Standard guide and line stop have 3-2 mm gap which is construction tolerance,because the gap can not be verified without field check, I normally don't put gap in the Caesar model.the practise is more conservative for most case.but if guide and line stop are close to rotation equipment nozzle (for example pump),I found bigger nozzle load in the Caesar modle with gap after trying two model which are with gap and without gap.Do I need to specify no gap for the standard guide and line stop in this case? Can sombody give me light? Thanks!

Joe,

It is common practice to specify a zero gap in restraints local to rotating equipment. There are a few considerations though. The restraints must be fixed after alignment of the machine, and an adjustable device may be in any case be preferable. The steelwork or foundation must be up to the task. There is no point specifying zero gap if the supporting structure is flexible.

Cheers,
MoverZ

Whilst it is common practice to specify zero gap restraints, in the real world they dont exist.

A shoe with a zero gap guide will lock out, whilst accuracy less than 2-3mm on a guide gap is as much as you can expect.

if your tolerances are that high, i would suggest a new routing method.
I have however, seen engineers request zero gap guides and it is difficult to argue against.

Tim

Tim,

A practically zero gap is quite simple to achieve although not on a microscopic scale, by use of screw adjustable cheek plates on stops and guides. In large compressors, particularly with top nozzles, rigid struts fitted with ball joint ends are an excellent solution, commonly found in offshore projects.

2 to 3mm of unwanted freedom in a large diameter line can equal a very large moment on a machine.

Cheers.

I sense that Tims view point is that an ordinary box guide or tab stop guide always has a contruction gap built into it in an uncontrolled fashion but the analysts results may indeed require a zero gap for the results to be correct. This is a common oversight amongst piping flexibilty analysts, neither software nor codes can control human oversights.

Sway Struts are zero gapped devices and are a wonderful thing....

The models results must always be connected to the real worlds supports, and if a gap or the lack thereof is a prerequisite the supports must indicat this.

And Cheers! (Go Blues)

Somebody mentioned that 3 mm gap is used as the most common welding electrode is 3/3.25 mm. Easy to use as gauge. Urban legend or not?

3/32" LH 7018 is used for most carbon steel welds from the hot pass out commonly....

So 3/32" = ~ 2.4mm

At least here in the U.S.A.

Specifying to weld stopper without gap after alignment on pipe support drawing will make guide and line stop without gap, for steel structure,if necessary,stiffenss can be used.

dear sir

if your result is dependent on the gap of guide or stopper you can not confide to this analysis ,because in the construction and installation this support may be installed with gap..

if you are using standard guide or stopper near the strain sensitive equipment such as pump and compressor ,... you must run the case in two situation with gap and without gap ,if your result is dependent on the gap of one support you must use special support to confide this support is no gap in construction

i have similar case in analyzing compresor
i use line stop with no gap and the case passed ,and when i enter 1 mm gap for line stop this case failed so i do not confide to this support and i use two rigid strut in respect of shoe



best regards

a.sadeghabadi

If your rigid strut is connect to a civil steelwork, and 1mm gap will let your analysis fail to pass, be sure that the civil steelwork is strong enough and will not to deflect even 1mm when applying your load. it is sometimes difficult to achieve.