The maintenance checklist for a plant shutdown can sometimes look intimidating and, in the face of a short timeline, unnerving. For aging facilities, year over year, the maintenance checklist becomes longer, and completion becomes harder. As staff is faced with greater challenges, bringing in specialists to help complete certain tasks is almost imperative. All facilities need water to operate, and a water treatment specialist should be one of the first outside contractors to be introduced to the shutdown team.
Inevitably, once maintenance has begun, other issues and concerns can arise. When it comes to the water system (steam boilers, cooling towers, pretreatment systems, etc.), these issues almost always need to be addressed right away to retain production and avoid costly damage to equipment. Waiting to call a water treatment specialist only during emergencies can be expensive. Having a scheduled water treatment specialist integrated into the plant shutdown plan shortens the maintenance checklist so internal staff can focus on other things. It also promotes faster and safer diagnoses and resolutions that mitigate costly unscheduled downtime.
“Every plant or facility needs water in some capacity to function,” explained Mahon Corkery, the regional manager at Pace Solutions. “A water treatment-related emergency can raise the cost of service calls by 2-3 times, garner a premium for parts and cause unscheduled downtime. Shutdown procedures should help prevent these inflated expenses.”
Water system issues aren’t always what they seem
In the face of increased corrosion, heavy deposition, scale, microbiological fouling and system leaks, operators often find themselves asking, “If a system was working fine for years, what changed?” There are several reasons:
- Higher dissolved oxygen content in the treated water.
- Changes in feedwater chemistry.
- Mineral or microbiological content and concentration.
- Aging or faulty equipment (seals, pipes, and valves).
- Greater demands on the system due to weather or increased production.
These causes start affecting the system through biofilm growth, corrosion, scale and accumulating deposits. Generally controlled by water treatment products, changes in feedwater or system conditions can throw off the ratios of treatment products, rendering them less effective. Not only does this affect system health, but it also greatly reduces system efficiency.
Why would feedwater quality change? Climate change has proven to have drastic effects on water quality, particularly in times of reduced snowpack. Upstream issues such as industrial monoculture farming and mining/quarrying can increase the sediment levels, mineral constituents and chemical content. Changes in water sources, such as moving from surface water to deep aquifers will result in drastic changes in water chemistry and quality. Lighter permitting standards and loosened wastewater runoff regulations can also impact the water table for surrounding communities.
Keeping on schedule
Merely relying on accrued work orders to determine the maintenance checklist is a good way to discover issues that throw the schedule off by days, perhaps even weeks. Thorough inspections by outside professionals several weeks before a scheduled production break can introduce new eyes, help in planning the full scope of the shutdown, inform proper part orders and reduce the total downtime.
A major cause of delays that extend downtime is waiting for vital replacement parts. Generally, these are ordered beforehand, however, not all issues are able to be anticipated. Having a water treatment specialist involved in the shutdown might lead to a faster solution. They have the skills and knowledge to provide support to operators and contractors or perform much of the maintenance and repair work on water treatment equipment.
For example, the technician can perform maintenance on dosing systems from replacing pump diaphragms and liquid ends to tubing and injection quills. Upgrading controllers, or installing, programming and commissioning new ones can take excessive time when done by untrained personnel. This also applies to replacing ion exchange and other pretreatment equipment controllers, heads and media, as well as programming and commissioning them. If reverse osmosis or nanofiltration membranes require cleaning or replacement, the technician can quickly and efficiently complete that task. By having the water treatment specialist perform this work, operators are free for other shutdown tasks while having the peace of mind that the job is done properly.
Water treatment: Planning for a shutdown
According to Corkery, the moment the water leaves the ground to the moment it is released to the municipal sewer lines is the space where water treatment operates.
“After integrating with the internal team to conduct the inspection and prep a shutdown action list, we work with supervisors to create a maintenance schedule that coincides with their timeline,” he explained. “We also meet with scaffolding, plumbing and electrical contractors to coordinate workflows. We go as far as reviewing safety permits to create lockout procedures and present a workplace safety plan.”
With a team of as many as five technicians, the water treatment staff will check nearly every inch of the system using a series of inspection and testing methods, applying years of experience in the field to identify potential issues.
Treatment product pumps, injectors, tubing and valves can succumb to time, particularly if they are not properly inspected and maintained. Containment tanks and storage tanks can display signs of corrosion, blockages, leaks and other physical damage that can cause danger to operators, waste products, increase costs and detrimentally affect the dosing rates leading to insufficient treatment. Probe and chemical injection piping racks need to be inspected and cleaned.
Often, valves that may have never been turned or resealed slowly corrode without showing external signs of degradation. Corrosion monitoring stations can detect some of these issues, but they too need inspecting for proper operation as well. On the other hand, deposits can form that will prevent proper seating of valves, will slow velocity through the piping, and reduce heat transfer efficiency in heat exchangers. Clean-in-place (CIP) systems can remedy some of these issues by using a mix of chemicals, heat and water to clean process pipes, vessels and machinery. The CIP reduces or eliminates the need to dismantle parts of the system.
What is discovered when checking and maintaining filtration systems may impact what needs to be done during a shutdown. Changes in feedwater quality can cause the media in carbon, multi-media, softeners or other filtering units and the membranes in reverse osmosis systems to foul sooner, leading to reduced efficiency, production rates and pressures. If the water quality has changed dramatically, resetting the proper maintenance schedule for these units requires testing and monitoring. Ion exchange units may need a deep cycle clean or require resin replacement to ensure throughput and exchange capacity is maintained.
Case Study: Evidence in the boiler
An oil and gas facility in Alberta planned a shutdown with all the proper checklists and schedules in place. Managers included a team of special technicians from the site’s water treatment servicer to assist with the maintenance, cleaning, refurbishing and installation of equipment related to the boiler system.
Although a specialist was invited to do a preliminary inspection, they were unable to do a full assessment until the system shutdown had fully drained the boiler and pipes. Once that was accomplished, technicians were able to get inside the vessels.
“If we have a guy who’s small enough, we get in there,” Corkery said. “Nothing beats a close inspection with the naked eye. If our participation is consistent, then we are able to take pictures and compare them to the previous shutdown. We can take samples and really get a clear idea of the scope of any issue.”
Climbing inside the deaerator storage tank of the boiler, technicians found dark red particulates at the bottom. This indicates excessive iron corrosion of a system component. A specially formulated polymer blend is dosed into system water to sequester dissolved solids and iron, holding them in suspension to be flushed from the boiler during regular blow downs. In this case, the amount of particulate matter exceeded the amount the treatment polymers being used were intended to treat. This resulted in particulates deposited in the condensate tank to be carried with the feed water to the boiler as well.
If left unaddressed deposits would collect on the boiler internals diminishing heat transfer efficiency and promoting under-deposit corrosion. Corrosion can cause pipe, tube walls to succumb to system pressure, potentially leading to a sudden rupture. Heated water or steam can escape, causing expensive leaking or flooding. In the case of steam boilers, catastrophic tube failures can lead to explosions and if staff is nearby, a serious injury can result.
Technicians walked the entire system, testing and searching for signs of corrosion. After a thorough examination, they discovered the problem was coming from a corroding valve to a bypass line. These lines are used for maintenance if there are issues in the main feedwater line system that requires other pretreatment equipment to be temporarily by-passed.
Bypass lines commonly remain flooded and this valve had likely stayed in a single position for several years without showing any outer signs of corrosion. On the bypass side of the valve, the water lacked corrosion-prevention treatment, causing the valve to corrode virtually imperceptibly from the bypass side.
The team diagnosed why it happened, replaced the valve, and repaired any further corrosion around the area. They then thoroughly checked the other valves and recommended maintenance procedures and schedules in the final report to ensure the same thing didn’t happen.
Conclusion
In many industries, scheduled plant shutdowns are unavoidable and necessary. Some maintenance activities are just too dangerous or impossible to perform during production. For water systems, some tasks can be performed without water flow or draining the system, but not many.
“A proper shutdown procedure for water treatment requires an experienced supervising technician who knows how to identify problems, anticipate issues, and plan a project schedule that integrates well with the other maintenance teams,” Corkery concluded. “They can work closely with internal water specialists or maintenance managers to ensure a smooth shutdown with no extensions or delays.”
Brad Allen is senior technical services manager at Pace Solutions, a water treatment and energy conservation company.
