Shrink wrap for module transport protection

The increasing popularity of offsite construction techniques

Where modules and pods are pre-fabricated in a factory ‘off-site’ before being transported and rapidly assembled at the building site, there is a requirement for a low cost but effective way to protect these modules during delivery from the factory to the building site. Shrink wrap covering has been found to provide an ideal solution. This article looks at some techniques and alternative solutions for shrink wrapping modules and pods.

Why use a shrink wrap cover?

A shrink wrap cover is a great way to protect large items for transport simply because it is heat shrunk. This means it moulds to the object it is protecting, becoming ‘tight as a drum skin’ and so it cannot flap or chafe even at high wind speeds. This tightness is the secret of the strength and durability of shrink wrap. In addition, shrink wrap is available in a variety of widths up to 12m. If an object requires a greater width or is particularly large, sheets of shrink wrap are easily heat welded together meaning that shrink wrap is an extremely versatile covering solution.

What options are available?

Tarpaulins

Tarpaulins or Tarps are cheap to buy but they are almost impossible to fit tightly. The result is that they often flap around and chafe the product at motorway wind speeds. In some circumstances they may flap around so much that they self destruct and are blown off the product completely.

Custom Cover

A re-usable or returnable fitted customer cover often appears to be a good solution. The perceived advantage is that the cover may be considerably more expensive than shrink wrap or tarpaulins but will last many years. Our customers’ experience with returnable covers is that they often fail to live up to the promised many years of service and will require increasing levels of maintenance. It is often found that shrink wrap covers could be used for less than would have been spent maintaining the old covers.

Another problem that has been reported by our customers is that returnable covers are not returned in good time, if at all. Where they are returned, additional costs are incurred for the return shipping. Shrink wrap covers can simply be cut off and disposed of for recycling at the destination.

Shrink-wrap sheeting

There are two main ways of shrink wrapping a module or pod. The first is to use shrink wrap direct from a roll, like wrapping a present using a sheet of wrapping paper. In this case the shrink wrap is pulled from a roll over the module and unfolded. The ends of the shrink wrap must be folded in and temporarily held in place using adhesive tape until they are heat sealed using the hot air gun.

The advantage of this method is that in terms of the shrink wrap materials it is the most cost effective way to protect a module or pod, although the the module or pod will take longer to wrap compared to alternative techniques, (see below). It would take two operatives perhaps 30-45 minutes to wrap an average size module or pod of 2.5 metres square with sheets of shrink wrap, because just like wrapping a giant present, the wrap must be folded and cut at the ends to ensure that it does not come off during transport and this can be time consuming.

In summary, using shrink wrap plastic sheeting straight from the roll is most suitable for particularly large modules and pods or where there is only a requirement to wrap products occasionally.

Shrink wrap bags for modules and pods

By using a pre-made or pre-formed shrink wrap bag, the bag can simply be dropped over a module or pod and be ready for shrinking immediately. Since the shrinking of the plastic wrap is the fastest part of the whole shrink wrapping process, this makes a huge difference to the amount of labour involved. It would take two operatives around 15-20 minutes to wrap a 2.5 metre square pod in this way, and of course the result would be very consistent since each bag is identical.

To help with getting the shrink wrap bag over the module or pod and to limit the use of ladders and working from height, a shrink wrap bag can be fitted with four loops, one at each corner of the roof. Using an overhead crane, the bag can simply be lowered straight down over the module.

For heat shrinking, a regular propane gas or industrial electric heat gun is used. Some propane gas heat guns can also be fitted with an extension to allow the sides of the module or the pod to be shrink wrapped without using a ladder.

It is not normally necessary to heat shrink the top of a shrink wrap covering over a module or pod. Finally a zipper door can be installed in finished shrink wrap cover if required. These come in a variety of sizes, from small zipped ‘hatch like’ openings to full height doors.