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Context

Piping systems are used to transport gases, liquids and suspended solids between units of a plant. The temperatures of the contents and the pipe when the plant is in operation are often quite different from the ambient temperature of the surroundings. The heat transferred during changes in temperature causes metal pipe to expand and contract. Piping designers must provide for movement due to temperature changes and forces caused by pumps, gravity and other elements of the piping system.

Proven engineering practices are included in various codes for piping services developed by professional societies such as the American Society of Mechanical Engineers. Most companies use these codes to develop specific standards for their products. The Manufacturers' Standardization Society has developed standards for pipe supports. Designs which satisfy codes are important to satisfy laws and to obtain financing and insurance for projects. Table 1 provides a list of some important standards.

Variable springs are one of the most important devices available to help support pipe. They are used to balance the concentrated gravitational load of vertical sections of pipe while allowing for thermal movement. Control of the direction and amount of movement of various sections of pipe is a major function of piping design. Computer models are used during design to predict the forces and movement at the point where a spring support is attached to the pipe. This is the information required to select the least expensive variable spring to use.

Variable springs are relatively inexpensive and very reliable. When replacement is necessary the engineer needs to determine if the original size is still appropriate or if the system has changed and different forces and movement must be considered.

FIGURE 1		TABLE 1 ASME B31.1 Power Piping Code ASME B31.2 Fuel Gas Piping ASME B31.3 Chemical Plant and Refinery Piping ASME B31.4 Liquid Transportation Systems (Hydrocarbons) ASME B31.5 Refrigeration Piping ASME B31.8 Gas Transmission and Distribution Piping MSS SP-58 and SP-69 Pipe Supports

Pipe support manufacturers produce catalogs which describe the items they routinely supply. The ENGINEERED SPRING SUPPORT section of our catalog contains detailed information on variable springs. The Load and Travel Tables on pages 17 and 18 contain the information required to size variable springs. An abbreviated version of this table is given in Figure 6 on page 3.

PT&P's Variable Spring Assembly Line

Variable Spring Supports Ready For Shipment

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