An improved gradient proportioning valve compensates for hydraulic inertia in a compact, reliably sealed valve assembly that is less susceptible to unswept volumes and gas permeation. A flat diaphragm is located within an accumulator volume integral to a valve manifold block. The compliance and damping of the diaphragm are optimized for the application's flow characteristics. Sealing of the diaphragm is provided by a sealing plug installed in the manifold block. The diaphragm has only one sealing joint. The sealing plug configuration allows for a more reliable clamping and sealing of the diaphragm which reduces and substantially eliminates the potential for leaks. Potential for unswept volumes is substantially eliminated by including the accumulator volume as a unitary part of the valve manifold. Air permeation into the fluid stream is substantially reduced by a reduction in surface area and exposed liquid volume in the accumulator, effected by including the accumulator volume as part of the valve manifold. Valve size is decreased by the elimination of the external tube accumulators and associate fittings. The valve that is more conducive to use and attainment of the benefits of in-line solvent degassing. More accurate delivery of the respective proportions of components of a liquid composition is achieved. Pump flow is positively impacted.
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