Variable Spring Hangers

The Variable Spring Hangers are a popular way to support piping systems while allowing vertical movement

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What Are Types of Variable Spring Hangers?

The story of variable spring hangers as piping supports is largely the story of a company called Grinnell. In the late 1800’s Grinnell patented the first commercial sprinkler systems for buildings. Then later on they were largely responsible for the devolopment and popular use of engineered spring hangers. The nomenclature they developed (Types A, B, C, D, E, F and G; and sizes 82, 268, 98, 100 and 110) are still used today by modern manufacturers of variable spring hangers. The different types are for the allowance of most situations where the space above and below the pipe informs the most advantageous type to use.

A-Type Variable Spring Hanger

A-Type Variable Spring Hanger

B-Type Variable Spring Hanger

A-Type Variable Spring Hanger

C-Type Variable Spring Hanger

C-Type Variable Spring Hanger

D-Type Variable Spring Hanger

D-Type Variable Spring Hanger

E-Type Variable Spring Hanger

E-Type Variable Spring Hanger

F-Type Variable Spring Hanger

F-Type Variable Spring Hanger

G-Type Variable Spring Hanger

G-Type Variable Spring Hanger

Variable Sizes

There are typically five different sizes of variable spring supports to accommodate differing loads and movement: 82, 268, 98, 100, and 110. Both 82 & 268 have a single spring, size 98 has two springs, size 100 has three springs and size 110 has four springs. A spacer plate is placed between the springs

Variable C-Type, Size 82

Variable C-Type, Size 82

Variable C-Type, Size 268

Variable C-Type, Size 268

Variable C-Type, Size 98

Variable C-Type, Size 98

Variable C-Type, Size 100

Variable C-Type, Size 100

Variable C-Type, Size 110

Variable C-Type, Size 100

Components of Variable Spring Hangers

Variable Casing

Variable Casing

Variable Helical Coil

Variable Helical Coil

Variable Pullbolt

Variable Pullbolt

F-Type Variable Load Column

F-Type Variable Load Column

F-Type Variable Base Plate

F-Type Variable Base Plate

Variable Compression Plate

Variable Compression Plate

Variable Bottom Ring

Variable Bottom Ring

Variable Top Plate

Variable Top Plate

ASTM Specification

A-153

ASTM A153 Specifies the parameter for the hot-dip galvanizing of spring hanger parts such as the casing in this image

How to Fabricate Variable Spring Hangers?

Although one can make variable support from a variety of standard structural steel types, the process usually begins with standard pipe which is cut to length.  Next slots on both sides of the pipe piece are cut to allow the compression plate to travel up and down. Next, either on a burn table or a water jet table, the other components are cut out of plate steel, drilled with holes as appropriate and then welded to the casing. All the subassemblies are then sent to be galvanized. Once galvanized all the components of the hanger are ready for assembly

Based on measurements taken in the field including loads and pipe movement, and appropriate sized canister and spring are selected. The casing is placed under a hydraulic press, the spring and compression plate are placed inside the can and then compressed to the appropriate load. While compressed the top plate is bolted to the casing thus sealing the components inside.

In all instances, variable spring supports are designed to meet the requirements of the Manufacturers Standardization Society’s MSS SP-58 “Hangers and Supports—Selection and Application” as well as the ASME Codes for Pressure Piping. Spring hanger casings to be utilized in corrosive environments are galvanized in accordance with ASTM Specification A-153

 

A-Type Variable Spring Hanger

A-Type Variable Spring Hanger

B-Type Variable Spring Hanger

A-Type Variable Spring Hanger

C-Type Variable Spring Hanger

C-Type Variable Spring Hanger

D-Type Variable Spring Hanger

D-Type Variable Spring Hanger

Load Scale Plate and Preset Stops

A Load Scale Plate is attached to each variable spring hanger casing directly adjacent to the slot in the casing. The Load Scale Plate contains information such as hanger size, type, figure number, customer Identification tag number, the spring rate, the installed load and the operating load. Installed and Operating position tags are permanently attached to the hanger casings on the Load Scale Plate. The position tags enable field personnel to easily view the position of the bottom of the com- pression plate in the hanger casing at anytime therefore enabling the field personnel immediately define the position of the pipe in the travel range. The travel scale is given in both Imperial and SI units enabling use anywhere in the world. The Load Scale Plates are made of 20 gauge stainless steel and are attached to the spring hanger casings with stainless steel rivets.

Load Scale Plate

Load Scale Plate

Load Scale Plate on an F-Type Variable Spring Support

The spring hanger is preset to the installed position. In such instances, the spring hanger loading will be set in the production shop to the reuired installed load and a preset piece will be placed between to top plate and the compression plate (the yellow piece in the image above) so that the installed load will be maintained. Preset pieces are to be removed after the spring hanger has been installed and the piping system is ready for operation.

Determining the Type and Size of Hanger to Use

A-Type Variable Spring Hangers in the Field

A-Type Variable Spring Hangers in the Field

A-Types are used where ample headroom is available and where it is desired to locate the spring hanger at a specific elevation. Structural attachment point is at a point above the top of the hanger.

The type of variable spring hanger to be used for specific applications depends upon controlling factors such as the amount of head room available, whether the pipe is to be supported from above or from below, the configuration of the structural steel from which the pipe is to be supported, etc.

The load to be carried in the operating condition and the installed to operating deflection must be accurately calculated by a stress engineer. This data can be determined analytically by computer analysis or estimated by manual calculations. To deter- mine the optimum load to be carried by the spring hanger in the operating position, calculate the weight of the piping system in the ” as installed condition” which is carried by a rigid support placed where the spring hanger is to be located. The calcula- tion should include 1.) the weight of the pipe, valves and fittings, 2.) the weight of the contents and insulation, and 3.) the weight of the hanger hardware below the spring hanger casing. Note: For a Type G spring hanger, the load to be carried by the hanger should also include the catalog weight of the hanger unit itself.

Once the load to be carried is determined, the installed to operating deflection can be calculated by performing an operating case analysis with the optimum load considered as a constant acting upward force. The analysis results will reflect the piping system deflection from the installed position to the operating position.

Spring hangers are designed and manufactured for the following ranges of movement: 1.25″ (Fig. 82), 2.5″ (Fig, 268), 5.0″ (Fig. 98), 7.5″ (Fig. 100) and 10” (Fig. 110). Knowing the ranges of movements accepted by variable spring hangers, the operating load and the installed to operating deflection, the correct hanger is ready to be selected for the one that best fits the requirements.

Note that the MSS Standard also states that the maximum load variation from the installed position to the operating position is 25%. That means that the maximum movement for a Fig. 82 spring hanger is approximately 3/4” (19 mm), for a Fig. 268 spring hanger is approximately 1 1/2” (38 mm), for a Fig. 98 spring hanger is approximately 3” (76 mm), for a Fig. 100 spring hanger is approximately 4 1/2” (114 mm) and for a Fig. 110 spring hanger is approximately 6” (152 mm).

Note also that for a variable spring hanger to be acceptable the operating load and the installed position must be within the working range of the given type and size. If the load variation for the piping system application is found to not be acceptable using a variable spring hanger, then one should consider the use of a constant effort spring hanger

B-Type Variable Spring Hanger in the Field

B-Type Variable Spring Hanger in the Field

B-Type Variable Spring Hangers are used where headroom is limited. Head attachment is a single lug.

C-Type Variable Spring Hanger in the Field

C-Type Variable Spring Hanger in the Field

C-Type Variable Spring Hanger is used where headroom is limited. Head attachment is side-by-side lugs.

D-Type Variable Spring Hanger in the Field

D-Type Variable Spring Hanger in the Field

D-Type Variable Spring Hanger is used where the spring hanger is mounted on top of a pair of back-to-back channels

E-Type Variable Spring Hanger in the Field

E-Type Variable Spring Hanger in the Field

E-Type Variable Spring Hanger is used where the spring hanger is mounted on top of a pair of back-to-back channels.

F-Type Variable Spring Support in the Field

F-Type Variable Spring Support in the Field

F-Type Variable Spring Support is used where the spring hanger must be placed under the piping to provide support from the floor or a structural member

G-Type Variable Spring Hanger in the Field

G-Type Variable Spring Hanger in the Field

G-Type Variable Spring Hanger is used where head room is insufficient to accommodate the spring hanger and the necessary associated hardware.

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