Installation bolt are extremely important for fixing equipment in chemical plants.
Since it is a mechanical part, it is a place where electromechanical engineers can demonstrate their true potential.
Many owner-engineers neglect bolts, but installation bolts are very important for reliable long-term use.
It’s a basic and important thing like a foundation bolt .
There are multiple ways to say bolts. Understand the fixing methods and choose the best one among them.
- leg type and bracket type
- leg type
- bracket type
- Anchor bolts are the basis of installation bolts
- Maintenance when using anchor bolts as installation bolts
- middle leg
leg type and bracket type
When installing a tank in a chemical plant, there are two types: the leg type and the bracket type .
In general you would choose the bracket expression .
The leg type has the advantages of the leg type, but I think the bracket type is adopted because the advantage of the bracket type stands out.
Let’s compare the differences.
Let’s start with the concept of the leg type and the bracket type.
It looks like the image below.
The tank is assumed to be vertical.
The leg type is a type in which the torso of the tank protrudes from the bottom as the name suggests .
When the legs are protruded from the torso, the torso and legs may be spot-welded directly, or the brackets may be removed and the legs bolted together.
If you want the legs to stick out from the bottom, you’ll probably have to weld them.
Attach a plate to the bottom of the leg and connect it to the concrete foundation with anchor bolts .
The bracket type is a type in which a bracket is welded to the body of the tank .
In this method , the beams on each floor are processed to receive beams, and the brackets are attached to the beams with bolts and nuts.
The reason why we are limited to vertical tanks (or agitation tanks) is as follows.
- The pump has a concrete foundation. The appearance is almost the same even if it is fixed on a channel basis.
- Horizontal tanks and horizontal heat exchangers are generally bracket type.
- Since the tower is small in a batch-type chemical plant, a bracket type is generally used.
Because the selection is almost automatically narrowed down to one.
Introduce the advantages of the leg system .
Advantages of leg type
- Beams and columns of the frame can be made thinner
I can only come up with this. sorry.
There are almost no benefits of the leg type.
Since the tank and liquid load can be deposited on the concrete foundation without depositing the tank on the frame ,
It is possible to reduce the strength of the building.
As a result, it may be possible to make beams and columns thinner.
Instead, a separate foundation should be embedded into the ground.
If you do not attach a platform or frame around the tank such as an outdoor tank, it is limited to a leg type.
If not, you will have to make a tank foundation separate from the platform and frame foundation.
remove from the plate
The most common way to remove the legs is to remove them from the body plate .
The image is as follows.
It is a method of welding the legs of the tank to the body plate.
Let’s go into a little more detail.
The body plate and legs are welded with multiple flat plates in between.
You might think you could weld the legs directly to the torso, but it would require a little ingenuity.
This is because the weld beads on the body plate and end plate interfere with the legs .
I often see a shape that cuts out the legs partially, but it’s uncool.
In some cases, a backing plate is attached to the body plate to increase its strength.
In this case, the leg is separated from the body plate by the thickness of the backing plate, so it may not interfere with the weld line.
A single plate may be used to connect the legs and body, but in many cases, multiple small plates are used to reduce the number of welds and material costs .
The manufacturer will typically choose this method if the user places an order with the manufacturer without providing leg instructions.
remove from the panel
Another method of removing from the body plate is to remove from the end plate .
It looks like the image below.
The leg position is different.
Let’s see the details.
The legs are welded to the panel.
There is no little ingenuity compared to taking it from the body plate.
If I dare say it, it would be about attaching a backing plate to the body plate and then attaching the legs.
Comparison between when removing from the body plate and when removing from the end plate
Let’s compare the case of removing from the body plate and the case of removing from the end plate.
direction of force on the tank
The direction of force applied to the tank is very different.
When the legs are removed from the body plate, a force that pulls the body plate in the axial direction is applied.
When the legs are removed from the head plate, bending stress is applied to the head plate as external pressure.
Materials generally have stronger resistance to tensile stress than bending stress, unless there are extreme circumstances.
Bending stress works as a moment, so the longer the arm, the greater the stress.
It goes without saying that the higher the strength, the more reliable the equipment will be, so it’s safer to remove it from the body plate .
This is probably one of the reasons why manufacturers typically remove the legs from the body plate.
In some cases, the end plate is one size thicker than the body plate. There is an opinion that
In some cases, the thickness of the head plate is the same as the thickness of the body plate, so it is better to treat it as an exception.
The main reason for removing the legs from the end plate is to reduce the leg pitch .
Japan, where factories are small, is very welcome.
If you specify the size of the tank and the leg pitch, the manufacturer will also design it so that the legs are removed from the end plate.
The overturning balance of the tank itself is more stable if it is taken from the body plate .
Since the leg pitch is larger than the tank diameter, the tank itself is less likely to tip over.
In extreme cases, if one leg supports the center of the tank, the tank is larger than the legs, so it seems like it would easily topple over.
It’s one of the reasons why the manufacturer removes the legs from the torso board.
Here are some advantages of brackets .
Advantages of leg type
- Since legs are not required, the bottom of the tank can be effectively used as piping and passage space.
- A separate platform is not required to access the top surface of the tank (frames and buildings can be used together)
- It is stable because it can support the load near the center of gravity of the tank.
- Inexpensive because accessories such as legs and templates are not required for the main body of the device.
It has many advantages compared to the leg type.
In particular , one space would be a big deal in any manufacturing industry in Japan.
If you try to minimize the building area in order to lower the investment cost to be competitive,
You will inevitably have the problem of effective space.
If there are obstacles such as legs here, the piping will be complicated and expensive.
Instead, on the upper floors, the bracket part becomes a factor that squeezes the work space. Not a big deal though.
2 platform on a case-by-case basis.
The fact that it is supported by the center of gravity of 3 ” is actually a blessing.
Supporting the center of gravity of the tank with brackets is clearly more stable than supporting the ends of the tank with legs.
A tank with a load cell would have the same problem, wouldn’t it?
The fact that you don’t need 4 legs or a template can also be an effort if you try to reduce costs.
The size of the pillars and beams of the building, which was an advantage of the leg type, has to be increased in the bracket type .
However, the impact will not be significant .
The size of the column is somewhat of an issue in terms of piping design, but it is not a design element that is absolutely rejected.
I think that there is not much difference in the beam size between the leg type and the bracket type.
This is because the size of the girders is determined by the size of the building, whether or not there is a tank load.
When it turns out that a bracket-type tank cannot be installed in a building that was originally designed with the intention of installing a leg-type tank, the plant is no longer applicable.
Plants that are inflexible and difficult to use will lose their competitive edge.
Here is a basic elevation drawing.
However, this is a schematic elevation view.
It is used to vaguely understand and express the installation image of the bracket.
In the case of the bracket type, a hole is made in the floor surface and the bracket and the beam are attached to each other.
This image is not limited to mechanical engineers, but is a level that anyone who works in a factory knows.
Next, I will explain the floor plan.
This is where the difficulty level rises.
A person in the manufacturing department who can observe the site well may be more knowledgeable than a mechanical engineer.
If you draw this diagram, you can fully discuss the installation design with civil engineering.
I will explain the structure of the system from the whole to the details.
Connect the four pillars with beams. These beams are called girders.
Direct connections between girders and tanks are not common.
Take two small beams so that they are perpendicular to the large beam.
Pass two small beams to connect the two small beams.
The four small beams now form a square shape.
Fit the tank into this square.
Insert diagonals into the joists to connect the joists and tank brackets. This is called a receiving beam.
Since the size of the girders is 4m, it should be possible to install a tank of nearly 4m!
Some engineers say that with a straight face, but you can understand it by looking at this floor plan.
Considering the plumbing, you can imagine that it is quite difficult.
At least in a batch chemical plant, it is better to think that the tank diameter can only be installed up to about half the length of the girder .
Support beam details
If you can understand the floor plan, the basics are OK.
I will explain the details of the receiving beam as an applied content.
Joining small beams and supporting beams
I will explain the relationship between the small beam and the receiving beam.
This figure is a cross section. Same orientation as elevation.
The configuration is a form in which a gusset plate, which is a connection plate, is welded to a small beam, and the supporting beam is connected with bolts and nuts .
It doesn’t matter, but don’t you worry about what you’re referring to because there are so many drawings in construction plans that it’s hard to tell which direction they’re pointing?
The figure of the small beam and the receiving beam is actually the same as this.
As long as the receiving beam is a diagonal member, it is difficult to describe it with the same cross section.
The above figure is divided into left and right because I intentionally wanted to express that the direction of the small beam is different.
Actually, both ends of the receiving beam are connected by two small beams.
Connecting beams and brackets
The connection between the support beam and the bracket also poses a subtle problem.
Basically, they are only connected with bolts and nuts, but in rare cases, the support beams are reinforced.
It looks like the image below.
In the case of H steel, a reinforcing plate is attached to the width of both ends of the bracket for reinforcement, although it is not often seen in C-shaped channels.
Since the bracket is supported only on one side of the support beam, it is easy to apply a bending moment, so reinforcement is desired.
Reinforcement on one side may cause distortion due to the heat of welding, so I would like to reinforce the other side as well.
There are very few examples of batch-type chemical plants that have been reinforced to this extent.
I think it would be nice to know as a device to increase strength.
Bolt system and installation bolt
Here is a typical bolt system for mounting bracket type equipment.
The image is as below.
This is an image of attaching a bracket and a C-type channel.
The situation is slightly different with H steel instead of C channel.
Size is always a topic of discussion when it comes to bolt systems.
Let’s organize the relationship between bolts and holes.
It may be a memorization level.
Bolt and hole size (mm)
The bolt diameter will be selected by the equipment manufacturer.
Prepare the bolts accordingly and drill the bolt holes properly.
First, let’s talk about slanted washers .
Use this for C-type channels.
That’s because there are many C-type channels when installing chemical plant equipment.
Attach the slanted washer to the following locations.
The C-type channel actually has a slope.
Even if you try to forcibly attach this with a bolt, the bolt will tilt and you will not be able to attach it properly.
An inclined washer is required to absorb that inclination.
Double nuts are commonly used in chemical plant equipment .
It looks like the image below.
Double nut means using two nuts.
Simple, but very effective for locking.
If you use only one nut, it may loosen due to vibration during operation, but the probability is greatly reduced by attaching two nuts.
Place the washer between the nut and the base.
Washers are standard equipment in chemical plants.
It looks like the image below.
The purpose of attaching the washer is to evenly transmit the tightening force of the bolt to the base.
There is no problem if the contact surface between the nut and the base is sufficiently secured.
This can only be used when the bolt size and bolt hole are determined by the minimum dimensions.
For example, pipe flanges.
When using M12 bolts, the bolt holes are Φ15, and when using M16 bolts, the bolt holes are Φ19.
Designed with minimum bolt hole size.
For large-scale equipment such as chemical plants, bolt holes are sometimes made large in order to absorb manufacturing errors.
In general, a long hole with only one side called an oblong hole is used, but there are also cases where the hole is simply enlarged.
Either way, the contact surface between the nut and the base will be smaller.
If the bolt and nut are occupied in this state, the base may be deformed.
Use washers to prevent this.
A liner is a thin plate.
Used for height adjustment when installing chemical plant equipment.
It looks like the image below.
Equipment in chemical plants is very large with a size of several meters or more, and manufacturing errors of the order of millimeters will inevitably occur.
Misalignment in millimeters also occurs during civil engineering work.
If you forcibly install it in this state, horizontality and verticality will not be obtained.
In the case of moving equipment, this has adverse effects such as energy loss and abnormal vibration.
In order to solve it, the height is adjusted with a liner at the time of installation.
Anchor bolts are the basis of installation bolts
I will explain the types of anchor bolts .
Chemical plants always involve the process of fixing large equipment to the building .
In a project, the most important factor is how to install the equipment at the on-site construction stage .
In some cases, it can greatly affect the construction period.
This content is useful when making adjustments to shorten the construction period or when proceeding with design work.
This is a more detailed area for civil engineers, but we have summarized what mechanical engineers should understand.
This article focuses on concrete foundations .
Please refer to the following article when fixing to the beam .
The basic method of setting bolts in concrete foundations is the embedded method .
The embedded formula is the image below.
Just insert the bolts when you mold the concrete.
Positioning is usually done by fixing bolts to the reinforcing bars in the concrete.
The advantage of the embedded type is its high strength . This is one point.
The point is whether the strength of the concrete is uniform.
The embedded type, which is a one-shot concrete finish and is in contact with bolts, is characterized by higher strength than other methods.
The disadvantages of the embedded type are two points: accuracy is required and cost is high .
Once the concrete foundation is made, the position of the bolts cannot be changed later.
It is necessary to match the bolt pitch of the mechanical equipment and the bolt pitch of the concrete foundation in the order of mm .
The gap between the bolt and the bolt hole is only about 3mm.
It is common to prepare a template in advance.
If you do not prepare a template, it is almost always impossible to install,
We are forced to open large bolt holes for mechanical equipment.
The more templates you need, the higher the cost.
The use of the embedded type is limited to large equipment .
Batch-type chemical plants are limited to large mixing tanks with legs placed on concrete foundations .
In the first place, fixing a large mixing tank with legs is an unreasonable idea, so it is rare to apply it.
The unboxed type is positioned as a simplified version of the embedded type.
The unpacking ceremony is performed in the following flow.
The concrete foundation is molded with holes (boxes) drilled only around the area where the bolts of the concrete foundation will be installed.
Install the equipment with the bolts set in the box.
Set the liner for horizontal level adjustment during installation.
Finally, fill with mortar and complete.
The advantages of the out-of-box type are the opposite of the disadvantages of the embedded type.
Inexpensive and position adjustable .
You don’t need a template, and you don’t have to think about position adjustment severely.
The disadvantages of the out-of-box type are the opposite of the advantages of the embedded type.
Strength is a little weak.
Concrete is not integrally molded, so there are discontinuous parts between concrete and mortar.
This is a big factor in weakening strength.
The double work of applying mortar after molding the concrete is also a disadvantage.
In batch-type chemical plants, box-out type is used in various places.
The unboxing type can be used in almost all cases where machines are fixed to concrete foundations .
The hole-in anchor is positioned as a simpler version than the unboxed type.
Hole-in anchors are constructed in the following flow.
As with the unboxing type anchor, open the box beforehand.
When setting the machine on the foundation, insert the bolts at the same time.
After plugging in, hit the head of the hole-in anchor bolt and you’re done!
The feature is that there is no liner adjustment or mortar process like the unboxing type .
The advantage of hole-in anchors is that they are inexpensive and easy to install .
Construction companies will love it.
It is also characterized by the fact that the hole in the box is small and the concrete foundation can be made compact.
The disadvantage of hole-in anchors is that they are weak .
The contact area between the concrete and the bolt is small, and only the widened portion of the bolt is in contact with the concrete.
When fixing equipment with bolts, the pull-out force of the bolts is directly related to the strength.
Since the pull-out force of the bolt is proportional to the contact area between the bolt and the concrete,
A hole-in anchor with a small contact area raises concerns about its strength.
Also, since water collects in the box , it is better to cover it with mortar or caulking.
Most batch chemical plants use hole-in anchors for small equipment .
This includes small pumps and cartridge filters.
The piping support is also a hole-in anchor.
Chemical anchors are similar to hole-in anchors, but the box is filled with adhesive .
The higher the strength, the easier the construction .
General construction companies are based on chemical anchors.
It is better to be careful when using chemical anchors in chemical plants.
Because we use chemicals as adhesives .
Unless the adhesive composition is examined to determine if it is compatible with the atmosphere of the chemical plant,
While using it, the worst possible outcome is that the equipment tilts or falls over .
Typical examples include vinyl ester resins and unsaturated polyester resins .
This is the same material as FRP .
There is an opinion that if FRP is used in a chemical plant, the same material can be used to fix anchor bolts.
There is a conflicting structure of opinions that it is safer and more secure not to use resins that are vulnerable to solvents as much as possible .
Maintenance when using anchor bolts as installation bolts
Anchor bolts are parts that require maintenance.
It’s just a bolt… and we can’t take it lightly.
Cap prevents external corrosion
Caps are an effective way to extend the life of anchor bolts .
Attach the cap, fill the inside of the cap with resin, and fill the gap with the concrete foundation with silicon caulking.
By doing this, you can greatly reduce the corrosion of the anchor bolts due to outside air and rain .
Anchor bolts are made of iron and will corrode with use.
If it is only fixed with a bolt nut, it can be replaced, but since the anchor bolt is fixed to the concrete, replacement is difficult.
I would like to add a cap as a basic set for construction using anchor bolts.
Mortar protection with stainless liner
It is better to use a stainless steel liner for the unboxed anchor type .
If you don’t think about anything, you will use the iron plate .
This iron liner. It rusts quite a bit.
As rust progresses, the volume expands, pushing up the liner and floating it.
Water runs through the gap between the liner and the concrete and corrodes the box and anchor bolts.
I would definitely like to do something that can be done easily at the construction stage and has a long-term effect.
Welding if all else fails
Welding bolts is also one way.
This is the last resort to try to shorten the construction period even if the bolt is corroded even with a cap and a stainless liner.
Although it is not actively adopted, it may be adopted depending on the usage conditions.
The method is to cut off the corroded part of the bolt and add the threaded rod.
It’s pretty pushy, isn’t it?
Welded bolts are naturally weaker than stock bolts.
If you use it poorly and the bolt breaks, it will be useless.
After carefully considering the number, size, and strength of the bolts , if it seems feasible, it can be adopted .
It’s a great trick, and it’s just right not to use it all the time.
When installing large equipment, keep the concept of intermediate legs firmly in mind.
The intermediate leg is an image like the figure below.
The image on the right is an image of the intermediate leg .
One leg is in the middle. Hence the middle leg.
There are a lot of merits in attaching an intermediate leg.
Advantages of intermediate legs
- You can design the building without knowing the bolt pitch of the equipment.
- Equipment can be transported over long distances using a short vehicle.
- Easy to transport equipment in narrow factories
- Subtle position adjustment during installation is possible
This idea is exactly the same as the piping flange .
If it is a large facility such as a reactor, it is better not to expect coordination with the building design in 1.
This is because if the center of gravity of large equipment is out of order, it is dangerous when vibration occurs.
In batch plants, there is almost no such equipment, and basically installation with machine bolts is sufficient.
It is easy to take advantage of the benefits of the intermediate leg.
In the case of dividing the on-site civil engineering work while simultaneously processing equipment design and building design in a short project period , the concept of intermediate legs is rather common.
Templates are similar to intermediate legs, but are used slightly differently.
A template is created at the equipment manufacturing stage.template flow
- step 1Exterior production of equipment
- step 2Attach legs to equipment
- step 3Bolt hole machining along with the template
- step 4Hand over the template to the customer
- step 5Foundation work using a template
- step 6Equipment delivered and installation completed without difficulty
A template is similar in concept to duplicating a key.
Once the machine and foundation are made, it is difficult to modify them, but high-precision production is required, so I want to put them together properly.
This is the part that the facility design engineer wants to be particular about .
When using the embedded anchor method without using a template, it is essential to process the base plate on the machine side.
Normally, the slotted holes are pre-drilled as shown below.
This example is often used to relieve equipment expansion at operating temperatures, such as heat exchangers.
It can also be used for adjusting the installation position.
What would you do if you started the installation work without using this process and without using the template?
I will cut the base plate using gas on site .
As an engineer, this is a loss. A clear failure .
It can be prevented by proper design, and as a designer, it must not occur.
In addition, the template is usually provided by the manufacturer, but there is also a reverse pattern. It’s now treated like a feat.
The installation story comes back to the bolt story.
The following books are good for deepening your knowledge about bolts.
Introduced the concept of the undercarriage, which is the first thing to consider when installing equipment for a chemical plant.
Explains the difference between legs and brackets, types of anchor bolts embedded and unboxed, hole-in anchors, chemical anchors, intermediate legs, templates, etc.
As a designer, I never want to fail.
Please feel free to post your worries, questions, and questions about the design, maintenance, and operation of chemical plants in the comments section. (The comment section is at the bottom of this article.)
*I will read all the comments and answer them seriously.