anti-vibration and noise reduction dampers for power transmission systems including new NRS noise reduction system


		Damping Flanges, Rings and Rods Tweet
		JBJ Techniques Ltd manufacture and supply a comprehensive range of anti-vibration and noise reduction components in a range of materials to suit a variety of application environment needs, such as oil and temperature resistance. Damping rings for use when vertical mounting (VI-construction) between bellhousing and tank lid or horizontal (B5-construction) mounting position between motor and bellhousing flange.
They consist of two reinforced aluminium rings which are connected by a rubber coat without any metal connection. The used materials (Nitrile) are resistant against mineral oils and suitable for working temperatures up to +80°C. The possible noise reduction will be approx. 3 - 5 db(A). Damping flanges for use in combination with bellhousings between electric motor and hydraulic pump. These damping flanges of two aluminium parts which are connected by a rubber coat (Nitrile) without any metal connection. Dampers are resistant against mineral oils and suitable for working temperatures up to +80oC, for short time +100oC. The possible noise reduction will be approx. 3 - 8 db(A). Damping flanges are available in two degrees of hardness with the description N - normal / H - hard.

NEW NRS retro-fit system
The Problem: www.hsimagazine.com/article
Standard bellhousings available on today’s market are generally made of metal. Rising costs have meant that the cast steel originally used has now been replaced by aluminium. To save material, the wall thickness – especially in the case of cast aluminium – has been reduced more and more, with the load level remaining constant.
This reduced wall thickness means that there is only minimal absorption of the noise made by the coupling in the bellhousing. Unlike their cast steel counterparts, the more lightweight aluminium bellhousings have comparatively poor damping characteristics.
The pulsation of hydraulic pumps generates very strong vibrations that are not damped sufficiently by an aluminium bellhousing. Moreover, at rigid bellhousings there is no isolation of mechanical vibration between the electric motor and the hydraulic pump due to the lack of damping characteristics.
Vibration studies have revealed that airborne and structure-borne vibration is at frequencies where human hearing is at its most sensitive.
Under certain unfavourable circumstances, the thin-walled aluminium bellhousing amplifies the running noise of the pump even more; in these cases, the bellhousing resonates in sympathy, similar to a real bell, which can then lead to an additional increase in oscillation amplitude.

Illustration 1: Generation of airborne / structure-borne vibration		Illustration 2: Noise level reduction NRS
Coupling	Output	NRS

Airborne vibration	Structure-borne vibration	Structure-borne vibration using NRS

The Solution:
In line with EC Directive "Noise" (2003/10/EG), the planned retrofitting measures are intended to resolve acute problems caused by poor soundproofing and vibration damping, including problems that occur in hydraulic apparatus already in use.
The best noise level reductions were achieved using the NRS System.
The NRS System is
• a newly-developed 3D “High Density- “ polyester structure
• tear-proof and temperature-resistant from - 40° C to +120° C
• resistant to most currently available hydraulic oil types
• easy to fit and 100% recyclable
• available in 4 different system widths and 3 lengths for retrofitting or as original equipment.
With the NRS System, it was possible to reduce the total noise emission level of a cast aluminium bellhousing in critical frequency ranges by more than 10 dB. This reduction is clearly audible to the human ear. The graph shows examples of frequency ranges of a standard cast aluminium bellhousing and a version with NRS.

Illustration 3:

link to pdf info for NRS, noise reduction system

Illustration 4:

Article no:
Width
b_NRS(1)
b_NRS(2)
Length
Circumference
of the circle
Bellhousing
A
B
C
D
L
(D - C)

   NRS60900*
60
900
ø250 bis ø350

250
190
19
120-175
250

300
234
20
144-196
300

350
260
26
188-256
350

   NRS80900*
80
900
ø250 bis ø350

  NRS100900*
100
900
ø250 bis ø350

  NRS120900*
120
900
ø250 bis ø350

  NRS601200
60
1200
ø400 bis ø450
400
300
26
204-256
178-230

  NRS801200
80
1200
ø400 bis ø450

  NRS1001200
100
1200
ø400 bis ø450
450
350
26
234-315
208-289

  NRS1201200
120
1200
ø400 bis ø450

  NRS601900
60
1900
ø550 bis ø660
550
450
26
248-315
222-289

  NRS801900
80
1900
ø550 bis ø660

  NRS1001900
100
1900
ø550 bis ø660
660
550
32
310-345
278-313

  NRS1201900
120
1900
ø550 bis ø660

Dimensions in mm,   *ex-stock

Please contact technical office for further details telephone: 01737 767493 or email: info@jbj.co.uk

See pages 1 - 3 of link to pdf catalogue for specification of damping flanges, rings and rods >>

Related links: Adaptor plates
Footbrackets
Couplings
ATEX

jbj Techniques Limited is ISO certificated, committed to international coordination & unification of industrial standards

© Copyright, jbj Techniques Limited,
28 Trowers Way, Holmethorpe Industrial Estate, Redhill, Surrey RH1 2LW. United Kingdom of Great Britain. telephone: +44(0)1737 767493 email:info@jbj.co.uk
E. & O. E., Disclaimer: Information throughout this web-site relevant to design, materials and/or specifications are subject to change without notice and liability therefore.