Tightening Torque for Plugs of Air Cooled Heat Exchanger Header Box

[DK44]

1. For Plug Type Air Cooled Heat Exchangers designed to API 661 and ASME Sec VIII div 1, How to calculate Tightening Torque for the Plugs.
1.1 Is it necessary to calculate Wm1 and Wm2 for the purpose, and if so are the formulas of Appendix-2 of Div 1 applicable.
1.2 In Wm2 calculations is it required to use b(effective gasket with = generally 1.25 mm) or N(gasket width = generally 2.5 mm)

 

[r6155]

Ohh NO. You are very confused.

Regards
r6155

 

[DK44]

Dear r6155.

I am sorry if I have not made it clear to you. But this is a real time issue in the specific product design seeking learned views / comments.
Here the Threaded Plug being of small size (1 5/8"), the metallic flat gasket ring around it is also of small diameter. Hence the query. Pl see the attached figure of the Plug.

 

[r6155]

See good information in:

https://www.parker.com/literature/Tube Fittings Division/Assembly_Installation.pdf

Regards
r6155

 

[XL83NL]

More specific, if these plugs are acc. ISO 1179-1, which I assume based on your sketch, see this Parker document, page S5;

https://www.parker.com/literature/Tube Fittings Division/Assembly_Installation.pdf

 

[SnTMan]

DK44, A general plan:

1) With gasket material identified, select a target seating stress. This can be gotten from a gasket manufacturer, or perhaps from Appendix 2, Table 2.5-1. I'd consider this value a minimum.
2) Pay no further attention to Appendix 2
3) Calculate a seating load = actual seated gasket area x seating stress from 1).
4) Select your favorite expression relating torque to force. i.e. T = k * F * d. Note: there are better expressions available.
5) Calculate the required torque. Expect a good deal of inaccuracy.
6) Torque the plug.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[SnTMan]

Also see this FWIW

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[DK44]

Thank you r6155 / XL83NL for your responses. The Plug what I referred is shoulder type plug used in Header Boxes of Air Cooled Heat Exchangers.

Thank you SnTMan for your simple guidance.
However, for the Gasket load for Maximum torque is it recommended to take 2 x ASME Seating stress y as a consideration of Gasket crushing as used in Taylor Forge method as 2 x y x 3.14 x G x N (G being mean gasket dia. and N being width of gasket). But this load will be very high.

 

[SnTMan]

I'd expect the load to seat a solid metal gasket to be high. I'd guess doubling Table 2.5-1 values would not be necessary, maybe 1 1/4. At a guess. Otherwise, forget Appendix 2.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[r6155]

Torque wrench is rarely used, and torque values are rarely showed in drawings.

Remember API 661
6.1.1 s) maximum and minimum plug torque values with recommended thread lubrication.

9.4.3 Plug gasket contact surfaces shall be machined to a finish of average roughness between 1.6 μm and 3.2 μm (63 μin. and 125 μin.).

12.4.2 After the final pressure test, plug joints and all gasketed joints shall be air-tested at 100 kPa gauge
to 170 kPa gauge (15 psig to 25 psig), testing for leaks either by applying a soap solution or by total
immersion in a water tank.

Regards
r6155

 

[XL83NL]

r6155, do you know if and where the design of plugs (and it's female counterpart) is specified in/for API 661? I mean design such as specified in ISO 1179-1 for the female part.

 

[r6155]

XL83NL. Yes, please search "plug" in pdf API 661 and you can see 56 instances.
I don´t have ISO 1179-1 but I understand may be 1179-4

ISO 1179 consists of the following parts, under the general title Connections for general use and fluid power — Ports and stud ends withISO 228 1 threads with elastomeric or metal-to-metal sealing:
• — Part 1: Threaded ports
• — Part 2: Heavy-duty (S series) and light-duty (L series) stud ends with elastomeric sealing (type E)
• — Part 3: Light-duty (L series) stud ends with sealing by O-ring with retaining ring (types G and H)
• — Part 4: Stud ends for general use only with metal-to-metal sealing (type B)

Regards
r6155

 

[XL83NL]

r6155, I understand, and did the same exercise myself. However, I couldnt find any sketch or reference to the design of such plug (ports) in API 661. Thats what Im after. There are some hints in the 56 hits to plus designs, but nothing like a clear sketch.
I know ISO 1179-1 (we use them extensively for high pressure and temperature threaded process connections, where NPT is less reliable).

 

[r6155]

XL83NL. Use ISO 1179-1 as you say. ISO is a Normative Reference in API 661.

Regards
r6155

 

We appear to be going down a rabbit hole here.
Fasteners and bolting science is extremely involved, and I suggest you retain a person experienced in your application.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."