constant support erection

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PIPE SUPPORTS LIMITEDUnit 22, West Stone,

Berry Hill Industrial Estate,DroitwichWR9 9AS

United Kingdom

Telephone +44 (0) 1905 795500Fax: +44 (0) 1905 794126

E mail: [email protected]

Erection & Maintenance Manual

Constant Effort Supports

Manual No; EM - CE - 01

Revision; 01

Dated; 10/02/09

Page; 1 of 7

Author; S J Barry

Signed ; M Collingwood

REV DATE DESCRIPTION RAISED APPRD01 10/02/09 Address revised AK MC

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Index

Section Description Page1.0 Introduction 32.0 Storage 33.0 Erection 34.0 Maintenance 5

Appendix 1 Typical drawing 7

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1.0) INTRODUCTIONThis manual gives guidance and recommendations for the erection,commissioning and subsequent maintenance of COMET constant effortsupports.

Constant effort supports deliver a nominally constant supporting effortto the point of attachment to the supported part; they replicate a very precisecounter-balance mechanism. Because of this it is important that thesuspended mass is reasonably close to the design load and not more than20% of said load in variance with it.

Constant effort supports exhibit frictional and geometric variancesfrom the nominal set load; that stated as being the design load for the unitselected. This is usually defined as the deviation and is a measure of thehysteresis of the load-displacement plot. The hysteresis of any particularsupport is usually within +/- 5% of the sets load but may be specified as +/-2.5% by special agreement.

The significance of hysteresis is that for a given range of load thesupport will remain static at its set position; in order for the support torespond to changing conditions the tension generated in the hanger rod orthe compression exerted on the supporting plinth must either increase orreduce by an amount slightly greater than the frictional resistance within thesupport. Therefore the balancing of a support is a critical exercise if thesupport is to be set at its true mean load.

It is essential that the support is erected in the correct position; error atthe erection stage can cause a re-distribution of the load and make it virtuallyimpossible to balance the supporting system.

When selecting the support at the design stage it is important that anyadditional load be added to the nominal design load of the supported part;large pipe clamps, spreader beams or even long hanger rods can imposesignificant increases in dead weight.

2.0) STORAGE;2.1 Supports should be handled with care and stored in a dry and dustfree environment, preferably off the floor and under cover.

3.0) ERECTION:3.1 Constant effort supports are mechanisms that rely on freedom of

motion; lack of adequate protection during storage, rough handling andabuse will significantly reduce the constancy of the support and maycause seizure of the mechanism.

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3.2 The support should be carefully lifted into its nominated position andsecured using appropriately sized fixing bolts.

3.3 Attachment to the supported pipework is made via the hanger rod andpipe clamp in the case of suspension type supports and via the plinth inthe case of compression type supports. The pipework should beaccurately adjusted to its correct elevation using either the turnbuckle orthe height adjustment nut.NB. It is important that the pipe is suspended naturally; sagging orhogging pipework will impose false loads at the support positions.

3.4 If the pipe work is to be lagged with thermal insulation after thesupports have been erected, the piston plate locking nuts which arelocated on both sides of the piston plate on either side of the springhousing, should not be retracted from their original position i.e. in contactwith the piston plate until lagging is complete.

3.5 If the pipe work is to be subjected to hydrostatic testing, this must takeplace with the piston plate locking nuts, which are located on the springside of the piston plate on either side of the spring housing, still in theiroriginal position i.e. in contact with the piston plate. Standard springsupports are designed to withstand an increased load during hydrostatictesting of up to twice the maximum load for the spring support.

3.6 Once satisfied that the pipework is at its correct elevation the processof balancing the system can commence. If the original assessment ofweight distribution was correct; the pipe has been supplied to thenominal weight, valves and lagging/ insulation are at their theoreticalweight and all the supports are in their correct position then it is simply acase of undoing the locking nuts and walking away! However this israrely the case.

3.7 The process of balancing the supporting system is very much aniterative one, adjustment to one support may manifest in a change atanother two or three positions away. It is best to work between fixedsupport positions or terminal points and work towards the centre wherethe piping is most flexible.

3.8 To determine whether a support is in balance or not it is necessary toobserve the spring compression plate locking nuts found either side ofthe spring away from the main mechanism. For balance these nutsshould all be relatively free to be unwound away from the compressionplate leaving the support in a static, self-supporting state. If this is thecase for any particular support we strongly recommend that the nutsshould be wound only 5mm away from the plate at this stage. This issimply a precaution to avoid the pipe work moving far away from its setposition if subsequent supports are not truly balanced.

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3.9 If the support is not in balance then either the forward (spring side)locking nut or the rear locking nut will offer significant resistance toturning. Should it be that the forward nut will not rotate then this signifiesthat the support is not providing sufficient effort and positive loadadjustment is required. This entails increasing the distance between themain pivot pin and the pin, which transfers the spring force into the levermechanism. This is achieved by rotating the load adjustment nutclockwise when viewed from above in the case of all types except the VI(Vertical Inverted Type Support) group for which the opposite should beapplied.

3.10 Subsequent supports should be balanced in the same way however itis necessary to continually check back to previous supports to ensurethat the effect of changing supports towards the centre of the pipe rundoes not alter previously balanced supports. If this is the case thensuitable adjustments should be made to overcome this and return thesesupports back to their correct position.

3.11 When all supports are floating, the locking nuts should be backed offfully to allow the system to operate correctly.

3.12 Where the constant effort support incorporates a limit stop (Reactionforce receiver), the forward (spring side) locking nuts will be positioned ata distance from the spring compression plate, as shown on the supportdetail drawing.

3.13 Prior to operating the plant we recommend that all supports arechecked to ensure -

The locking nuts are fully retracted.

No debris has been allowed to fall into the support, especially inthe spring housing.

The support is free from visual damage, all fixing bolts are securedand the rotational path of the lever mechanism is clear ofobstructions.

We also suggest that a cold survey after installation and hot surveyduring normal operation of the plant is carried out and a record of all loadadjustment settings and travel scale readings is taken.

4.0) MAINTENANCE:4.1 COMET constant effort supports are designed to be maintenance

free, they incorporate dry bearings and brass/ptfe thrust washers.However common sense should prevail; threaded items require greasingat intervals to suit the environment, but not longer than 2 years, periodicinspections are necessary to ensure the supports have not beendamaged or obstructed by such items as temporary scaffolding,

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additional equipment or debris that may have fallen into the unit.Protective coatings should be periodically inspected and if necessaryrepaired.

4.2 Unfortunately due to the wide- ranging environments these devicesare employed in, it is impossible to compile a fully comprehensivemaintenance procedure. It should be remembered that constant effortsupports are mechanisms and the health and longevity of the pipingsystem depends on the reliable operation of the pipe supports.

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constant support erection

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