The production process
Startup of a new system must be done together with the system provider. The largest and most technical components; the electrical system, the pumps and the water delivery system must be tested first. The water does not need to be filtered and clean, but can not contain elements that will clog the filters in the production units. All pipes must therefore be well flushed before the fan guns are attached and turned on.
The production process will depend on if the system is distributed along the courses or is a central system producing snow in a large depot. For a central system the ground surface should be paved such that rocks and sand is not mixed in with the snow when it is lifted into the trucks or trailers for transportation. The amount of work for the snow production part is less for a central system, but the cost and logistics affiliated with the transportation can be both expensive and difficult.
The work load for a distributed system will vary with the size of the system, with the operators’ expertise and the level of automation. Because of the risk affiliated with the high water pressure, cold temperatures, etc. it should always be at least two persons present during operation. It is always necessarry to check that the fan guns are working as expected, and that the snow is produced on the course and not in the forest or an adjacent field. In windy conditions it is necessary to check and adjust the angle and direction of the fan guns regularly. If the system or a fan guns stops, it is necessary to immediatelly disconnect and drain the hoses such that they do not freeze.
For a well functioning snowproduction system it is also important to have a warm building or garage where the operators can get warm in between their inspection rounds, where tools can be stored and where hoses and other equipment can de-ice and dry out. Additionally, a toilet must be available.
Since production equipment easily freze in cold temperatures, is it important to have tools that can be used for removing ice, such as pick-axes, shovels, propane torches, heat-guns etc. Water repellent and warm boots, gloves, pants and jackets are also necessary for working outside in the cold.
The snow production must take place following the advice in the manuals provided with the equipment being used, and according to the operational safety routines for the venue. In Norway, national guidelines for operational safety routines in alpine venues have been published (www.alpinanleggene.no). Much of these are also applicable for Cross-Cuntry and Biathlon venues.
Strict requirements for staff education must be implemented, and the health and safety for personell must be prioritized. Operational staff must verify and sign that they have read all safety manuals and instructions provided for use of fan guns and snow lances, compressors, pumps etc.
For smaller venues that are operated by ski clubs it is extra important that volunteers, parents, etc. recieve proper operational training and that the club’s insurance covers any insidents or accidents (NOTE: It is important to check that volunteers and retired persons are covered by the insurance).
Before the startup every season, the snow production system must be checked for potential damages, water leaks etc.
- check all pipes by starting compressor and water pump
- check if any repair of hydrants or valves are required
- when controlling air hydrants it is exra important to be careful
- water intake must be cleaned
Operational instructions covering tasks before and during daily operations must be written (and followed).
- Before operational start:
- Control that snow and ice are not blocking air- or water hydrants
- Control that all valves are working properly
- For manual start of fan guns it is normal that two persons are involved; one will regulate the water supply, the other will stand below the fan gun/snow lance to control the snow quality
- For hydrants that are not used, the handle should be closed and locked
- The radio batteries must be charged before each shift is starting
- General control of pump station and compressor station
- During operations:
- The snow production system must always be watched when in use
- Unauthorized persons should not be allowed inside the snow production area
- If the snow production takes place during the venue’s opening hours, the production area should be roped off, and the public/users must be informed that snow production is going on
- Pumps, compressors and fan guns/snow lances will start automatically if this option is set (in an automatic system)
- For manual start of snow lances the water hydrant should first be opened by 1/2 rotation of the handle. Immediatelly when the water comes out, the air hydrant should slowly be turned on to a fully open position.
- Control or move fan guns. Use the grooming machine to move fan guns in steep and icy sections.
- Control all hoses for leaks. Exchange damaged hoses and mark the leak by tying a knot at the location.
- At startup, all attachments must be checked before opening the hydrant
- When opening the air/water hydrant, the snowmaker must stand behind the hydrant and be in radio- or visual communication with another staff person.
- The snow production must the stopped if there are safety concerns related to high wind, fog, icing, injuries or damages, functional problems etc.
- The staff at the hydrants and fan guns should communicate using standard and agreed on signals:
- Visual communication: Right arm ready for startup, arms in cross to mark stop
- In the dark at night: Green light for start for start, red light for stop
- If visual communication is not possible, radios with headset/headphones must be used.
- Precise information must be given to the next/on-coming shift
- During operation the hoses must continuously be checked to avoid rubbing against sharp rocks, etc
- Be aware of the risk of unexpected movements – or even somersault – of the fan gun due to high wind, steep terrain, sudden change in water pressure or movement of the hoses.
- Make sure that any vibration in the hydrants are minimized
- Never be alone if a fan gun under pressure needs to be moved
- Move or adjust the fan gun often, preferably every 1 – 2 hour, such that moisture can be released
- Produce the snow downhill and in tail-wind
- Let the air-droplets/snow get as much air-time as possible
- If a hose becomes jammed, for example by icing, the production must be stopped until the pressure is lowered. If this takes too long time, a puncture or rapture may happen.
- Always follow the plan for which sections of pipes that are being used. NOTE: Write down which fan guns that should be moved (and other instructions) for the next shift.
Production with fan guns and snow lances both require careful mixing of water and air. It too much water is supplied, the snow becomes wet and can easily freeze. It the air supply is too high, the snow becomes too dry.
- For manual systems it is important to watch for changes in temperature, since this will require adjustments in the amount of water needed for optimal snow production and quality.
- The temperature and fan guns should optimally be controlled and checked once per hour.
- Snow lances do not need to be adjusted since they function on a different operational principle.
The quality of the produced snow is categorized on a scale from 1 – 9, where 1 is powder snow and 9 is sleet or almost rain. By holding a straight arm below where the snow falls (and catching it on the sleeve) it is relatively easy to see where on the scale the newly produced snow is. Normally the snow should be produced with quality 5 or 6.
- The density/weight for snow with quality 5 is 300 – 400 kg pr m3
Production for Cross-Country/Biathlon
For a distributed Cross-Country/Biathlon system, the snow is produced in 3 – 4 meter high piles (or “whales”) along the courses. After drying out, the piles are pushed out by the grooming machines. Optimally, the snow should be produced at least every 50 meter, but the grooming machine can push the snow over longer distances is needed (up to a couple hundred meters).
Process (with photos from the new 2022 Olympic venue north of Beijing):
- Place the snow fans along the course and in the stadium, attach power, data cable and hoses (move to the next hydrant when finished etc)
- Start the pumps and fan guns, produce snow on the 6 – 8 meter wide courses by regularly moving/adjusting the fan gun according to the wind direction
- Create snow piles ca. 3 – 4 meter tall, and let them dry out for ca. 1 – 2 days
- Push the snow piles using the front blade, and create a ca. 30 – 50 cm deep snow surface
- Groom the course with the tiller and create a nice corderoy surface
- After the snow has “settled” and hardned a bit, the ski course is ready for use
There is no requirement or standard for the snowdepth of a course or a stadium, but due to heavier use, the stadium should have a deeper snow layer. For biathlon ranges, the shooting ramp requires special grooming (often manual) since it needs a harder surface and a standard depth (30 cm) all winter long.
Production in alpine venues
Snow production must take place acording to the user manuals for the equipment in use, and according to the venues’ safety routines. In Norway, national guidelines for operational safety routines in alpine venues have been published (www.alpinanleggene.no).
For all alpine venues it is important that the instructions and requirements in the snow production operations plan are followed, and that the plan includes clear guidelines for what the control before and during operation, as well as routines for the different shifts (night, morning, afternoon).
For alpine slopes there are no rules regarding the depth of the snow layer. The depth can vary from section to section within the ski area. Where wear and tear is common, especially in steep sections, a thicker layer should be produced. Skiers will often stop on the upper edge of a steep section, and this causes increased wear and tear (the skis also emit energy/heat). The grooming machines will also have a tendency to push snow off these edges.
It should also be given consideration to sections where training and competitions take place, and where gates (especially slalom) must have at least a 50 cm snow layer. Use a drill and auger to check the depth. The table below provides guidelines for depth in different category slopes.
|Green/Blue||20 – 30 cm hard packed snow|
|Red/Black||40 – 50 cm hard packed snow|
|Competition||50 – 70 cm hard packed snow|
When the snow is produced during early season (when mild weather is still expected), it may be best to produce in large piles. Snow piles are very resistant to mild temperatures and rain.
When snow is produced in cold and stable weather, and a race arena is being prepared, it pays off to produce in thin layers to secure a high quality and to cover a large area as fast as possible. This means that the fan guns must be moved often.
Snow production is about treatment of water in below freezing temperatures. Standing water in those conditions will freeze to ice, so it is important that the water in the snow production pipes and equipment is constantly moving. It is therefore important and neccessary that water is flowing or drained at the end of every “dead end” water line. To make full use of all the water, it is therefore smart to place a fan gun at these locations. It is also important that any excess (drained) water is piped or ditched to a nearby creek, and is not just freezing to ice on the course or ski slope.
Problems with freezing (or ice) in the fan guns themselves are normally caused by wrong alignment of the fan gun in relation to the wind direction. If the fan gun blows snow into the wind, it will become covered with ice and create big operational problems. For example, a fan gun will stop operating when ice builds up on the fan and the internal mesh behind the fan becomes covered. If a fan gun ices up, the hoses will soon also ice up.
Removing ice from the fan gun is done by carefully using a torch or by trying to chip off the ice with an appropriate tool. Often the best solution is to bring the fan gun inside the maintenance building/garage and let it completely thaw.
The hoses will not freeze/ice as long as the water is moving. When the snow production stops, the hoses must be drained by laying them along the ground on a downhill gradient. When starting up again, water should first be sent through the hoses before connecting to the fan gun. This will avoid that ice particles clogg the fan gun’s filter.
Air hoses in high pressure systems can often build up an internal layer of ice due to the condensation. This can be removed by connecting the hose to the water hydrant and letting water run through the hose for a little while. It may be beneficial to regularly swith the hoses used for air and water (use air hoses for water and vise versa). Running water will “eat” ice.
Production in Snow Parks
When the snow park is designed and it is time to produce and push snow on the slopes/course, the following principles should be followed:
- A clever procedure when building a snow park is to first produce enough snow to cover the surface of the course, and then produce the snow needed for the elements that will go on top. The most important reason for this is that all types of elements require an even and straight snow surface to start building on. It is also important to ensure that there is enough snow in between the elements. So, the first step is to produce and groom a straight base layer such that the elements can be optimal.
- The produced snow must have a moist quality such that it can easily be pushed as well as provide enough grip for the grooming machine when it is building the elements.
- The snow is too wet if it becomes ice when freezing or drying out. The snow is too dry when the machine starts spinning or is difficult to push. It will take more time to build the elements when the snow is dry.
- The snow should not be produced exactly where the elements are planned.
- There must be room to work the snow. The machine must first crush and mix the snow before pushing it in place. This will create an even snow quality and avoid sugar snow or uneven layers in the finished element. The snow should be homogene with an even consistency from top to bottom.
- It is simplest and cheapest to produce and push the snow from a location above the planned element
- It should be enough space between the planned element and the produced snow for the machine to crush and mix it, as well as moving it without needing to change the direction of driving.
- If the snow pile is too close to the planned element, it creates extra work by needing to move the snow in several turns and directions.
- Ca. 10–15% of the element’s total snow must be produced or pushed from below
- with exception of small elements such as blue jumps (rarely needed)
- The snow that is placed below the element is used to build up and even out the landing and transition area after the main part of the element is built from above
Production on Ski Jumps
For smaller Ski Jumps the inrun, landing hill and outrun must be snow covered. In larger and modern hills the inrun is created by snow slurry or water that is cooled down to ice. The inrun track is then cut by the mechanical track setter.
For smaller hills it must be decided if the snow should be produced in a snow pile at the bottom or directly along the hill. To take advantage of a early days with cold tempratures it may be smart to produce in a large pile. For large hills it is normally no problem to produce snow directly on the hill.
The reason for considering this question is that wind will always blow snow off the hill and create some loss. Blowing snow may also cover and “ice up” stairs, bleachers, guardrails, equipment etc and create lots of extra snow clearing work.
The depth of the snow on the landing hill is determined by the homologated profile of the hill – the normal depth is about 30 – 45 cm. It is important to not produce too large of a pile of snow on the knoll (with the purpose of pushing downhill). Due to the steep gradient the pile may avalanche, rip the snownet and create safety issues for the staff. It is important that the produced snow is not too wet since this will build a wet layer between the surface and the snow and possibly create another avalanche situation.
The best method for placing the snow correctly with a grooming machine is to produce and push the snow from the bottom (K-point) and up.
When laying down snow on summer hills (snow on top of plastic) a few special methods must be used.
- A strong net must be strung and anchored both on the top and on the sides. Several 2″ x 4″ wooden planks are place across the landing hill. These are fastened by parallel wires. To ensure that the planks are well covered, an extra thick snow layer is used.
- The wires must be well anchored due to the weight of the snow (especially on a slick surface).
The newly produced snow must be dried out a couple of days (but no more than 72 hours) before being groomed. Artificial snow often contains more moisture than natural snow, and will require more work and time to distribute and groom.