URETHANE INDUSTRY GLOSSARY - V

That portion of the mixing head that is responsible for diverting the various flows simultaneously between recirculate and operate. These may be very simple, manually operated individual valves or more complex automatic devices that may divert from 2 to 6 components simultaneously.

The practice of catching in individual cups the output of all fluid streams simultaneously for an indefinite time period in order to check the ratio between fluid streams, but not the flow rate per minute.

The ability to be able to change the flow rate of any or all components as desired, usually within a fixed minimum and maximum limitation. See fixed flow rate.

A lead-lag problem, under some conditions of metering and mixing machine operation, in which pressures are exactly balanced (see pressure balance). This can be caused by unequal velocities of the components , perhaps due to extreme differences in viscosity or quantity. Under these conditions one material will reach the mixing-pumping zone before the other and will be expelled from the mixing chamber before enough of the other component has been blended in to bring the mixture back on ratio. This problem is more likely to occur with extreme differences in viscosity between the various components and can often be corrected by changing the diameter, length or direction of discharge of the metering ports as required.

Special foam cutting bandsaws in which the portion of the blade that is used for cutting is in the vertical plane. This type of saw is usually characterized by large moving tables that carry the foam Blocks past the cutting blade.

A term which generally refers to those pour-in-place operations in which the cavity to be filled is extremely long in its vertical dimension (height) in comparison to its thickness and generally is higher (vertically) than its width (horizontally). This would give the cavity a large 'surface to volume ratio'. This is also called a high-rise Application.

A term sometimes used to describe a special fitting on the suction side of a rotary pump that is used to isolate the pump from the tank by means of a rubber coupling or bushing so that stresses on the pump casing are reduced. This is particularly important when the pump is mounted directly beneath the tank.

A term often used to describe foam, particularly flexible slab foam, that has not been processed in any manner other than cutting to shape. It is a means of differentiating between rebonded, laminated or pieced together foam and the original or 'virgin' material.

A term which generally refers to the flow characteristics of a material which is not completely rubber- like, not really rigid and not readily fluid.

The resistance of a fluid to being fluid (or flowing readily). For example, a low viscosity material would flow readily from a container on being poured, while a high viscosity material would only pour slowly from a tipped container. See centipoise and poise.

The scope of viscosities, between stated maximum and minimum limits, that can be handled properly by a metering machine, pumping system, pump, mixing head or other specified item. Usually viscosity range is coupled with flow rate range and under some conditions can cause confusion, since a particular machine may not be able to achieve maximum flow rate with maximum viscosity material or may not be able to achieve stated Accuracy of flow at the minimum flow rate with the minimum viscosity material.

A term generally used to describe any fluid more resistant to flow than water. The degree of viscousness (viscosity) is generally expressed in centipoises in the foam industry. For clarification, see poise or centipoise.

A term occasionally used as a synonym for pour-in- place. When used it generally refers to filling structural cavities rather than the filling of molds.