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Coldwater is the world’s largest manufacturer of suction roll seal materials. From the largest and fastest machines in the world, to older and narrower machines, Coldwater seals are there. More suction rolls contain Coldwater seals than any other product. Coldwater seals have been sold around the world for over 15 years by all major paper machine builders, and various international distributors, under a variety of trade names. These names include, among others: AppleSeal, Duraseal, Robaseal, ValSeal, SealPak, BelSeal, GSS, E-9000 and Moray.

Today there are stocking and machining distributors of Coldwater seals on six continents.

Coldwater seals are made from a proprietary Rubber-Graphite material specifically designed for the suction roll seal, that has never been used for any other application. The Coldwater seals material was originally developed in the mid-1980s to replace asbestos seal products. The Coldwater Rubber-Graphite seal material has many unique features that make it the standard by which all other seal materials are compared.

There are other “rubber-graphite” seals on the market, but only the original Coldwater Rubber-Graphite offers the security and piece of mind of thousands of successful operations over many years. Technically, there are many important differences between Coldwater Rubber-Graphite and other rubber-graphite materials – as shown by the following tests and data.

simulation machine   failure analysisinfared Thrmograph of roll shell    comparative testing
Coefficient of Friction: Dry Against SST Panel
COLDWATER Rubber Graphite “A” Rubber Graphite “J”
Static .19 .24 .22
Dynamic .12 .20 .19
Coldwater has the lowest.
Coefficient of Linear Thermal Expansion [K~1]
COLDWATER Rubber Graphite “A” Rubber Graphite “J”
10 x 10-6 13.6 x 10-6 23 x 10-6
Coldwater expands the least.
Water Absorption [% Volume]
COLDWATER Rubber Graphite “A” Rubber Graphite “J”
.18 .46 1.0
Coldwater has the smallest volume change.
Hardness vs. Temperature: Shore D
COLDWATER Rubber Graphite “A” Rubber Graphite “J”
Room Temp. @ 20°C 77 76 87
Normal Operation @ 60°C 74 75 86
Dry Running @ 100°C 40 72 82
Only Coldwater is designed to accelerate wear, release graphite lubrication, and reduce heat near the shell as seal temperatures approach 100°C from dry friction.
COLDWATER Rubber Graphite “A” Rubber Graphite “J”
E-Module [N/mm2] 7384 14280 9000
Tensile [N/mm2] 35.1 60.6 44.4
Elongation [%] .62 .76 1.33
Flexural [N/mm2] 48.3 93.3 77.5
Coldwater is consistently lower in all categories because of its higher graphite content. More graphite means better lubrication when running dry. Lower physical properties also allow the seal to wear-in to the shape of the roll sooner, giving faster vacuum on start-up and better fit to rough shells.
Thermal Conductivity [W/mK]
COLDWATER Rubber Graphite “A” Rubber Graphite “J”
7.0 10.4 8.6
Coldwater is the lowest, to keep heat out of the roll.
Seal Temperature vs. Time graph
Dry Running Conditions:
Speed 1500 m/min
Air 0.5 bar
Coldwater Protects Roll Covers from Heat Damage
If seals run against the shell without lubrication, they heat up due to friction. The Coldwater Seal softens as seal surface temperatures approach 100°C. This allows the hot material to wear away exposing new cooler seal material, and releasing more graphite for lubrication in place of water. The process repeats over and over until dry contact stops, but the overall temperature of the Coldwater Seal remains constant. In a suction roll this wear would stop once enough material had worn for lubrication to again pass between the seal and the shell, or when clearance was established.RG-A and RG-J, the other rubber graphite seals, have high thermal conductivity, and the heat builds in the seal material as time goes by. Heat in the seal near the shell can cause damage to rubber or polyurethane roll covers when the machine stops, and heat transferred into the suction box can effect internal bearing life. The phenolic seal did not wear with time, but continued to get hotter and hotter from dry friction. Phenolic seals have been linked to failures in duplex stainless steel shells because of the high heat generated.**Some rubber graphite seals require Depolymerization to occur before graphite is released (see brochure for RG-A). This typically occurs at temperatures in excess of 300°C. Such temperatures inside a suction roll from dry friction can cause severe damage to covers, wires or felts, and internal bearings. Coldwater Seals release graphite with any dry contact, no matter how light, because the Coldwater graphite particles are not part of the polymer chain, but only housed between strands, where they can be freely released on contact.
Seal life graph
Dry Running Conditions:
Typical Behavior In A
Suction Roll
Coldwater Seals Last 2 Years or More
Inside a suction roll, dry running happens because of a lack of lubrication. Too high air tube pressure, a rough shell profile, thermal expansion of the roll at start-up or even a plugged shower nozzle can cause this to occur. When Coldwater Seals experience dry contact with the shell, wear begins and graphite is released. Wear removes hot seal material from the surface of the seal and reduces the pressure of the seal against the shell in the dry area allowing either lubrication from other areas to move in, or for the seal to wear until no longer in contact with the shell. Wear is usually brief until a new equilibrium is reached. Coldwater’s low thermal conductivity prevents any heat from dry friction from transferring into the roll where damage can occur. Most wear will occur in short intervals of dry running and then stop, as Coldwater Seals quickly adjust to the changing conditions. Coldwater Seals will typically last 2 years or more in well maintained suction rolls.
Coldwater Rubber Graphite Properties Graph

Coldwater Rubber Graphite is Unique
Only Coldwater Rubber-Graphite seals are designed to soften in hot conditions brought on by dry running. The lower hardness at elevated temperatures allows wear to accelerate, releasing graphite to lubricate the shell surface and reduce the heat from friction as quickly as possible until a new equilibrium is reached. If a seal stays hard at high temperatures, it can hold heat of over 100°C near the shell. If the machine stops for any reason, this heat can transfer from the seal through the roll shell and cause severe damage to rubber or polyurethane covers on the outside diameter. Hot suction roll seals are one of the leading causes of roll cover failures on suction rolls. Such failures are not possible with Coldwater Seals.
Coefficient of Friction graph

Coldwater Has More Graphite – Less Friction
Coldwater Seals have the highest graphite content and the lowest dynamic coefficient of friction, therefore the lowest horsepower consumption.Horsepower consumption is a hidden cost of using seals with a higher coefficient of dynamic friction than Coldwater’s.

Even a 10 amp savings in the power to drive a suction roll adds up:

For a DC Drive:
10 amps x 440 volts = 4400 watts = 4.4 kilowatts
4.4 kW x $0.06/kW-hr (avg. US cost) x 24 hrs/day x 365 days/year = $2,313.00/year

For an AC Drive:
10 amps x 440 volts x 1.73 (3 phase) x .85 (power factor) = 6470 watts = 6.5 kilowatts
6.5 kW x $0.06/kW-hr (avg. US cost) x 24 hrs/day x 365 days/year = $3,416.00/year

Power Savings
Cost Savings
(DC drive)
Cost Savings
(AC drive)
10 $2,313 $3,416
20 $4,626 $6,832
40 $9,525 $13,664
60 $13,878 $20,496
80 $18,504 $27,328
100 $23,130 $34,160
Air Tube Pressure vs. Horsepower graph

Coldwater Prevents Wasted Power
In a test of Coldwater Seals versus a competitor with a Teflon insert, a dramatic difference in horsepower consumption was noted as air pressure was increased from .3 bar to 1.0 bar. The Coldwater Seal caused little change in horsepower consumption because of its low coefficient of friction and high wear rates when in contact with the shell. The competitor material with Teflon had a very high coefficient of friction in the base material and did not wear with contact, causing a severe braking effect on the roll. An additional 100 amps was required to keep the roll at the same rpm with the air pressure increased to 1.0 bar.100 amps in continuous operation for one year at $0.06/ kW-hr equals $23,000 to $34,000 per year of wasted power depending upon the type of drive used!
coldwater Blue vincon

The air tube under the suction roll seal is actually designed to be compressed in usage, not expanded. This is a common misunderstanding.The tube is really a variable tension spring, and is not supposed to expand beyond its static round shape when inflated. The air pressure in the tube should only offset the weight of the seal and return the tube to round with the seal resting on top and just touching the shell.In operation in the suction roll, the lubricating water from the shower should pass between the seal and the shell. The seal should glide on a film of water at all times. For this to happen, the seal must compress the tube enough for the water to squeeze through, which requires the pressure inside the tube to be very light. Typically 0.3 bar or less is recommended by all major suction roll builders.When properly fit to the roll, the seal should just touch the shell when resting atop a round air tube. If this is not the case, the seal may be too short for the roll and the height of the seal should be adjusted (see our Efficiency Inspection Service brochure). If the air tube has to lift the seal up to the shell, considerable pressure may be required in the tube to do this. Pressure above .5 bar in the tube will make the tube hard to compress, and lubrication will not be able to pass between the seal and the shell. Seals will wear prematurely, and shower water intended for the seals is cut-off, and may fall and rewet the sheet.Tubes with rapid expansion at low pressures push the seal into the shell like a brake. Horsepower consumption increases, and seal life decreases.
Air Loading pressure graph

Coldwater Blue Vincon Tubes Expand Less
The more a tube expands, the greater the force on the seal, and the shorter the seal life.Some air tubes are sold on the basis of greater “stroke” or expansion. This is supposed to eliminate the need to custom fit seals to the shell, since these tubes expand rapidly with little air pressure, raising even short seals up to the shell. However, this expansion pushes the seal into the shell with more force at lower air pressure settings than with Blue Vincon. If the seal is pushed into the shell it causes a braking effect on the roll and increases horsepower consumption. Lubrication is also cut off, as water can no longer pass between the seal and the shell, at much lower air pressure settings. Seal life will typically be dramatically shorter. Machine downtime from premature seal wear becomes a real possibility.Custom fitting of seals to the roll is the best way to extend operating intervals, and seal life.