the gassing head and hose connections closely. Use harder gaskets on the gassing heads and softer
seals on the corebox. Gasket joints should be angle-cut and glued. Train operators to prevent excess sand from accumulating between the box seal surface and the gas- sing head or manifold. Excess sand will prevent a good seal and over time damage the seal. Deteriorated seals and gaskets should be removed and replaced. Seal main- tenance is an ongoing task.
2
ENSURE Proper Vapor Delivery
Ensure the amine in your system is effectively vaporized
and remains in the vapor state until it exits the core. Clas- sic symptoms of amine condensation within the vaporizer piping system, tooling and core include a dramatic increase in the amount of amine used during the colder winter months and cores that emerge from the corebox wet with amine. Heat tracing and insulation can improve marginal performance, but give serious consideration to redesigning or replacing a system with significant deficiencies. If you use a centralized amine generator, it should
be physically located as close as possible to the corebox gassing head to help maintain vapor temperatures and minimize the amount of nitrogen that has to be evacuated from the line each cycle. Avoid running vertical vapor lines with upward flow to prevent condensate from pooling in the lower parts of the lines. Eliminate 90-degree elbow fittings wherever possible, as heat loss and condensation will increase with each directional change. Use heated flex hoses and a “Y” fitting instead of a “T” if splitting from one line to two at the corebox. Run a few heat-up cycles at the start of each shift with
hot purge air to pre-heat the supply and tooling. Vapor lines and gas hoses should be sized for the
machine blow weight. As a general guide, use a 1-in. line for small boxes and a 2-in. line for larger boxes. Newer injection-style vaporizer units are inherently more efficient and allow more precise control of amine delivery and dosing rates.
3
IMPROVE Venting
Audit each job and reduce amine use to the minimum
based on its current venting arrangement. Reduce your amine gas timer by one second or one pump-stroke at a time and observe which portions of your cores fail to solidify. If no failure occurs, run three or four cycles and reduce the gas again. At the point of failure, try adding a second to the purge cycle, which sometimes can complete the cure. Repeat this process after making any significant change to venting design to optimize your results. Check for obvious venting design problems. Vent tubes
or input vents should be offset from exhaust vents to force amines to travel sideways through the core sand. Review
Don’t allow elbows or loops in the flex house. November 2011 MODERN CASTING | 37 Don’t use hoses fitting like a “T” or at 90 degree elbows. Don’t
the design particularly for cores with variable cross sec- tions. You should prevent excess flow through thin sections, which require more gassing time to cure. Block or restrict some of the vents in your thin sections to encourage flow to the thicker sections, or add new vents to the thicker sec-
Do
Use hoses that fit in a “Y” configuration. Don’t
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