Why do you want to clamp it? The answer may help in addressing the question. Maybe its a belt threaded down a slope or maybe the clamp is used to pull two belt ends together on the horizontal.

LKN ■

I do not recommend single clamp procedures on significant inclines or declines for safety reasons.

The degree of clamping depends on clamp friction and belt fricition. Both need to be studied to give a proper recommendation and clamp design.

We prefer an air reulated platen system w/ manual air valves on a 100 psi system. The platen size needs to be computed with the following details.

In a dual clamp where there can be a significant variation between static and dynamic friction due to belt surfaces ( silicon release agents, or others affecting sliding friction wrt pressure et al) we use a coefficient of friction of 0.20 on the holding press and regulating press.

CDI recommends the air bag concept as used by Canada Conveyor Belt. This clamp system is similar to the vulcanizing press system of Shaw-Almex. The Shaw-Almex has s special patented platen that is now also used by Wagner.

The holding press is sized to hold three times the expected load or have a safety factor of 3:1 with f=0.20. The factor of safety includes a failure of one holding air bag. The regulating press has a similar set of specifications with one bag failure and still be able to regulate and bring the belt to a stiop.

The factor of safety is approximately 6:1.

There are other systems sucessfully used on light to moderate inclines and declines. Here the drag is applied by screw clamps and torque wrenches in place of the air bag system. The clamps are initally tighted and released one-by-one as a series of success individual clamps tied together in an assemby. THis is a full manual system. Special preodeures are required to be set up. ■

I did not state the holding force. This is taken as the vertical gravity force less a rolling friction with a DIN F = 0.01. THis is caluclated similar to the belt tension formula. ■

You can achieve a columb friction coefficient f=0.5 to 0.6 of dull surface rubber on dry non-polished steel. As the design catalogs note, rubber on a pulley surface is normally taken as f=0.25. Any change in the surface texture or lubricant equivalence should have an adjustment to the friction factor to a lower value.

New belts may have release compounds that alter the friction. Going to a f=0.40 value is risky. Prudent engineering may allow it. It is up to your level of efficacy.

THere are many things that can alter the coefficient number. For instance you have not talked about the means of control. High clamping impulses (clamp operator and regulator) and platen chatter will reduce control. You define the purpose and then the means to enable the necessary control.

I think you need to look at the risk and benefit. If the belt installation has an issue of personnel safety, don't be foolish. ■

Shane,

Larry has given you some pretty good guidelines on clamp selection. The commercial clamps around are wide and varied but you need to work through the clamping methodology as part as any selection as some can fail despite their "rating" due to slippage. As far as what you need, essentially what you are clamping the belt for is to restrain its natural inertia i.e. its weight so the clamp force is about belt weight and belt lift. Anchoring clamps is extremely important particularly if the belt weight is high and you are talking say a drift conveyor. In many instances prudence dictates you build into the structure a belt clamping station. If overall stresses are high having back up inertial failsafe braking is also usually warranted. To give you anything but these general guidelines requires a lot more info about your specific need.

Col Benjamin ■