When a peristaltic pump is equipped with an open-head sensor interlock, or an existing pump is fitted with a stand-alone system, the drive will automatically shut off when someone opens the pump head for any reason. This technology provides added protection for technicians and operators when servicing or replacing tubing during preventative maintenance.
A peristaltic pump is used for solving difficult fluid handling problems and is especially useful when handling sterile, shear-sensitive, or high-purity fluids. The design inherently exposes the fluid to only one component the tubing which can be specifically selected for the liquid being pumped or regulatory requirements. Exposure to only one component ensures compatibility of the fluid path when the correct tubing material is selected. This prevents contamination and early failure of the tubing. The peristaltic pump can pump continuously or dispense in defined amounts. The peristaltic pump system is a positive displacement pump and includes three components: the drive, the pump head, and the tubing.
A pump head consists of only two parts: the rotor and the housing. The tubing is placed in the tubing bed between the rotor and the housing where is is occluded (squeezed).
The rollers on the rotor move across the tubing, pushing the fluid. The tubing behind the rollers recovers its shape, creates a vacuum, and draws fluid in behind it.
A "pillow" of fluid is formed between the rollers. This is specific to the ID (inside diameter) of the tubing and the geometry of the rotor. Flow rate is determined by multiplying speed by the size of the pillow. This pillow stays fairly constant expect with extremely viscous fluids.
Since the tubing is the only system component that comes into contact with the fluid, peristaltic pumps are easy to clean, have excellent priming abilities, and are well suited for many different applications from chemical feed to medical devices and pharmaceutical production. However, when the tubing is replaced for preventative maintenance or a new single-use application, the operators are required to open the pump head. This action exposes the rollers.
Until recently, most peristaltic pumps relied on the operator to shut down or turn off the pump motor prior to servicing. This is considered an SOP (standard operating procedure) when working with electromechanical devices. Cutting the power or shutting down helps prevent inadvertent operation of the device.
Peristaltic pumps need to have the tubing serviced and replaced periodically. In some older pumps, the pump head needs to be removed to replace the tubing. Newer pumps, with easy loading capability, allow the operator to replace the tubing with the pump head still mounted to the drive. With this advancement, the potential for being exposed to a rotating rotor became evident. The increasing regulatory and safety focus of industry drove an opportunity for improving workplace ergonomics and the development of the open-head sensor interlock feature.
Integrated open-head sensor interlocks provide added protection for technicians and operators tasked with tubing changes and routine maintenance in busy production environments. This new feature is particularly beneficial for peristaltic pumps operating in a system where a PLC or SCADA computer can control the pumps from a remote location. Unexpected remote actuation of the pump is prevented by the open-head sensor interlock, similar to lockout/tagout procedures. Open-head sensor interlocks can also safeguard inexperienced or infrequent users of peristaltic pumps from injury while loading or changing tubing. This sensor technology couples with quick-loading pump heads to shut down the drive when the pump head is opened, eliminating the exposure to moving rollers connected to the drive shaft.
In addition, a stand-alone sensor system is an option for owners who have peristaltic pumps without an integrated open-head sensor interlock, such as the Masterflex pump systems with L/S® Easy-Load® II pump head or I/P® Easy-Load pump head. When an operator opens the pump head, intentionally or accidentally, power is removed from the pump drive that is connected to an interlock box. Power to the pump drive will not be restored until the operator closes the pump head.
The stand-alone system is comprised of an interlock control box and a new open-head sensor interlock pump head. The pump head with the open-head sensor interlock easily connects to the interlock control box that houses a control board which contains suitable relays for cutting off line voltage when the pump head is opened. If the pump head is opened during operation, the interlock control box instantly shuts down the drive. Power to the pump drive will not be restored until the operator closes the opened pump head. An indicator light on the box provides a visual status of the condition of the sensed head.
The interlock control box on the stand-alone system accepts input signals from up to two stacked pump heads and will respond to either head being opened. The box is supplied with a sensor-shorting plug to allow single-channel operation. When dual channel is desired, this plug is removed and the second head is connected. This stand-alone system is also NEMA 4X / IP66 rated for washdown making it ideal for food processing and other industries having critical cleaning protocols.
The open-head sensor interlock and stand-alone system can play an important part in protecting the technicians and operators who work with peristaltic pumps. The technology will enhance workplace safety as more companies continue to add the feature to their peristaltic pump fleets.