JACKING & SKIDDING 225MVA TRANSFORMER

JACKING STEPS

The first step in the jacking and cribbing procedure is to set up a safe jacking arrangement. This arrangement consists of two cribbing piles and two identical, hydraulically interconnected (hydraulically interconnected jacks are jacks that share a common hydraulic supply line from a single hydraulic manifold and pumping unit in a configuration so that the lifting pressure in both jacks is always equal) jacks placed at one end of the piece of transformer at the manufacturer-approved equipment support points.

The cribbing piles at the jacking end provide safety in the event that the hydraulic jacks fail to support the load. These piles will also support the load when the jacks are not used or removed. The other end of the equipment rests hard on cribbing to provide stability. This is very important because it prevents the load from rolling during jacking. This arrangement provides predictable loads in the jacks and at the cribbing points and prevents two-pointing. During the jacking operation, the cribbing piles adjacent to the jacks should be continuously shimmed to minimize the distance that the load will settle in the event that a jack fails.

The next step is to extend the two interconnected jacks high enough to install the cribbing layer. The jacks will extend equally because the opposite end is resting hard against its cribbing. Install the layer of cribbing under the jacked end. Shim the cribbing tight with steel shims or hardwood. Next, slowly release the pressure in both jacks using a common needle type valve. This method will allow the jacks to slowly retract and gradually load the cribbing pile. Because the cribbing is shimmed tight, the load will not move downward other than to slightly compress the cribbing pile and shims. However, the load should be lowered slowly while watching the cribbing pile to ensure that the cribbing is adequately holding the load. Repeat this jacking and cribbing procedure at this end.

 

SKIDDING STEPS

Moving a transformer by skidding requires services and equipment which can be supplied only by an experienced millwright team or heavy-equipment moving contractor

Unless your utility or operation has proven experience with transformer moving, the service of a thoroughly qualified engineering, millwright, or machinery moving consultant should be obtained

If lifting by crane is impractical, the transformer can be moved along the ground by Skidding on greased rail beam Moving transformer along the railway involves four distinct steps

  1. a) Building the railway; Setting Supporting Beams, Wooden Block, and Rail, setting between Foundation and Multi Axle
  2. b) Moving the Transformer from the multi axle to the railway;
  3. c) Skidding or rolling along the railway;
  4. d) Positioning the transformer on designated place.

Although details of moving procedure will vary with the size and weight of the transformer, the condition of the ground over which it must be moved and the distance must be traversed the following general precaution must be observed

  1. a) The work surface must be level as possible and absolutely firm. Multi axle deck should be jacked up off their hydraulic suspension and securely blocked to be both level and firm;
  2. b) The transformer never be raised by jack placed anywhere except at the jack steps. Jacking operation must be carefully controlled. The transformer should never be raised at only one corner nor should jack alone by used to support the transformer in a raised position;

c) When the transformer is to be moved on Skid way must be level and firm. Skid way timber should be large and solid. If the transformer must be turned on the skid way the turning area surface must be large enough to allow working space for men and equipment. Movement of the transformer must be controlled all times.

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