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"EQUAL" SPRING HANGER GENERAL INFORMATION
WHEN SHOULD SPRING HANGERS BE USED?

When pipe moves vertically, either up or down, and when loads on attached equipment are required to not vary significantly when the pipe moves, then a spring hanger should be seriously considered. Spring hangers are therefore used to provide support to a pipe at a support location at the time the pipe is installed, while the pipe is moving and in the pipe's final or operating position. The pipe movement is generally caused by thermal expansion or contraction of the piping system itself but it can also result from the movement of the equipment to which the piping is connected. The underlying objective for using a spring hanger is to minimize the change of load applied by the piping on the connected equipment.

Spring hangers are frequently used at the first pipe support location adjacent to rotating equipment such as a turbine, compressor, pump or expander-compressor. At these first support locations, the amounts of vertical piping movements are typically small, but the controlling factor in placing a spring hanger in these locations is: "Can the connected equipment absorb its share of the load previously carried by the rigid support adjacent to it when the pipe moves upward, or can the connected equipment absorb its share of the additional load imposed on it by the adjacent support when the pipe tries to move downward but is restrained by the support?" If the answer is "NO," then a spring hanger is required.

In all instances where the use of spring hangers is contemplated, evaluate the alternatives considering factors such as cost, ease of installation and ease of operation. If spring hangers are the most economical and most satisfactory alternative, then by all means use them.

DESIGN FEATURES

· Hanger casings are made of pipe or heavy gauge plate for long life and durability.

· Spring coils are pre-compressed into the hanger casings reducing the overall casing length and insuring that support loads can be obtained by making only a small adjustment.

· Available finishes for hanger casings are primed, hot-dipped galvanized or neoprene coated, allowing for a full range of choices for the customer.

· Mechanically closed units allow AAA Technology to stock components from which hangers can easily and quickly be assembled for your hanger requirements. Mechanically closed units also allow AAA Technology to insure that all components are properly finished and that no welding is required after the finishes are applied.

SPECIFICATIONS

AAA Technology's "EQUAL" brand variable spring supports are designed to meet the requirements of the Manufacturers Standardization Society's MSS SP-58 "Pipe Hangers and Supports Materials, Design and Manufacture" and MSS SP-69 "Hangers and Supports - Selection and Application" as well as the ASME/ANSI Codes for Pressure Piping. Spring casings to be utilized in corrosive environments or severe weather conditions are galvanized in accordance with ASTM Specification A-153.

LOAD SCALE PLATE

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, hanger 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 casing on the travel scale to indicate these customer-designated positions. In addition, the travel scale on the Load Scale Plate allows field personnel to easily view the position of the spring coil and the compression plate in the hanger casing at any time. The travel scale is given in both imperial units and SI units for use in any country. The Load Scale Plates are made of twenty-gauge stainless steel sheet and are attached to the spring casings with stainless steel rivets.

PRESET PIECES

Normally, when customers order variable spring hangers, the installed load is specified and AAA Technology is requested to supply the spring hanger preset to the installed position. In such instances, the spring hanger will be compressed in our shop to the customer specified installed load and a preset piece will be cut to the correct length and placed between the compression plate and the top of the hanger casing. The preset piece will insure that the spring hanger will not be more lightly loaded than the installed load. Preset pieces are to be removed after the spring hanger has been installed and the piping system is ready for operation.

TRAVEL STOPS

Travel stops are furnished only upon request. Full travel stops limiting both upward and downward movement may be supplied; or upward or downward travel stops individually can be supplied. Full travel stops effectively convert the hanger assembly to a rigid support until they are removed. Upward travel stops restrict upward movement beyond a customer specified point on the travel scale. Downward travel stops restrict downward movement beyond a customer specified point on the travel scale and are frequently employed during erection and hydrostatic testing. To each travel stop, a red tag will be attached to emphasize the need to remove the travel stops before the piping system is placed in service.

LIFTING LUGS

Upon customer request, lifting lugs may be welded to the casing of a designated spring hanger to provide a sure means of attachment for use in installation. Contact AAA Technology for details.

FIELD ADJUSTMENT

Once the piping and the spring hangers are installed and testing, which could cause spring hanger load variations has been completed, the spring hanger should indicate that it is carrying the designated installed load. If it is not carrying the designated installed load, then it should be adjusted to the installed load position. After the piping system is placed in service, the compression plate should indicate that the load being carried is the designated operating load. If the hanger is not carrying the proper load, then it should be adjusted to operating load position.

To adjust the load carried by the spring hanger, do the following: For Hanger Types "A," "B," "C," "E," and "G," turn the turnbuckle clockwise or counterclockwise, as necessary, until the compression plate indicates on the travel scale that the proper load is being carried. For Hanger Type "D," loosen the lock nut on top of the adjustment nut located on the rod above the hanger casing. Then, turn the adjustment nut until the compression plate indicates on the travel scale that the proper load is being carried. For Hanger Type "F," turn the load column clockwise or counterclockwise, as necessary, until the compression plate indicates on the travel scale that the proper load is being carried.

DETERMINING THE HANGER TYPE TO USE

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. Review the characteristics of the seven standard hanger types shown on the next page and select the type that best fits your requirements.

DETERMINING THE SIZE AND SERIES TO USE

Before determining the size or series of the required hanger, the load that is to be carried in the operating condition and the installed to operating deflection must be calculated. This data can be determined analytically by computer analysis or manual methods if the piping system is not yet installed and operating, or it can be determined by field measurement if the piping system is installed and operating. To determine 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 calculation should include 1.) the weight of the pipe, valves and fittings, 2.) the weight of the contents and insulation, 3.) the weight of the hanger hardware below the spring hanger casing and 4.) the downward force of any other possible load such as snow or ice. 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. This analysis will yield the desired deflection.

"EQUAL™" spring hangers are designed and manufactured for the following ranges of movements: 1.25" (Fig. E-82), 2.5" (Fig. E-268), 5.0" (Fig. E-98) and 7.5" (Fig. E-100). Knowing the ranges of movements accepted by "EQUAL™" hangers, the operating load and the installed to operating deflection, you are now ready to select the spring that best fits your requirements. Turn to the "Hanger Size and Series Selection Chart." Moving from left to right between the upper and lower boundaries of the Working Range, find the first occurrence of your operating load. Since the movement that you have calculated is from the installed position to the operating position and you are now at the operating position on the chart, you must move on the chart by the amount of the calculated movement but opposite to the sign of calculated movement in order to determine the installed load.

In order words, 1.) if the actual piping movement is down from the installed position to the operating position, then you must move up on the chart by the amount of the calculated deflection from the operating load position to the installed position to determine the installed load, 2.) if the actual piping movement is up from the installed position to the operating position, then you must move down on the chart by the amount of the calculated deflection from the operating load position to the installed position to determine the installed load.

If the calculated deflection is less then 1.25 inches, begin this operation using the Fig. E-82 deflection scale. If the calculated deflection is less than 2.50 inches, begin this operation using the Fig. E-268 deflection scale and so forth. Having found the first occurrence of the operating load, then move to the installed position on the chart. If the installed position is within the working range, then the hanger you have selected is acceptable if the load variation can be handled. In other words, if your piping system anchor loads are within the allowable ranges when the piping system is analyzed in the installed condition and in the operating condition, then your selected spring hanger is acceptable. If it is determined that the piping system anchor loads are not acceptable in your analysis of the installed condition, then move to the next spring series, i.e. from a Fig E-268 to a Fig E-98 and so on until you find a spring hanger with both an installed load and an operating load that yield acceptable anchor loads in your analysis, of these cases. If the loads, deflection or available space prohibit the use of a variable spring hanger, then you should consider the use of a constant effort spring hanger.

ORDERING HANGER TYPES "A", "B", "C" and "E" - Specify: Fig. Number, Size, Type, Installed (Preset) Load, Operating Load, Installed Position to Operating Position Deflection, Customer's Tag Number and the Finish Desired.

ORDERING HANGER TYPE "F" - Specify Fig. Number, Size, Type, Installed (Preset) Load, Installed Height, Operating Load, Installed Position to Operating Position Deflection, Customer's Tag Number and the Finish Desired.

ORDERING HANGER TYPE "G" - Specify Fig. Number, Size, Type, Installed (Preset) Load for each spring hanger, Operating Load for each spring hanger, Installed Position to Operating Position Deflection for each spring hanger, the center-to-center rod dimension, Customer's Tag Number and the Finish Desired.

ORDERING OPTIONS - In addition, you may request any of the following additional options: Preset Pieces, Travel Stops and Lifting Lugs.

EXAMPLES
Fig. E82 Spring Hanger, Size 15, Type C, Installed Load = 4,860 lbs., Operating Load = 5,400 lbs., Movement = .250 inch down, Tag SH-315A, Finish = Hot Dip Galvanized.

Fig. E-268 Spring Hanger, Size 8, Type F, Installed Load = 825 lbs., Installed Height = 13", Operating Load = 750 lbs, Movement = .50 inch up, Tag SH-34, Finish = Hot Dip Galvanized.

Fig. E-98 Spring Hanger, Size 11, Type G, Total Installed Load = 3,040 lbs. (1,370 lbs. on one hanger and 1,670 lbs. on the other hanger),Total Operating Load = 3,400 lbs. (1,550 lbs on one hanger and 1,850 lbs on the other hanger), 40 inches center-to-center rods, Movement = 1.06 inches down, Tag SH-22, Finish = Primed.

Fig. E-100 Spring Hanger, Size 15, Type D, Installed Load = 4,635 lbs., Operating Load = 6,075 lbs., Movement = 4.00 inches down, Tag SH-354-2, Finish = Black.

TYPE A

Used where ample headroom is available and where it is desirable to locate the spring hanger at a specific elevation.

TYPE B

Used where headroom is limited. Head attachment is a single lug. Typically used in conjunction with a Fig. 15 Beam Bracket, a Fig. 20 Forged Steel Clevis or back-to-back angles.

TYPE C

Used where headroom is limited. Head attachment is side by side lugs. Typically used in conjunction with a Fig. 21 Welding Lug or can be used with a Fig. 23 Weldless Eyenut.

TYPE D

Used where the spring hanger is mounted on top of a pair of back-to-back channels. Provides for adjustment of the load from above the supporting channels.

TYPE E

Used where the spring hanger is mounted on top of a pair of back-to-back channels. Provides for adjustment of the load from below the supporting channels.

TYPE F

Used where the spring hanger must be placed under the piping to provide support from the floor of a structural member. Typically supplied with a load flange but can also be supplied with a roller.

TYPE G

Used where headroom is insufficient to accommodate the spring hanger and the necessary associated hardware. Also used where an interference exists directly above the support location. Note: if the piping system being supported is not centered between the spring hangers, each hanger will then carry its proportional load.

Note also, that the weight of the G Type Hanger should be included in the calculation of the installed loads and the operating loads.