Preventive Valve Maintenance

Preventive Valve Maintenance

 

Imagine that your area experienced some extreme weather over the past winter - heavy snows and temperatures far below zero.  Then snowmelt occurred suddenly, causing flooding that washed out several roads and took some water transmission lines with them.  As you''re driving to the scene of the repairs, you realize you have no idea where the nearest shutoff valve is ó your system maps are not up to date.  Now what do you do?

 

X Marks the Spot

 

Rather than finding yourself in this situation, you should be proactive.  Know the status quo of your distribution system documentation.  Take a look at existing maps.  Does the map denote valve locations and depths, as well as denoting what portion of the distribution system is affected by a given valve's operation?  Do your files contain information on valves, such as manufacturers, models, types, sizes, materials, types of operators and flanges?  Record information that will help you locate the valve, schedule its exercising and stock replacement parts.

 

If your system does not have current maps, you may want to establish the locations of valves and hydrants using a geographic information system (GIS).  Using GIS coordinates makes locating valves in times of emergency easier ó you don't have to look for landmarks that may have been eradicated in a storm or flood, and you know where to dig if the valve's been buried by debris.  GIS technology has decreased dramatically in price over the past few years and may be affordable for you.  GIS can increase efficiency, cost-effectiveness, and accuracy for your system, but don't forget to protect this data with cyber-security from intrusion by hackers.

 

You may also be able to establish partnerships with other utilities in your area ó perhaps the phone or electric company buried lines and used your distribution valves as markers, and would be willing to share their data with you.  Such partnerships require coordination of the mapping software for compatibility.  But if you are unable to negotiate a partnership and don't want to use GIS, you can still use surveying techniques to map the location of valves and hydrants.

 

Whichever method makes sense for mapping your system, consistency and communication are very important.  Make sure the same symbols are being used for valve types and flanges in all the mapping documentation, and the keys to the symbols appear on all maps.

 

While you're looking at your distribution system, determine which customers would have priority in case of an emergency.  Hospitals, retirement homes or factories that use process water and run continually all might fit the category of critical customers.  Denote which valves control the water supply to your critical customers, and make sure that they are marked as such on your maps.  Think about how water could be supplied to the critical customers during times of emergency.  How would these customers would be affected if a valve failed in the full-open position, the full-closed position, or somewhere in between?  It may also be useful to denote which customers use water the most during certain times of the day or week, such as schools or churches with regular schedules.

 

Exercise Keeps Valves Working

 

Now you're ready to exercise some valves.  How should you progress through your system?  You have to adopt a method that makes sense for the resources you have.  Some ideas you might use:

 

• Check the valves supplying critical customers first, and then the not-so-critical valves.
• Check valves on north-south lines first, and then valves on east-west lines (or vice versa).
• Check the valves on the line closest to your system first from beginning to end, and then move to the next-closest line.

 

If your distribution system covers a small area, you may be able to exercise all of the system valves in a single year.  If your system covers a large area, you may want to consider exercising critical valves every year, and then the rest on a two- or three-year schedule.

 

Valves can be obscured by vegetation overgrowth or street maintenance (also known as, ìMan, those guys paved over EVERYthing!î).  You may want to invest in a locator.  Metal detectors, magnetic locators, and radio transmission units (also known as line tracers) can be used to find metallic pipes, valve boxes and covers.  Metal detectors have an audible signal that changes pitch or volume when the detector senses metal.  They're inexpensive and effective for finding metallic covers and boxes on or near the ground surface, but won't work for detecting deeply buried pipes.  Magnetic locators sense magnetic field imbalances and generally can detect an 8-inch ductile iron pipe buried eight feet deep.  However, they do not detect non-iron metals (like copper).  Radio transmission units detect pipe by transmitting a signal that bounces off buried pipe  and receiving the signal to determine where the pipe is.  Radio transmission units can work over a long distance for continuous metal pipes, but rubber gaskets on the pipes will interrupt the signal.

 

If your system is comprised of high-density polyethylene (HDPE), polyvinyl chloride (PVC), fiberglass, or other non-metallic pipes, metallic tape or tracer wire was probably buried with the pipe at the time it was installed to ease future location with metal tracking devices.  Even if no tracer wire was buried with the pipe, you may be able to locate the lines using a non-metallic pipe locator.   This type of locator uses a transmitter to send small shock waves through the water in the pipe, and a receiver to pick up the resulting vibrations from the soil surrounding the pipe.

 

Once you locate the valve, record its location, bury depth, pipe material, valve material, size, normal valve position (open, closed, or somewhere in between), and which direction the valve operator should be turned to open it.  Most valves work on the "righty tighty, lefty loosey" theory, but some do not, and you can break a valve by trying to open it the wrong way.

 

Pop the valve cover off, and clean the valve box out.  Move the valve from its fully open position to its fully closed position and back very slowly, to minimize the effects of water hammer.  Water hammer can cause mechanical failure, including burst pipes, damaged supports and thrust blocks, and valve trim, packing or gasket failure.  The valve may be exercised manually using a T-bar, an automatic valve operator, or a mechanical valve exerciser attached to your truck.

 

If the valve is corroded into position, a lubricant NSF-certified for use in drinking water systems may be used to help loosen it.  Tap gently on the operator to loosen the corrosion, try the valve, and repeat as necessary.  Open and close the valve slowly a few times to check its operation, note whether the corrosion has damaged the valve to the point where it needs repair, position it as normal operation dictates, and then move on to the next valve.  Line maintenance crews should be notified immediately if a valve is broken, corroded or leaking.

 

Preventive maintenance is the most effective kind of maintenance - it helps you know your system and catch problems before they become catastrophes.