A bunch of time today was spent on other projects, but I did get two things done on the stabilizers. The first was to reinstall the battery charger. I had to cut off the wire lugs to remove it so new ones needed to be crimped on with shrink-wrap sleeves. The first picture shows it all back together.
The next was starting to install the oil cooler which requires some re-plumbing of the raw water intake for the starboard engine. I've been waiting for a 2-1/2" x 5" pipe nipple that I ordered and it finally came in today, so I started putting it together. But first, one of the old fittings had to be removed from the strainer, and my 14" pipe wrenches couldn't budge it. A quick trip to the local plumbing supply shop armed me with two 24" wrenches, and that did the trick.
The last two pictures show the cooler in position straddling the front of the engine. Water comes out of the strainer, through the cooler, then down under the engine where it loops around to the pump. The new hose run will be a few inches shorter than before, but of course the length of the cooler is being added. This cooler body is a good bit larger that what's required to cool the hydraulics, but provides less intake restriction on the engine.
Tomorrow AM I plan to cut and hook up the water hoses, then mount the oil filter and sort out the return hydraulic hoses. After that, I think I'm done.
Hi Peter,
ReplyDeleteAs you know, I’ve been on quite a journey resolving the design shortcomings of the hydraulic system on N5535. Since doubling the number of hydraulic pumps, we’ve encountered overheating in the hydraulic oil cooling system during periods of high load—particularly when operating the thrusters and anchor wash simultaneously.
The existing raw water cooling pump is a Jabsco Model 1673-2001, which provides a nominal flow rate of approximately 8.9 gallons per minute (GPM), or 40 liters per minute (L/min), at 1500 RPM.
The current heat exchanger is a SEN-DURE model #15222-1-7, rated for 7–21 GPM water flow and 1–27 GPM oil flow. Its specified heat rejection at 7 GPM water flow and minimum oil flow, assuming 150°F oil in and 90°F water in, is 5,200 BTU/hr.
ABT has proposed upgrading to a SEN-DURE model #13078-1-7 (with ¾” NPTF ports), rated for 7,700 BTU/hr. A rough calculation suggests this would represent a theoretical 48% increase in cooling capacity.
While this appears to be a meaningful improvement, I have some reservations. In the unlikely event that both emergency bilge pumps were operating concurrently with other hydraulic loads, I wonder whether a 50% increase in capacity would still leave us vulnerable to overheating. Although the proposed parts are not inexpensive—at over USD 5,000—my instinct is to err on the side of overdesign. Additional cooling capacity has minimal downside beyond cost, and offers greater margin during extreme or failure scenarios.
Given that the hydraulic demands on N6060 appear identical to ours, and that you’ve upgraded that system, I’d very much appreciate your comments on this proposed solution. Specifically, I’d be interested to know which SEN-DURE heat exchanger you selected, the specifications of the raw water pump feeding it, and whether you found your chosen upgrades sufficient—or if you would recommend additional capacity or alternative components.
Best Regards, Mark
Hi Mark, I don't think I can add anything beyond ABT's suggestions, or really make any comments on whether it's a good or bad plan. I didn't have any hydraulic cooling issues on N6062, and it had ABT part number 32725 for the cooler. I don't know how that translates to a Sen-Dure part number. It's a tandem cooler with two separate oil loops, one for the main hydraulic return oil and the other smaller one for the case drain. I'm not sure why a separate loop is needed, but ABT's engineering has always been really solid, so I'm presuming there are good reasons for it.
ReplyDeleteOn N6837 I also have a tandem oil cooler, this time ABT part number 36429. It's bigger than the one on 6062, but I have no idea what it's capacity is.
On N6837, I almost have the opposite problem, and it's something to keep in mind. Underway when only the stabilizers are in use, the hydraulic oil is almost too cool, often only 10F or so above the ambient temp in the engine room where the tank is located.
I presume you have disassembled and cleaned your existing cooler? And I presume your pumps, both new and old are variable displacement? The stall-our issue you had a while back now makes me wonder of the new pumps are fixed displacement? I'd be surprised if they are, but worth asking just to be sure. Did the overheating issue start after you added the new pumps, or has it always been an issue?
Hi Peter,
DeleteThanks for your response.
All our pumps are Rexroth A10VO45DFR/31L variable displacement axial piston pumps with a swashplate design. We did not experience any overheating issues before adding the extra pumps. ABT has since confirmed via email that the additional pumps will require increased cooling capacity.
Also, thanks for the note about the possibility of overcooling; given the warm waters we operate in, I doubt that will be an issue.
Best regards, Mark McGillivray