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  1. TerryOsser

    Pneumatic Testing for valves in Gas Service

    PLant air a utility service, whilst Hydrocarbon Gas is hazardous. 3 types of pneumatic test are used generally. The low pressure seat test, and the 110% seat test, and a high pressure body test. Low pressure seat tests are used to test seats at low pressure differential, and where seating is...
  2. TerryOsser

    Pump Automatic Recirculation Valve

    Try www.blackhall.co.uk/ARV.htm Its a better product.
  3. TerryOsser

    Thickness Tolerance of Large size pipes and Fittings

    It depends where you using the pipe - offshore or onshore, and what the material is. Offshore weight is prime importance - there reduce tolerances and reduce weight. Same principle for exotic materials - reduce tolerances and reduce weight = reduced cost if the items are being made to order. For...
  4. TerryOsser

    Flange Dimensions

    Paddymac - send e-mail to kerrywoodcock@hfx.eastlink.ca
  5. TerryOsser

    Flange Dimensions

    Paddymac - Still need BS4504?
  6. TerryOsser

    Thickness Tolerance of Large size pipes and Fittings

    If you are concerned about the mill tolerance on fittings (in that it will affect the minimum wall thickness, and therefore increase your actual wall thicknesses) write an additional clause (or addendum) to your Piping Specification or whatever document you are using as a project reference /...
  7. TerryOsser

    Reducing Flange Dimensions

    ASME B16.5 doesnt mention WELDNECK reducing flanges, only THREADED and SLIP-ON (see page 69). From this my assumption is that the standard intimates that WELDNECK reducing flanges are not covered by the standard. No reason why you couldnt use a flanged reducer though.
  8. TerryOsser

    Standards for butterfly valves

    If fire-testing is a requirement then valves to be tested to the relevant fire test specification e.g. API 609 valves tested to API 607, BS valves to BS 6755 Part 2,etc)
  9. TerryOsser

    Eccentricity understanding

    Tomoe Tritec have a good visualisation of the triple eccentricity in butterfly valves - get a sales representative to send you a copy (www.tomoetritec.co.uk).
  10. TerryOsser

    Double-Block Valves and Double Block and Bleed Valve

    Nottingham, whilst Double Block & Bleed is an arrangement it can be acheived using a valve arrangement of twoo isolation valves in series with a bleed isolation valve in between, or using a single bodies double block & bleed valve. Certainly within certain provinces in Canada, depending on the...
  11. TerryOsser

    How long should the pressure sustained during hydrotest?

    Surely the client can determine the extent of the pressure test. Pipelines as DSB123 states is normally 24 hours. Topsides are noramlly 1 hour. Both are overridden by the client, and normally in the project Pressure Testing Spec it is written a minimum test duration, or 'until the client is...
  12. TerryOsser

    What factor should we consider about ball valve?

    Ensure all the necessary certification / firetesting / code approval has been obtained. An enhanced performance test on a typical valve size and class is also a good idea. Ask for all fugitive emmission testing, and extended bench testing that the manufacture has carried out.
  13. TerryOsser

    double block and bleed

    Double Piston effect seated Ball valves work by having a seat design such that both line pressure and body cavity pressure (if the first seat should leak), when the ball is in the closed position, will force the seat seal onto the ball. This is apposed to Self Relieving Seats that lift off the...
  14. TerryOsser

    why must gate vale must be open &ball valve half-open duratin in test

    Line is pressure tested with Ball valves in half open position so that the seats are not subjected to 1.5 times design pressure which can and do damage them.
  15. TerryOsser

    API 682 for rotary valves packing

    What are you trying to improve the packing for, fugitive emissions? Stipulate your required maximum stem leakage, and get the manufacturer to comply. Take a look at ANSI/ISA 93.00.01 - Standard Method for the Evaluation of External Leakage of Manual and Automated On-Off Valves. Most...
  16. TerryOsser

    Ball Valve - Drain & vent connection

    BS 5351 specifys the requirement for drain tappings for valves of sizes NB 2 and above. Drain tapping sizes as follows: NB 2,3 & 4 - tapping size = 1/2" NB 6 & 8 - tapping size 3/4" NB 10 to 16 - tapping size 1". This is regardless of type (floating or trunnion mounted) or...
  17. TerryOsser

    STAINLESS STEEL FLANGES MATED WITH GALVANISED CARBON STEEL

    Stuarte, galvanic action only occurs if electrolytes are present. Are you concerned with internal or external corrosion. If internal figure out if your fluid is electrolytic. If its external the only area that will get corroded is around the bolts. The gasket will / should insulate, and the...
  18. TerryOsser

    why must globe & gate vale must be open duratin in test

    qeqe - because if the valves where closed the line pressure might not reach the rest of the line. Gate valves are isolation valves. Globe can have tight shut off. I guess you want to pressure test the whole line???
  19. TerryOsser

    Valve Wall Thickness

    It is always best to specify your required CA and get the vendor to either conform compliance or state his offered CA. Bear in mind a high CA can reek havoc around sealing areas unless CRA overlay is used to ensure sorrect sealing. 6mm CA might mean you need to reselect body material, use...
  20. TerryOsser

    Applications of Concentric vs Eccentric-Disc Butterfly Valves

    Both are for bi-directional flow. Due to the fact of the eccentricity of the eccentric butterfly valve it has a preferred direction, the force required to open the valve when the flow is in the non-preferred direction is slightly higher. In clean water service they are the most economical valve...

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