Solon, OH —Fluid systems that process biopharmaceuticals must be validated to meet the mandates of the U.S. Food and Drug Administration (FDA). As part of the FDA approval, the agency performs detailed inspections to verify that the entire system is capable of consistently producing the biopharmaceutical product. A major component of validation is the ability to thoroughly drain, clean, and sterilize each system—including all of its valves—to prevent contamination of product.
The majority of fluid systems in biopharmaceutical production use weir-style valves. The body block of a weir-style valve contains two chambers bisected by a weir, which is a dam-like structure. A diaphragm is sealed to the upper face of the weir valve body with four bolts. As the diaphragm is actuated downward, it seals the top face of the weir and the valve is closed. When the diaphragm is opened, fluids flow over the weir to the adjacent chamber and through its associated port.
Weir-style valves contain areas, particularly between the valve body and the diaphragm seal, where product residue can become entrapped during processing, making the cleaning of these valves difficult when fluid systems are flushed. Consequently, disassembly of weir-style valves may be required for ensuring cleanliness. If any valve or part of the system is not properly cleaned, the system is out of validation and the biopharmaceutical company may be forced to scrap the entire processed batch.
A new valve, the radial diaphragm (DR series) from Swagelok (Solon, OH) enhances the complete cleaning of fluid systems. "It maintains a boreline seal between the valve body and the diaphragm, which eliminates entrapment areas that are typically difficult to clean in the weir-style design," says Matt Smith, a mechanical engineer and the Engineered Products Manager at Swagelok.
The DR's patented design includes a bowl-shaped chamber topped by a radial diaphragm that opens and closes on an inlet port at the bottom of the bowl. Engineers used finite element analysis to optimize diaphragm shape, minimize stresses, and maximize cycle life.
Fluid enters the DR body cavity through the orifice at the bottom center and exits at the outlet port. Swagelok conducted computational fluid dynamic (CFD) analysis to optimize the shape of the valve bowl, which is based on consistent, smooth radii that promote drainage and eliminate areas that could collect residue. The "clean sweep" shape also ensures an optimal flushing action for system cleaning fluids, according to Swagelok.
In the DR series valve, the lip of the diaphragm is contained in a recess of the valve body and is radially loaded. The lip is rigidly clamped between the valve body and the actuator around the 360-degree circumference, which creates the boreline seal at the inside diameter of the lip.
Smith adds, "our diaphragm flexes and seals without affecting this boreline seal. In a weir-style valve, the diaphragm overlaps the body bore, creating a face seal. Opening the diaphragm in this valve causes relaxation at the innermost edge of that face seal and allows migration of process fluid into the area between the diaphragm and the top of the valve body."
The two wetted parts of the DR series valve are the body and the diaphragm. The body is manufactured from 316L VAR (vacuum arc remelt) stainless steel. VAR material is easier to electropolish into a surface finish that is free from significant defects. The diaphragm is machined from modified PTFE material. Because the diaphragm is contained in a recess in the valve body, PTFE cold flow is under control. Cold flow is the tendency of PTFE material to extrude or deform under load. Because the DR series valve diaphragm is contained in a recess of the valve body, it tolerates repeated cycles of steaming and cooling associated with system cleaning, without the need to re-torque the fasteners in the valve.
Swagelok makes DR valve bodies with 18 different port and valve configurations, with either one or two valves integral to the DR body. DR valve bodies are also available with three, four, five, or six integral valve and port configurations. "We reduce the required footprint and the holdup volume of the total valve assembly, which also simplifies cleaning," says Smith.
Additional details...Contact, Swagelok, 31400 Aurora Rd, Solon, OH 44139, (440) 349-5934; www.swagelok.com .
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