CPA VARIABLE EFFORT SPRING SUPPORTS
A variable effort spring support is a resilient device which absorbs/accommodates the vertical displacement of a piping system, thus preventing excessive pipe stress. The variable support is recommended for relatively small displacement (up to about 75mm).
CPA offers two categories of variable effort spring supports; ‘AV’ and ‘LV’. The AV (‘Asian Variable’) spring supports feature a fully enclosed, dimpled spring can with compact unilock travel stops. The LV (‘Locking Variable’) spring supports feature multilock locking rods on either side of the spring.
Both the AV and LV spring supports are produced in four basic travel ranges; 35mm, 70mm, 140mm and 210mm.
These travel ranges indicate the maximum working range of the springs. This full travel can be used provided that the necessary calculations are carried out to ensure that the connecting equipment and pipework can withstand the load changes that occur during pipe movement. Most national standards do limit the load variation to a maximum of 25%. It is therefore usual to select variable spring supports on this basis.
The standard and optional design features of CPA variable supports are as follows:
Standard Design Features:
1. Precompression of the spring coil into the casing saves headroom and erection time.
2. For each series there is a reserve travel at the upper and lower limits of the unit.
3. All steel construction that is rugged and compact.
4. Grade 316 stainless steel is used for scale plate and name plate.
5. Load indicator clearly visible.
6. Spring Pressure plate serves as a centering device.
7. Finish - hot dip galvanized - specialized coatings are also available.
8. All ‘F’ type floor/base mounted units are inclusive of load flange and internal load column guide.
9. Travel stops – The Carpenter & Paterson design is supplied with stops to take the preset and hydrostatic test loads.
10. No maintenance required.
Optional Design Features:
1. Limit stops permanently installed to prevent the movement of the pipe beyond predetermined distance or load within the travel range of the spring.
2. Lifting lugs are available on large sizes to facilitate erection and installation.
3. For extreme environmental conditions we are able to manufacture our units in a range of austenitic stainless steels.
CPA CONSTANT EFFORT SPRING SUPPORTS
A constant effort support is preferred when the use of a variable effort support may be not appropriate for the following reasons:
1. The vertical movement is too great for a variable effort support (approx. > 75mm).
2. Only a small change in load is acceptable (e.g. close to sensitive equipment).
3. Space considerations prevent the use of variable effort supports.
The constant effort support designed and manufactured by CPA incorporates the latest design concepts to produce a support which provides an essentially constant supporting effort throughout the total travel of the unit. The robust and simple construction of the well-proven C&P design using a bell-crank lever has been enhanced to include universal locking of the load arm.
With a cylindrical spring housing of substantial construction, and several support configurations to suit the position relative to steelwork and available space, the unit can be installed in many arrangements. The spring housing prevents the ingress of foreign bodies such as construction debris, thus reducing the danger of damage or restriction of the unit’s function.
The universal locking mechanism allows the load arm to be locked in any position for the purpose of hydrostatic test, maintenance and decommissioning. The locking is done at the load arm so that excessive loadings are not transferred to the spring tension rod and spring coil. The threaded rods which are used for universal locking, are removed once the support has been installed and are stowed on the side of the spring housing.
Standard Design Features:
1. The standard range of CPA constant effort supports are constructed to accommodate loads between 8kg and 33500kg with a standard range of travels between 40mm and 610mm in 10mm increments.
2. Constant effort supports are manufactured having maximum deviation of +/-5% of the specified load.
3. Universal Locking of the load arm is provided as standard.
4. Upper and lower travel stops are incorporated in all units to prevent excessive overtravel.
5. All supports are fitted with a clearly visible travel scale.
6. Supports are supplied with hot-dip galvanized finish as standard.
7. Spring coils are supplied plastic-coated as standard.
8. Screw Threads are ISO-metric coarse pitch series (6mm pitch series above size M64).
Special Design Features:
1. Special Constant Supports can be designed for higher loadings or travels than are covered by the standard range.
2. Supports can be designed for hydrostatic test more than twice the operating load.
3. Supports can be supplied with special paint finish or manufactured from corrosion-resistant materials.