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stuffing box corrosion

Allowing the packing box to drip helps keep the water in the shaft log from becoming oxygen depleted. This may be all that is required, but each time the nut is tightened, it squeezes and compresses the packing further, forcing it tighter around the shaft. Even more disastrous, it puts an unattended boat at risk of sinking. 6. The EagleBurgmann ABC of Mechanical Seals contains more than 2.000 key-words related to technology and periphery of mechanical seals. Dutch windmill water pumps were among the first to use stuffing boxes. Bearings overheat 16. This stuffing box leak detector is of simple construction with corrosion resistant parts. It consists of a threaded sleeve and a hollow nut, through which the prop shaft passes. Our new-to-us 2012 R29 came with some engine corrosion, presumably from stuffing box spray. Periodically spraying the stuffing box with a corrosion inhibitor will reduce accumulation of this material and make service easier. Most stuffing boxes are designed to accept three rings of packing.  The joints should be oriented 120° apart from each other. While it may look ordinary, the hose used with conventional stuffing boxes is, or should be, proprietary. These joints should be spaced 120° apart, or at the 12, 4 and 8 o’clock position. If necessary, this entire procedure can be carried out while the vessel is afloat.  Once the packing nut is removed simply secure several wraps of a rag around the stuffing box where the shaft exits to temporarily stem the flow of water.  Water will leak during reassembly; however, provided you work quickly it will be comparatively little. If your stuffing box leaks … Bronze will nearly always develop a green patina, or verdigris; and stuffing boxes are no exception, this is a completely natural and harmless phenomenon.  Heavy verdigris, however, can make disassembly and adjustment difficult.  Periodically spraying the stuffing box with a corrosion inhibitor will reduce accumulation of this material and make service easier.  For fiberglass vessels, in order to mitigate the effects of stray current corrosion, stuffing boxes should be connected to the vessel’s bonding system using a minimum of an 8AWG wire.  Make certain the ring terminal is not located between the primary and lock nuts on the tie rod type stuffing box; nor should it be located between the hose and stuffing box body.  The installation should utilize heat shrink tubing, conductive grease and corrosion inhibitor to maintain a low resistance and durable connection. I recently wrote an editorial for a marine industry publication, lamenting the lack of a formal marine industry apprenticeship in the United States.  While there are schools and programs here and there, there is nothing nationwide, nothing unified or standardized as it is elsewhere, in other countries with a mature marine industry like the one here in the United States. Use the search box above for best results, Chesapeake, VA – week of December 6, 2020. Tee Base Inverted Stuffing Box (IVSBT) Combines IVSB and cross-tee with 1-in. Bronze rudderstocks, particularly those that have seen many sea miles, are also known for wearing, or hourglassing, within stuffing boxes, where the flax rides against the stock. Shaft sleeves are cylindrical metal tubes designed to protect pump shafts from erosion, corrosion, and wear at critical points, such as at the stuffing box. Do Twin Sheets Better Control the Mainsail? A stuffing box—also called a stuffing gland, packing gland or packing box—forms a seal between the prop shaft and the hole in the hull through which the shaft passes while allowing the shaft to turn freely. Stuffing Box Basics. Next month I’ll delve into the intricacies of dripless stuffing boxes. 13 posts • Page 1 of 1. Chronically leaking stuffing boxes lead to more than just wet bilges.  These clamps are seriously corroded as a result of regular exposure to seawater. Our industry, and a lot of other industries, is faced with finding people to fill the jobs.”  Â. For fiberglass vessels, in order to mitigate the effects of stray current corrosion, stuffing boxes should be connected to the vessel’s bonding system using a minimum of an 8AWG wire. bottom connection; 3-in. At launching and while underway check for leakage, which to a small degree is normal.  The vessel should be slowly run up to cruising speed, roughly three fourths of wide open throttle, all the while monitoring stuffing box temperature and water flow/leakage,  and operated there for fifteen minutes.  If all is well, run up to full throttle for approximately five minutes, again while monitoring stuffing box temperature. Only boats with inboard engines have stuffing boxes. The more you tighten either type of gland, the more the packing gets compressed against the shaft. Save my name, email, and website in this browser for the next time I comment. Ninety percent of all sailboats with auxiliary inboard engines have a flexible stuffing box with traditional packing gland that usually goes unattended until it begins to leak, usually at the worst possible time.   Anything more than that which is required to keep a stuffing box cool is simply leakage. The stuffing box is connected directly into the well production string, for example, by threading the lower end of a pack off assembly into a conventional flow tee or pipe fitting. 8 - Good Corrosion Resistance: corrosion resistance sulfur jar mandrel; stuffing box and other products, our advanced product's corrosion-resistance and wear-resistance have reached the international advanced level. “The Marine Retailers Association of the Americas is listening to dealers who increasingly express concern about a workforce shortage. Equipped with a cone-shaped bottom insert and integral O-ring that directs pressure to the inside of the seals instead of the outside. In cases where maximum corrosion resistance is required—stuffing box and bilge pump hoses—then the higher price of 316 alloy clamps is easily justified.  Bronze studs, on the other hand, are virtually immune to this phenomenon. A stuffing box is an assembly which is used to house a gland seal. High speed vessel installations will usually have a water injection hose plumbed to the engines raw water cooling systems, which helps reduce heat generated between the two contact surfaces. To see this page as it is meant to appear, please enable your Javascript! If unchecked, the fluids will cause corrosion pits, deformities and eventual failure of the polished rod… The standard adapter will fit most stuffing boxes in use in the United States, and custom adapters can be special ordered to fit other stuffing box designs. bleeder; Eliminates one-threaded connection; Lower profile than classic models; Side outlets: 2-in. Corrosion and leaks are common problems you’ll encounter when inspecting your stuffing box. Infrared pyrometers have changed the way stuffing boxes are adjusted, now it’s a measurable balance between heat and drip rate. Packing consolidates in the stuffing box due to loss of packing volatiles at high temperatures. It is not uncommon to see stuffing boxes leak at a much higher rate. Good propeller shafts don't break because they don't corrode. for all Sectors of Industry. What are the consequences of this leakage? Simple stuffing box splash guard. It is important that the polished rod be protected to the fullest extent possible from the corrosive effects of the fluids being pumped. Ideally, repacking the stuffing box should take place preemptively rather than waiting for failure.  Taking this approach means the task can be carried out while the vessel is hauled for seasonal storage or bottom painting, although if necessary it can be accomplished while afloat.  While the frequency with which repacking takes place varies, one thing is certain, if, because of chronic leakage, the stuffing box requires repacking on a frequent basis, then it’s an indication of another problem, likely an issue with the shaft’s surface, it may be corroded, water flow may be impeded, or the packing installation or adjustment technique may be flawed. it will be prone to corrosion.  High tech packing materials should, therefore, be used with caution and monitored closely after the initial installation.   In some cases, a hybrid arrangement of conventional and high tech packing materials may provide the best results. Inverted cone seal-type stuffing box with standard cone seals. DOuBLE PACkED STuFFINg BOx “BS” BODy ASSEMBLy TOP CAP uPPER PACkINg RINg CONE PACkINg (1) SET BODy LOWER PACkINg RINg 5/8"-11 x 2-1/4" FLANgE BOLT & NuT/WASHER (6) BASE COMPRESSION SCREW (2) gLAND NuT gLAND PACkINg (2) O-RINg COMPRESSION RINg … Frank Lanier is an accredited marine surveyor with over 30 years of experience in the marine industry. All Photos, Text and Website Copyright © 2007-2020 SDMC Inc. Impeller or casing, or both, has short life 19. The good news is the aforementioned failures are easily avoidable, and prevention begins with regular inspection.  Stuffing boxes should be reviewed on a regular basis, including a daily cursory inspection and a more thorough inspection, using a mirror to look at the bottom half of the hose and clamps, on at least a monthly basis.  Cracked or otherwise irregular hose calls for replacement, as do corroded clamps. * Corrosion-resistant coatings available, contact customer service 01/01/2017 "Make Your Connection with WSI" 4. The stainless steel studs used on some stuffing boxes can suffer from corrosion.  In many case these can be cleaned, and the studs corrosion inhibited; if extreme, however, these should be replaced. Replacing clamps is straightforward and relatively easy.  Replacements should be made from all 316 alloy stainless steel, including the screw, and their bands should be solid rather than perforated (for more on hose clamp selection and use see Marine Systems Excellence Hose Clamps Part 1 and Part II).  For large diameter, heavy-walled hose,  conventional band clamps may have difficulty imparting the necessary compression to effect a watertight seal. Reduced chance for trapping air and running the box dry and cooking it. Unpack stuffing box using standard methods. We’re not faced with a job-creation challenge today. Capt. Water helps lubricate the packing material so its OK for a stuffing box to leak a few drips (3 to 4 per minute) while the vessel is underway. Repacking and adjusting a conventional stuffing box is a task that intimidates many, however, this shouldn’t be the case.  With the right instruction and tools, and a little practice it’s well within the reach of most handy do it yourselfers. Too much of a good thing; if three wraps don’t stem the flow, another problem is almost certainly present. Perhaps this is a case of hose clamp overkill; the additional clamps are of no real value and could be detrimental if they aren’t located over the stuffing box or shaft log.  Stuffing boxes should be equipped with double, high quality hose clamps at each end.  Furthermore, too many clamps, combined with a hose that is too short, could prevent the stuffing box from “floating” on the shaft, and self-aligning. Â. . The watch phrase when repacking a stuffing box, regardless of the material, is careful monitoring for the first few hours of operation.  Using an infra-red pyrometer, the stuffing box temperature should be monitored during this time, shooting the stuffing box and not the shaft (highly reflective surfaces such as shafts and hose clamps will often give erroneous readings); adjustments should be made if necessary.  No part of the stuffing box should exceed more than 30°F-40°F above ambient seawater temperature, regardless of drip rate, while at any speed.  In fact, with access to an infrared pyrometer, drip rates are much less important than they once were. Stuffing box made of brass with wiper ring and double O-ring seal made of EPDM. To locate yours, trace the propeller shaft from the transmission to the point where it exits the hull. Corrosive sealing water and environments can cause deterioration and subsequent leaks if the stuffing boxes aren’t corrosion-resistant. for Dynamically Sealing Pump Shafts, Valve Spindles, Plungers, Agitators, Fans etc. While it may look ordinary, the hose used with conventional stuffing boxes is, or should be, proprietary.  Ordinary raw water or exhaust hose may utilize two or three plies, while proprietary stuffing box hose incorporates five plies.  Because hose used in stuffing box applications lives an especially hard life, it’s submerged, vibrated and routinely twisted in forward and reverse, the added heft of five plies is a clear value added, and equates to longer life.  Replacement of the stuffing box hose is invariably time consuming in that it requires separation of the propeller shaft from the transmission coupling.  It is also, therefore, a task that must be carried out while the vessel is hauled.  Conventional, conservative wisdom dictates that stuffing box hoses should be preemptively replaced approximately every five to seven years or when warranted by visible hose deterioration.  One critical issue involves hose length, or more importantly, the length of “free hose” between the stuffing box pipe to hose adapter and the shaft log.  This free hose length must be long enough to allow the hose to float freely on the shaft, avoiding side-loading, binding, and the overheating it can cause. Thats where your stuffing box will be (unless you have a newer, dripless style shaft seal installed instead). Low Friction while graphite platelets and surface lubricants reduce stem friction. In those cases T-bolt clamps may be required.  However, if T bolt clamps are used avoid the variety that relies on a folded, spot welded design, as these are susceptible to crevice corrosion. Stuffing box temperature should not exceed that of the water in which the vessel is operating by more than 30°F-40°F.  The one shown here is clearly starved for water and is overheating.Â. Conventional Wisdom for Conventional Stuffing Boxes, Laying up Potable Water and Sanitation Systems. Depending on access, and stuffing box design, removal of the old packing can be challenging.  Here a cork-screw like packing removal tool(above), as well as a pick (top), are being used. The shaft log hose (which connects the stuffing box … A leaking stuffing box can cause a number of issues, from corrosion (the spinning shaft slings excess water all over your engine compartment) to sinkings, particularly if the boat is left unattended in the water for longer periods of time. ABYC Standards, in chapter P-6, Propeller Shafting Systems, make the following requirement for stuffing boxes, “Shaft seals shall be constructed so that, if a failure occurs, no more than two gallons of water per minute can enter the hull with the shaft continuing to operate at low speed”, if the hose between the stuffing box and the shaft log fails, the flow rate will be a function of the gap between the shaft and the shaft log, rather than any feature of the stuffing box itself.  If, however, the seal/packing itself fails, then the flow rate will be dictated by the gap between the stuffing box body and the shaft. Â. The packing nut should be made snug, not much more than hand tight initially.  How tight is a subjective measure, however, it doesn’t matter because it will likely be adjusted once the vessel is launched and the engine run.  Initially, it is far better for it to be too loose than too tight.  It’s critically important that the locking nut(s) be tightened against the packing nut using two wrenches, i.e. If a stuffing box is allowed to drip, even at a slow rate, it allows for excellent cooling, longer shaft life, less opportunity for crevice corrosion and less opportunity for trapped air to run the box in a totally dry state and cook it. Folded, spot welded T bolt clamps are prone to crevice corrosion.  The one shown here, used on a stuffing box, has parted; the fold was oriented along the bottom of the stuffing box hose. Of course, 316 clamps could be used throughout any vessel. This works to a point, but as the packing gets smaller it also gets harder. LP with 2-in. Inspect pump sleeve to insure that it is in good condition (Sleeve conditions have a direct impact on the service life of packings in pumps). Schraubenwelle Edelstahl Durchmesser 25 mm mit … LP with 2½- or 3-in. Packing should be cut at a 45° angle to provide a leak-resistant lap joint. This salt stalactite tells a story, this stuffing box is almost certainly leaking too much. 10 m/s and max. Surveyor recommended a splash guard, and I finally got around to making one last weekend from a $15 commercial cutting board and cheapo … Over the last 10-15 years there has been a dramatic rise in crevice corrosion of prop shafting. “The problem is multifaceted — to wrap your head around it is pretty difficult,” MRAA president Matt Gruhn said. Schraubenwelle Edelstahl Durchmesser 25 mm mit … Because of their resistance to corrosion, interlocking, as opposed to spot welded, hose clamps are ideally suited for conventional stuffing box use. Stuffing box made of brass with wiper ring and double O-ring seal made of EPDM. Mechanical seal leaks excessively 14. by jaredjensen on Thu Jan 09, 2020 12:11 am . If a bronze stock rudder is chronically leaky, disassemble the stuffing box and check for excessive wear. While I’ll share that editorial in its entirety once it’s printed, it is destined for the marine industry, and I’d like to give this subject broader reach.  This excerpt,  from an article published a few days ago in Soundings Trade Only, another industry publication, sums up what I believe is a potentially bleak scenario. Valve Stem Leakage Block valves are the most common valve in plants and often experience costly leakage. Although some stuffing boxes are rigidly mounted to the shaft log, where they serve as a pseudo shaft support, most ‘float’ via a length of flexible hose, which is retained to the log at one end, and the stuffing box at the other end, using hose clamps, typically two in each location. Most packing consists of a square plaited material and comes either as traditional greased (or waxed) flax, or a more modern version impregnated with Teflon. Mechanical seal has short life 13. Please also view our Upcoming Events webpage. Enter a marine trades apprenticeship program, one that I believe would produce a steady flow of well-trained, vetted, enthusiastic professionals to fill this ever-widening void.  Such a program would raise the standards, thereby ensuring greater satisfaction and cost effectiveness for boat owners, which would in turn increase boat ownership ranks, something the marine industry has rightfully been wringing its collective hands about for a decade.  Furthermore, I would argue that the higher skill level that results from an apprenticeship program would in fact drive down the cost of boat ownership, as diagnosis would occur more quickly and repairs would be carried out correctly, the first time.  As I say in the closing lines of the editorial, “We as an industry need to take matters into our own hands, if for no other reason than self-preservation.  We need an organized trade apprenticeship program, and we need it now.”. Bearings have short life 15. Modern variations on the traditional waxed flax packing include Teflon and Gore-Tex, as well as graphite-based packing.  While these packing variants tend to be more slippery and longer lasting than flax, they can in some cases work too well.  That is, they may not allow enough water to pass, especially if improperly adjusted, which leads to stuffing box overheating and excessive shaft wear.  As for packing using graphite, there is yet another caveat; graphite is both slippery and a highly noble metal, which means that when it comes in contact with almost any other metal, a stainless steel alloy shaft for instance, and the two are immersed in an electrolyte, such as seawater, the shaft will be anodic, i.e. Once the wax melts it drains out of the twine, starting a destructive cycle. Keep compressing it and it will eventually score the propeller shaft, which will then have to be replaced before the stuffing box will seal properly.

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