IR on ice: Bringing condition monitoring to curling

In this installment of What Works, ice technicians maintain quality using thermographic tools and techniques.

Infrared (IR) thermography is a familiar condition monitoring approach on the plant floor, enabling crews to detect equipment flaws quickly and non-invasively under operating conditions. The same benefits apply even when IR tools are focused on the floor itself – especially when the floor is made of ice. 

"There aren’t many secrets to good curling ice," says Shawn Olesen, Ice Technician for the United States Curling Association (USCA), the national governing body of the sport of curling in the United States. "It just takes time and attention to detail."

Curling is catching on more and more in the United States, with played in more 165 clubs in approximately 40 states, with approximately 16,000 curlers registered with the United States Curling Association (USCA). In curling, two teams of four players each take turns sliding granite stones down a sheet of ice toward a target, known as the "house.” Teams score points through positioning their stones closer to the center of the target than the opposing team, with sweeping used to increase the distance and/or influence the path the stone travels.

Curling stones are typically made of granite and weigh approximately 42 pounds, with lighter 24-pound stones available at many clubs for younger children to use. The bottom of a curling stone is concave with only a 8-inch circular running surface in contact with the ice, a circle that is just 6-mm wide around the edge. When the stone is thrown, it is given either a clockwise or counter clockwise rotation.  This friction between the running surface and the pebble will cause the rock to curl toward its destination.

"On a flat surface the stone would be nearly impossible to deliver to the intended target," says Shawn Olesen. "The running surface rides on only a few pebbles at a time - imagine someone crowd surfing - so the sweepers affect the travel of the stone by brushing the surface with their brooms, warming the pebbles slightly, and causing the stone to travel straighter and further."

Olesen is quick to credit the family atmosphere cultivated by curling enthusiasts across the US, from athletes and coaches to ice crews and fans. "Even though curling is growing by leaps and bounds, we are still a relatively small community, the most fun and biggest payoff is seeing your curling family at each event. The best way to learn more is to volunteer outside of your home club to see how others do it and to network with other icemakers.

what works curling
Figure 1. USCA ice technicians seek to maintain a playing surface that enables the athletes to be able to call any shot they need to, from the beginning of the first game to the last shot of the Championships.

"In the case of a National Championship, we begin with an advance site visit," Olesen says. "We check the facility and look at their plant, air handling system, dehumidification capabilities, and  water quality. We ask that when we arrive for the competition that the ice surface be within 0.5 inch of level, which is checked by our team upon arrival via a laser transit." This is followed by applying and properly sealing game markings and decorations with up to 30 coats of fine water spray mists, flooding the ice multiple times to further level the ice surface, and perfecting the surface for game play by pebbling and scraping the ice.

"Pebbling is done by sprinkling water evenly across the sheet, leaving small individual drops to freeze on the ice surface," Olesen continues. "Once the pebble freezes, we shave the ice surface several times to fill any low spots while cutting off the high spots, and then apply 'game pebble' which is perfectly pure water applied in small singular drops as a surface for the 42-pound granite curling stones to travel on.  A base coat is applied at or near room temperature, followed with a hot coarser top coat. This way the finer pebble is there waiting if the coarser pebble should wear away."

At a national event, the surface installation crew can number from 12-20 people; once the competition starts, a crew of 4-6 is adequate for maintenance. "We monitor conditions constantly, using remote sensors to watch ice temp, air temp, humidity, dew point, and brine temp. When the tournament is over every team usually finds us before they leave and thanks us, and if they didn’t win they let us know what we could have done better! In fairness, they are usually faster with their thanks and compliments"

Olesen and crew monitor conditions with hand held equipment, using a Fluke Ti32 Infrared Camera for their initial assessment of the space and for spot checks. "Thermography is an extremely helpful tool because if we are able to look at a space with a thermal imager as soon as we arrive, we can instantly see things that may not reveal themselves for days, such as airflow issues, or cooling problems in the floor. We are always better off if we can anticipate an issue rather than reacting to a problem."

The ice crew also will use a Fluke 62 MAX IR Thermometer and 971 Temperature Humidity Meter for continual environmental quality checks, and a Fluke 52 II Dual Input Digital Thermometer ("Old Reliable," says Olesen) that is installed immediately on arrival and used as a baseline for the whole event.

what works curling2
Figure 2. Thermography helps diagnose ice surface issues quickly and non-invasively that otherwise might not reveal themselves for days, such as airflow issues or cooling problems in the floor.

Pebble wear, rock speed, and curl often act as lead indicators for changing air and ice conditions that are being monitored by the ice crew. The bottom of a curling stone is concave with only a 8-inch circular running surface in contact with the ice, a circle that is just 6-mm wide around the edge. When the stone is thrown, it is given either a clockwise or counter clockwise rotation. This friction between the running surface and the pebble will cause the rock to curl toward its destination.

"On a flat surface the stone would be nearly impossible to deliver to the intended target," says Olesen. "The running surface rides on only a few pebbles at a time - imagine someone crowd surfing - so the sweepers affect the travel of the stone by brushing the surface with their brooms, warming the pebbles slightly, and causing the stone to travel straighter and further."

And pebble is easily affected by many things – air temperature and flow, ice temperature, dew point, and wear and tear from stones and players. "If the pebble wears either too quickly or inconsistently, the stones will not react the same at the end of the game as they did in the beginning, thus changing the choices the players have for shots to call," Olesen explains.

"And to quote Vince Lombardi, perfection is not attainable, but if we chase perfection we can catch excellence."

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