Running torque

The closing, opening, breakaways, running torques are all applicable in all valve operations. And is significant to understand the operating force required to operate the valve with ease. Also in selecting the actuators. These values are to be analysed especially in valves of very large diameters. Shell prescribes a max. of 350N operating force. Most vendors are not interested in giving these data in the bidding stage. My suggestion is to make it a mandatory requirement to submitt these data in the bidding stage. Plant operational personnel can aprreciate the importance of these torques. Member's views are highly appreciated.

Running Torque.

The running torque of a gearhead is the amount of torque needed to drive the gearhead under a no load condition. This is separate and different from starting torque, which is the torque required to start the gearhead in motion (often referred to as 'breakaway torque'). The running torque is a constant amount of torque needed to overcome the accumulated friction, inertia and resistance of the gearhead. Friction comes from many areas, including the seals, bearings, and somewhat from the limited sliding action of the gears themselves. Inertia is primarily a function of the diameters of the gears themselves. The primary cause of resistance is the lubricant, as it impedes the rotary motion of the gears.Friction and inertia require a constant running torque to overcome, which does not vary by speed. Resistance, however, varies with speed, as it takes increasing amounts of torques for the gears to move through the lubricant itself. This can be displayed as a formula, with a constant running torque, and a variable torque which is a function of speed.

With regards,Kannan.