Spreading the word on valves
The safety and operational integrity of valves is fundamental to those running water treatment sites. Which is why Auma is taking a proactive stance in furthering knowledge.
Steve Farrow, a field engineer and instructor for Auma UK, explains: "The safety and operational integrity of valves is a primary concern for those responsible for the smooth running of any water treatment site, and correct actuator/valve commissioning is essential for extended, trouble-free valve operation.
"As an actuator manufacturer, it is appropriate that our primary focus and concern is the actuation technology that we supply. However, we understand that valve integrity is of paramount importance and appreciate that a single damaged valve can easily shut down or seriously impair the efficiency of an entire site."
Against this backdrop, Auma advocates an approach to training that includes an initial overview of products covering basic valve design and technology. This prefaces more comprehensive detail about actuation systems, which is our area of specialist expertise.
As part of the valve review, applications are considered with a particular focus on the working environment relevant to the valve installations that the engineers will encounter. An overview of the challenges that arise as a result of these applications is given and additional commentary is provided regarding the typical demands faced by the valve type selected for a particular duty.
Farrow says: "It is important to emphasise that, in addition to providing information about the actuator, the full flow control system needs to be considered. In no way do we try to replace the expertise, experience and advice of valve manufacturers.
"However, an understanding of basic valve technology is advocated to support trainees in their selection of actuators, maintenance issues and commissioning considerations."
Water treatment works use several different valves for controlling fluid flows, and many of these are operated automatically using actuators. To ensure trouble-free commissioning, and long-term system operation, the interaction between valve, actuator and control system should be understood by designers and operators alike.
Comprehending this interaction is vital in ensuring the long-term reliable operation of a valve, especially in the more demanding applications within a water treatment works.
Farrow says: "The starting point of comprehending any valve system is assessing the demands of the application. This includes media, valve function, pressure, flow rate and frequency of operation. This knowledge enables selection of the valve type, which in turn determines the type and size of actuator required.
"Actuator / valve functionality must then be considered, for example, should an on/off or regulating actuator be selected. Consideration needs to be given to the control system, failsafe modes, alarm conditions and level of feedback to the plc."
He says valve training should be carefully tailored to meet the specific needs of the industry being addressed. As part of this focus, it should offer relevant OPEX (operational experience) examples, ensuring that the course content is not only engaging but that it has impact upon those in attendance.
"To provide an insight into the level of detail that is required from effective, targeted training, we can use the example of a butterfly valve. Initial questions that may arise are whether the valve in question is wafer, double flanged, rubber lined (vulcanized or replaceable). Is it of a high performance design with an offset or even triple offset disk? What line and or differential pressures will it encounter? Additionally, does the valve have an ISO actuator flange or not.
"For control applications such as filter bed outlets, which is one use of butterfly valves, substantial consideration must be given to the relationship between valve and pipeline size. The required angle at which the disk will perform control, given correct flow and velocity calculations, often results in a valve of smaller nominal bore than that of the pipeline within which it is to be fitted. Correct selection is critical to stable actuated flow control."
After considering different valve / actuator designs, Auma training courses spend a considerable amount of time reviewing correct commissioning and set-up procedures. Some typical field problems arising due to poor valve actuator knowledge and set-up are: valve damage caused by incorrect torque settings or actuators programmed to shut-off on limit switches rather than torque; process problems caused by valves either closing too slowly or not at all and valve spindle damage caused by incorrect commissioning procedures.
Although Auma actuators are generally maintenance free many valves need occasional attention. Lubricating rising valve stems helps to prevent premature wear of the thread at the actuator drive sleeve.
"Another activity we encourage is the exercising of valves - i.e. occasional operation to avoid valve sticking - often caused by valve corrosion or contamination build-up within or around the valve itself. Consideration to this activity is perhaps more relevant to the sewage industry, where remotely located valves may not be operated for months, even years, but then be critical in nature when called upon to do so," says Farrow.
Fault avoidance, substantial increases in valve life and faster predictive maintenance practises are but a few of the many benefits associated with a training programme that considers complete systems, rather than just one manufacturer's component parts. The confidence and capabilities of on-site staff increases as a result of their enhanced knowledge and, as a result, the partnership relationship between client and manufacturer develops.
Farrow says that among the water utility organisations that have invested in vocational actuation training from Auma is Anglian Water. Engineers have been coached in valve and actuator maintenance and staff have benefited from the training being set in the context of the complete automation system.
Designed to reduce downtime and improve efficiency, Anglian Water reports that the courses have given engineers the confidence, knowledge and practical skills to assess on-site maintenance requirements. As a result, the utility's staff are equipped to address and action, as appropriate, situations including the re-setting, repairing and commissioning of valves and actuators, he adds.
Auma's training ethos is that education should be tailored to provide practical guidance to those working in the front line of actuation at water utility organisations, and field engineers provide a highly responsive service if required.
Farrow would encourage managers of water works to invest in training for front line field technicians responsible for valves and actuators. "A practical insight into actuation backed by examples tailored to the engineers' experience is an invaluable aid to the smooth running of the works flow processes.