The torque load of the coupling must be determined from the output of the driven machine and the coupling speed.
Rated coupling load TN = 9550 · PN / nN
(TN in Nm; PN in kW; nN in rpm)
The rated coupling load so obtained must be multiplied by factors and compared with the rated coupling torque. An ideal but expensive b is to measure the torque characteristic on the coupling. For this Flender offers special adapters fitted with torque measuring devices.
The rated coupling torque TKN is the torque which can be transmitted by the coupling over an appropriate period of use, if the load is applied to the coupling purely statically at room temperature.
Operating factors are to express the deviation of the real coupling load from the "ideal" load condition.
Coupling load in continuous operation
The operating principles of the driving and driven machines are divided into categories and the operating factor FB derived from these in accordance with DIN 3990-1.
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Operating factor FB
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Torque characteristic of the driven machine
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Torque characteristic of the driving machine
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regular
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regular
with moderate surges
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irregular
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very uneven
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regular
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1,0
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1,25
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1,5
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1,75
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regular with moderate surges
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1,25
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1,5
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1,75
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2,0
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irregular
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1,5
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1,75
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2,0
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2,5
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Examples of torque characteristic of driving machines:
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regular: Electric motors with soft starting, steam turbines
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regular with moderate surges: Electric motors without soft starting, hydraulic motors, gas and water turbines
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irregular: Internal-combustion engines
Examples of torque characteristic in driven machines:
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regular: Generators, centrifugal pumps for light fluids
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regular with moderate surges: Centrifugal pumps for viscous fluids, elevators, machine tool drives, centrifuges, extruders, blowers, crane drives
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irregular: Excavators. kneaders, conveyor systems, presses, mills
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very uneven: Crushers, excavators, shredders, iron/smelting machinery
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Temperature factor FT
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|
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Temperature Ta on the coupling
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Coupling
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Elastomer material
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Low temperature
°C
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under –30 °C
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–30 °C to 50 °C
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to 60 °C
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to 70 °C
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to 80 °C
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to 90 °C
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to 100 °C
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to 110 °C
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to 120 °C
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N-EUPEX
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NBR
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–30
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–
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1,0
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1,0
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1,0
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1,0
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–
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–
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–
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–
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N-EUPEX DS
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NBR
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–30
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–
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1,0
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1,0
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1,0
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1,0
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–
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–
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–
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–
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RUPEX
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NBR
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–30
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–
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1,0
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1,0
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1,0
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1,0
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–
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–
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–
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–
|
|
RUPEX
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NR
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–50
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1,1
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1,0
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1,0
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–
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–
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–
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–
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–
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–
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BIPEX
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TPU
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–30
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–
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1,0
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1,0
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1,0
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1,0
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–
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–
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–
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–
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ELPEX
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NR
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–40
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1,1
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1,0
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1,25
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1,40
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1,60
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–
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–
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–
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–
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ELPEX-B
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NR
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–50
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1,1
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1,0
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–
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–
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–
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–
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–
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–
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–
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ELPEX-B
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CR
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–15
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–
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1,0
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1,0
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1,0
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–
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–
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–
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–
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–
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ELPEX-S SN, NN, WN
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NR
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–40
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1,1
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1,0
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1,25
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1,40
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1,60
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–
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–
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–
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–
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|
ELPEX-S NX
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VMQ
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–40
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1,1
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1,0
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1,0
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1,0
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1,0
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1,1
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1,25
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1,64
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1,6
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NR = natural rubber, natural-synthetic rubber mixture
NBR = nitril-butadiene-rubber (Perbunan)
CR = chloroprene rubber (FRAS fire-resistant and anti-static)
VMQ = silicon
TPU = polyurethane
Coupling size TKN ≥ TN · FB · FT
In the case of ARPEX and ZAPEX coupling types, no temper-ature factor (FT = 1.0) need be taken into account.
Coupling load under maximum and overload conditions
The maximum torque is the highest load acting on the coupling in normal operation.
Maximum torques at a frequency of up to 25 times an hour are permitted and must be lower than the maximum coupling torque. Examples of maximum torque conditions are: Starting operations, stopping operations or usual operating conditions with maximum load.
TKmax ≥ TMax · FT
Overload torques are maximum loads which occur only in combination with special, infrequent operating conditions.
Examples of overload torque conditions are: Motor short circuit, emergency stop or blocking because of component breakage. Overload torques at a frequency of once a month are permitted and must be lower than the overload torque of the coupling. The overload condition may last only a short while, i.e. frbs of a second.
TKOL ≥ TOL · FT
Coupling load due to dynamic torque
load
Applying the frequency factor, the dynamic torque load must be lower than the coupling fatigue torque.
Dynamic torque load
TKW ≥ TW · FF · (FB – 1,0) / 1.5
Frequency of the dynamic torque load
ferr ≤ 10 Hz frequency factor FF = 1.0
Frequency of the dynamic torque load
ferr > 10 Hz frequency factor FF = √(ferr/10 Hz)
For the ZAPEX and ARPEX series the frequency factor is always FF = 1.0.
Checking the maximum speed
For all load situations nKmax ≥ nmax
Checking permitted shaft misalignment
For all load situations the actual shaft misalignment must be less than the permitted shaft misalignment.
Checking bore diameter, mounting geometry and coupling type
The check must be made on the basis of the dimension tables. The maximum bore diameter applies to parallel keyways to DIN 6885. For other keyway geometries the maximum bore diameter can be reduced. On request couplings with adapted geometry can be provided.
Coupling behavior under overload conditions
The ZAPEX, ARPEX, N-EUPEX, RUPEX and BIPEX coupling series can withstand overloads until the breakage of bl parts. These coupling series are designated as fail-safe.
The N-EUPEX DS, ELPEX-B, ELPEX-S and ELPEX coupling se-ries throw overload. The elastomer element of these couplings is irreparably damaged without damage to bl parts when subjected to excessive overload. These coupling series are designated as non-fail-safe. These types that fail can be fitted with a so-called fail-safe device. This additional component enables emergency operation, even after the rubber element of the coupling has been irreparably damaged.
Checking shaft-hub connection
The torques specified in the tables of perbance data of the coupling series do not necessarily apply to the shaft-hub con-nection. Depending on the shaft-hub connection, proof of b strength is required. Flender recommends obtaining proof of b strength by using calculation bs in accordance with the current state of the art.
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Shaft-hub connection
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Suggestion for calculation b
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Keyway connection to DIN 6885-1
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DIN 6892
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Shrink fit
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DIN 7190
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Spline to DIN 5480
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|
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Bolted flange connection
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VDI 2230
|
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Flange connection with adapter bolts
|
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Fitting recommendations for the shaft-hub connection are given in catalog section 15.
Checking low temperature and chemically aggressive environment
The minimum permitted coupling temperature is specified in the FT Temperature Factor table. In the case of chemically aggressive environments, please consult the manufacturer.
