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  1. DYV1973

    varistor use / damage

    LS, On a pcb near the 230 VAC connections, there are 3 varistors towards the switching power supply (for 24 VDC and 5 VDC). Q1: Why are there 3 varistors (between PE and neutral, PE and live, live and neutral), instead of 1 between live and neutral? The pcb is fed by an isolated power supply...
  2. DYV1973

    pressure pulsations in fuel system due to slow steaming?

    Thanks Chief for your reply. I am aware of pulsations in a fuel system, but problem for this specific case is that it only occurs during slow steaming. Could a retaining valve behind the engine cause this, if it comes in resonance with pulsations of the fuel pumps, which is then not happening at...
  3. DYV1973

    Heavy Fuel Oil Quality and Quantity Monitoring System

    I think you need a real-time laboratory. Depending on how you define quality, you need to do various types of measurements. Biggest challenges lie in added chemicals / unwanted substances, that you will only find if you know what you need to look for. Of course it will be possible to measure...
  4. DYV1973

    pressure pulsations in fuel system due to slow steaming?

    LS, A superintendant informed me about the fact that slow steaming could cause heavy pressure pulsations in a ships fuel system. Can someone explain why this happens / what causes this phenomenon? Is there someone who has experience with this, and may be also in combination with a large...
  5. DYV1973

    pressure pulsations in piping

    Thanks for your replies. The fluid viscosity is in the range of 12 mPas, with a density of approx 0,94 kg/l. Piping diameter is a DN50 steel pipe (exact material specs are not known). The frequencies of the pulsations are depending on the point of operation and are between 1 Hz and 10 Hz. We...
  6. DYV1973

    pressure pulsations in piping

    @ BigInch Pressure pulsations are caused by a piston pump. As customer does not want to take precautions, we can just warn him. At least I want to make a calculation for our delivered equipment. With normal flow, I can use Darcy-Weisbach to make a pressure drop calculation, but this will not...
  7. DYV1973

    pressure pulsations in piping

    LS, If a piping system for the transport of oil is suffering from pressure pulsations, how can the effect further in the piping be calculated. Pressure is approx 4 bar, and pressure peeks up to 25 bar (in miliseconds). What will the effect on the pressure be 50 metres further in the piping...
  8. DYV1973

    pressure pulsations in ships fuel system

    Thanks for your reply, and I indeed meant the high pressure (circulation) part of the fuel system. Do you mean engine or booster module manufacturers? I have contacted both parts, but in the moment neither of them seems to have an answer (or does not want to give an answer). Class (GL/LR)...
  9. DYV1973

    pressure pulsations in ships fuel system

    LS, What kind of pressure pulsations can be expected in a ships heavy fuel oil supply system (amplitude and frequency). And are there any regulations from classification agencies concerning these pulsations. (I have searched in GL rules, but haven't found them so far). Thanks. DYV
  10. DYV1973

    pressure drop filter

    Is there a way to calculate the pressure drop over a basket strainer. I know that suppliers can, but I want to do some calculations in advance in Excel or something. I assume that based on flow, viscosity, filter area and mesh widt, this should be possible. Fluids are heavy fuel oils (newtonian...
  11. DYV1973

    pressure drop due to obstruction in pipe

    Unfortunately I do not have CFD. The picture I just found on the internet, to illustrate what I meant.
  12. DYV1973

    epoxy with fibres or alternative

    With stiffness I mean the stifness of the overall part. But due to the fact that EPS does not give any stiffness, this should come from the top coating. In the EPS also some (electronic) components are integrated, which need to be covered with a coating for protection and also for the look...
  13. DYV1973

    Over - design

    Over design will always create a larger surface. But make sure that this area will in series (extra pass) or longer plate / pipes. You will have the same shear and thus reduce the risk of increased fouling. Adding more plates in parallel for a PHE will make that the PHE will foul more easily and...
  14. DYV1973

    Surface Finish For Stamped Parts

    Depending on where you want your surface improved, and how large your products are, you can consider using a vibratory bowl or tumbler. DYV
  15. DYV1973

    epoxy with fibres or alternative

    Thanks Berkshire, I have found some on the internet. Both epoxy with chopped fibres and even polyurea with chopped fibres. I will contact the supplier and see what comes out. The production rate is not very high: lets say approx 5 m2 per week. But reducing man hours is important, so using a...
  16. DYV1973

    epoxy with fibres or alternative

    LS, For creating a topcoat on an EPS250 part, we have experimented with hot spray polyurea. This material gave enough strength, but stiffness was to low. Product is round (diamters from 200 to 1000 mm), and the basic EPS is 40 mm. Application temperature is from 15°C to 55°C. Now we are...
  17. DYV1973

    burner flowrate

    Is there a return flow?
  18. DYV1973

    Design Of A Plate & Frame Heat Exchanger

    PHE has a smaller surface area and larger pressure drop than shell and tube. Use smaller fouling coefficients. Brazed PHE's are cheap, but can not be repaired and cleaned very limited. Limited to small capacities, and thermal length. Welded PHE's can withstand higher temperatures and...
  19. DYV1973

    flow through bypass

    Correct: density / viscosity (and also temperature, but that could also be done in main stream). Flow would not be possible as it is a by-pass. Flow is what I would like to estimate.
  20. DYV1973

    Coating a plate. Looking for lubricity and heat resistant

    What is the purpose of the coating? Does it needs to be non-stick, or is it a sliding surface contact to reduce friction?

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