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  1. Scotsinst

    Radiography of Castings

    100% usually refers to the quantity of valves RT'd. For example it is typical to RT 10% of CS valves CL600 but the same project could require 100% of SS valves CL900 and above to be RT'd. The percentage is of each valve size and type. 2" and below are normally DP tested because they're...
  2. Scotsinst

    Stellite on ball

    The valve body (and bonnet if it is top entry) and stem are pressure retaining and require to be supplied per NACE. The ball is not pressure retaining and not strictly required to conform to NACE. Of course if it is closed for long periods the face of the ball will be under pressure and this...
  3. Scotsinst

    Help with system curve/outlet pressure

    I think you are exactly correct, however, it is very difficult to design the discharge system to match the calculated frictional loss exactly (unless you can vary the elevation). Normally you would use a valve to trim the system pressure drop to match your desired outlet pressure/flow.
  4. Scotsinst

    Valve sizing for flashing liquids

    rmw: I apologize if my post was offensive to you. I thought you were answering the posed question. JimCasey: I used to have your faith in valve application engineers (I was a valve application engineer for Masoneilan and Fisher many years ago) and I'm sure if you work in Houston, London or...
  5. Scotsinst

    Valve sizing for flashing liquids

    PaoloPemi, I agree that you can get different vendors to size 2-phase flow for a sizing check but make sure your process engineer does a flash calc to check the vapor/liquid fractions. Many times the vendors overestimate valve Cv due to flashing. The effects of subcooling also reduce the...
  6. Scotsinst

    Valve sizing for flashing liquids

    Renoyd, your question is incorrect. The downstream pressure is 10psig. The valve flashing calculation does not affect the downstream pressure. Imagine you were discharging to atmosphere. Downstream pressure is 0 and will always be 0. Like JimCasey mentioned; the effective pressure drop...
  7. Scotsinst

    Lug / Wafer Type Butterfly Valves

    In the refining and O&G production industry, exposed bolts can expand and be a leakage risk during a fire. A wafer type is therefore only installed in flammable service if protected by rigid fire insulation. Lug type valves are used in end of pipeline service. Lug types can be threaded or with...
  8. Scotsinst

    what is comparison between GOST standards and API for F&G cable?

    There are no free sites I am aware of. Ask the client for a vendor list of cable suppliers to GOST. I am not sure what you mean by "from GOST to API". If the cable is going to Russia then it must meet the GOST requirements and should be purchased as such. It is more expensive to buy the...
  9. Scotsinst

    Relief Valves for PD Pump Protection

    You can also check to see if the downstream piping diameter is large enough. Since the diaphragm pump has instantaneous acceleration you can't use the nominal flowrate to determine required pipe size. There's a small chance the piping friction loss is sufficient to push the pressure above the...
  10. Scotsinst

    Multiple hole orifice plate

    Approximately; if you calculate you need a 5" diameter orifice then you will need 25 1" orifices to achieve the same differential pressure.
  11. Scotsinst

    Equalization Line Placement

    You may consider installing a small parallel slide gate valve on the bypass too if you want tight shutoff.
  12. Scotsinst

    Butterfly type control valve wrongly inserted

    JL Seagull: we install the downstream triple offset butterfly valve in a DB&B installation backwards for isolation if downstream will be pressurized. They are bi-directional with a preferred pressure direction and the actuator thrust requirement is less for shutoff in the preferred direction.
  13. Scotsinst

    Control Valve-Supersonic Flow-Propylene Gas

    1. The flow will be sonic, not supersonic. 2. The noise of 90dBA can be mitigated by heavier wall piping downstream and/or insulation if lo-db trim is deemed undesirable. 3. Depending on flowrate, a v-ball with diffuser could reduce the noise below 85 dbA. If flow and pressure drop are constant...
  14. Scotsinst

    Instrument Impulse Line Air Purge

    Impulse lines may be purged to have a velocity of 1 fps (you are just trying to keep dust out). The pressure upstream of the RO should be sufficient to ensure critical pressure drop (roughly twice the outlet pressure) but it may be higher if desired so I'd set it at, say, 12 psig. Calculate the...
  15. Scotsinst

    valves in vacuum conditions

    If a control valve will see vacuum under all process conditions then you can install V-ring packing upside down. If the valve will see both pressure and vacuum then you can install "double packing" where half the chevron rings are inverted. I recommend bellows if air will contaminate the process.
  16. Scotsinst

    Pressure Drop across Butterfly Valve

    I recommend you download a vendor program (Emerson, Valtek, Metso, Masoneilan). Use the FL and Xt factors for your particular make of butterfly valve (noting how the FL factor changes with opening) and you can calculate the valve openings (you will need to iterate the FL factors for different...
  17. Scotsinst

    swagelok/parker

    1. There are cheap alternatives. 2. Don't buy them. 3. There is a reason Swagelok, Parker and Gyrolok have a large market share and that is quality. There are other quality vendors but beware of a product substantially cheaper than the rest of the market. 4. I inherited an offshore project...
  18. Scotsinst

    Valve Back Pressure

    nctexan22: You need to test your valve to determine the flow coefficient, Cv and pressure recovery factor, FL at different travel positions. These cannot be calculated or even approximated for a multistage 'low-noise' trim ball valve. Check the Neles Q ball or Fisher V-ball with insert to...
  19. Scotsinst

    3-way valve: mixing or diverting?

    One situation where a three-way valve can replace 2 2-way valves is in a heat exchanger series/bypass line to prevent the possibility of line being shut in. The 3-way valve eliminates the requirement for a liquid safety valve (if this would be an expensive solution).
  20. Scotsinst

    Back Pressure Regulating Valves

    zdas04 is correct.

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