Flanges 1

[Mechanicalestimator]

Good evening,

I am a mechanical estimator based in the uk, I am wondering if I can ask if you can lend some of your expertise my way. I have been estimating for 15 years in the mechanical and public health spheres, my strongest subjects are public health and water services and from drawings I can perform full engineering take offs, mechanically i.e lthw,chw etc however I am slightly weaker. I know about screwed and welded steel pipework and fittings I.e screwed up to 50mm and welded 65mm and above. I also know about valves and the different sizes I.e screwed or flanged. My biggest weakness at the moment is flange allowances. I know that generally 65mm and above valves need to be flanged with a slip on flange. My question is

* when using 65mm and above welded steel pipework on a lthw or chw project, how many flanges per metre do you genrally allow ? And what type ? Slip on flange ?

Any response on this would be greatly appreciated

Many thanks

 

[Drazen]

i consider slip-on flange some tradition that rejects to fade away, but never ever use or specify them.

you need pair of flanges for each valve or valving assembly where few elements are connected to each other directly. however, if pump is in-between usually you will need some reducing pieces, so you need to check dimensions of all valving to find out which ones can be connected to each other. balancing valves will often have different dimensions compared to piping, though there are still many designers around who always match balancing valves to piping dimension.

 

[Mechanicalestimator]

Thank you for your response it is much appreciated.

So I will need 1 pair flange per valve?

At the moment I am allowing 2no single flanges per valve connection.

Do you need any flanges installed at intervals in pipe runs for welded pipework I.e every 3 Metres?

Many thanks

 

[SAK9]

Flanges requirement is concentrated in the plant room and air handling unit connections.You would need to allow flanges for the following:

1.Valves and strainers- 2 required one either side of the flange on the valve body
2.Pumps- 1 each for inlet and outlet connections(generally supplied by pump suppliers)
3.Equipment(chiller,LTHW generator,HEX etc):1 each for inlet and outlet connections
4.Pipe Headers:1 end/blind flange and ring flange on either end of headers to blank off pipe

Usually an additional pair of flange is required for all pump and equipment connections to facilitate removal of equipment so it runs like this : branch connection pipe>flange pair>pipe spool>flange pair>equipment connection.Generally equipment suppliers provide the flange pair that goes into final equipment connections as sometimes it may be difficult to get a match in case they are using a nonstandard flange.

Other than the above there is no requirement for flanges in the risers or horizontal pipe runs.

 

[dynamo78]

You also have to consider the flanges as Union, like as source of disconnection from valve or equipment or where the space is so tight for a weld joint where you cannot maneuver but just slip between the spool.
Happy Holidays Bros!!

 

[lukaiENG]

I would add to this that the requirement for flanges in pipes at locations other than valves/fittings is entirely dependent on the client and contractors preferred methods of installation. If they don't want/allow welding insitu then additional flanges will be required.

Also, sometimes site conditions make welding impossible in particular instances.

Typically these days, pipe sections are prefabricated offsite, then brought to site in manageable sections. On site they are put in place with final connections made by welding or at flanges (valves or otherwise).

I would raise this question with the Client/contractor to determine if they are happy with insitu welding.