Variable Springs are used to support piping which is subject to thermal expansion and other factors that may cause the pipe support point to shift. The force of spring varies through the range of travel, hence the name “Variable Supports”. As the supported structure moves upward the force exerted by the spring decreases while the opposite occurs during downward movement.
Variable supports are typically installed where thermal movements cause the system’s position and dimensions to change; however, if the variability surpasses 25%, Rilco recommends our Constant Supports or the Rilco Cam Roller Constants.
All of the Rilco spring units are designed to meet or exceed the requirements of the ASME Code for Pressure Piping, ASME B31.1, B31.3, and MSS SP-58.
View our Variable & Constant Spring Catalog for complete specs.
In order to manufacture a variable spring, some of the following data will need to be known:
One of the first 5 conditions in the chart below must be met (condition 6 is used to obtain pricing only)
| Condition | Known | Unknown |
| 1 | Part No., Size, Hot load, Movement & Direction | Cold load |
| 2 | Part No., Size, Cold load, Movement & Direction | Hot load |
| 3 | Hot load, Movement & Direction | Part No., Size, Cold load |
| 4 | Cold load, Movement & Direction | Part No., Size, Hot load |
| 5 | Hot load, Cold Load & Spring rate | Part No., Size & Movement |
| 6 | Figure, Size, Type | Hot load, Cold load, Movement & Spring rate |
| Drawing | Rilco Type | Description |
|---|---|---|
 | A | Hanger-Type Support: Design for use where headroom is unlimited. Top of spring housing is a rod which allows the spring to attach to a support. |
 | B | Single-Lug Hanger Type Support: Designed for use where headroom is limited. Top of spring housing has a single lug to accommodate a double-lug beam attachment from the top support. |
 | C | Hanger-Type Support: Designed for use where headroom is limited. Top of spring housing has double lugs to accommodate a single-lug attachment from the top support. |
 | D | Hanger-Type Support: Designed for use where variable spring hanger is positioned above supporting structure with spring adjustment made from the top. |
 | E | Hanger-Type Support: Designed for use when spring adjustment must be below the structure on which the spring housing is being supported. |
 | F | Base-Type Support: Designed for supporting piping from below. |
 | G | Hanger-Type Support: Designed for use where headroom is limited or where an obstruction prohibits the use of a single spring hanger. |
| SpringSize | Rod Size (in.) | Load (lb.) | Spring Rate (lb./in.) | |||||
|---|---|---|---|---|---|---|---|---|
| Minimum | Maximum | RVS-82 | RVS-268 | RVS-98 | RVS-3X | RVS-4X | ||
| 0 | 1/2″ | 50 | 88 | 30 | 15 | 7 | 5 | 4 |
| 1 | 74 | 126 | 42 | 21 | 10 | 7 | 5 | |
| 2 | 95 | 162 | 54 | 27 | 13 | 9 | 7 | |
| 3 | 123 | 210 | 70 | 35 | 17 | 12 | 9 | |
| 4 | 165 | 282 | 94 | 47 | 23 | 16 | 12 | |
| 5 | 221 | 378 | 126 | 63 | 31 | 21 | 16 | |
| 6 | 5/8″ | 294 | 504 | 168 | 84 | 42 | 28 | 21 |
| 7 | 392 | 672 | 224 | 112 | 56 | 37 | 28 | |
| 8 | 525 | 900 | 300 | 150 | 75 | 50 | 38 | |
| 9 | 3/4″ | 700 | 1200 | 400 | 200 | 100 | 67 | 50 |
| 10 | 910 | 1560 | 520 | 260 | 130 | 87 | 65 | |
| 11 | 1190 | 2024 | 680 | 340 | 170 | 113 | 85 | |
| 12 | 1″ | 1575 | 2700 | 900 | 450 | 225 | 150 | 113 |
| 13 | 2100 | 3600 | 1200 | 600 | 300 | 200 | 150 | |
| 14 | 1 1/4″ | 2800 | 4800 | 1600 | 800 | 400 | 267 | 200 |
| 15 | 3780 | 6480 | 2160 | 1080 | 540 | 360 | 270 | |
| 16 | 1 1/2″ | 5250 | 9000 | 3000 | 1500 | 750 | 500 | 375 |
| 17 | 1 3/4″ | 7000 | 12000 | 4000 | 2000 | 1000 | 667 | 500 |
| 18 | 2″ | 9320 | 15970 | 5320 | 2660 | 1330 | 887 | 665 |
| 19 | 2 1/4″ | 12380 | 21230 | 7080 | 3540 | 1770 | 1180 | 885 |
| 20 | 2 1/2″ | 16450 | 28200 | 9400 | 4700 | 2350 | 1567 | 1175 |
| 21 | 2 3/4″ | 21875 | 37500 | 12500 | 6250 | 3125 | 2083 | 1563 |
| 22 | 3″ | 29173 | 50010 | 16670 | 8335 | 4167 | 2778 | 2034 |
Finish or coating on the spring housing is dependent upon the environment in which the springs are installed.
Possible Finishes Include:
| Component | Rilco Standard? | Description/Comment |
| Coil | Yes | Neoprene or powder coated & designed per MSS-SP58 |
| Travel stops | Yes | Hydrostatic & Upper stops are standard |
| Metal name plate | Yes | Stainless steel etched with client tag, Rilco part number, size, type hot load, cold load, spring rate & movement. Loads and movements available in imperial or metric unit. |
| Guided load column (Type F only) | No | Specify guided load column when required. |
| Lifting lugs | No | Recommended for spring weighing more than 100 lbs. or 45 kg. |
| pward movement | If cold load is greater than hot load |
| Downward movement | If hot load is greater than cold load |
| Movement | = (Cold load – Hot load) / Spring rate. If result > 0 then movement direction is up. Otherwise, it’s down. |
| Variability (% load change) | = (Movement x Spring rate) / Hot load x 100 |
