What is Soft Foot?

What is Soft Foot

Forward:-

Rotating machines are used in every industry, from Oil & Gas, to water and waste water and beyond.  A vast array of machines ranges from Electric Motors, Pumps, Blowers, Engines, Gearboxes etc.  HP Range from 10 hp to 10,000 hp +

Soft-Foot has been an issue all rotating equipment now and will be for many years to come.

What is soft-foot?

Soft-foot is a condition when 1 or more feet on machine do not make good contact with the baseplate / sole plate. 

Possible Reasons for your Softfoot issue: -

• Bent machine foot
• Warped Baseplate / Soleplate
• Dirt on underside of foot, (grease, Paint etc.)
• Old Shims, bent, dirty
• To many shims
• Step Shims
• Degraded grout. (Baseplate / Soleplate)

Issues caused by Soft-foot:-

• Overheating bearings
• Increased vibration
• Excessive bearing wear
• Seal leakage
• Coupling failure
• Bent shafts

How to resolve sSoft-foot issues:-

• Clean the surfaces both the mounting surfaces and the underside of the component feet.
• Do NOT re-use old shims
• Use only new shims, maximum 4 shims.
• Only cut your own shims as last option.
• If a spacer plate is utilized, ensure its machined flat both sides.
• Re-Grout baseplate / soleplates
• Machine mounting surfaces co-planer, use RP686 as guide.

References: -

API RP686 Shaft Alignment Handbook, 3rd Edition, by John Piotrowski http://thealignmentblog.com/blog/2010/06/04/soft-foot-what-it-is-and-how-to-minimize-it/ https://www.techtransfer.com/blog/what-is-soft-foot-and-why-does-it-affect-shaft-alignment/

Why Should I Use RotaChocks?

Installed RotaChock

Why Should I Use RotaChocks?

Implementation of the RotaChock product into your machinery system lowers the total life cycle cost of your machinery.

Whether you:

• Fabricate to sell
• Fabricate to rent
• Operate

  Or

•  Own machinery your objective is to produce at the lowest cost, at the production line and throughout the total cost management of the equipment.  

• The RotaChock improves the bottom line!

WOW!!

Machinery mounting takes on many forms in all types of industries:

• Power Plants
• Gas Compression Systems
• Pumping Systems
• Industrial Production Systems
• Energy Discovery, Well Head, Mid-Stream and Up-Stream
• Marine Propulsion and Power

The RotaChock will minimize or eliminate the number one reason for poor performance of the machinery.  The poor transfer of forces from rotating machines to their foundations.

What??

All machinery breaks and we hope it operates as long as possible within the maintenance parameters and required duty cycle wherein the machinery just wears out.  Fact is - most of the time it does not last as long as projected.

Most machinery breaks down or prematurely wears out due to some unplanned vibration in the system.  Most studies cite the cause of the problem as a poor or degrading mounting plane for the machinery.  Whether on a ship, or skid or inertial mass (concrete block) the mounting plane of the machine helps to maintain the oil film thickness in the bearings, ring clearance in the piston head, face seal or impeller to volute clearances.  These clearances are critical to the machine’s function.  And far too many times issues start with the mounting plane.

We are the best at creating the mounting plane!  From design to wear limits our device will make mounting plane.  Just a word of caution – The RotaChock does not fix poor foundation design or correct for poor system maintenance protocols.  But the RotaChock makes the whole system easier to design and service at the lowest cost possible.

RotaChock Introduction

The RotaChock is an adjustable, self-leveling and reusable equipment mounting chock.  The RotaChock is a blend of engineering and years of field experience to produce a strong, stiff and elegant device to end machinery softfoot.   

Okay enough – just tell why I should use the RotaChock?

Foundations degrade, Skids rack in transportation and **it happens.  The mounting plane over the lifecycle changes – the chock needs to be adjustable and able to accommodate the small deviations that exist from time the engineering package is issued until their steel in field.  

We design flat foundations – in the real world they are never flat.  There is steel tolerances, twisting in transportation, welding, more transportation and racking of the skid.  All create non-coplanar surfaces for the feet of the milled flat feet. 

Alignment and softfoot is measured in 0.001” (thousands of an inch).  We offer alignment and mounting with zero softfoot. 

Zero softfoot within minutes and for the lifecycle of the equipment!

Zero softfoot, a sound foundation and good alignment will result the best possible vibration signature for the equipment.  Minimal or no vibration in the system will be long lasting system.

Mounting with the RotaChock is a minute’s process.  

• No longer a trial and error method of shims.  

• No longer milling foundations or making liners.  

• No longer pouring epoxy resins.

Whether in the shop or a field installation:  Align, Install the RotaChock, and Release the jacking bolts, Install and Tighten the mounting hardware – finished!!

And best yet!

If the alignment needs to be changed in life of the machine – adjust the chock to recreate the perfect mounting plane.  The RotaChock is reusable!

MAC's "Mechanically Adjustable Chocks" for API Applications

API 610 Draft 12th Ed

Incorporate Mechanically Adjustable Chocks (MAC’s) as a mounting option for drivers and driven components.

Introduction of Mechanically Adjustable Chocks (MAC’s)

What is a MAC? 

An adjustable mounting chock that fits between a machine foot and its baseplate / soleplate / skid once installed the MAC is stiff, strong and eliminates machine softfoot.

                       

Today, the MAC is a proven success in many applications ranging from small industrial 
pump and compressor installations, oil and gas exploration thru midstream pipelines, marine vessel propulsion systems, to the most hazardous duties of military Grade A shock applications.  Power range 5 hp to 20,000 hp.

Why use a MAC?

                All operating machinery has one thing in common - it is somehow affixed to a foundation.  Attaching a machine to its foundation in nearly all cases require an intermediate product to accomplish the interface.  The intermediate product in API standards is called a “shim.” There are many types of shims such as: shim stock (obviously), milled liners, poured compounds and “new to the marketplace” are MAC’s.  In most cases implementing a MAC eliminates the cost of milling foundations, the trial and error method of installing shims and the best attribute is they are reusable.

                We are a manufacturer of MAC’s.  We have extensive experience with all types of machinery mounting solutions and we honored to introduce the MAC to the API Committees.

History of MAC’s

                Let’s start this new technology discussion with some background the first US patients for mechanically adjustable mounting systems were issued in 1874 – so it isn’t factually new.  The concept is found in your home – looking at some heavy appliances washer, dryer and refrigerator they are a similar technology that is actually pretty close to the 1874 concepts.  The MAC for API class of applications is necessarily a little more robust.  So the idea of the MAC has been around for a long time.

               

Before the development of the CAD/CAM manufacturing during the 1970’s the MAC’s were not economically viable for an industrial - heavy duty machinery application.  With improvements in manufacturing techniques coupled with the evolution of machinery, specifically more power in smaller component foot prints, the mounting of machinery has become ever more critical!!

Our team’s background is machinery alignment and mounting. We have comprehensive experience using all the mounting systems listed in the introduction.  But, with the MAC we developed a technique that improves the mounting plane of the machinery during the production line process, at commissioning time and for the life cycle of all types of rotating machinery. 

From production line through the life cycle, there is no faster way to guarantee a no softfoot installation of critically positioned machinery than implementation of a MAC.      

MAC Configurations for API Related Environments

The most versatile MAC configurations are composed of self-leveling elements through the use of spherical matching parts and have some type of thread to accomplish adjustment.  Some MACs use an opposed wedge system as the adjustment feature.  The key to all these systems is that they are reusable.  Meaning they have the same life cycle as the host system.  Whenever the pump, motor, engine or compressor needs to repositioned as part of an alignment check or overhaul the MAC will be reusable!

The MTR (mean time to repair), relative to the alignment and mounting will be same as on production line minutes.  Not hours or days but minutes to a perfect no softfoot machinery installation!

 

Technical Improvements for API Standards

              
                No Softfoot

Soft Foot is not a designed feature of pump systems but it occurs at 80% of all pump installations.  The pump skid racks in transportation or is twisted at the final field condition.  Commissioning engineers are left to identify and correct the mounting plane.  The inherent to the MAC’s design racking / twisting of the skid is a non-issue.

                Adjustment Range

Some adjustment range is needed, pipework settles in the refinery, the milled spacer plate is machined to correct the pipe strain, the motor/gear will need to be realigned to suit.  The MAC’s adjustment range eliminates any need for machining of mounting surface elevations.

               

                Proven technology

The technology within the MAC’s is not new, MAC’s have been sold and used under many different types of equipment for more than 20 years.

Life Cycle Cost Enhancements

               

With a typical Shimmed application, shims are replaced, each time an alignment is done.  The MAC’s are re-usable, they last the lifetime of the equipment.

               

Issues for Implementation

               Gap for existing systems

Existing systems have typically have 3/8” shim pack, the MAC will not work in these situations, unless a raiser block is installed and is removable.

                Why does it work?

The MAC’s consists of the spherical washer top assembly and the lower a threaded 2 part assembly, with the MAC installed and the foundation bolt tightened the friction in the threads top the MAC from loosening.

Chocking Technique Comparisons:

Poured and Mechanical chocks address angular softfoot like no other technique.

Shims are not expensive for the parts but the trial error alignment / mounting techniques create a life cycle risk

Epoxy Resins are a good solution but the owners must understand that they will have to inspect and probably have to change the chocks periodically

Give us a call to look at your project

610 Specific Failure Scenario: Pump Locked Rotor Condition and/or Nozzle Loads!!

The pump and baseplate have been designed to survive with maximum loads per API 610 for each possibility by the system’s designers.  Relative to the mounting system, the mounting hardware is sized to survive these loads as a minimum.

Consequently, if either or both operating scenarios occur the designers anticipate that the mounting bolt will fail before damaging the pump or foundation.

The design of most currently known MAC’s is robust.  Some have a set of rigorous testing protocols and results to comply with marine classification or institutional societies to validate the rating and design of the MAC such that the mounting hardware will always be the weak link in the mounting system.

Factually, we have never experienced a MAC failure due to a machinery developed dynamic load event.  In all cases, the MAC only fails in the lab or events where we are specifically examining the MAC for failure modes i.e. during live fire (military) examinations.

Recap

               

Mechanical Adjustable Chocks “MAC’s”

• Perfect fitted chock
• Adjustable
• Self-leveling
• Strong
• Zero Softfoot
• Re-Adjustable of the lifetime of the machine

Principles for Chocking Rotating Machines

Our organizations have experience with mounting most rotating machines and during our evolution we collaborated with many OEM’s, builders and operators for heavy industry and their customers. All have experienced an adverse vibration, premature seal or bearing failures. Some have even seen catastrophic shaft or gear failure. Some of these failures were attributed to a poor chocking installation or a breakdown of the mounting system. A goal of our organizations is to eliminate chocking system breakdowns and identify symptoms of and configurations that create a failed mounting system while making the chocking solution more economical for the production line and the lifecycle of the machine.

Let start with accumulating terms and establishing a baseline of chocking techniques:

· Milled Liners:

o Blocks of steel or stainless steel milled to suit the gap between foundation and machine foot. Further the foundation or sole plates for the machine are milled to exacting tolerances. Liners never breakdown but their failure is mostly attributed to the craftsmanship and inspections during the alignment and mounting process. Each liner is a “Mona Lisa” in as much each one is unique, never reusable, never transferrable and always expensive.Evidence of a failed chock is machinery vibration and losing / losing hardware.

· Epoxy Resin Chocks

o Chemically bounded materials are the perfect chock – for a time. If the chemicals are properly mixed and poured, they usually have a predictable service life. The poured chock is never reusable, never transferrable. The cost for the installation is less than milled liners but it is a near certainty that the poured chock will need to be replaced during the lifecycle of the machine. A breakdown of the poured chock can occur if the application, mixing and pouring instructions were not followed or if the clamping force exceeds the rating. Evidence of failed chock is a crack in the compound, pulverized chock compound and first evidence is vibration in the machinery and losing /failed hardware.

· Shims

o Shims are thin metal shapes that usually end up in laminations and found generally in combination with milled foundations. Shims dominate the chocking techniques for industry.Many successful installations are found in lower power applications and several industries have restrictions for the allowable number of layers of shims. The shims are generally inexpensive so reusing the shim is not recommended. The failed shim mounting system has machinery vibration, losing hardware and shims that “walk away” from the machine.

· Mechanical Chocks

o Mechanical chocks are adjustable to suit the gap between the foundation and equipment. The mechanical chock first patented in the 1870’s are considered the new technology.Though engineered for more than 130 years the production technique required for the spherical style mechanical chock was cost prohibitive until the late 1980’s. The mechanical chock is reusable, transferable and good for the life of the machine. Since the 80’s the cost for mechanical chocks has been decreasing as more applications / industries adopt the technology. The mechanical chock is similar to milled liner in that it does not breakdown but loosening hardware is an indication that machinery vibration will soon follow.

This is the first in series of articles to present and discuss some of the solutions and mounting techniques for chocking machinery and equipment.

Shims

To enable rotating equipment to be aligned correctly to within 0.002” to 0.010” depending on type of equipment, thus maintaining operating time and reducing lifecycle cost.  Rotating Equipment which is not aligned correctly will have higher lifecycle costs due to leaking seals, overheated bearings and premature failure of coupling.

Let’s look at shims in a bit more detail, shims come in many shapes and sizes. Standard shims come in 2x2, 4x4, 6x6 and larger, these have  a slot cut into one side to allow them be slid into position while clearing the foundation bolt typical these are 316L stainless steel.  

The shims vary in thickness from 0.001” to 0.5”, they should flat and burr free. 

Shims have been in use for many years, they work well for nice flat parallel surfaces between the bottom of the machine foot and the foundation / skid. 

How are shims used?  Say for an electric motor driving a pump, the pump skid would typical be designed to have a 3/16” shim pack under each motor foot this shim pack typical consists of 3 shims.  Once these are installed under each foot, the foundation bolts are installed and tightened. A softfoot check is then carried out.  That is with dial indicator mounted close to the foundation bolt, the bolt is loosened, if any movement is found a shim of the desired thickness is a fitted to fill any space between motor foot and foundation. (note: most laser alignment system have a softfoot check option)

But how often are these surfaces parallel?  Not very often, a few opinions are available if you discover this issue.

1.      Step shim, that is cut a standard stock shim to fill the gap a close as possible, you may have to cut 2 or 3 more shims for this to work. Thus you have a custom shim pack per bolt location.

2.      Machine the mounting pads on the skid (base plate) to ensure in the coplanar.  This is expensive option, for the following reasons.

a.                The skid has been installed at the plant, typical grouted in.

b.                Field machining is expensive, small pump skids machined at a Shell refinery cost $3000 each to machine as an example.

What Other option do you have?

USE RotaChocks, Self leveling and Adjustable, no more shims!!

Tug Boats—Engine & Gearbox Mounting

Intracoastal Iron Works recently installed their first set of Cummins Engines with Reintjes Gearboxes on RotaChock. As the latest 72 foot tug is delivered we ask the builder for his thoughts. Peter Viguerie, the yard owner stated, “We love the quick and easy installation of the RotaChock. We don’t have the heartaches of the old style of installation of shims and epoxy anymore. We do the alignment, install and adjust the RotaChock one time, and we’re finished.”

 

He went on to say, “We have a lot of work lined up over the next few years so far and it’s nice to know that this process isn’t going to be one of those areas that are going to cost a lot of time in labor or product cost. It helps us concentrate on other critical issues, saving us time and money, ultimately making our customers happy, especially when alignment and mounting issues are, or “were”, one of those costly company headaches. I would recommend using the RotaChock on any application like this. It’s the easiest and fastest way to mount aligned equipment…and, we’ve never had an issue with an alignment after a vessel has left our yard.”