Questions regarding control valve for urea plant

[adex87]

First of all, I apologize for my complete lack of knowledge in this industry. I've recently been asked to look into a product that I am not familiar at all, control valve for an urea plant. The user gave me this spec and I have very little clue what these meant(minus those that are self explanatory).

Body size & Rating: 1" ANSI 150# RF
Type: Globe, Single Port, Plain Bonnet
Process Flange CL to CL: ANSI Standard
Body Material: 316SS
Seat, Plug, Bushing, Stem Mat'l: 316SS
Packing: PTFE
Port / Seat Leakage Class: EQ% / ANSI Class IV
Cv: Shall be calculated by Mfg on quotation
Actuator / Painting: Spring Diaphragm / Corrosion Proof Coated
Actuator Casing Bolts & Nuts: Corrosion Proof
Air Failure / Valve Action: Valve Open / Air to Close
Input Signal: Pneumatic 3-15 psi
Handwheel: Side Mounted Handwheel
Tube & Fitting: 1/4" or 3/8" NPT, fitting & tube shall be 316SS
Accessories: 1. Pneumatic Positioner Assy with Gauges, 1 set.
2. Air Filter Regulator Assy with Individual Gauge, 1 set

Service Condition
Process Fluid: Carbamate (Urea) Solution
Flowrate (kg/hr): 2579 to 3000
Operated Temperature (deg C): 45
S.G: 1.0
Density (kg/cm2): -
Upstream Pressure (kg/cm2): 4
Diff. Pressure (kg/cm2): 0.3
Maximum Delta P (kg/cm2): 4
Required Cv: 6.39

I gave the manufacturer these spec and they asked for a "process data". The "service condition" section above, is that the "process data" or is it something else that I must get from the user?

How do I determine if this is a high pressure or low pressure control valve? I'm also wondering about the size of this control valve, is it small or large? I'd like to get an idea how this thing look like, if someone can point me a link on the net to give me an idea I would appreciate it alot. Lastly, what is the approximate price for this kind of valve?

Once again, I apologize for my lack of knowledge. Hopefully someone is kind enough to enlighten me on this subject.

Cheers

 

[gerhardl]

Some points and questions that could help you further regarding valve specification and control of offer:

1.

http://en.wikipedia.org/wiki/Urea

2. Solution properties: Dissolved in water? Concentration? Will temperature vary? Likely to crystallize in valve if valve emptied and valve/pipeline dry? Ammonia vapours inside pipeline/valve to regard for sealing and material selection. PTFE and 316 ok for all? (ref corrosion free requirement?)

3. Service condition

a) Comment: The description gives the outer limits and not the actual day to day operational requirements, hence process and regulation properties and demands must be clarified. (Not unusual! This is very often forgotten or hidden in other specifications, or not at all given to people actually selecting the valves)

b) Description of typical normal flow, maximum flow and minimum flow, with ingoing and outgoing pressure, with duration! Note that 4 in 0 out must be caretaken - could give problems if duration is long or lasting. Operational duration qualities for the valve (maintenance-free operational requirement?)

c) How fast is reaction-time expected to be? Please remember that corrections in regulation should be done as slow and smooth-curved as possible as the process allows, signals and measurements for correction from linear and stable sources/places in pipelines.

d) If needed: normal instrument air pressure. Electrical signals in/out in addition to pneumatical? Voltage?

e) Clarify instrument, air and electrical borderline for delivery and all signals and connections in and out included and described?

f) Mounting requirements from process and supplier described in full? (Mounting brackets, supported valve, pipeline free stretches in and out, positioning of valve vertical- horizontal?)

g) Surrounding requirements not described? Climatic or inside? Ex-proof area? Emission to surroundings?


.... etc.

Good luck!

(Note: I have not checked valve-size and flow data!)