|The CHOCKFAST system
is used for mounting all sizes and types of main and
auxiliary machinery. It eliminates all machining of
foundation surfaces and will conform precisely to the
surface profiles presented. The individual chocks are
arranged similarly to conventional iron ones. Removal of
grease, oil, mill scale and/or rust or flaky paint is the
only preparation usually necessary for machinery
supporting surfaces. These surfaces should be cleaned if
covered by other than a thin coat of inorganic zinc paint
or similar primer. Inorganic zinc is recommended where
machinery base and foundation corrosion resistance is
required, as in the case of deck machinery and other
equipment constantly exposed to water.
Which Grade of CHOCKFAST to Use
When alignment must be maintained precisely, or when the operating temperature will exceed 52C (125F) but not 90C (194F), then CHOCKFAST ORANGE must be used. Examples of this class of machinery are propulsion engines and gearboxes.
Where alignment does not have to be maintained precisely, usually because the equipment is self-contained, and the operating temperature will be below 52'C (125'F), then CHOCKFAST ORANGE or CHOCKFAST GRAY may be used. Typical applications would be winches, pumps and skid mounted diesel generators.
a. Stress on the chocks due to the machinery's weight should not exceed 7 kgf/cm2 (100 psi). Known as deadweight loading.
b. Static stress on the chocks due to the Deadweight plus the Bolt Tensions is typically designed to be 35 kgf/cm2 (500 psi). See the appropriate classification approval for higher stress, most approve at least 45 kgf/cm2 (640 psi)
c. Hold down bolt tensions must total at least 2.5 times the machinery weight. This is to ensure the machine will not move.
down bolt stress must be at least 4.73 kgf/mm2 (6720
psi). This is to ensure the bolts will stay tight.
e. Continuous chock temperature should not exceed 90C (194F). Unless otherwise stated it may be assumed that a diesel engine's chocks will not exceed 80C (176F).
f. Where thrust has to be transmitted, thrust chocks are not required if the total static chock load exceeds 3.33 times the thrust.
It is suggested that chocks be designed for 12mm to 45mm (1/2" to 1' 3/4") thickness. Any thickness of chock can be cast. Consult your distributor for advice on thinner or thicker chocks.
Design for Deck and Auxiliary Machinery
If the temperature will not exceed 52C (125F), machinery and equipment which does not have to be precisely aligned may be chocked as follows:
Using CHOCKFAST ORANGE, maximum continuous static stress 84.5 kgf/cm2 (1200 psi). Using CHOCKFAST GRAY, maximum continuous static stress 56 kgf/cm2 (800 psi). It is not necessary to limit the deadweight loading. Chock thickness recommendations are as for precise alignment.
Design for Higher Stress than 84.5 kgf/cm2 (1200 psi), Non-Critical Alignment
When the chock stress will be above the previously given limits it is advisable to consult ITW Philadelphia Resins. Continuous stress of 250 kgf/cm2 (3550 psi) has been approved for mooring winches and this is also a typical stress under crane rails. Transients and shock loads of 700 kgf/cm2 (10000 psi) can be accepted with suitable design guidance.
General Guidelines for Marine Engineers
Bolt Tension and Tightening Torque
There is no absolute relationship between tightening torque and bolt tension. The generally accepted formula is:
As has been explained, there is a minimum desirable bolt stress and the following table gives the MINIMUM tension for various size bolts. It is normally advantageous to use more than the minimum shown here. When the bolt material is unknown, a safe maximum tension is 3 times the value given in this table.
|CONVERSION FACTORS||lbs.ft to kgf.m .......... multiply by 0.138|
|kgf.m to lbs.ft ....... multiply by 7.23||kg to lbs ..................... multiply by 2.2|
|N.m to kgf.m ...... multiply by 0.102||lbs to kg ................... multiply by 0.45|
EXAMPLE - PROPULSION ENGINE
Application Instructions - Marine
INSTRUCTIONS FOR USING ITW PHILADELPHIA RESINS
instructions apply to normal CHOCKFAST installations on
steel foundations, where the chock thickness are within
CHOCKFAST ORANGE 12mm-70mm (1/2" - 2 3/4")
CHOCKFAST GRAY 12mm-50mm (1/2" - 2")
Outside these ranges please consult your CHOCKFAST distributor for guidance.
I. MATERIALS REQUIRED
IV. MIXING AND POURING
|V. AFTER POURING
NOTE: CHOCKFAST ORANGE ONLY
Under some circumstances a reduced amount of hardener is used. Refer to Bulletin 693, excerpted below, or consult a Chockfast distributor for guidance. Because there are so many variables in chock size, chock thickness, metal temperature, heat sink, etc., it is advantageous to condition the resin to 20C - 25C (68F - 77F). The decision on exactly how much hardener to use is to be made by the technician in charge. Bulletin 693 and the graph below are a guide only.
For chocks less than 20mm (3/4") thick always use full hardener. For chocks less than 12mm (1/2") or chocks that must be poured in layers consult a Chockfast Distributor for advice. Always use maximum hardener with Chockfast Gray.
|TECHNICAL SERVICE AND
SUPERVISION ARE READILY AVAILABLE. CONTACT YOUR LOCAL