Horizontal Skidding: A Comparison

People in the industry mix and match to get their desired results in a certain situation. The results can vary. It would be better if i compare similar operations with examples of actual projects

Let us take the case of installation of  Condensers in a Thermal Power Plant.

1. Winch/Chain Pulley and Roller- This technique has been adopted by Indian Mechanical contractors due to its low cost. It's not skidding but still we can say its close to it. However, there is a big risk involved in such operation.  For example...What if there is an error in the inclination of the roll? The roll is uncontrollable at certain point. It's always a heart stopping affair. Then again in countries like India where projects are won by lowest price bidders, risks are neglected most of the times. 
   
2. Strand Jacks and Rollers- Recently introduced. Cost is slightly above the "winch and roller system". Instead of winches, Strand jacks are used to pull the frame on which the condenser is mounted. The problem again is the controllability of the procedure. Manual stoppers are used to stop the roll. Also, when the frame is pulled which is mounted on the rollers. The rollers tend to displace from their intended place and then has to be corrected manually.
   The total time to skid in is 3days.
   Photographs: Left top- Rollers adjusted after dislocation. Left middle- View from the pulling end. Left bottom- Single strand jacks pulling the condenser. Right- View from side showing the U rail.
   
   
   
   
   
   
3. Push Pull Cylinders on Skidding Tracks- Probably the safest method because of the controllability of the skidding process. The push pull cylinders can either push or pull the package. The Package is placed in the skid shoes and inturn the skid shoe is over a teflon matted skid track. Liquid soap etc. is used to reduce friction over the teflon mats.
   
   
   
   

Horizontal Shifting- The unconventional way

In my last blog posts i have been discovering through the history about the ways people tackled the challenge of shifting heavy loads. I will explore the heavy lifting in my upcoming posts. For now i will stick to the horizontal shifting.

Why unconventional means of shifting if you have modular transporters (Modular Trailer or SPMT)?

There are situations where these conventional methods cannot meet the challenges. In cases where there are space constraints. In cases where site situation is such that the use of conventional techniques cost seems too high with respect to the project cost.

I will start with a seemingly funny (mind it, its genius stuff) but effective example shown below.

This photograph is reported from the Indian state of Kerala where a coconut tree was shifted to clear the area for construction work.

Instead of chopping the tree off these ingenious guys decided to shift the tree instead. Commercially i can not compare the cost between chopping off the tree with this method but i can surely say that the life of the tree was definitely saved, which is priceless.

In heavylift lingo, this method is known as "Skidding".

Skidding can be done either pulling or pushing. In heavy lifts we use either 

1. Winches or Strand Jacks
2. Push Pull Cylinders (Compensating Technique)

In both the cases skid tracks, friction reducing materials like Teflon or PFC and Power Packs are common. Elevation cylinders for negating the effects of unevenness of the underlying surface is also used on case to case basis.

Below is an example of use of Strand Jacks for Skidding.

Installation of strand jacks

Getting in the strands

Skidding is in process

Load out of 14500T Jacket. South China Sea, 130km offshore Sabah in East Malaysia. Executed by SARENS.

I will explore other Skidding techniques and the its importance in my next blog.

The heaviest monolith quarried and transported

We often are awed by the heavy lift marvel jobs which happen today. Not to mention, the heavy lift contractors themselves try to gain as much publicity when they do the "heaviest" or the "biggest" lifts or transports.

I used to think that todays equipment and engineering has made us far better in heavy lifts than what we were say 100 years back. I was wrong...point blank.

I recently came across an event in the history which happened in the year 1768. This was the shifting of a 1250T monolith for a distance of 6km. Wikipedia states that its still holds the record for the heaviest quarried and moved monolith.

I am talking about the Thunder Stone at St Petersberg.

The shifting equipment was designed and the project was ingeniously engineered and executed by Marinos Carburis, the first Greek to hold a diploma in Engineering.

Since, the stone had to be shifted from marshy terrain, they waited till winter so that the soil is frozen and hard. It was then transported from the quarry area to the ship and then to the city.

"He developed a metallic sledge that slid over bronze spheres about 13.5 cm (6 inches) in diameter, over a track. The process worked in a way similar to the later invention of ball bearings"- Info Source http://en.wikipedia.org/wiki/Bronze_Horseman#Thunder_Stone

I was humbled. Designing and use of balls for sliding or skidding before even invention of ball bearings is out of the world. To surprise you more...this technique of shifting is used even today by heavy lift contractors!

Introduction to Alternate Lifting

This is my second blog inspired by the overwhelming response to my first blog heavytransportindia.blogspot.com 

I have been trying to get this through for the last 6 months.

While my first blog was related to the heavy transportation industry, it struck me that transportation is a part of heavy lift. So, i decided to create this blog which deals with heavy "Lifts" majorly aimed at alternate lifting and its relevance in India.

Generally heavy lifts are associated with cranes, which is understandable as today most of the heavylifts are done by extensive usage of heavy duty cranes and thats a huge subject in itself.

In this blog I will try to explore the very rarely explored world of Alternate Lifting, which we in the industry generally call it. That is an irony in itself...because this heavy lift technique has been practised way before cranes were invented.

Alternate lifting cannot be defined as a set of heavy lift techniques. Its a lifting technique which  may use multiple lifting of shifting techniques combined to resolve critical heavy lift challenges and get the desired result.

Arguably, the construction of the Egypt pyramid is THE major heavy lift project humans accomplished in the ancient world. There are different theories on these heavy lifts and shifts which even today are argued upon.

The world of Alternate lifting is only limited to ones imagination.