3 Column Square HSS Stand Design for Hydrocyclone Mounting

[CollinM7]

Hi everyone, hopefully this is an appropriate place to post such a request (this is my first time using this forum).

I am an Engineering Intern and have been tasked with the mounting of a Hydrocyclone (purpose not important) within our plant. I have attached a drawing file of the hydrocyclone, and the stand that it is ordered and mounted with. The problem with the current 3 leg Hydrocyclone stand is that it measures only 4 ft tall however, the location in which the Hydrocyclone is to be installed has changed within the plant and we now require a 12 ft stand. Seeing as the manufacturer is unable to make a 12 ft stand, it was requested that we design the mounting arrangement for the Hydrocyclone. My current proposition is to keep the Hydrocyclone on the existing 4 ft stand (no additional cost as it is already ordered) and place it on 3, 8 ft tall stainless steel (required for environment) square HSS columns with a matching filet welded top face to bolt directly with the existing Hydrocyclone stand feet. I have completed critical buckling and yield calculations for a 2x2x3/16 square HSS column however, I seek assistance in the design regarding whether or not a cross bracing would be required, design against seismic forces (Region: Illinois, USA), the stand will be indoors so wind force is ignored, deflection calculation, footing design, bracing, and weld size for the column footing and top face. The structure should be designed with a safety factor such that if a person (estimated 300 pounds max) was to fall onto the hydrocyclone from the top walkway (8 ft from the ground), it would remain stable. The loading conditions for the 3 columns would be as follows:

-Floor: Concrete, indoor ground
-End Condition: Fixed-Free
-Column Quantity: 3 legs (spacing as displayed within the drawing attachment, noting all dimensions in mm)
-Material: 316 Stainless Steel
-Column Length: 96 inches = 8 ft
-Weight of static Hydrocyclone during operation: 400 lbs.= 180 kg
-Account for: Seismic forces, and Horizontal force of 300 lb person falling onto Hydrocyclone from walkway that is 8 ft in the air

Thank you for any assistance in calculation or advise you may be able to provide me as I continue to work on this project. As a student of mechanical engineering I could use any structural help that I am offered!

Example of the Hydrocyclone and stand to be mounted:

 

[BAretired]

Does the pedestal need to be stainless? How about a 6" or 8" dia. RHS by 8'-0" long? This eliminates a dust collector as well as messy bracing. Provide a base plate with holes for anchor bolts into the floor and cap plate with holes to match the holes in the upper assembly. If the upper assembly is stainless, use appropriate separators between cap plate and assembly.

BA

 

[CollinM7]

Hi sorry for the late reply.
The structure does indeed need to be stainless as it's located within a wash train area in which corrosives are present; 316 grade it to be used. When you say RHS do you mean rectangular or round hollow section? I was confused because you said diameter following RHS. Neat idea though! I like the idea of a single column "pedestal", with a large base plate with concrete anchor bolts and a "cap plate" for the top would be 20" diameter to support the 3 leg hydrocyclone stand (also stainless stand). Would you be able to direct me to a source for the calculations for such a setup? The hydrocyclone only weights 400 lbs however, I must provide a Factor of safety for the structure before I present the idea. Also, I need to determine the thickness of this cap plate as well as the weld size to attach RHS and cap plate. I am curious, with a 8" column supporting a 20" diameter cap plate with 400 lbs sitting on it would this be safe in terms of overturning moment etc.?
Thanks for the idea! Any further opinion/assistance is not expected but very much appreciated.

 

[BAretired]

Collin,
RHS = Round Hollow Section
HSS = Hollow Steel Section (same designation for square or rectangular) Edit: HSS = Hollow Structural Section

I suggested RHS because the triangular arrangement of the upper legs fits a circle better than a square or rectangle, but any of those shapes could be used if preferred.

This is an unusual application, so I cannot direct you to a source for specific calculations but it is similar to the installation of a free standing jib crane. See the following:

https://www.harringtonhoists.com/pr...FreeStanding Jib 350 Series Owners Manual.pdf

Table 2-1 indicates mast diameter for various spans and capacities as well as some suggested foundation details.

BA

 

[dauwerda]

First, let's get the terminology straightened out.

HSS = Hollow Structural Section -

https://www.aisc.org/technical-resources/hss/

RHS = Rectangular Hollow Section -

https://www.aisc.org/technical-resources/cidect-design-guides/

CHS = Circular Hollow Section -

https://www.aisc.org/technical-resources/cidect-design-guides/

SHS = Square Hollow Section

RHS, CHS, and SHS all fall into the HSS category.


Overturning moment will be the same whether you use 1 central pedestal or 3 individual legs. This will be resisted by the base plate and anchors. I am not familiar with stainless steel design but you may find it beneficial to start by looking at the AISC Steel construction manual. You essentially have a cantilever column that needs to be designed.

 

[BAretired]

I agree with dauwerda's definition of HSS and have revised my earlier post in accordance with his post. I normally use the term "HSS" to refer to all hollow sections, rectangular, circular or square but I thought I had seen "RHS" used in reference to round columns on Eng-Tips (I could be mistaken).

The 2004 CISC handbook lists "ROUND HOLLOW SECTIONS", "RECTANGULAR HOLLOW SECTIONS" and "SQUARE HOLLOW SECTIONS". So far as I can see, the Canadian handbook avoids the terms RHS, CHS and SHS, but I have no argument with the abbreviations as defined by dauwerda. When specifying HSS shapes, the dimensions indicate the type of HSS without further clarification.

BA