Durastatic Installation and Design
|Coefficient of Thermal Expansion|
|pH Range||5 to 10|
|*ESTIMATED VALUES FOR STANDARD PRODUCTS ONLY. SPECIAL FORMULATIONS MAY BE AVAILABLE WHICH CAN INFLUENCE HARDNESS, TEMPERATURE ETC.|
|Durometer, Shore A||92|
|100% Modulus, psi||1400|
|Bell Brittle point||-80°F/-63°C|
|Die C Tear, pli||550|
|D470, Split Tear, pli||100|
|Resliency, % Bashore||41|
Relative Abrasion Resistance (Wet Sand Test)
|410 Stainless Steel||65|
|304 Stainless Steel||78|
|Polyethylene (low density)||138|
|Hard Oil-Resistant Rubber||800|
|*Relative to 100|
When expansion occurs, it will deflect laterally depending on the spacing allowed in the support system. Adequate space must be allowed to accommodate the curvature associated with this deflection. When contraction occurs the pipe will tend to become taut between the anchor points. This added stress is not harmful to the pipe but care should be taken not to damage pipe system connections.
These procedures are recommended for installation of Durostatic AR:
- If the temperature or the weight of pipe and fluid are very high, continuous support is needed.
- Supports which run underneath the pipe and do not grip the pipe, should cradle the pipe for a length equivalent to at least one (1) diameter and no less than l20 degrees of the circumference of the pipe. These supports should be free of sharp edges or protrusions.
- If movement was a design consideration, the supports should be capable of restraining the pipe from lateral or longitudinal movement. lf the pipeline is designed to move during expansion, the sliding supports should provide a guide without restraint to movement.
- Pipe lines across bridges or in a constrained area may require insulation to minimize thermal movement. Fittings and flanges should be supported on either side.
Proper anchoring should be considered to prevent lateral displacement at fittings. Anchors should be placed as close to an elbow as possible. If flanged connections are used, anchors may be attached to these flanges as long as no bending is induced between pipe and flange.
Adhesive Systems for Joining Durostatic AR
The following steps are suggested to assure a good bond between materials when using urethane adhesives:
- Cut and pre-assemble pipe and fittings without cement. Determine that the required fit is possible. Mark alignment of elbows, couplers and flanges. All saw cuts in pipe should be made as square as possible.
- Solvent clean all mating surfaces. Acceptable solvents are methylene chloride, methyl ethyl ketone (MEK) or denatured alcohol.
- Abrade both surfaces where adhesive is to be applied. The gloss finish must be removed from Durathane AR. Do not clean with solvent again after roughening.
- Spread a thin even coating of cement over the total mating area of both pieces to be joined.
- Push and twist the two pieces together until they are Completely seated. Make sure that the elbows and flanges are in the correct alignment.
- With an applicator or disposable cloth, smooth excess cement into a fillet at the edge of the joint.
- For best results, joints should not be disturbed for a minimum of 24 hours.
- Recommended cements include: #7540 Equal-Mix Urethane Adhesive from Lord Corporation, Erie, PA (814-868-3611 /Fax 814-864-3452) and SIKAFLEX-1A One Part Adhesivefrom Sika Corporation, Lynhurst, NJ (800-933-7452/Fax 201-933-7326)
The installation of a polyurethane piping system presents unique installation requirements. The physical properties of any piping system will dictate the anchoring and support requirement as well as the methods needed to compensate for thermal expansion and contraction.
Because urethane is an elastomeric material, "normal" installation criteria used for other piping systems will not always apply. Temperature changes should be considered in the design of an above ground Durothane AR application. The coefficient of thermal expansion or contraction for Durothane AR is .95X10-4in/in/°F from +32°F to +75°F.
These values are based on empty pipe which is free to move. Generally, pipe laid over smooth terrain and allowed to move freely in every direction will perform adequately. However, if large changes in temperature are experienced over short periods of time, movement of the pipe can be concentrated in one area and kinking can occur. By using proper anchors or restraints, the possibility of kinking can be minimized.
Normally, if fluid flow is continuous, expansion or contraction of the polyurethane system will be minimal after normal operating conditions are established. The effect of daily and seasonal temperature changes should be anticipated for both seasonal and operating conditions. This is especially true when the piping system is not used on a continuous basis such as when alternating lines are used. The preferred method of limiting expansion and contraction is to properly anchor the pipe at set intervals along its length.
The forces which affect the installation of a horizontally supported pipeline are those developed by the weight of the pipe and its contents between supports. If sag or deflection between supports is minimized, then the degree of stress and strain within the pipe wall will be controlled within safe limits.
The design basis for supported or suspended horizontal pipelines is based upon support spacing which minimizes the mid-span deflection using simple beam analysis. An additional benefit of using maximum deflection as a design criteria is that the relevant support spacing allows the user to control thermal expansion and contraction.
Since this analysis considers weight and pipe stiffness only and doesn't factor in temperature, if the installation is accomplished at or near the maximum service temperatures, the thermal sag will be minimized. At lower temperatures, the system will stay taut because of the decreased linear dimension.
Support brackets, hangers and clamps should beat least one diameter in width and a minimum of 4 inches. If the operating temperature is expected to be more than 10°F higher than the installation temperature, continuous support is recommended to control thermal expansion and prevent excessive droop. Vertical piping should be supported at its base and spring hangers or collars used at 10 ft. intervals.
Joining Durostatic AR
In gravity feed systems where pressures are negligible it is possible to join the Durostatic AR piping system using slip-on flanges and couplers without any other assembly requirements. Care should be taken to ensure that the pipe is supported in order to assure that the line will not separate. It may be necessary to use sheet metal screws to keep the pipe together. Other mechanical means to insure a tight joint include hose clamps and "Dixon" style clamps. The "Dixon" style clamp also offers an excellent means of supporting the Durostatic AR piping system as braces can be attached to clamps. Care should be taken to avoid exposure of the polyurethane to any welding or cutting devices if used during clamp assembly.
The 50 psi pressure rating for Durostatic AR piping systems is accomplished using bonded Durostatic AR flanges and couplings. The pressure rating for mechanical connections must be determined by the user.
Coupling devices for grooved pipe similar to those provided by Pace, Victaulic, or Stockham can be used. The Victaulic "Hugger," the Morris compression coupling, or other similar devices that are designed to grip the ends of pipe or fittings can also be used. Care should be taken to ensure that the pipe is firmly anchored in place to prevent the joints from separating.
Durastatic AR has been formulated to resolve issues with static build-up common to pneumatically conveyed dry media.