Mason 30N Spring and Double Deflection LDS Rubber Hanger

Overview

The Mason 30N is a combination vibration isolation hanger from Mason Industries that places a steel spring and a double deflection rubber element in series inside one steel hanger box. It is used to suspend piping, ductwork, fans and other equipment from the building structure while stopping both low frequency vibration and high frequency noise from travelling up the hanger rods. Mason describes the Series 30N as its top-of-the-line hanger, recommended for all highly critical locations where it is equally important to isolate noise and vibration. The 30 in the name means that the lower rod can swing through an arc of 30 degrees from side to side in any direction before it contacts the rubber bushing.

Seven Star LLC supplies the Mason 30N and the related Mason hangers, spring mounts and restrained mounts to mechanical contractors and consultants in Muscat, across the Sultanate of Oman and the GCC. Pipe risers and headers connected to chillers and pumps are among the most common paths for noise into occupied spaces, and we help project teams select the hanger series and capacity for each support point with engineering support in Muscat.

Working Principle

As general engineering background, a hanger isolates in the same way as a floor mount: the suspended load deflects the resilient element, the supported system gets a natural frequency below the disturbing frequency, and only a small part of the vibration is passed to the slab above. Springs provide the large deflection needed for low frequency isolation, while rubber elements absorb the high frequency components that a steel coil can transmit. Placing a spring and a rubber element in series combines both advantages, but only if the hanger rod never touches the steel box, because a rod rubbing on the box short circuits both elements.

The Mason bulletin explains that Series 30 hangers were designed after a consultant complained of seeing rods rubbing on the bushings of standard hangers on job sites. Mason developed springs that are larger in diameter and shorter, giving the 30 degree angular capability, and in the Mason 30N added a double deflection Low Dynamic Stiffness (LDS) rubber element above the spring. The rated deflection published for each 30N size includes this double deflection element. The LDS rubber is described as bridge bearing natural rubber chosen to minimize noise and vibration transmission, and the springs have additional travel to solid equal to 50% of their rated deflection.

Engineering Design of the Mason 30N

In the Mason 30N the upper rod attaches to the top of the hanger box through the double deflection LDS element, and the lower rod passes up through the bottom of the box into a spring cup. The spring sits in an LDS cup with a projecting bushing that lines the bottom hole of the box to prevent steel to steel contact. Mason boxes are made by bending steel flats into an inverted U shape with return bends at the bottom and arc welding them to thick steel washers, which the manufacturer considers stronger and safer than spot welded sheet metal; the upper steel washer in the rubber element is larger than the hole in the box, so the load remains captive even if the rubber is damaged.

Several variants of the Mason 30N are offered for different site needs. The PC30N version of the Mason 30N is precompressed in the factory to its rated load by a washer and adjusting nut at the bottom and has a deflection scale, so long pipe runs can be installed at fixed elevation and then released. The PC30NS adds seismic restraint, and the RW30N includes a rebound washer of 1/4 inch LDS rubber that cushions upward movement where cable cross bracing is used. The 30N-100 series uses the 2, 3, 4 and 5 inch deflection springs of the SLF-100 mounts, and Mason publishes vertical G ratings in tension and compression for each size.

Key Features

Key features of the Mason 30N described in Bulletin H-610-10.1 are:

• Steel spring and double deflection LDS rubber element in series for noise and vibration isolation.
• 30 degree rod swing in any direction before the rod contacts the rubber bushing.
• Spring cup with projecting bushing that prevents steel to steel contact.
• Welded heavy steel hanger box with a captive upper washer as a fail-safe feature.
• Precompressed PC30N and seismic PC30NS and RW30N variants with deflection scale and rebound washer.
• Nominal 1 inch series from 12 to 2760 lb, and 30N-100 series with 2 to 5 inch deflection springs.
• Published vertical G ratings in tension and compression for seismic design.
• Springs with additional travel to solid equal to 50% of rated deflection.

Industrial Applications

Combination spring and rubber hangers such as the Mason 30N are specified for chilled water, condenser water and heating water piping for the first runs from pumps and chillers, for refrigerant and steam lines in plant rooms, for suspended fans, fan coil units and in-line pumps, and for ductwork connected to air handling units. Mason recommends precompressed hangers for the first three suspension points near equipment, so loads can be determined accurately and pipe weight and stress are kept off the equipment flanges, and for large diameter piping of 6 inches and over where ordinary spring hangers would change elevation during installation. The Mason 30N is the hanger of choice where plant rooms sit above sensitive spaces such as auditoria, hospital wards, hotel rooms and studios.

In Oman and the GCC the Mason 30N is used in district cooling plants, hospitals, hotels, airports and high-rise residential and office towers in Muscat, Sohar, Duqm and Salalah, typically on the piping connected to chillers and pumps that sit on Mason spring mounts or inertia bases. Seven Star LLC supplies the Mason 30N with the matching spring mounts and restrained mounts, so the whole isolation package for a plant room comes from one source.

Technical Specifications

The figures below for the Mason 30N are taken from Mason Bulletin H-610-10.1; consult the downloadable bulletin for full dimensions, rod sizes and G ratings.

How to Order

To order the Mason 30N, send Seven Star LLC your hanger schedule with the load at each support, rod size and required deflection, and we will prepare a formal quotation. The Mason hanger bulletin is available as a datasheet download on this page. Seven Star LLC supplies Mason vibration isolation products in Oman and the GCC with engineering support in Muscat. For complete building services packages we also supply items such as Belimo LF24-SR Spring-Return Damper Actuator 4 Nm, 2-10 V, Rittal Blue e+ Wall-Mounted Enclosure Cooling Units and ABB ACQ580 Water and Wastewater Drive.