Chemical pipeline guide bracket selection: material, load bearing and case study

Confused by the guide bracket just after taking over a chemical project? I was wondering: Will this thing blow up if I choose the wrong material? How tight is the bolt? Do not panic! Today we will use the big truth to break the selection of crushed - after all, the wrong installation of a bracket, the entire pipeline may be scrapped!

First, material selection: not just grab a piece of iron can be used

​Newbies are most likely to fall prey to materials. For example, you give high temperature steam pipe selected ordinary carbon steel bracket, the results of half a year after the corrosion fracture, the pipe directly smashed equipment on ...... Remember these pit avoidance points:

1. ​High-temperature and high-pressure piping (>400°C): must be onAlloy steel or stainless steelOrdinary carbon steel becomes "soft" at high temperatures.
2. ​Corrosive media (acid/alkali piping)::
   • Stainless steel tubing with carbon steel brackets?Rubber gasket must be added in the middle! Otherwise galvanic corrosion will teach you a lesson in minutes.
   • Concentrated alkali solution pipework is tougher - gotta use it!Special coated stainless steelIt's not even an ordinary 304.
3. ​Cryogenic piping (e.g. liquid nitrogen transport):.austenitic stainless steelIt's a life-saving option. Carbon steel is brittle as a biscuit at low temperatures.

Blood tears lesson: a plant DN200 concentrated alkali pipe with ordinary 304 stainless steel bracket, 8 months after the intergranular corrosion perforation, lye leakage shutdown for a week---The money saved on material costs is not enough to cover the loss of production!​

Second, load-bearing calculations: do not be scared by the formula to lie down!

​Nine times out of ten, a pipe crushed by a support is a miscalculation of the load.Don't be dissuaded by mechanics formulas, remember these three "fool's laws". Don't be dissuaded by mechanics formulas, remember these three "fool's rules":

1. ​Vertical load = (pipe weight + medium weight + insulation weight) × 1.35​

   • For example, a 4.2 metre section of DN150 water pipe:
     Pipe weight 821N + water weight 902N = 1723N × 1.35 ≈ 2326N
   • ​Don't ignore the insulation.DN200 steam pipe insulation accounted for more than 20% of the total weight!

2. ​Horizontal thrust = vertical load x 0.3​

   • Still DN150 pipe above:2326N×0.3≈698N
   • ​The coefficient of friction is taken as 0.3is an empirical value (steel to steel sliding)

3. ​Bracket span look-up table::

   Pipe diameter (DN)	Bare gas pipe (m)	Liquid pipeline bare pipe (m)
   100	3450	6100
   200	7950	10500
   300	9150	12900

​slacking off: The spacing is set directly according to the smallest pipe diameter! For example, if there are DN100 pipes in the pipe group, it is correct to set up the bracket according to 5 metres spacing.

III. Practical case studies: bloody lessons learnt

Case 1: Vibration cracking of heat pipes in a chemical plant

• ​impunity: Cyclic cracking of weld seams in DN250 steam pipe compensators
• ​autopsy report::
  • Compensator sidesNo guide frame.Tube twisting during thermal expansion
  • Nearest bracket to elbowOver 1 metreThe inertial force is all over the weld.
• ​Rescue programme::
  1. Add 1 metre before and after the elbowFour-way limit guide frame​
  2. Fixed frame at 32 times pipe diameter on both sides of the compensator (approx. 8 metres)

Case 2: Fertiliser plant vertical pipe "jumping incident"

• ​devastation: DN300 liquid ammonia pipe broken in the middle of an 80-metre tower
• ​fatal error::
  • Only the top of theload-bearing frameNot in the centre.guide frame​
  • Metal fatigue fracture due to wind loaded pipe amplitude exceeding 30cm
• ​correct handling::
  • Over 4 metres of riser must be addedCentral guiding frame​
  • Tower connecting tubeFull guide frame after the first bracket​

Question and answer time

​Q: Why is the pipe still clunking even though I installed the brackets at standard spacing?​
A: 80% guide frameIt's stuck.! Remember: guide frameTransverse only, not axial. If you dead tighten the bolts, the pipe suffocates internal injuries when it expands thermally - it has to be able to slide where it should!

​Q: Why does the 304 stainless steel bracket still rust?​
A: Mostly.Welding is the problem.! Temperatures above 450°C during soldering can lead tointergranular corrosion. Teach you two tricks:

1. expense or outlayLow carbon stainless steel (304L)​
2. weldPickling and passivation​

​Q: Can I use spring holders and guide frames together?​
A.It's too good.! For example, where the pump outlet vibrates a lot:

• first usespring-loaded rackCushioning vibration
• Plus 2 metres.guide framecontrol direction
  But remember: the spring-loaded frameYou can't use yourself as a guide.​

After twenty years of piping design, I have seen too many people planted in the "almost on the line". Guide bracket looks like a small part, is actually the pipe's "spine" - you fool it, it will collapse to you. Finally, three words of truth:

1. ​Don't save on gaskets.! Stainless steel pipe directly on the carbon steel frame is equal to burying a corrosion bomb for themselves!
2. ​Long-distance pipeline corridors: A guide frame must be inserted after every two sliding frames, otherwise the tube can be twisted into a twist!
3. ​Take a bank card and stick it in the gap during acceptance-Can be inserted but does not wobble (3-5mm gap) to be considered qualified

(Fingers on the table) Remember, guys: chemical piping is a game of life, not a Taobao shopping stent--Those who just look at the price tag will lose their trousers sooner or later!​