Highly flexible couplings ELPEX series

ELPEX couplings are highly torsionally flexible and free of torsional backlash. Because of their low torsional stiffness and damping capacity, ELPEX couplings are especially suitable for coupling machines with a very non uniform torque pattern. ELPEX couplings are also suitable for connecting machines with high shaft misalignment.

Standard ELPEX coupling types are designed as shaft-shaft connections or flange-shaft connections. Application-related types can be implemented on request.

Область применения

The ELPEX coupling is available in 9 sizes with a nominal torque of between 1600 Nm and 90000 Nm. The coupling is suitable for ambient temperatures of between –40 °C and +80 °C.

The ELPEX coupling is frequently used for high-quality drives which have to guarantee very long service life in harsh operating conditions. Examples of applications are mill drives in the cement industry, marine main and secondary drives or drives on large excavators powered by an electric motor or diesel engine.

Дизайн

Design and function

The ELPEX coupling's transmission characteristic is determined essentially by the flexible rings. The flexible rings are manufactured from a natural rubber mixture with a multiply fabric lining. The flexible rings are split so that they can be changed without having to move the coupled machines.

The flexible rings are fastened to the hub with a clamping ring and to the outer flange with a clamping ring, using pins and bolts.

On the type EFG, the outer flange is designed with connection dimensions for connection to e.g. a diesel engine flywheel. On ENG types, the outer flange is fitted to a second hub part, which then enables the shaft-shaft connection.

Materials:

	Type
	Cast iron	Steel
Hub part 1	Grey cast iron EN-GJL-250	Steel
Hub part 2	Steel	Steel
Retaining ring, outer ENG, ENGS	Grey cast iron EN-GJL-250	Steel
Outer flange EFG, EFGS	Grey cast iron EN-GJL-250	Steel

Flexible ring materials:

Material/description	Hardness	Identification	Ambient temperature
Natural rubber	70 ShoreA	Size - 2	–40 °C to +80 °C

ELPEX coupling types

Type	Description
ENG	Coupling as shaft-shaft connection
EFG	Coupling as flange-shaft connection
ENGS	as ENG with fail-safe device
EFGS	as EFG with fail-safe device

Types ENG/ENGS

Types EFG/EFGS

Further application-specific coupling types are available.
Dimension sheets for and information on these are available on request. The following versions have already been implemented a number of times:

ELPEX coupling with brake drum, brake disk or flywheel mass
ELPEX coupling with axial backlash limiter
ELPEX coupling with adapter
ELPEX coupling in combination with a safety slip clutch
ELPEX coupling for engaging/disengaging during standstill
ELPEX coupling as part of a coupling combination

Fail-safe device of ELPEX coupling

Types ENGS and EFGS are provided with a fail-safe device. In normal operation the torsion angle of the flexible rings is smaller than the gap between the cams. In normal operation there is no metal-metal contact.

If the flexible rings fail, cams transmit the torque from the inner part and outer part. These enable the coupling to be used in emergency mode for a short time. This option is frequently required e.g. in the case of marine drives.

Fail-safe device

Конфигурация

The ELPEX coupling is especially suitable for rough operation. An application factor different from that in catalog section 3 is therefore sufficient for all applications. In the case of machines which excite torsional vibration, FLENDER urgently recommends carrying out a torsional vibration calculation or measuring the coupling load occurring in the drive.

Coupling selection

Coupling load in continuous operation

The operating principles of the driving and driven machines are divided into categories and the application factor FB derived from these in accordance with DIN 3990-1.

Application factor FB	Torque characteristic of the driven machine
Torque characteristic of the driving machine	uniform with moderate shock loads	non uniform	very rough
Electric motors, hydraulic motors, gas and water turbines	1.0	1.3	1.4
Internal combustion engines	1.3	1.4	1.6

Examples of torque characteristic in driven machines:

uniform with moderate shock loads: generators, fans, blowers
non uniform: reciprocating compressors, mixers,
conveyor systems
very rough: crushers, excavators, presses, mills

Temperature factor FT		Temperature T_a on the coupling
Coupling	Elastomer material	–40 °C to –30 °C	–30 °C to +50 °C	to 60 °C	to 70 °C	to 80 °C
ELPEX	NR	1.1	1.0	1.25	1.40	1.60

NR: Natural rubber mixture

Select size with: T_KN ≥ T_N · FB · FT

Coupling load at 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.

T_Kmax ≥ T_max · 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 maximum overload torque of the coupling. The overload condition may last only a short while, i.e. fractions of a second.

T_KOL ≥ T_OL · FT

Coupling load due to dynamic torque load

Applying the frequency factor FF, the dynamic torque load must be lower than the coupling fatigue torque.

Dynamic torque load
T_KW ≥ T_W · FT · FF · 0.6 / (FB – 1.0)

Frequency of the dynamic torque load
f_err ≤10 Hz frequency factor FF = 1.0

Frequency of the dynamic torque load
f_err >10 Hz frequency factor FF = √(f_err / 10 Hz)

Checking the maximum speed:

The following must apply to all load situations: n_Kmax ≥ n_max

Checking permitted shaft misalignment and restorative forces

For all load situations the actual shaft misalignment must be less than the permitted shaft misalignment.

Checking bore diameter, mounting geometry and coupling design

The check must be made on the basis of the dimension tables. On request, couplings with adapted geometry can be provided.

Checking shaft-hub connection

Please refer to catalog section 3 for instructions.

Checking temperature and chemically aggressive environment

The permitted coupling temperature is specified in the Temperature Factor FT table. In the case of chemically aggressive environments, please consult the manufacturer.

Особенности

The ELPEX coupling is suitable for horizontal and vertical mounting positions or mounting at any required angle. The coupling parts can be arranged as required on the shafts to be connected.

The split flexible rings can be changed without having to move the coupled machines.

The flexible rings are mounted without backlash and give the coupling progressive torsional stiffness, i.e. torsional stiffness increases in proportion to coupling load.

The ELPEX coupling is especially suitable for reversing operation or operation with changing directions of load.

The coupling is delivered preassembled. The flexible rings are completely assembled. On the type ENG, the coupling halves have to be bolted together after the hub has been mounted. On the type EFG, after mounting the coupling hub, only the outer flange has to be connected to the machine.

Outer flanges with different connection dimensions are available for the type EFG.

If the flexible rings are irreparably damaged or worn, the metal parts can rotate freely against one another, they are not in contact with one another.

Технические данные

Power ratings

Size	Rated torque	Maximum torque	Overload torque	Fatigue torque	Dynamic torsional stiffness for 100 % capacity utilization	Stiffness		Permitted shaft misalignment at speed n = 1500 rpm
						Axial	Radial	Axial	Radial	Angle
	T_KN	T_Kmax	T_KOL	T_KW	C_Tdyn	C_a	C_r	ΔK_a	ΔK_r	ΔK_w
	Nm	Nm	Nm	Nm	kNm/rad	N/mm	N/mm	mm	mm	Degree
270	1600	4800	6400	640	22.0	660	770	2.2	2.2	0.2
320	2800	8400	11200	1120	38.0	780	910	2.6	2.6	0.2
375	4500	13500	18000	1800	63.0	970	1130	3	3	0.2
430	7100	21300	28400	2840	97.0	1160	1350	3.4	3.4	0.2
500	11200	33600	44800	4480	155	1410	1630	3.8	3.8	0.2
590	18000	54000	72000	7200	240	1710	1990	4.2	4.2	0.2
690	28000	84000	112000	11200	365	2060	2390	4.6	4.6	0.2
840	45000	135000	180000	18000	685	2570	2990	5	5	0.2
970	90000	270000	360000	36000	1100	3020	3510	5.5	5.5	0.2

The damping coefficient is Ψ = 1.1

Torsional stiffness

The dynamic torsional stiffness is load-dependent and increases in proportion to capacity utilization. The values specified in the selection table apply to a capacity utilization of 100 %. The following table shows the correction factors for different rated loads.

C_Tdyn = C_{Tdyn 100 %} · FKC

	Capacity utilization T_N / T_KN
	20 %	50 %	60 %	70 %	80 %	100 %	200 %
Correction factor FKC	0.3	0.56	0.65	0.74	0.82	1	1.9

Torsional stiffness also depends on the ambient temperature and the frequency and amplitude of the torsional vibration excitation. More precise torsional stiffness and damping parameters on request.

Permitted shaft misalignment

The permitted shaft misalignment depends on the operating speed. As the speed increases, lower shaft misalignment values are permitted. The following table shows the correction factors for different speeds.
The maximum speed for the respective coupling size must be noted!

ΔK_perm = ΔK₁₅₀₀ · FKV

	Speed in rpm
	500	1000	1500	3000
Correction factor FKV	1.6	1.25	1.0	0.70