Wednesday, December 31, 2014

Basic Troubleshooting Guide for Watermakers

Your Watermaker is not making good product water anymore. What do you do?

If your water maker (or desalinator) is no longer making good water, there are several possible causes. I will try to break it down into logical troubleshooting steps for you, so you don't spend a lot of money replacing parts or membranes hunting for the solution.

Every desalinator needs to have an operating log of some sort. You don't have to record every time you use it, but it best practice to document the operating conditions when newly installed, at every seasonal startup, after cleaning chemicals are used, and whenever major components are replaced. This information is critical to understanding whether your system is performing as it should.

First of all, every seawater desalinator needs the following in order to function:
  • Filtered feed water, supplied under pressure
  • High-pressure pump
  • Reverse Osmosis (RO) membrane in a pressure vessel
  • Pressure regulator (back-pressure type or needle valve)
  • Pressure gauge to measure RO system pressure
Optional features that make operation and troubleshooting easier:
  • Flow meter for product water
  • Flow meter for feed water or brine (I prefer to measure feed water)
  • Pressure/vacuum gauge to measure feed water pressure
  • TDS meter to measure product water dissolved solids (mostly salt)
  • A method to separate the product flow in multi-membrane systems
  • Helpful, but rarely seen, is a pressure gauge on the feed inlet side of the pressure vessels
  • Thermometer to measure feed water temperature
  • Refractometer or high-concentration TDS meter to measure salinity of feed water

Check Your Calibrations

Before you assume that something is seriously wrong with your reverse osmosis system, make sure you check the calibration of your TDS meter, and inspect all pressure gauges and flow meters.

As the battery in a TDS meter fails, or the electrodes become fouled, the readings can change dramatically. Make sure the electrodes are clean, and the battery has plenty of juice in it. Borrow a handheld TDS meter from a neighbor and compare the reading you get with their's.

Inspect your pressure gauges for damage or bent pointers. Has the damping fluid drained out? Does the pointer move when you tap the gauge? Is there any leakage or rust around the fittings?

Inspect your flow meters for fouling and damage. A dirty flow meter will not be accurate. Most can be taken apart and cleaned. Be careful not to scratch the inside of the float chamber or bend the guide rod. Note that all flow meters that use a "floating" ball or slug need to be installed vertically, and they are read at the widest point of the float.

Check Your Product Water from Each Pressure Vessel

If you have more than one pressure vessel in your system, check the product water flow rate and TDS from each vessel. Typically, the first vessel in the set will yield more product flow at lower TDS than then next vessel. This is because the feed water for the second vessel is brine from the first vessel - lower flow and higher salinity.

Check Your Strainer, Pre-Filters and Boost Pump

High-pressure pumps require the feed water to be supplied under pressure to prevent cavitation. Make sure your sea strainer (you do have a dedicated thru-hull and strainer for your watermaker, right?) is clear, and the sediment filters are clean enough to allow good flow to the high-pressure pump.  Make sure your boost pump is working properly. This is why we strongly recommend a pressure/vacuum gauge between the last pre-filter and the high-pressure pump. Don't make your high-pressure pump "suck" the feed water, or it will soon "suck" at making pressure!

Check Your Feed (Source) Water

Feed Water Temperature

Before you send an email or make a phone call, you need to know what your feed water temperature and salinity are. A simple thermometer will tell you the feed water temperature.

Effect of Feed Water Temperature on Product Water:

  • Increasing Temperature:
    • Higher TDS
    • Higher product flow rate
  • Decreasing Temperature:
    • Lower TDS
    • Lower product flow rate
Feed water temperature can make a significant  impact on your product water flow rate. Reverse osmosis systems are rated based on feed water conditions of 32,000 ppm, 77° F, and operating at 800 psi. At 90° F, you can expect to be making approximately 25% more water, and at 48° F, you should expect 50% LESS!

Feed Water Salinity

Measuring the salinity of the feed water is quite simple with the right tool. The Boundless Outfitters Yacht Services department uses a refractometer to measure feed water salinity. A refractometer is a  simple-to-use device that uses light to measure the salinity. You just dip the end into the feed water source and hold it to the light. Look into the viewer and read the salinity directly. The reading will not be as precise as a high-concentration digital TDS meter, but at one tenth the cost, it is close enough for our purposes.

Effect of Feed Water Salinity on Product Water:

  • Increasing Salinity:
    • Higher TDS
    • Lower product flow rate
  • Decreasing Salinity:
    • Lower TDS
    • Higher product flow rate
Feed water salinity can make a significant impact on your product water flow rate. At 35,000 ppm, you can expect to be making approximately 10% less water, and at 25,000 ppm, you should expect 25% MORE!

If you are cruising and don't have access to a refractometer or high-concentration TDS meter, you can still get an approximate value for feed water TDS. It just requires a some simple math, and some careful measuring. You do need to have a handheld TDS meter for this.

Carefully measure 1/2 cup of feed water. Use a good measuring cup - the Pyrex types used for cooking are not very good, as the thick glass and printed markings make for inaccurate measurements. Molded plastic measuring cups have the markings molded in, so they are more accurate than the glass ones.

In a clean container (a 6 quart pan works well) add the 1/2 cup of feed water to one gallon of distilled water. Mix it well and let it sit for about five minutes. Then measure the salinity with your handheld TDS meter. Multiply the reading by 33 to get the approximate salinity of the feed water.

Check Your High-Pressure Pump

There are components inside your high-pressure pump that are susceptible to wear and tear. Valves and seals are critical elements for ensuring consistent flow and pressure. You should keep a manifold rebuild kit in your spare parts locker. Make sure there pump oil is at the proper level.

Your high-pressure pump should move the same amount of water regardless of the pressure it is producing, as long as it is within its design limits. Measure the feed flow rate with the system pressure at Zero (open your bypass valve, or back off the regulator fully). A feed or brine flow meter is great for this, but if you don't have one,  you can use the empty jug from the distilled water you just used for the last test. You will also need a stopwatch. Measure the time it takes to fill the jug from the overboard (brine) discharge of your watermaker.

Now, increase the pressure of your system to 800 psi (or whatever pressure is appropriate for your conditions). Measure the feed flow rate again. This is why I prefer to have a flow meter measuring feed water before it gets to the high-pressure pump. You just read it directly. This meter should never vary during operation. If you have a flow meter measuring brine discharge, you need to add this flow rate to the product water flow rate to get the total feed flow. I have seen many systems with brine flow meters, and most use different units from the product flow meters. Make sure you convert to consistent units before you add the product flow to the brine flow.

If you don't have a flow meter for feed or brine, you will need to get your jug and stopwatch out. Make sure the product water is being rejected back into the brine stream so you measure total flow.

If there is any difference between the feed flow rate at Zero pressure and the total flow rate at operating pressure, you will need to carefully inspect the high-pressure pump, motor and wiring, and repair as needed. Some small DC-powered watermakers may run slightly slower under load due to resistance in the wiring, and battery draw-down. Please keep this in mind while troubleshooting.

Check the Voltage at the High Pressure Pump

Over time, vibration and salt air can cause increased resistance in electrical connections. The results are reduced voltage for equipment, and temperature rise in electrical components. A further complication for motor circuits is that the current draw increases as well. This is because most electric motors use a constant amount of power (Watts). Since power consumption is the product of voltage and current (P = V x A), if the voltage goes down, the current goes up. Current is what causes heat to build up in areas of high resistance.

Ideally, the voltage measurement at the connections nearest the high-pressure pump motor should be at least 97% of the voltage at the power source in all running conditions. Worst case, the motor voltage should be no less than 90% of the source voltage. Reduced voltage causes motors to run slower, which reduces the flow rate of your high-pressure pump.

Effect of Feed Water Flow Rate on Product Water:

  • Increasing Flow Rate:
    • Lower TDS
    • Higher product flow rate
  • Decreasing Flow Rate:
    • Higher TDS
    • Lower product flow rate

Check Your Pressure Regulator

If your filters, pumps and all of your measuring equipment is in good working order, you can check your pressure regulator. Does the system pressure vary? Some systems use a "set it and forget it" pressure regulator arrangement. While running your system at operating pressure, adjust the regulator up and down (do not exceed 950 psi!), and watch the pressure gauge. Does it increase and decrease smoothly? Can you set it to any pressure and have it hold steady? Most regulators can be taken apart and inspected/cleaned.

Effect of Feed Pressure on Product Water:

  • Increasing Pressure:
    • Lower TDS
    • Higher product flow rate
  • Decreasing Pressure:
    • Higher TDS
    • Lower product flow rate

Check Your Pressure Vessels and Membrane Elements

Make sure all the plumbing is in good condition and free of leaks. A cracked or corroded end cap in your pressure vessel can cause leaks, and on rare occasions, brine contamination of the product water.

If you are having trouble with a new membrane, open up the pressure vessel and check the installation.
  • Verify that the brine seal is installed correctly
    • The brine seal prevents the feed water from bypassing the membrane
    • The sharp edge of the brine seal faces upstream (toward the feed inlet)
    • There should only be one brine seal
    • The brine seal can be at either end of the pressure vessel as long as it is facing the correct direction
  • Inspect the membrane product tubes for scratches or nicks
  • Inspect the o-rings, and replace as needed
  • Use proper o-ring lubricant for assembly
If the brine seal is not oriented correctly, feed water can bypass the membrane. This will reduce product flow rate and increase TDS.

Be very careful when changing the product water o-rings (the ones on the inside of the end plug, where the membrane product tube enters). If you scratch or nick the grove where the o-ring sits, you can create a path for brine to contaminate the product water.

Effects of Failures Inside Pressure Vessel:

  • End Plug Crack or Corrosion
    • Higher TDS
    • Higher product flow rate
    • Leaks
  • Brine Seal Damaged or Installed Backwards
    • Higher TDS
    • Lower product flow rate
  • Product Water O-ring or O-ring Groove Damage
    • Higher TDS
    • Higher product flow rate
  • Membrane Product Tube Damage
    • Higher TDS
    • Higher product flow rate
  • Membrane Failure
    • Higher TDS
    • Higher product flow rate

Conclusion

Reverse Osmosis Watermakers are complicated systems that require careful maintenance. Many cruising boaters are quick to blame the membranes if the product water flow is reduced, or TDS increases. As you can see from the above troubleshooting tips, there are several possible causes for reduced (or increased) product flow and increased TDS.

Happy Cruising!
Tim Allen

Monday, December 15, 2014

Dropping the Hook - Wrong Ways and Right Ways to Set Your Anchor

Anchoring: The Most Important Part of Boating

After purchasing our sailing catamaran, Unbound, out of a charter fleet in BVI, we spent many weeks enjoying the local fun and fare that the British Virgins have to offer. Our cruising carried us through the peak holiday season, between Christmas and New Year. We made shocking observation during that time - many boaters do not know how to properly anchor!

After observing this fact - charter boats dragging anchor everywhere, bumping into other charter boats and private yachts - we decided to watch the charter companies and their "checkout" process. We saw that the charter fleet captain would take a new charter guest on a sea trial, verifying that the captain knew enough to safely operate the charter boat. They would raise and lower sails, tack this way and that, start the engine, and use the VHF radio. Not once did we hear the clatter of a windlass, or see any mention of anchoring. In the BVI, charterers are encouraged to pick up one of the abundant public rental moorings.

Moorings in the BVI are great. There are lots of them in all the best hot spots and popular anchorages. That is until Christmas. It seems every boater and wannabe cruiser on the planet finds their way to the Caribbean for the holiday week. Available moorings are now scarce, and suitable anchorages fill up rapidly. This is where the fun begins. Overnight anchoring in the Caribbean is not the same as dropping your hook to have lunch off the Brewsters on a clear day in Boston Harbor.

During winter, Trade Winds blow pretty steadily and predictably throughout the Caribbean. At night, the winds change dramatically around mountainous islands. Differential cooling of the mountain slopes create lots of strong updrafts and downdrafts that translate to sometimes wildly shifting winds near shore. Improperly anchored yachts are at the mercy of these winds.


The Wrong Way

The "Dumper" (Very Common)

We have seen many boaters make this common error - dropping a pile of anchor chain or rode right on top of their anchor. Boaters simply place their bow over their chosen spot and dump anchor and chain. Sure, they have calculated how much chain or rode to lay out, and, hopefully, their rode is marked in some way so they know how much has been released. The problem with this method is that the pile of rode fouls the anchor, and chain may snag on an anchor fluke while the anchor is being set. This may hold for a while, but creates a dangerous opportunity for the anchor to trip, and likely have trouble resetting.

The "Short Story"

We have all seen this: A boater drops anchor and lets out just enough rode for the anchor to stop the boat from drifting. This is great in in 5 knots of wind from a windward shore. Not so great when the wind or tide shifts. The anchor will almost always trip and not reset.

The "Long Haul"

Some boaters are firm believers in the More is Better philosophy. They lay out lots of anchor rode - sometimes all of it - and create a problem for all the other boats in the anchorage. Keep in mind that the placement of your anchor roughly determines the center of a circle that your boat will swing in. You may think that 150 feet of chain is a good idea, but if every other boat in the anchorage is riding on 75 feet of chain or rope, you create a hazard when the wind or current shifts, because your boat will swing in a much larger arc than the rest.

The "Cowboy"

We saw a person on a small boat do this once: The boater took his little Danforth-style anchor by the chain, and whirled it around like a lasso. Then threw it in the general direction where he wanted the anchor. He immediately took up all the slack (no time for the anchor to dig in) and tied the rode to the bow cleat.

The Right Way

Select the Center of Your Anchor Circle

Carefully review the anchorage, and have an understanding of the wind and current changes that will take place while you are anchored. Boats with shallow keels and high windage (like powerboats) tend to align with the wind, whereas boats with deep keels and low windage tend to align with the current. Pay close attention to your neighbors and any underwater obstructions that may be within your swing circle.

When in Rome

Study the anchoring techniques of the boats that are near your selected spot. Are they using one anchor or two? Are some boats on moorings? Ideally, you want your boat to swing in a similar manner to the other boats in the anchorage. Do what they do, and you should be fine. Boaters with local experience are a great resource to learn the best way to keep your yacht secure at anchor.

Lay Your Rode Carefully

Don't be a "Dumper!" Approach your anchoring spot slowly, and stop the boat with the bow over where you intend to set your anchor. Lower your anchor until it just touches bottom, then allow the boat to slowly drift back while laying chain and rode. Pay out the rode at the same pace as the drift. Don't let one get ahead of the other! Your rode should drop almost straight down from the bow as you lay it out.

Use Proper Scope

Scope is the term used to refer to the ratio of the length of chain and rode to the distance from the bow roller to the bottom. For example, if the water is 10 feet deep, and your bow roller is 5 feet above the water, you will need to pay out 105 feet of chain and rode to achieve a 7:1 scope [(10 + 5) x 7 = 105 feet]. The amount of scope you need depends on the wind and current conditions, they type of bottom, and your ground tackle. Rope and chain rode requires more scope than all chain rode.

Set Your Anchor

Lay out some extra rode for setting your anchor. If you plan to ride your anchor at 5:1, lay out 6:1 or 7:1 for setting the anchor. Setting the anchor allows the flukes of your anchor dig in to the bottom. Sailboats can do this more quickly than powerboats, because sailboats can "back down" on the anchor. Powerboats must wait it out.

Sailboats:

On a sailboat, once the boat's drift has taken up the slack in the rode, gently put your engine in reverse at idle. Line up a "range" using a two fixed points off to port or starboard, one further away than the other - a piling and a rock, a tree and a spot on the beach, a parked car and a building, etc. Watch your range points closely while the engine is in reverse. When they no longer appear to be getting closer to, or further from, one another, you have stopped moving. Your anchor is now set.

Powerboats:

Since powerboats tend to create a lot of thrust in reverse, they must be patient and wait while wind and waves set the anchor. In calm conditions this can take more than an hour. It is best to set a waypoint on your chartplotter and watch for drift from this point.

After your anchor is set, haul in the rode until you are at the proper scope.

Secure Your Rode to a Bow Cleat

Your windlass is not designed to take the load of your boat riding on anchor. It is just designed to raise and lower it. Your anchor rode should be securely fixed to a cleat at your bow.

Tricks for All Chain Rode

Use a Snubber or Bridle

All chain rode is noisy when tied off on deck. As the boat gently swings at anchor due to wind and waves, the chain clatters as it shifts around in the bow roller. No big deal when you are having lunch, but this becomes quite annoying for someone trying to sleep in the v-berth!

A snubber is a short length (usually 10 to 15 feet) of nylon rope appropriately sized for anchor rode. At one end, a chain hook is spliced on. There are many types of chain hook available designed for this purpose. A bridle is similar, but involves a longer nylon rope with the chain hook in the middle.

Secure the hook to your anchor chain and the bitter end of the snubber or bridle to the bow cleat. Let out more chain until the snubber or bridle takes the load. Now sleep better!

Cut Down on Swinging

Some boats just seem to swing like crazy while anchored. Subtle changes in wind cause high windage boats to swing significantly, especially if the boat has a shallow keel. A trick we learned while cruising on our sailing catamaran was to lay out a lot more chain once the bridle was in place. When the boat is fairly settled in place, let out enough chain to make a pile on the bottom, right below the bow roller. You will be amazed how much this keeps the boat from swinging!


Conclusion

Your anchor and ground tackle are like the brakes on your car. They are the most important safety equipment! Whether you are just lazing about in a peaceful cove, or holding your yacht off a lee shore, proper anchoring technique is essential to safe boating. Your crew and guests, and your insurance company, will thank you.

Happy cruising,
Tim

How to Preserve "Pickle" Your Watermaker Membranes

Preserving your reverse osmosis membranes for long-term storage is quite easy, and we strongly recommend this procedure if you will be unable to flush your watermaker with fresh water for more than three weeks. This procedure will protect your membranes for up to six months. If you wish to keep your system preserved for longer than six months, you will have to thoroughly flush, then re-preserve your system every six months. Extended storage can cause some rubber and plastic parts to decay, so don't over do it. Membrane preservative (or storage chemical) is available in two forms:
  • Cartridge Form
  • Powder Form (bulk powder)
The type of preservative you use depends on your system design. I will discuss how to use both types of pickling chemical.

Cartridge Form Preservative

First, lets discuss how to use the cartridge form of storage chemical. This type requires your desalinator system to have a recirculating loop to cycle the brine discharge back into the water inlet before the low pressure boost pump. Some watermakers (like those made by Village Marine) include a valve that creates a recirculation loop. Village Marine calls this valve the "cleaning valve." Here is a sample plumbing diagram for Village Marine Little Wonder Modular watermaker:
Watermaker Plumbing Diagram
Note the cleaning valve, and how it returns the discharge to the boost pump inlet. Before preserving your membranes, first thoroughly flush your watermaker with fresh water. Then remove your prefilter from the housing and discard it. If you have two prefilters, remove the 20 micron filter. Install the preserving cartridge in place of the prefilter. Note that the cartridges we sell fit both standard and "Big Blue" 10" housings. Switch the cleaning valve to the cleaning (recirculate) position. If you do not have a cleaning valve, disconnect the brine discharge hose and connect it to the boost pump inlet.

Close the seacock. Make sure the product water will not go into your tanks. Also, make sure the system pressure is reduced to ZERO before running with chemicals in the system. Use your fresh water flush valve to purge any trapped air from installing the preserving cartridge. Run your desalinator for 30 minutes to thoroughly disperse the preserving chemical. Shut it off, and leave it for up to six months!

Powder Form Preservative

Now let's talk about how to use the powder form of the preserving chemical. Use this method for larger desalinators and systems that do not have a recirculating loop. After thoroughly flushing your watermaker with fresh water, disconnect the brine discharge hose and run it to a clean bucket filled with fresh, dechlorinated water. You can use RO product water or tap water that has been run through a carbon filter.

Disconnect your boost pump inlet hose (make sure you close the seacock) and run it to the same bucket. Make sure you don't allow the boost pump to lose its prime. Add the preserving chemical to the bucket so that you end up with a 2% solution overall. The preservative needs to be 2% by weight of the total water in the system, not just the bucket! Here is a quick way to estimate the total water in your system:
  • Start with the water in your pressure vessels:
    • 2.5 x 21" Membranes - About 3 Lbs each
    • 2.5 x 40" or 4.0 x 21" Membranes - About 6 Lbs each
    • 4.0 x 40" Membranes - About 15 Lbs each
  • Then add the water in your prefilters:
    • 2.5 x 10" Standard Housings - About 2 Lbs each
    • 2.5 x 20" Standard Housings - About 4 Lbs each
    • 4.5 x 10" Big Blue Housings - About 5 Lbs each
    • 4.5 x 20" Big Blue Housings - About 10 Lbs each
  • Then add the water in the plumbing system and your bucket:
    • Plumbing - About 1-2 Lbs
    • Bucket - 8 Lbs per gallon
For example, a system with two 2.5 x 40" membranes and two 2.5 x 10" prefilter housings will have about 17 pounds of water, not including the bucket. If you add two gallons for the bucket, the total water in your system will be about 33 pounds. Calculate the amount of preservative powder to use:
Total Water (Lbs) x 0.02 = Preservative (Lbs) In our example, 33 Lbs x 0.02 = 0.66 Lbs, or 2/3 of a 1 Lb Jar
Carefully mix the preservative chemical in the bucket of fresh water. Wear safety goggles and a mask, and work in a well ventilated area. This stuff is pretty harsh. Set the system pressure to ZERO, and make sure the product water will not go into your tanks. Run your watermaker boost pump and feed pump to recirculate the preservative for 30 minutes.

Freeze Protection

To preserve your watermaker for cold climates, it is best to use Food-Grade Propylene Glycol (Non-Toxic Antifreeze will work) to protect your system. For best freeze protection, a 60% propylene glycol to 40% water ratio should be used. Calculate how much PG to use by the method above. Please note that PG alone will not prevent organic growth. Non-toxic antifreeze contains some growth inhibitors, and will provide protection of your desalinator for up to six months.

Recommissioning After Storage

After long-term storage, you will need to flush the chemicals out of your watermaker thoroughly before making any product water. Switch your cleaning valve to "Run," or reconnect your brine discharge and boost pump inlet hoses. Replace your prefilter(s) with new, and replace your fresh water carbon filter. This is a good time to consider changing your high-pressure pump oil, also.

Open the seacock, and run your desalinator at ZERO pressure, making sure the product water (if any) gets dumped overboard. Let the system run at ZERO pressure for 30 minutes to flush the storage chemicals out of the nooks and crannies. Slowly increase the operating pressure to 800 PSI (or to the maximum rated product flow if you are floating in brackish water). Make sure the product water is dumped overboard, and let the system run for another 30 minutes.

Compare your product water quality and flow rate with your benchmark values from when the membranes were new. (You did write that down, didn't you?) Write the new values in your watermaker log. After adjusting for temperature and salinity differences in the raw water, if your product flow rate has reduced by more than 10% you should run a cleaning cycle - first with organic detergent, then with scale remover. The procedure is almost exactly the same as for preserving your membranes.

Happy cruising,
Tim

Tuesday, December 9, 2014

An AIS Receiver Can Save Your Life!

Cruising Old School

While cruising the Caribbean, we really enjoyed sailing through the night. The tranquility is empowering, and the spookiness is exhilarating! Our biggest concern was trying to figure out what the various tankers, freighters and cruise ships were doing. We were cruising "21st Century Old School," with a GPS chartplotter and a VHF. No radar. No AIS. No loud hailer.

One night, while sailing in the Northwest Providence Channel heading to Florida, we encountered a container ship on the horizon. No big deal, we though. We could see the white and red navigation lights, so it was going to pass us on our port side. Just to make sure we were seen by the helmsman, we had a habit of turning on the deck light to illuminate our sails. Now we didn't leave the deck light on - that would ruin our night vision.

After continuing on our course for about 15 minutes, I scanned the horizon again. Now I could see white and GREEN navigation lights! The ship had changed course, and would now pass to our starboard. It was still about 10-12 miles away, so that was not a big deal. We were ghosting along at about 6 or 7 knots. I adjusted our course a few degrees to the left to give us more room.

Another 10 minutes passed and it was time to scan the horizon again. The ship is much closer now, probably 5 or 6 miles, and I could see the white mast light, as well as BOTH RED and GREEN lights! It was heading straight for us!! I turned on every light we had - anchor light, steaming light, deck light, cabin lights and even a flashlight to make us more visible. Then I got on the VHF radio. Calling on channel 16 I called a PAN-PAN with our name, position and heading, and attempted to get in touch with the container ship. Of course, not knowing the name of the vessel, it was like yelling "Hey You" in Times Square. Nothing.

Now it was time to grow concerned. We have a rogue container ship bearing down on us, and we have no way of raising them on the VHF. For all I know English wasn't even spoken on board. I cranked up the engines and turned 90 degrees to the right, heading for deeper water and trying to put some distance between us and the ship. It sure would have been nice to be able to call the ship by name.

Enter Our Hero - Automatic Identification System (AIS)

This where an AIS receiver would have been handy. AIS is a technology that commercial vessels and large yachts use to broadcast their particulars to other vessels using VHF frequencies. The broadcast includes their position, heading, speed, and, importantly, Vessel Name. This would have helped us tremendously with our encounter above. All AIS-equipped vessels in range will be displayed on your chartplotter. The details of each vessel is visible by clicking on the screen icon. If we had known the name of the container ship, we very likely would have been able to have a conversation about their intended course.

One Better - Digital Selective Calling (DSC)

One other key piece of data that is broadcast by commercial vessels and large yachts is their Maritime Mobile Service Identity (MMSI). This key piece of information about a large vessel allows other vessels to call them like a telephone. If your VHF radio has its MMSI number configured, you can use its DSC features to call another vessel directly. Just like calling them on the telephone. Punch their MMSI into your DSC-capable VHF, and you can make a direct call to that vessel. Now that is the way to cruise! With some integrated VHF/Chartplotter systems, you can even make the DSC call with just a few taps on your chartplotter.

Modern technology is wonderful at making cruising safer and more enjoyable. However, there is no substitute for a diligent and watchful captain. Keep your eyes peeled at all times, and operate your boat defensively. Nobody wins in a collision.

Happy cruising,
Tim

Monday, December 8, 2014

Vented Loops Help Prevent Your Boat from Sinking

As you already know, Vented Loops are an integral part of any plumbing system that uses a thru-hull connection below the waterline, and has the potential for siphoning water into the boat.

The most common application of a vented loop I have seen is in the black water discharge for holding tank pump-outs. We all know that you should NEVER pump your holding tank into inland lakes or waterways. That would be disgusting! Take your boat out past the 3-mile limit before pumping. Some engine exhaust systems also employ vented loops.

Other applications for vented loops, less commonly installed, are engines and generators mounted low in the boat. Many installers don't even give it a second thought - they install the engine or generator with the factory plumbing. Engines and generators come from the factory with the raw water pump outlet going directly to the heat exchanger using a short, often pre-molded, hose. Please don't trust this setup if your engine or generator will be mounted near or below the waterline.

Recently a service client of Boundless Outfitters experienced a boaters worst nightmare - his sailboat sank at the dock, right behind his house! Now, he is not blind, nor inattentive - he just doesn't use the boat much. The boat didn't hit bottom. I say it "sank" because it flooded with raw water beyond the capacity of the bilge pumps (more on that later). Fortunately, our client saw the boat riding low on her waterline and investigated. He immediately installed a portable sump pump to remove the excess water and bring the boat back to her proper waterline. Then he call us to investigate the cause.

What I found was surprising. The entire interior of the boat was coated in black goo up to about one foot above the cabin sole. It took a while to determine what the mess consisted of. I set about looking into all bilges looking for water flowing into the hull. I found nothing! I then looked at the main engine (a turbocharged Yanmar, 4JH4-TE, installed as a re-power) and found water dripping from the air intake screen near the turbocharger. At first I thought maybe the water accumulated in the air intake when the water level rose, and was still dripping. So I pulled the screen off, and saw that the water was still coming from the crankcase vent hose! Drip-drip-drip. This can't be good!

As it turns out, raw water had found its way past the raw water pump impeller and filled the water-lift muffler. It then proceeded to fill the engine through the open exhaust valves. (By the way, this is why you don't keep cranking your engine if it fails to start - the muffler fills with water!) This particular boat is a center-cockpit ketch, with the engine below the cockpit sole, very low in the boat. Too low, as it turns out.

After filling the engine with raw water, the overflow ran into the bilge. This should have been no problem for the bilge pumps to keep up with - it was just dripping quickly as far as I know. Now it occurred to me what the black goo was - ENGINE OIL! Engine oil, being less dense than water, floats. When the engine began to fill with raw water, the oil was the first thing to overflow. Turns out bilge pumps hate engine oil. They failed. Now it was just a matter of time before the boat began to fill with raw water, carrying that slick of black, gooey engine oil on top, coating everything that got wet with a film of used engine oil. This was a total mess. Not to mention the damage to the engine from being filled with salt water for such a long time.

Root cause: The engine is installed completely below the waterline. This engine, that was installed brand new about five years ago, used the factory hose between the raw water pump and heat exchanger. The installer did not consider the consequences of water getting past the pump with the engine stopped. The water did not siphon into the engine, it just slowly filled because it was below the waterline.

Lesson learned: Install a vented loop! The loop needs to be in the portion of the system that gets pressurized when the system is operating. It cannot be installed in the suction side of a pump, as it will do its job and let air in. The hose connecting the water pump to the heat exchanger on a main engine or generator must be extended to a vented loop well above the waterline. Optionally, a vented loop can be installed after the heat exchanger if there is a hose between the heat exchanger and the exhaust elbow. Check your engine installations to see if the raw water pump and heat exchanger are near the waterline. If they are, install a vented loop downstream of the pump. If you can't install a vented loop where needed, close the seacock every time you moor, and place the engine key near the valve handle as a reminder.

You, or a professional technician, should review all your boat's plumbing installations on a regular basis. Inspect for worn, kinked or cracked hoses, rusted hose clamps, leaks and so on. Make sure all hoses are the proper type for the application. Exercise all your seacocks at least twice per year. If any appear questionable, replace them at your next haul-out. Don't forget about your fresh water plumbing. That is a subject for another article...

Happy cruising,
Tim

Wednesday, December 3, 2014

Crevice Corrosion Can Ruin Your Watermaker!

You may have heard of Crevice Corrosion. Perhaps you  have confused it with galvanic corrosion (electrolysis), but the chemical process is quite different.

Without explaining all the chemistry (as some of it is beyond my Chemistry 201 studies!), I will explain what happens. Essentially, Crevice Corrosion occurs to Stainless Steels when in the presence of seawater that has been depleted of oxygen. How does this happen?

Seawater that is trapped against stainless steel equipment loses its oxygen over time by causing oxidation of the materials it is in contact with. Crevice corrosion does not require dissimilar metals to occur. In fact, it can even occur where a plastic part is clamped to a stainless steel part (or even painted stainless steel!), if seawater is allowed to become trapped between the parts.

The result looks a lot like galvanic corrosion, but is not caused by the same problems.

Common boating equipment that frequently suffers from crevice corrosion is trim tabs. I have seen trim tabs that have been properly maintained, with zincs replaced regularly, fall prey to crevice corrosion. This usually occurs between the hydraulic ram base and the tab itself. You should inspect yours, and always make sure that the components of your trim tabs are well bedded in a waterproof compound (3M 4200 or 5200 or similar adhesive). Don't trust silicone for this critical task.

Another piece of equipment that we see suffering from crevice corrosion is your watermaker high-pressure pump and high-pressure fittings. This is due to inadequate fresh water flushing of your desalinator. Would you believe that some watermaker manufacturers still build systems with no easy method for fresh water flushing?

The potential for crevice corrosion is why I personally prefer Titanium Alloy or Nickel Aluminum Bronze (NAB) for high pressure watermaker pumps.

To learn more about crevice corrosion, please see this Wikipedia article on crevice corrosion.

Happy cruising!
Tim

Welcome

Ahoy! Welcome to Boundless Outfitters' new Blog. While I am more of a technical guy, I will attempt to educate and entertain you with stories and informative articles. Wish me luck - I hope I don't put you to sleep!

Tim