PT&P manufactured B type constant spring supports for a hydrocracker application at a refinery in Port Author, TX. These custom designed constants are 83″ x 41″ x 20″, and designed to support a 53,000 lb. riser pipe through two trunnions. The constants are designed for an operating load of 26,700 lb. with 10-1/2″ of total travel. They are fabricated from A36 carbon steel and underwent standard load and travel testing prior to shipment.
A constant spring support is a pipe support that uses a spring coil (or series of coils) to accommodate pipe movement from the initial (installed) condition to the final (operating) condition of the piping system. For all constant spring supports there is no difference in load and the supported load will remain uniform throughout the deflection cycle.
We refer to our spring supports as any assembly which includes a spring(either variable or constant) that can accommodate both a pipe load and a pipemovement.
For variable springs there are 23 sizes with loads ranging from 50 lb. through 50,000 lb. For constant springs, there are 110 sizes with travel ranging from 1″ to 14″ and loads ranging from 0 lb. to 90,000 lb.
PTP-8 Type C Variable Spring Assemblies
Figure 100 C-Type Constant Springs
PTP 100-C Size 84 Constant
To check the load setting, examine the position of the bottom of the load indicator with respect to the scale on the spring's tag. Read from the bottom of the load indicator to determine position. Next, look at the size of the spring located on the tag. Then, refer to the appropriate load and travel table (Constant Load & Travel Table or Variable Load and Travel Table) to determine the respective spring rate and the “0” load (minimum working range load). Multiply the spring rate by the position value and add that to the “0” load value.
In order to size a constant spring support, you must know the load and the anticipated travel. From that you can determine the amount of total travel and then refer to the constant spring support load and travel table to locate the correct size spring for your design.
Constant Spring Supports with Neoprene Coating
The “cold” setting on a constant spring support refers to the location of the pipe at the installed position. The “hot” setting refers to the design location of the pipe at the operating position. In general, prior to installation, all spring supports are set at the “cold” setting.
Cold Setting Indicated by the White Diamond on a Constant Spring Support
Piping Technology & Products, Inc. custom designed and manufactured four PTP-100 Type G constants and three PTP-100 Type C constants for a power station in Missouri. The PTP-100 Type C constants are designed for operating loads of 8,300 lbs. to 25,200 lbs. and have a travel range of 2.5 to 3.5. These constants are fabricated from A36 carbon steel with dimensions ranging from 66×18 to 88×20.
The PTP-100 Type G constants are designed for operating loads ranging from 2,800 lbs. to 38,800 lb. and a travel range of 2.5 to 3.5. They are fabricated out of A36 carbon steel with dimensions ranging from 75×26.5 to 95×50. Standard load and adjustment testing was performed to ensure quality prior to shipping.