Bi-Parting Doors Gain in Cleanroom Applications
New designs save space
By Jon Schumacher, Rite-Hite Doors
Pharmaceutical manufacturers have always used bi-parting cleanroom doors, yet there were perceptions that the doors took up too much space, compared with fabric rollup or “upward acting” doors. Designs have evolved to make them more compact, while maintaining speed and efficiency.
Any industrial door used in a drug manufacturing plant is designed to let users maintain a specified level of cleanliness and positive air space pressure. Most facilities incorporate multiple pressure steps within the building’s structure. The steps typically range from 0.02 to 0.05 w.g. between rooms, although they can reach, or even exceed, 0.20 w.g. Generally, a pressure differential of 0.1 w.g. or less is maintained between rooms. A properly designed door helps ensure the facility’s makeup fans can satisfy the required amount of makeup air needed to maintain pressure.
Fabric rollup doors have gained use in cases where bi-part doors won’t fit. These doors require very little wall space because their curtain collects in a head assembly at the top of the door when it’s opened. By comparison, a rigid-panel door that opens from the center requires considerable wall space on each side of the door in order to function. For example, a rigid panel door spanning a six-foot wide opening requires approximately three feet of wall space on each side.
However, new bi-parting doors have been designed to use much less wall space, while operating safety and at high speeds (video clip: http://bit.ly/jaonyW). Newer designs reflect the following changes:
Fabric bi-parting doors conserve space. A significant change in bi-parting doors involves the use of a fabric curtain in place of stainless steel or fiberglass panels. The curtain opens from the center and collects in the side frames on opposite sides of the door when it’s opened. The rolled-up curtain takes up approximately one foot of wall space on each side of the door, allowing bi-parting doors to fit where they couldn’t before, including at openings close to perpendicular corridor walls.
Seals and stabilizer struts for enhanced environmental control. Mechanisms, such as stabilizer struts that resist air pressure on the door’s fabric curtain, are incorporated into bi-parting doors to maintain a tight seal on all four sides of the door opening. Some doors also use multiple layers of seals within the side frames. A tight fabric curtain, combined with speed and extra sealing capability, addresses the need to maintain pressurization. Some doors of this type have been rated to withstand pressures up to 0.20 w.g. The end result is less air movement between cleanrooms and other areas.
Drive systems advance productivity: Advances in various door technologies, including drive systems, allow fabric bi-parting doors to consistently and safely operate at high speeds. Some bi-parting doors operate up to 120 inches per second. By comparison, older rigid-panel doors typically operate at approximately 30 inches per second. A high-speed bi-parting door that opens from the center also means the fabric curtain has half the travel time of a roll-up door. The result is almost immediate access to the opposite side of the door opening, which results in increased productivity. Additionally, a bi-parting door provides full-height access when compared with some roll-up doors. A door that opens in the blink of an eye and quickly closes also reduces the potential for air transference between rooms.
Cleanliness and ease of cleaning: Bi-parting doors engineered for pharmaceutical applications incorporate a variety of features that take cleanliness to new levels. Examples include non-porous fabric curtains, stainless steel headers and side frames, and sloped headers to minimize dust and debris collection. The materials used in advanced doors can also withstand repeated cleaning in keeping with cGMP initiatives.
Maximum uptime: Advanced bi-parting doors that open in a split second minimize the potential for door impact, resulting in increased uptime when compared with slower-moving rigid-panel doors. The flexible curtain on some doors can also withstand incidental impacts without damage, while the movement to fewer moving parts has reduced routine maintenance requirements.
Safety: An advanced bi-parting door that opens quickly from the center provides near-instantaneous, top-to-bottom visibility to the opposite side of the opening for enhanced safety. Some curtains also incorporate large windows for high visibility when the unit is closed. Manual override systems also allow the doors to be opened in the event of a power outage.