For help or guidance please seek the services of a qualified practitioner. The STEP provisions 1st Edition were in need of updating to reflect both changes in the law and practical problems in administration.
The main change proposed is to introduce the concept of narrower and wider powers. The proposal is to have two wide powers which can be selected to apply but if no selection is made then by default the narrower powers apply. The wider form powers are:. In each case by adopting the wider powers the settlor is relying on the trustees appointed to act reasonably and fairly as the exercise of each could be open to abuse.
In effect, the clause provides the trustees with the power to ignore the remaindermen entirely and invest only to produce income for the life tenant and equally would permit the trustees to avoid investing for income perhaps because the life tenant has extensive personal funds or has no need of income because she is being cared for at state expense and go exclusively for capital growth. The clause is similar to clause 3 4 of the 1st Edition but by putting it in the wider powers section it will not apply unless the settlor has instructed that it be included.
For both the powers relating to income and capital and the power to appropriate the only protection from abuse is to be found in the provisions preventing conflicts of interest in clause 8 which would prevent a trustee who was also a beneficiary from taking decisions for his own benefit without the existence and consent of an Independent Trustee.
Most of the changes compared to the 1st Edition are to provide a wider clause then those permitted under the general law, for example, the Trustee Act now permits trustees to invest Trust Property in any manner as if they were beneficial owners apart from property which has to be a legal estate in the UK.
In particular, income may be applied for a leasehold sinking fund policy. It permits the special dividend to be retained as capital even though the payment would otherwise be strictly classified as income. One interesting tweak is the addition to the power to apply or pay income for the benefit of a minor to their parent or guardian or the young person if 16 years old of the power to apply capital in similar fashion. This could be helpful for dealing with small sums of capital which are better paid out than held in trust.
Obviously it is discretionary and not compulsory so the trustees would have to use their judgment in any particular case.
The clause dealing with the liability of trustees has also been reworked and now protects both lay and professional trustees from strict liability unless negligent and continues to protect the lay trustee but not the professional trustee from negligence.
The clause has been enhanced by the inclusion of protection for the trustees from claims from unknown beneficiaries of which the trustees were not aware at the time of making a distribution. A new innovation is to allow trustees to adopt if required any subsequent edition of the STEP provisions.
This gets over the problem that a document cannot incorporate by reference another document which does not exist at the time of its inception. All in all the draft proposals present a useful update to the 1st Edition — we shall have to wait and see the outcome of the consultation on the draft before we can adopt the use of the 2nd Edition.
In Trusts , Wills. For example, consider the use of an appropriate soil filter or a geotextile filter fabric along the boundary of the incompatible materials. The aforementioned criteria may need to be modified if one of the materials is gap graded. Materials selected for use based on filter gradation criteria should be handled and placed in a manner that will minimize segregation. Cementitious backfill materials. Although not specifically addressed by this manual, use of these materials is beneficial under many circumstances.
Slope trench walls or provide supports in conformance with safety standards. Open only enough trench that can be safely maintained by available equipment. Place and compact backfill in trenches as soon as practicable, preferably no later than the end of each working day. Place excavated material away from the edge of the trench to mini- mize the risk of trench wall collapse.
Water control. It is always good practice to remove water from a trench before laying and backfilling pipe. Although circumstances occasionally require pipe installa- tion in conditions of standing or running water, such practice is outside the scope of this chapter. Prevent runoff and surface water from entering the trench at all times. When groundwater is present in the work area, dewater to main- tain stability of in situ and imported materials.
Maintain water level below pipe bed- ding. Use sump pumps, well points, deep wells, geotextiles, perforated underdrains, or stone blankets of sufficient thickness to remove and control water in the trench. When excavating, ensure the groundwater is below the bottom of the cut at all times to pre- vent washout from behind sheeting or sloughing of exposed trench walls. To preclude loss of soil support, employ dewatering methods that minimize removal of fines and the creation of voids within in situ materials.
Running water. Control running water that emanates from surface drainage or groundwater to preclude undermining of the trench bottom or walls, the foundation, or other zones of embedment. Provide dams, cutoffs, or other barriers at regular inter- vals along the installation to preclude transport of water along the trench bottom. Backfill all trenches as soon as practical after the pipe is installed to prevent distur- bance of pipe and embedment. Materials for water control.
Use suitably graded materials for foundation layers to transport running water to sump pits or other drains. Select the gradation of the drainage materials to minimize migration of fines from surrounding materials see Sec.
Where trench walls are stable or supported, provide a width sufficient, but no greater than necessary, to ensure working room to properly and safely place and compact haunching and other embedment materials. The space between the pipe and trench wall must be 6 in. For a single pipe in a trench, minimum width at the bottom of the trench should be 1.
For multiple pipes in the same trench, clear space between pipes must be at least the average of the radii of the two adjacent pipes for depths greater than 12 ft 3. The distance from the outside pipe to the trench wall must not be less than if that pipe were installed as a single pipe in a trench.
If mechanical com- paction equipment is used, the minimum space between pipe and trench wall or between adjacent pipe shall not be less than the width of the widest piece of equip- ment plus 6 in. In addition to safety considerations, the trench width in unsupported, unstable soils will depend on the size and stiffness of the pipe, stiffness of the embedment and in situ soil, and depth of cover.
Specially designed equipment or the use of free-flowing backfill, such as uniform rounded pea gravel or flowable fill, may enable the satisfac- tory installation and embedment of pipe in trenches narrower than specified earlier.
If the use of such equipment or backfill material provides an installation consistent with the requirements of this manual, minimum trench widths may be reduced if approved by the engineer. Support of trench walls. When supports such as trench sheeting, trench jacks, or trench shields or boxes are used, ensure that support of the pipe embedment is maintained throughout the installation process.
Ensure that sheeting is sufficiently tight to prevent washing out of the trench wall from behind the sheeting. Provide tight support of trench walls below viaducts, existing utilities, or other obstructions that restrict driving of sheeting. Supports left in place. Sheeting driven into or below the top of the pipe zone should be left in place to preclude loss of support of foundation and embedment materi- als.
When top of sheeting is to be cut off, make the cut 1. Leave walers and braces in place as required to support cutoff sheeting and the trench wall in the vicinity of the pipe zone. Timber sheeting to be left in place is considered a permanent structural member and should be treated against biological degradation e. Note that certain preservative and protective compounds may pose environmental hazards. Determination of acceptable compounds is outside the scope of this manual. Movable trench wall supports.
Do not disturb the installed pipe or the embed- ment when using movable trench boxes and shields. Movable supports should not be used below the top of the pipe embedment zone, unless approved methods are used for maintaining the integrity of embedment material. Before moving supports, place and compact embedment to sufficient depths to ensure protection of the pipe.
As supports are moved, finish placing and compacting embedment. Removal of trench wall support. If the removal of sheeting or other trench wall supports that extend below the top of the pipe is permitted, ensure that neither pipe, foundation, nor embedment materials are disturbed by support removal. Fill voids left after removal of supports and compact all material to required densities. Pulling the trench wall support in stages as backfilling progresses is advised.
Excavate trench a minimum of 4 in. When ledge, rock, hardpan, or other unyielding material or cobbles, rubble, debris, boulders, or stones larger than 1. The native material may be used for bedding and initial backfill if it meets all of the criteria of the specified pipe zone embedment materials. Trench preparation is dis- cussed in Sec. The risk of unstable conditions increases dramatically with slope angle. Installing pipes aboveground may be a preferred method for steep slopes, because aboveground structures such as pipe supports are more easily defined and, therefore, the quality of installation is easier to monitor and settlement easier to detect.
This may include treatment in the backfill or on the ground surface. Proper Bedding Support b. Figure Examples of bedding support in backfill adjacent to building foundations, sanitary landfills, or in other highly unstable soils, requires special engineering and is outside the scope of this manual.
Provide a firm, stable, and uniform support for the pipe barrel and any protruding features of its joint see Figure Provide a mini- mum of 4 in. Bedding material. In general, the bedding material will need to be an imported material to provide the proper gradation and pipe support. It is preferable that the same material be used for the initial backfill. To determine if the native material is acceptable as a bedding material, it should meet all of the requirements of the initial backfill.
This determination must be made constantly during the pipe installation pro- cess because native soil conditions vary widely and change suddenly along the length of a pipeline.
It is becoming common practice to leave the bedding uncompacted for a width of one third of the pipe diameter centered directly under the pipe. This reduces concentrated loads on the invert see Figure Rock and unyielding materials. When rock or unyielding material is present in the trench bottom, install a cushion of bedding, 6 in. If there is a sudden transition from rock to a softer mat- erial under the pipe, steps must be taken to accommodate possible differential settle- ment.
Figure b illustrates one method; however, other methods are also possible. Unstable trench bottom. Use a suit- ably graded material where conditions may cause migration of fines and loss of pipe support.
Place and compact foundation material in accordance with Table For severe conditions, a special foundation, such as piles or sheeting capped with a con- crete mat, may be required. The use of appropriate geotextiles can control quick and unstable trench bottom conditions. Localized loadings. Minimize localized loadings and differential settlement wherever the pipe crosses other utilities or subsurface structures see Figures and or whenever there are special foundations, such as concrete-capped piles or sheet- ing.
Provide a in. If the trench bottom is excavated below intended grade, fill the overexcavation with compatible foundation or bedding material and compact to a den- sity not less than the minimum densities listed in Table If trench sidewalls slough off during any excavation or installation of pipe zone embedment, remove all sloughed and loose material from the trench.
Place pipe and fittings in the trench with the invert conforming to the required elevations, slopes, and alignment. Provide bell holes in pipe bedding, no larger than necessary, in order to ensure uniform pipe support. Fill all voids under the bell by working in bedding material. Pipe should be laid on flat, uniform material that is at the appropriate grade.
Do not bring pipe to grade by using mounds of soil or other material at discreet points along the length of the pipe. When pipe laying is interrupted, secure piping against movement and seal open ends to prevent the entrance of water, mud, or foreign material.
Elastomeric seal gasketed joints. Mark pipe ends, or verify that pipe ends are marked, to indicate insertion stop position and that pipe is inserted into pipe or fitting bells to this mark. Push spigot into bell using methods recommended by the manufacturer, keeping pipe true to line and grade. Protect the end of the pipe during homing and do not use excessive force that may result in overassembled joints or dis- lodged gaskets.
If full entry is not achieved, disassemble and clean the joint and reas- semble. Use only lubricant supplied or recommended for use by the pipe manufacturer. Adhesive bonded and wrapped joints. When making adhesive bonded and wrapped joints, follow recommendations of the pipe manufacturer. Allow freshly made joints to set for the recommended time before moving, burying, or otherwise disturb- ing the pipe.
Angularly deflected joints. Large radius bends in pipelines may be accom- plished by rotating the alignment of adjacent lengths of pipe i.
Work in and compact the haunching material in the area between the bedding and the underside of the pipe before placing and compacting the remainder of the pipe zone embedment see Figure Do not permit compaction equipment to contact and damage the pipe. Use compaction equipment and techniques that are compatible with materials used and located in the trench. If compaction is required, use surface plate vibrators, vibratory rollers, or internal vibrators.
The compacted lift thickness should not exceed 12 in. Ensuring Firm Pipe Support b. Figure Proper compaction under haunches D relative density. These soils may behave as a soil containing few fines or as a soil containing a signifi- cant amount of fines. The methods of compaction and density determination should be based on the method that results in the higher in-place density. These soils should be compacted with impact tampers or sheepsfoot rollers.
The maximum density occurs at the optimum moisture content. Less effort is required to reach a given density when the moisture content is within 2 percentage points of the optimum moisture. A rapid method of determining the percent compaction and moisture variation is described in ASTM D Determination of the in-place density of soils. The applicable test method will depend on the type of soil, moisture content of the soil, and the maximum particle size present in the soil.
When using nuclear density-moisture gauges ASTM D and ASTM D , the gauge should be site-calibrated in the proximity of the pipe and in the excavation as recommended by the gauge manufacturer. Minimum density. The minimum embedment density should be established based on an evaluation of specific project conditions.
Densities higher than those rec- ommended in Table may be appropriate. Minimum densities given in Table are intended to provide satisfactory embedment stiffness in most installation conditions. Densification using water. Densification of pipe zone embedment using water jetting or saturation with vibration should be done only under controlled conditions. Backfill around angularly deflected pipe joints. Minimum cover. To preclude damage to the pipe and disturbance to pipe embed- ment, a minimum depth of backfill above the pipe should be maintained before allow- ing vehicles or heavy construction equipment to traverse the pipe trench.
The minimum depth of cover should be established based on an evaluation of specific project conditions, such as pipe diameter and stiffness, soil type and stiffness, and live load type and magnitude. In the absence of an engineering evaluation, the following minimum cover requirements should be used. Where construction loads may be excessive e. If there is a risk of pipe flotation, the minimum cover should be 1 pipe diameter.
If a specific analysis is made of the buoyant force of an empty pipe compared to the sub- merged weight of soil over the pipe, this minimum cover may be reduced. When differential settlement can be expected, such as at the ends of casing pipe, when the pipe enters a manhole, at anchor blocks, or where foundation soils change stiffness, provide a flexible system capable of accommodating the anticipated settlement. The short length of pipe, called a rocker pipe, shall be installed in straight alignment with the short pipe section coming out of the rigid structure.
The rocker pipe should have a minimum pipe stiffness of 36 psi kPa to transition between lower stiffness pipe and the rigid structure. Multiple rocker pipes should not be used. Alternatively, attach the pipe to the rigid structure with a flexible boot capable of accommodating the anticipated differential movement. Extra care and caution must be taken to replace and properly compact backfill adja- cent to any rigid structure.
Construction of concrete structures will frequently require overexcavation for formwork, etc. In these areas, compact backfill to achieve the same soil density as specified for all pipe backfill but not less than required to achieve a soil modulus Msb of at least 1, psi 6. The use of cement-stabilized backfills adjacent to large structures has been found to be effective in preventing excess defor- mation where diameters are larger than about 60 in.
Other methods of accommodating the differential settlements may be acceptable. Vertical risers. Provide support for vertical risers as commonly found at service connections, cleanouts, and drop manholes to preclude vertical or lateral movement. Prevent the direct transfer of thrust due to surface loads and settlement and ensure adequate support at points of connection to main lines.
When excavating for a service line connection, excavate material from above the top of the existing pipe before removing material from the sides of the pipe. When backfilling excavations of existing lines, the materials and construction methods used should restore the instal- lation to its condition prior to excavation. Pipe caps and plugs. Secure caps and plugs to the pipe to prevent movement and resulting leakage under test and service pressures.
If lines are to be tested under pressure, any plugs and caps must be designed to safely carry the test pressure. Parallel piping systems. Compact the soil between the pipes in the same man- ner as when compacting the soil between the pipe and the trench wall, taking special care to compact the soil in the haunches. Conduct deflection measurement programs early in a project to verify that the construction procedures being used are adequate. The allowable deflection at the time of installation is the long-term allowable deflection reduced by the effects of deflection lag.
If necessary, also consider the effects of vertical ovalling during compaction. Complete all deflection checks prior to conducting any pressure tests. Pressure testing.
Most pressure pipelines are tested after installation to detect leaks, installation flaws, damaged pipes, or other deficiencies. As a general rule, such tests should not be conducted using air pressure unless special precautions, not within the scope of this manual, are used. Some sections of the line may be left uncov- ered provided suitable lateral and longitudinal restraint is provided.
If the test pressure gauge is not installed at this location, determine the correct pressure by calculation. Second ed. Washington, D. Thrust forces are: 1 hydrostatic thrust due to internal pressure of the pipeline and 2 hydrodynamic thrust due to changing momentum of flowing fluid. Since most pres- sure lines operate at relatively low velocities, the hydrodynamic force is very small and is usually ignored. The equations in this chapter are presented with inch-pound units in the left-hand column and metric units in the right-hand column.
The thrust in dead ends, tees, laterals, and reducers is a function of internal pressure P and cross- sectional area A at the pipe joint. Unbalanced uplift thrust at a vertical deflection is resisted by the dead weight of the fitting, earth cover, and contained fluid. Typical thrust blocking of a hori- zontal bend elbow is shown in Figure The design engineer must select the proper bearing strength of a particular soil type.
Typical values for conservative horizontal bearing strengths of various soil types are listed in Table If it is impractical to design the block for the thrust force to pass through the geo- metric center of the soil-bearing area, the design should be evaluated for stability.
After calculating the concrete thrust block size, and reinforcement if necessary, based on the bearing capacity of soil, the shear resistance of the passive soil wedge behind the thrust block should be checked because it may govern the design. For a thrust block having its height HB less than one-half the distance from the ground sur- face to base of block h, the design of the block is generally governed by the bearing capacity of the soil.
However, if the height of the block HB exceeds one-half h, the design of the block is generally governed by shear resistance of the soil wedge behind the thrust block. Determining the value of the bearing and shear resistance of the soil and thrust block reinforcement is beyond the scope of this manual. Consulting a qual- ified geotechnical engineer is recommended.
Knowledge of local soil conditions is necessary for proper sizing of thrust blocks. Figure shows several details for distributing thrust at a horizontal bend. Section A—A is the more common detail, but the other methods shown in the alternate sections may be necessary in weaker soils.
Figure illustrates typical thrust blocking of vertical bends. Design of the block for a bottom bend is the same as for a horizontal bend, but the block for a top bend must be sized to adequately resist the vertical component of thrust with dead weight of the block, bend, water in the bend, and overburden. Most thrust block failures can be attributed to improper construction.
Even a correctly sized block can fail if it is not properly constructed. A block must be placed against undisturbed soil and the face of the block must be perpendicular to the direction of and centered on the line of action of the thrust. A surprising number of thrust blocks fail because of inadequate design or improper construction.
Many people involved in construction and design do not realize the magnitude of the thrusts involved. As an example, a thrust block behind a in. Another factor frequently overlooked is that thrust increases in proportion to the square of pipe diameter. A in. Figure Typical profile of vertical bend thrust blocking approximately four times the thrust produced by an in.
Properly sized thrust blocks have been poured against undisturbed soil only to fail because another utility or an excavation immediately behind the block collapsed when the line was pressurized. If the risk of future nearby excavation is high, the use of restrained tied joints may be appropriate.
Depending on the installation and field conditions, the passive soil resistance of the backfill may be included to resist thrust.
The selection of a value for the coefficient of friction f is dependent on the type of soil and the roughness of the pipe exterior. Design values for the coefficient of friction generally vary from 0. Determination of earth cover load should be based on a backfill density and height of cover consistent with what can be expected when the line is pressurized.
This method fastens a number of pipes on each side of the fitting to increase the fric- tional drag of the connected pipe to resist the fitting thrust. Since thrust diminishes from a maximum value at a fitting to zero at distance L from the fitting, requirements for longitudinal strength to resist thrust can be calculated for the pipe length immedi- ately adjacent to the fitting and prorated on a straight-line basis for the remainder of the pipe within the tied distance L.
Frictional resistance on the tied pipe acts in the opposite direction of resultant thrust T. Section A—A in Figure shows the external vertical forces acting on a buried pipe with horizontal thrust and the corresponding frictional resistance. Uplift thrust restraint provided by gravity-type thrust blocks, shown for the top bend in Figure , may also be provided by the alternate method of increasing the dead weight of the line by tying adjacent pipe to the vertical bend.
Section A—A in Figure shows the vertical forces acting on a buried vertical uplift bend used in determining the thrust resistance by dead weight.
As previously stated, both of these analyses ignore the passive soil resistance of the backfill against the pipe. Depending on the installation and field conditions, the pas- sive soil resistance of the backfill may be included to resist thrust.
Vertical downward bends are resisted by bearing of the trench against the bottom of the pipe. Properly bedded pipe should not have to be investigated for this condition. Different design provisions and supporting methods may be applicable for specific project requirements, larger diameters, or a particular piping product. Consult with the manufacturer and the piping engineer for appropriate design considerations. In addition to pressure resistance and life limitations, the effects of thermal expan- sion and contraction should be considered.
A number of methods accommodate the length changes associated with thermal expansion and contraction. Guides, expansion loops, and mechanical expansion joints are installed in straight lines and are anchored at each end. Experience has shown that direction changes are the least expensive method of accommodating thermal expansion.
Guide spacing is the next most economical method, followed by mechanical expansion joints and expan- sion loops. For small temperature changes and piping systems that consist of short run lengths, it is usually unnecessary to make special provisions for thermal expansion. However, any system should have the capability of accommodating length changes.
Experience has shown that aboveground piping systems need anchors at approxi- mately ft m intervals. NOTE: This value may vary for larger pipe sizes. These anchors limit pipe movement caused by vibrations and transient loading condi- tions. Anchors should fasten all transition points within the system.
Transition points are places where pipe diameter, material, elevation, or direction changes or where manufacturer changes. Anchors at transition points limit the transfer of thermal end loads from line section to line section. The low modulus results in lower end loads that require restraining equipment less strong than that used for metallic pipelines.
Internal pressures in the piping system can result in some length change. Experience has shown that this elon- gation is often insignificant and may not need to be considered in the design. When con- traction occurs, the pipe experiences tension. With anchors installed, guides are an economical method for deal- ing with expansion.
The relatively low modulus of fiberglass pipe allows it to absorb the thermal stresses as compressive stresses in the pipe wall. Compressive stresses from expansion may result in buckling, unless the pipe is constrained at close inter- vals to prevent columnar instability.
The lower value of the two calculations will sat- isfy the interest of conservative design. Compare guide intervals with the intervals for supports, then adjust guide spacing for a better match with support spacing. For example, adjust intervals so a guide replaces every second or third support.
Remember, all guides act as modified supports and must meet the minimum requirements for supports, anchors, and guides, as pre- scribed in other sections of this chapter. Figure Typical expansion joint installation 8. Various types of expansion joints are available and suitable for use with fiberglass piping systems. Because the forces developed during a temperature change are rela- tively low compared with metallic systems, it is essential to specify an expansion joint that activates with low force.
Remember that fiberglass pipe will expand more than most metallic systems. The required movement per expansion joint and the number of expansion joints may be greater for fiberglass systems. The allowable activation force for expansion joints depends on both the thermal forces developed in the pipe and the support or guide spacing.
Guide spacing at the entry of an expansion joint is typically 4 pipe diameters first guide and 14 pipe diam- eters second guide from the inlet of the expansion joint Figure These guides and locations give proper alignment. The spacing of the remaining supports should remain within the maximum calculated interval. Pressure thrust is the design pressure times the area of the expansion joint.
In all applications, the activation force of the expansion joint must not exceed the thermal end loads developed by the pipe. The cost and limited motion capability of expansion joints makes them impractical to use in many applications.
In these cases, loops, guide spacing, or short lengths of flexible hose can handle thermal expansion. The expansion joint needs an anchor on both sides for proper operation.
Figure Expansion loop dimensions 8. This design method is used to calculate the stress developed in a cantilevered beam with a concen- trated load at the free end and ignores flexibility of the loop leg, the leg parallel to the line. Two guides on both sides of each expansion loop ensure proper alignment. The rec- ommended guide spacing is 4 first guide and 14 second guide nominal pipe diame- ters.
Additional guides or supports should be located so the maximum spacing interval is not exceeded. If the maximum allowable bending stress of the fittings is greater than the maxi- mum for the pipe, the bending moment of the fitting does not need to be considered. In other cases, the fitting manufacturer will provide allowable bending moments for the fittings. The results are compared and the larger value is used. Pipelines with heavy-wall pipe and rela- tively thin-wall fittings are most likely to require verification of the LA dimension.
In these cases, thermal expansion procedures may be limited to the use of anchors and guides or expansion joints if the bending moment is not available.
Directional changes that involve some types of fittings, such as sad- dles, should not be used to absorb expansion or contraction. The bending stresses may cause fitting failure. Stress in the pipe at a given directional change depends on the total change in length and the distance to the first secure hanger or guide past the dir- ectional change.
In other words, the required flexible leg length is based on the maxi- mum change in length. Recommended support or guide spacing cannot be disregarded. However, flexible or movable supports, such as strap hangers, can provide support while allowing the pipe to move and absorb the changes in length.
Supports must prevent lateral movement or pipe buckling. Where large thermal movements are expected, a short length of flexible hose installed at a change in direction will absorb some of the line movement. This method of handling thermal expansion is usually the most economical means of compensating for large displacements when the guide spacing method cannot be used.
The equation for calculating the length of the flexible pipe leg i. Allowable bending stress is much lower than the allowable torsional stress. Figure Guide support shown in Figure , will typically absorb pipe movement. However, the unanchored leg must have a free length equal to or greater than Lsh, as calculated from Eq How- ever, the guides must be attached rigidly to the supporting structure so that the pipe moves only in the axial direction Figure All guides act as supports and must meet the minimum requirements for supports.
Refer to Sec. Pipe anchors divide a pipe system into sections. They attach to structural material capable of withstanding the applied forces. In some cases, pumps, tanks, and other similar equipment function as anchors.
However, most installations require additional anchors where pipe sizes change and fiberglass pipe joins another material or a prod- uct from another manufacturer. Figure Anchor support changes in direction of piping runs, and major branch connections. Saddles and later- als are particularly sensitive to bending stresses.
To minimize stresses on saddles and laterals, anchor the pipe on either side of the saddle or anchor the side run.
Figure shows a typical anchor. Operating experience with piping systems indi- cates that it is a good practice to anchor long, straight runs of aboveground piping at approximately ft m intervals. These anchors prevent pipe movement due to vibration or water hammer. One anchoring method features a clamp placed between anchor sleeves or a set of anchor sleeves and a fitting.
The sleeves bonded on the pipe prevent movement in either direction. Sleeve thickness must equal or exceed the clamp thickness. To achieve this, it often is necessary to bond two sleeves on each side of the clamp. Anchors act as supports and guides and must meet minimum requirements for supports.
Pipe analyzed as simply supported single spans two supports per span length with the run attached to a fitting at one end, or any other section of less than three span lengths. Beam analysis for other types of spans, such as a section adjacent to an anchor, is sometimes used to obtain a more accurate span length.
When the mid-span deflection is limited to 0. For instal- lations that result in more than 0. In fact, cyclic bending tests have shown that the stresses are not additive as expected and that the safety factor is conservative.
Cyclic bending tests consist of cyclic pressure testing of pipe bent to stress levels at or above the design bending stress. For low stiffness pipe with a relatively thin wall, the local bearing pressure at sup- ports is often significant. Pipe analyzed as a continuous beam—three spans—all loaded.
Pipe analyzed as a continuous beam—four spans—all spans loaded. Pipe analyzed as a beam fixed at both ends—uniformly distrib- uted loads. NOTE: In cases where the wall thickness to diameter ratio is low, the possibility of buckling failures at the supports is a concern.
This may require the use of empirical equations and special bearing stress calculations that were determined or verified by testing. Six basic rules control design and positioning for supports, anchors, and guides.
These are described in the following paragraphs. Do not allow pipe to bear against ridges or points on support surfaces. Use metal or fiberglass sleeves to protect pipe if these conditions exist. Supports failing to meet the minimum must be augmented with a protective sleeve of split fiberglass pipe or metal.
In all cases, the support must be wide enough that the bearing stress does not exceed 85 psi kPa. Prepare all pipe and sleeve bonding surfaces by sanding the contacting surfaces. When frequent thermal cycles, vibrations, or pulsating loadings affect the pipe, all contact points must be protected.
This is typically accomplished by bonding a wear saddle made of fiberglass, steel, or one half of a section of the same pipe to the wall. Figure Fiberglass wear protection cradle 8. Install guide collars using the same spacing intervals used for horizontal lines Figure Figure Vertical support 8. Certain fittings, such as saddles and laterals, may be more susceptible to bending failure than other types.
Consult the manufacturer for recommendations and limitations. However, in most heat transfer situations, the heat loss or gain for pipe is controlled by the resistance to heat flow into the surrounding media i. This reduces the insulating effect of a relatively thin fiberglass pipe wall. For this reason, thermal insulation tables for steel pipe can be used to size the insulation for most fiberglass pipelines.
The coefficient of thermal conductivity varies for different types of fiberglass pipe. A typical value for an epoxy resin pipe is 2. A typical value for polyester or vinyl ester resin pipe is 1. When using either method, three criteria govern the maximum ele- ment temperature: 1. The average wall temperature must not exceed the temperature rating of the pipe. The maximum recommended chemical resistance temperature of the pipe must not be exceeded at the inside wall of the pipe.
The maximum tracing element temperature using this methodology applies only to applications involving flowing, nonstagnant, fluid conditions. For stagnant conditions, the maximum allowable trace element is the chemical resistance temperature of the pipe.
This value is compared with the inside wall temperature Ti. The published value must be greater than Ti. The internal operating pressure for fittings is generally based on one fourth of the ultimate short- term failure pressure as determined by ASTM D Also, the tensile, bending, and compressive moduli may differ significantly, thus it is important to use the correct value.
The moduli depend on the type of resin, amount of glass, and orien- tation of the glass filaments. Precise values for the moduli for specific conditions of loading and temperature should come from the manufacturer. Typical values are often obtained by drawing a tangent to the stress—strain curve at the point equal to one fourth of ultimate failure load. This power is particularly useful where a married couple are leaving their respective share of the family home to their children but allowing the surviving husband or wife to remain living there.
Quite often, as the survivor grows old they will want to downsize the property. This power therefore allows the trustee to use the value of the deceased's share in the family home to put towards the purchase of another property which will be owned jointly with the survivor.
This power is also useful where a property is to be purchased for a minor beneficiary to live in with their guardian s. The trustee is able to use money from the estate to put towards the purchase of property which would then be jointly owned with the guardian. This is particularly relevant where you are benefitting a minor and you do not want them to receive any monies absolutely before reaching a certain age, for example 18, 21 or The trustee can accumulate any income generated on their share of your estate rather than giving it to them or their guardian outright as and when it is generated.
This power is self-explanatory and can be exercised with the power to purchase property jointly with another. This power allows the trustee to carry on the trading of any business you may own or in which you have an interest. This is to ensure that the business carries on as normal after your death.
The trustee will usually then seek someone to undertake this duty more long term if the business is to continue trading. When you are benefitting young children, you want to make sure that they are provided for when they grow up. The trustees are able to advance monies to the guardian s of your children to ensure that your children are well provided for. This power is also used where you have decided to postpone your children or any other person inheriting, for example, until the age of 21 or
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