by replacing the surface sand. This residue is easily washed away on a cement floor.

A cement floor is much easier to make ice on, especially with less experienced personnel. A sand floor requires gently misting the sand surface while avoiding puncturing the pipes until there is an ice layer thick enough to walk on and eventually drive a Zamboni on. When installed properly, a cement floor always ensures a precisely level surface to form the ice base. A sand floor can deviate over the years with use.

It is advisable to maintain 1 3/4" to 2 1/2" of ice on a sand floor to reduce the chance of puncturing pipe during ice events. Cement floors only require 1 ¼" of ice for safe use. Periodically measuring the ice surface thickness by drilling holes (ice taps) is much easier with a cement floor. With a sand floor added attention must be taken to ensure that no pipes are punctured while edging or re-surfacing. This special care is not necessary on a cement floor.

Once the ice is in place, there can be a small amount of difference in energy consumption between a sand floor and a cement floor. The same amount of BTU's will enter the ice surface regardless of the style of floor. A well-designed cement floor will typically have 1" of cement cover and 1" of ice cover above the cooling pipes. A sand floor will typically have 2" of ice cover above the pipes. Ice has a K value of 1.3 and cement has a K value of 0.54. The K value is the rate a substance conducts heat with a higher K value conducting heat faster than a low K value. So, theoretically the cement floor would have to operate a little colder than the sand floor for the same amount of heat to be exchanged. However, in reality, many sand floors usually develop small hills and valleys over the years, which requires the ice level to be kept thicker in many areas, which reduces the efficiency.

Whichever way you choose to build your ice skating facility, rest assured that with proper care and attention a great ice surface can be maintained on either a sand floor or a cement floor.

Solving Humidity Problems in Ice Rinks

If you can control the humidity in your facility you are one very large step towards creating the ideal ice skating environment.

Humidity enters an ice rink with incoming ventilation air, the opening of doors, from the use of showers, and through the normal respiration of the people within the building.

If your facility is in a cold environment such as Winnipeg, Manitoba the incoming air can easily be 00F and 50% relative humidity during a typical winter day. If this entering cold air is warmed up to 400 F the humidity will now fall to less than 20% because warm air has the ability to hold more moisture. This lower humidity level poses little problem to the proper operation of the facility.

However if your facility is in Los Angeles, California the incoming air could easily be 650 F with a relative humidity of 65%. If this entering warm air is reduced to 500 F inside the skating rink the humidity will skyrocket to 100% relative humidity because the cold air will not hold as much moisture. At this point there is only one place for the water vapour to go, it condenses into water droplets and the problems begin.

Just as a boiling kettle deposits moisture on a cold window on a winter's day, airborne moisture in an ice rink will also deposit on cold surfaces, and of course the coldest spot is very likely the ice surface itself. When this happens, the ice will cloud over, losing its desired sheen and will start to become sluggish to skate on. The glass around the ice surface will also fog over, obstructing the view of the audience.

In addition to the aesthetic inconveniences caused by excessive humidity the condensing moisture releases a tremendous amount of heat into the ice surface that must be removed at the expense of operating the refrigeration equipment longer than would normally be required. Condensation can permeate your building insulation, drastically reducing its effectiveness and of greater consequence, structural steel will start to rust and wood will start to rot, further reducing the integrity of your facility.

In addition to the aesthetic inconveniences caused by excessive humidity the condensing moisture releases a tremendous amount of heat into the ice surface that must be removed at the expense of operating the refrigeration equipment longer than would normally be required. Condensation can permeate your building insulation, drastically reducing its effectiveness and of greater consequence, structural steel will start to rust and wood will start to rot, further reducing the integrity of your facility.

Luckily, with proper design, humidity can be controlled effectively and efficiently. The two commonly used styles of dehumidification systems are the mechanical dehumidifier and the desiccant dehumidifier.

Typical Recreational Ice Floor Configuration

• Full size hockey arena floor is normally 200' x 85'
• Olympic size hockey floor is 200' x 100'
• Curling sheets are 14' x 146' but are usually laid out at 15' x150'
• Refrigeration Load can range from 45 to 300 tons for an arena

Cooling Floor

The floor surface is occasionally constructed entirely with sand but this limits the use of the facility. More commonly the floor consists of a 5" or 6" cement pad reinforced with Rebar.

The brine is supplied to the floor via 6" to 10" headers. The headers are constructed of PVC or steel. The headers feed an in-floor-cooling grid consisting of 1" polyethylene or steel pipe spaced on 3" to 4" centers.

The cooling floor brine is usually a calcium chloride solution mixed to a freeze point of -5 to -10 deg. F. The pH should be maintained at a level of 7.5 to 8.5 The brine should be tested annually by a lab regularly engaged in testing arena brine samples.

Heating Floor

The rejected waste heat from the refrigeration plant typically provides the heat source for the heating floor but boilers or electric resistance heaters are occasionally used as well.

The heated calcium is usually supplied to the heating floor via 4" brine mains. The mains in turn feed a 1" polyethylene grid spaced on 12" to 24" centers The heating floor is positioned approximately 1' under the cooling floor and is separated by insulation and a vapour barrier.

The heating floor brine should be kept at a freeze point of 10-15 deg. F. The pH should be maintained at a level of 7.5 to 8.5 The brine should be tested annually by a lab regularly engaged in testing arena samples.

Computer Control System

Most new recreational facilities utilize computer control for their various mechanical systems. The ice rink refrigeration equipment is no exception. Tremendous temperature control and energy efficiency can be obtained with modern computer systems. It has been our experience that the manufacturer of the refrigeration system should supply the computer control system that controls it. We have seen too many occasions where a building automation system is installed and the control algorithms and programming are totally inappropriate for the operating characteristics of the ice plant.

Two general types of computer control systems are available. A canned system which provides enough inputs and outputs for all required points and a predetermined program with easy to follow set up and operational procedures. Usually the latitude of control adjustment is limited but effective for the average operator.

The second style of system is an open architecture, completely programmable style of controller. A refrigeration contractor with excellent ice rink control capability can squeeze every ounce of efficiency out of a refrigeration system with this style of controller.

The computer control system is able to accurately calculate the deviation from temperature set point that the ice is operating at and select just enough compressor capacity to recover without excess electrical consumption. Through proper programming the computer can determine which size of fan motor, brine pump, and compressor will be the most efficient for the present weather conditions and facility usage. Various programs can be run for hockey, figure skating, and public skating.

*Infra-IceTM infrared temperature control can be used to precisely monitor the ice surface temperature in order to catch any heat loads at their source. This style of computer system will provide you with the most consistent ice temperature possible. It includes a customized graphics package tailored to your facility. You will have the ability to monitor and control the system remotely from any PC. The system can be programmed to dial out in the event of a failure, reducing down time. Trend logging and graphing makes trouble shooting randomly occurring problems very easy

*Infra-IceTM is a product designed by Accent Refrigeration Systems.

Header and Header Trench Construction - Accessible Header Trench

The preferred method of installation is to install a header trench outside the ice surface with removable covers. This permits service procedures to be carried out in the event of leaks or blockages. The addition of a header trench will increase the initial cost of the facility but will pay for itself with the ease of repair of just one problem. When headers are installed in an external trench it is important to provide frost protection in the viewing area to minimize a slip hazard. When PVC headers are installed in an accessible header trench there is approximately a 1% power penalty due to heat gain through the header. To insulate the headers is not usually cost effective. The money would be better spent elsewhere in the system.

Header and Header Trench Construction - Burried Header Trench

The main reason to install a buried header trench is a cost consideration. With the buried header trench, the time and material to form a trench and the supply of frost protection and trench covers are eliminated. With the elimination of the trench it is easier to make use of viewing area at the end of the ice rink.

The header trench can be positioned at any point along the ice surface, which can reduce piping runs to compressor rooms that are positioned along the side of the facility. The headers can also be placed under the boards at the end of the ice surface.

Brine leaks or blockages can be very expensive to repair, especially if they are in the heating floor. When the headers are buried there is no easy way to block off a leaking heating floor circuit or isolate a leaking cooling floor circuit while repairs are being performed.

Header and Header Trench Construction - High Density PVC Headers

High density PVC headers when properly installed will provide very little chance of leaking due to all of the PVC joints being welded. HDPE headers can be buried in cement or left open in a trench. They can be curved to form the perimeter of the rink, eliminating any chance of frost in the public viewing area. They can be quite expensive to install, but like PVC will not rust or foul over the nipples as readily as steel.

Header and Header Trench Construction - PVC Headers

If constructed properly PVC headers will provide years of reliable service with no chance of rust and minimum fouling at the nipples. Schedule 80 PVC headers are inexpensive and easy to work with. It is recommended to install PVC headers only in a trench that is accessible. As PVC is breakable, care must be taken not to subject the headers to direct impact. All polyethylene pipes should be double clamped with high quality stainless steel clamps and compatible cement used on all fittings.

Header and Header Trench Construction - Steel Headers

Steel headers have been used for years in ice rinks but fell out of favour due to the tendency to rust on the outside and foul on the inside at the nipples. If the brine is rigorously monitored it will greatly reduce the problems associated with rusting. Steel headers can be used in an open header trench or a buried in the cement if protected from rusting. Due to their strength there is very little chance of breaking or damaging a steel header. They can be provided in straight sections or in curved sections forming the perimeter of the rink to eliminate frosting in the viewing area. As with PVC headers all polyethylene pipes should be double clamped with high quality stainless steel clamps. The cost of Steel headers is quite a bit higher than PVC headers.

Header and Header Trench Construction - The Header Trench

The purpose of the header trench is to provide a protected and preferably accessible location for the header to facilitate service. Depending on the design of the building and the installation budget, the trench can be accessible across the end of the ice surface in the viewing area or even buried below the cement slab at any location below the ice surface.

Header and Header Trench Construction-Brine Headers

The purpose of the headers is to provide an ample quantity of secondary coolant to the cooling floor grid in an efficient manner.

If the headers are too small there will be energy robbing pressure drop and the possibility of insufficient flow to meet the system requirements. The headers can be made of Schedule 80 PVC, High density PVC, or Steel.

Adding Calcium to the System

To add calcium to the system, connect the brine mixing barrel as shown. If there is a good level in the blending tank, open valve #3 until the barrel is 1/2 full. If the brine level is low fill the barrel 1/2 full with cold tap water. Turn on mixing pump with valve #1 and #4 open and valves #2 and #3 closed. Slowly pour calcium into barrel while vigorously stirring by hand or with an electric mixer. Stir until no sign of crystals remain and let the brine circulate in barrel for a few more minutes. To add to system open valve #2 and close valve #1. Pump brine mixture into system until barrel is nearly empty. Repeat process to add more calcium. If the balance tank is full and the brine is still too weak, some of the brine mixture will have to be drawn off and stored.

Brine Filtration System

It is extremely important to keep your brine in a very clean condition. Dirty brine will shorten the life of the brine pump seals, impede heat transfer in the chiller, and restrict the flow of brine to the cooling floor grid.

The illustration on the right shows a cut-away single cartridge brine filter. The brine flows to the outside of the filter cartridge removing all of the contaminants as it passes through the pleated filter. The clean brine returns to the system.

The illustration below depicts how the brine filter is connected to the system in a by-pass stream arrangement. Cleaning the filter can be done without disrupting normal plant operation.

Brine System Maintenance Tips

• Do not let the balance tank run dry
• Check and record levels on each shift
• Use side stream filtration to keep the brine clean
• Keep the pH between 7.5 and 8
• Abnormally high pH levels can mean an ammonia leak
• Keep the cooling floor freeze point between -5 and -10 F.
• Keep the heating floor freeze point between 10 and 15 F.
• Run pump once a month during the off season
• Repair brine leaks immediately
• Do a brine analysis every year

 

Determining if there is Air in the Brine System

A good way to determine if you have air in your brine system is by observing your balance tank. The two illustrations below depict a situation where there is air in the brine system. The illustration on the left depicts the brine pump running. This is evident by the pressure on the brine pressure gauge. Note that the brine level in the balance tank is quite low. The reason for the lower brine level is that all of the air in the system is being compressed by the brine pump. The pressurization of the air reduces the volume of air in the floor piping grid. This reduced air volume is then replaced by brine from the balance tank. The illustration on the right shows the system after the brine pump has shut off. Note that the pressure gauge is now at 0 PSI pressure. The air decompresses and returns to its original volume which displaces brine from the floor piping grid back into the balance tank. If there is a great deal of air in the system it will displace so much brine that it will overflow down the drain as shown in the right hand illustration. The real hazard here is each time the pump cycles on and off more air will enter the system and eventually a great deal of brine will be lost potentially destroying the chiller.

Potential Problems In Brine Piping System

Cracked or broken brine lines can be detected by a loss of brine in the balance tank or by a visual sighting of brine on the arena floor or in the header trench. The leaks must be located and repaired to ensure the brine system stays full.

Caution:

Never let the chiller and pumps go dry.

The headers should be inspected annually for leaks and repaired where required. Any rusted areas should be cleaned up and primed. Worn or poor insulation should be replaced.

Air can be detected in a system by the lowering of the brine level after starting the brine pump. Gauges and thermometers should be inspected regularly for proper operation.

Air can be worked out of the brine system at the header purge valves and through the balance tank. To assist in rapid air removal, full sized tees are highly recommended in the brine mains for the balance tank line takeoffs.

Over a period of years some of the nipples from the headers can become partially or totally restricted. This becomes evident by soft strips of ice running lengthwise down the ice. If the headers are an older steel version, it is best to replace them with non-rusting PVC headers. PVC headers will not rust and cause fouling in the system.

Side stream filtration is a good method of removing dissolved solids. A filter can be permanently installed for this purpose.

Reducing Refrigerant Loss

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Removing Air from the Brine System

Air is extremely harmful in a brine system. It will promote an aggressive rate of corrosion, causes cavitation in the pumps, and can displace brine to the extent that the brine will overflow down the drain. After the initial installation there should be no air in the brine system. However, it you have carried out some brine system maintenance or have had a leak you might have a situation where air has entered the system. The proper installation of full size tees in the brine mains as shown in the lower left illustration is the best way to eliminate air from the system. The brine discharge service valve is only left open until all of the air has worked its way out of the system. Occasionally you might have to work air out at the headers. This method is shown in the right hand illustration below. The best way to do get the air out is to shut the brine pump off and let the air rise to the top of the header and release it at the header purge valve. This can take a long period of time and you will have to start and stop the pump many times to "Bump" the air into the headers.