Your questions answered: The next step in achieving predictive maintenance
Additional questions on achieving predictive maintenance from a November 8 webcast relating to mechanical seal performance are answered.
Mechanical seal performance data is often the best and earliest indicator of a critical system problem, even when the seal is not the root cause. However, there are few options for monitoring mechanical seal internal performance or accurately understanding how the pump and seal interact in various operational environments.
Webcast presenter Chris Riché, IoT product manager – Pumps and Seals, Flowserve, answered additional questions from the Nov. 8 webcast “The Next Step in Achieving Predictive Maintenance” on topics such as seal failure detection, monitoring points and more.
Question: What are the signs and technologies available to detect that a seal is about to fail?
Riché: Current monitoring is focused on temperature, pressure, flow and liquid level in different parts of the seal support system and the seal chamber. Any commercially-available sensor can be used to take the readings, the real value comes in knowing what the reading means and how it is related to other parts of the system.
Question: How do you increase the life of a seal?
Riché: Provide a favorable environment in the seal chamber by using and maintaining the proper support system.
Question: Does seal monitoring apply to atmospheric side systems?
Riché: They can, though atmospheric side systems are normally used to control or detect seal leakage whereas seal monitoring is used to prevent leakage.
Question: How often is data sampled by the sensors?
Riché: Every 30 minutes for wireless sensors and every 30 seconds for wired sensors.
Question: Why were wireless sensors not used for seal monitoring?
Riché: Wireless sensors were developed for seal monitoring and will be released for hazardous areas in early 2023.
Question: Have these seal support monitoring points/systems been used in FDA/USDA/3A food and beverage processing? Am curious about cleaning the orifices and if the monitoring systems have been approved for use there.
Riché: Seal support systems are used in FDA/USDA/3A industries. I don’t know about how they are cleaned or maintained. Seal monitoring systems need review for cleaning and self-draining design, which is possible.
Question: We use a piping plan 53 and we monitor the seal using the seal pot level and its pressure. Is this enough?
Riché: The answer depends on the failure modes are you seeing and the application conditions of the service. Level and pressure are important though you may also need seal chamber pressure for comparison and you could need barrier temperatures and flows if you are seeing overheating failures. It’s hard to say whether it is “enough” since that depends a lot on what you’re trying to achieve.
Question: Where do you place the sensors that monitor the seal’s temperature?
Riché: Seal chamber temperature is taken from a port in the seal gland or in the pump head/back cover. Either one can be a dedicated port or a shared flush port. Barrier/buffer fluid temperature is taken from a port in the seal gland (dedicated or shared) or in the tubing between the support system and the seal.
Question: How much analytics can be directly inferred on legacy pump installations- assuming we add sensors to the legacy seal plans? – wireless works?
Riché: Analytics are highly dependent on which sensors can be installed. The age of the pump is less important than the space available for installing aftermarket sensors.
Question: Is the monitoring also applicable for gas lubricated mechanical seals?
Riché: It is applicable for gas lubricated seals in pumps, mixers, blowers and fans. This version is not applicable for centrifugal compressor seals; that technology is being developed now.
Question: What is the main reason for the mechanical seal overheating?
Riché: The answer is application-specific. Seals can overheat for a wide variety of reasons. Monitoring seal conditions can help you narrow the search to the system conditions that exist when the seal overheats.
Question: Is the only action when there is a predictive seal fault to replace the seal?
Riché: Not necessarily. Predictive seal faults can find when support system performance is deteriorating and suggest corrective actions that prevent seal failure. A good example is catching a seal cooler that is beginning to foul and suggesting the cooler is cleaned before the seal overheats. Another example is refilling a seal reservoir when a low level alert is triggered to maintain barrier/buffer circulation.