PeterF

When I worked for ICI designing chemical processing plants, if we were using NRVs to prevent backflow and needed to calculate the reverse flowrate we had some conservative rules. If we had 1 NRV then we assumed that the reverse flow was the full flow that would occur should the NRV be stuck open. If we used 2 NRVs in series (which had to be of different type and manufacturer to avoid common mode failure) then we would assume that we had a flow area equivalent to 5% of the fully open flow area of one of the NRVs to allow for leakage due to failure to shut off tight and the other NRV was stuck open. I know this is different to plumbing and the consequences of getting this wrong is rather dire on a chemical plant, hence a very conservative approach. I am currently designing and starting up some reactors that inject pure oxygen into a hydrogen / natural gas mixture and combust this at 300 - 600psig (20 - 40barg). We have about 4 layers of protection on the oxygen supply as reverse flow of hydrogen back up the oxygen supply pipe is real no no.

Chris G, I did some basic calcs and the expansion of the calorifier itself has some impact from 2 viewpoints. 1. The increase in pressure from cold at say 30psig to hot at say 45psig if the calorifier was designed for 45psig would expand by less than 0.1% on volume, this is because the design stress from PD5500 (rather than ASME VIII) is around 51Mpa and Young's Modulus is 115GPa, four orders of magnitude difference so little actual expansion. Thus I agree with your view that it is very small. Even at the point of yield copper will only expand by 0.5% linearly (1.5% on calorifier volume), which is when it will be permanently deformed. 2. The calorifier itself expands by about 0.33% in volume during heating up from 20°C to 85°C compared to the water expanding by about 3%. Makes an effect but hardly a dominant one. i.e., if a 60l calorifier requires 1.83l of extra water volume from 20°C to 85°C (from my physical properties tables water expansion = 3.04% over this temperature range), then 0.24l is taken up by the calorifier warming up and expanding and the increased interla pressure also causing it to swell further (but elastically, i.e. it will return to originla size on depressurisation). Therfeore, expansion vessel has to take up 1.59l of water, a small change. Therefore, expansion lies elsewhere. Other effects. 1. There may well be air trapped at the top of a horizontal calorifier because the internal tube will not be exactly at the top. I have previously reported I used to have a horizintal calorifier without an EV. The calorifier had the outlet tube slightly to one side so had a large amount of stored air and never dribbled from the PRV. I had an NRV direct on the calorifier inlet. The hot taps did not drip and I had not found any plumbing leaks. Now some people argue that this air pocket should dissolve with time on line into the water. Hwoever, I believe that this may well be a fallacy because as you warm water up the solubility of air in water reduces. Also, the water as supplied is already contains a lot of air, especially on a boat where we tend to use a hose pipe to balst the water into a tank, mixing it well with air first. Sometimes water arrives from the water treatment plant saturated with air, how has at times run off a glass of water and seen small air bubbles forming on the inside of the glass. Why do so many creatures go to feed in the arctic waters when they are so cold - because they are so cold they have a high level of dissolved oxygen so plankton etc. can flourish. Back on topic, we charge the calorifier with cold water which contains lots of air and then heat it up which drives off the air. OK argue Henry's law back at me in that the water in the calorifier is under pressure and the pressure will hold more of the air in solution at the higher pressure. Yes agreed, but reduction in solubility due to increased temperature is a larger effect than the increase in solubility due to increased pressure. Additionally, oxygen is soluble in water but nitrogen is much less soluble in water and close to 80% of the air is nitrogen. I am happy to believe that a horizontal unit may well contain some air permanently at the top but a vertical one probably will not. 2. There is also the plastic pipework that many of us use now, but this is such a small volume as to be insignificant, at most there would only be 2l of liquid in this so offering limited expansion potential. 3. Water compresibility - forget it, increasing pressure from 30 to 45psig would reduce water volume by 0.005% or 0.003litres in our 60l calorifier example (less than a teaspoon). PeterF.

Yes, BW have stated that for every 10 new marina berths created they will remove 1 on line mooring from the vicinity of the new marina berths. There was a BW survey some time ago which apparently had as one conclusion "the majority of boaters would like to see a reduction in on line moorings". I am not condoning or greeing with the above, just reporting it. PeterF

Go to the waterscape stoppages page. Stoppages Select Calder & Hebble, press find stoppages button and see that they have been cancelled. 03 - 21 Nov 2008 ! Stoppage: Ganny Lock This stoppage has been cancelled. Associated Regional Office: BW Yorkshire Replacement of gates and cills to include general repairs Towpath diversion will be in place with appropriate signage. (Enquiries: 01642 633273) 23 Feb 2009 - 13 Mar 2009 ! Stoppage: Ledgard Lock This stoppage has been cancelled. Associated Regional Office: BW Yorkshire Replacement of flood gates to include general repairs This section will be closed from Mirfield Town Centre to Ledgard Flood Lock. Diversion will be signed. (Enquiries: 01642 633273) Ledgard flood gates will also not be repaired now, which is a bugger as I moor at Shepley Bridge and these have been waiting for at least 2 years now.

Is 10,000 lock operations getting towards the limit. if we say 6 boats / hour for 12 hours per day for 7 days per week for 26 weeks of the year to cover May to October as peak season then we get 13,104 boat movements per year. I know its rough but in terms of order of magnitude there ain't all that much capacity spare.

Yes, the replacement of the gates etc. has been cancelled. Pretty hard to use this lock in August because the top gates were in need of replacement. Guess it is just one of the maintenance cut backs due to reduced income and major breaches elsewhere in the system and something we will all be getting more experience of over the coming years.

Have replaced all seals on both my cassettes plus the screw caps and the float valves on the air vent to stop that leaking when you pick it up. Due to boat having been left unused for some time by old owner before we bought it, seals etc had dried out. There are several people on ebay who sell thetford cassette spares.

Polyethylene, like polypropylene is quite a difficult substance to join. Often it will be welded because not many of the solvent based adheseives that will bond say PVC will work. Suggest you try a hot melt glue gun, may hold for some time but will probably fail long term. PeterF.

I asked our local supplier in Late September when I last filled up and he said yes he would still be selling. But he then went on to say that there had been an inspection of the installation and with a high tank, not fully bunded he was probably going to have to spend a lot of money improving his tank and supplly pipes etc. His set up is not uncommon so I wonder if there is going to be more boatyards needing to improve storage. Then they will be wanting to get money back from sales to pay for the work.

Lightening things up, a few years ago I was at a meal at a busines conference and I was asked by the young waitress what wine I would like. So I said I would start with some of the white then have some red. So she half filled my glass with white wine and then topped it up with red . The 8 of us on the table just sat there stunned. We had a good laugh when she had left and I drank it up so yes they do mix. Poor lass obviously had not been given any training really. PeterF

Luckily shire 40 and 45 which are the subject of most of the posts on this thread are both fitted with PRM150 at 2:1. As we have been discussing like for like this is not an issue. Thanks for reminder in future as it slipped my mind. PeterF

Confirm what others have said, this seems underpropped. We have 55ft narrowboat with Shire 40 engine. We have an 18x12 fitted. I have run trials with GPS. 1600rpm cruises at 4mph which is reasonably relaxed. Will rev up towards 3000rpm for 7mph if pushed on the northern rivers and canals. Would have thought on that basis that a 19x12 would go with a Shire 45, about 11% more blade area (19x19/18x18) and 12.5% more engine power. PeterF

Thanks Liam and everyone else who responded - I will take a photo when I am on the boat next and post. I have been able to get it working well, long weekend a couple of weeks ago used probably 10kg and it was on most of the 3 days and kept in overnight with some smokeless fuel that seemed to burn longer than house coal. Cheers, PeterF

My boat was second hand and the stove had no instructions. We have managed to get it working and get good heat out from it and keep it in overnight, but it was all suck and see. I do not know the make. This post has prompted me with a question - the stove has a variable air vent below the grate to let air in and there is a variable damper located under the chimney. Id o not not if there is a proper way to balance the two, but we just tend to keep them in sync, if we open the lower air vent a bit we also open the damper a bit and vise versa. Does anybody know if there is a proper way to run the two adjusters. Cheers, PeterF

I am afraid you got your terms the wrong way round. 1kg of water raised by 90°C requires the fllowing energy 1 x 4184 x 90 = 376,560 Joules The energy is supplied at a rate of 1kW = 1000 Joules/sec so the time required is 376,560 / 1000 = 377 seconds. re the OP, how did you work out your skin tank is short by 1kW and at what water temperature. Empirical calc, gut feel. Do not forget that if your thermostat is set to 80°C, then if the water gets to say 90°C it will loose more heat to the river / canal water as you then have a larger temperature driving force from the skin tank to the external water.

You would have to back check some of the bids - I did some calcs some time ago for the Yorkshire area, one winning tender was £800 vs the guide price of £1116 or 28% below guide price. There were quite a few winners with between 18% and 26% below guide price. I did not record the locations in my spreadsheet though.

We moor at Shepley Bridge and the level is confirmed as well down. Last 2 trips out we noticed that the level at Cooper bridge up to Kirklees was also down around 12" so assume some of the wier has also gone from there.

Looks very reminiscent of Tuel Lane on the Rochdale with the very large rise and top gate perched up in the gods and that does not leak anything like that. We had our boat right up to the front wall on the way up and only got a light spray. Hopefully they can get it sorted as well as Tuel Lane otherwise a it will be a bit of a problem.

Many years ago on the Trent and Mersey downstream from Burton we spent many hours while two boats were removed from a bridge hole at the bottom of one of the locks. SOmeone said that the locks were wide enough for 2 x narrowboats but the bridge holes were slightly narrower than the lock and the boats have to leave one at a time. Not sure if this was true or not, but they were old boats that had spread.

Hit it on the head I think. The resonant amplitude (and maybe the frequency) can be altered depending upon the stiffness of the shaft, how well the shaft is supported, the amount of damping in the stern tube, the water flow to and around the propellor, the propellor speed etc etc. In terms of design, I doubt that anyone has gone so far as trying to optimise the narrow boat propellor using computational fluid dynamics such as has been used for optimising the design of large ships propellors. Here are a couple of images of large ship propellors modelled using computational means showing the shedding of vortices from the outer edge of the propellor to illustrate this further.

If the edge of the blade is blunt, then any flow over a blunt edge creates turbulence, eddies and can also create something called vortex shedding by where the eddies generated at the edge have a specific frequency. If the frequency of the vortices happens to be very close to the natural frequency of the propellor then the propellor be excited by the vortices and will resonate. If the natural frequency of the propellor happens to be in the audible range then you will hear it. If the edge of the blade is sharpened then this alters the frequency at which the vortices are shed and the power contained in the vortices. The ultimate demonstration of this is the Tacoma Narrows bridge failure where the vortices generated by the wind caused the bridge to resonate and then fail. Tacoma Narrows bridge failure

I took the number from the one she has stored on her mobile so I assume it is right and it is some central BW number and she states that when she has called they then put her through to a local contact who knows the state of the C&H. AFIK BW do not have a presence in Brighouse. Anyway, twice this year she has used that number, we have been stuck for 48hrs at Brighouse once and my son for 24 hours on a different outing when he borrowed the boat.

I bought one of a guy in the small adds in the back of Waterways World and it works fine. No website address though - if you want details PM me, do not believe I should be posting this guys name & address etc. on an open website.

My wife got this number for details 01384 215785 which is a BWB number that she saw on a notice at Brighouse. They will put you through to someone local to the C&H who should know if the flood gates are closed or not. We have used it a couple of times when we have been on the C&H this year.

Confirm it is a good mooring spot, we arrived late afternoon and stayed 2 nights in bank holiday week at the end of May (before officially opened). 3 boats on the first night, only ourselves on the 2nd night. Seems to be room for 4 50-60 ft boats on the visitor pontoon. Only disturbance was late one night when what sounded like a hen party came past (screeching / cackling etc.). Funily enough, despite the good location etc., of the 5 berths that have appeared on the BWB mooring tender only 1 appears to have been won.