Flowstopping and Filling Voids

Popular flowstopping and void filling techniques used by the Steve Vick International (SVI) Contract Service team primarily involve the use of expanding polyurethane resin foam. Depending on the application a variety of methods are available, all of which are deployed in ‘gas free’ conditions and approved for use on all UK Gas Distribution Networks.

The patented products and techniques applied by SVI can reduce or completely remove the need to cut customers off gas and require much smaller excavations resulting in significantly lower reinstatement costs. These cost savings are significant, especially when compared with conventional flowstopping operations.

Pipes

Completed and fully cured FOAMBAG™ operation

Low pressure

The SVI FOAMBAG™ flowstopping system involves the injection of expanding foam into a fabric bag which is placed in the pipe. The bag holds the liquid foam in place whilst it expands, providing a gas tight seal at full expansion.

This technique is used on diameters from 12” – 36” low pressure gas mains.

The SVI Contract Service team has been successfully carrying out FOAMBAG™ operations for over 30 years.

 

 

 

 

Installation of FOAMBAG™ into a 6'' medium pressure main

Medium pressure

Using the FOAMBAG™ technique, flowstopping operations are carried out on medium pressure gas services and mains from 3/4” up to 8” at pressures of up to 2bar.

Problems associated with flowstopping tapering, vertical pipes, bends and non-standard sizes are easily resolved using the SVI methods.

 

 

 

 

 

 

Preparation of DRAINBLOCK BAG™ prior to remote installation

DRAINBLOCK BAG™

DRAINBLOCK BAG™ is based on the highly successful FOAMBAG™ system and is used as a permanent seal where the prevention of water ingress/egress or odour is a priority.

In conjunction with CCTV equipment, Contract Service operatives locate the exact seal position which can be up to 20m from point of access. Using drain rods, the self-actuating foam sachet contained within a bag is then pushed in place and left to cure.

DRAINBLOCK BAG™ will start to act as a permanent seal against water and odours within around 30 minutes. A full cure will be achieved in approximately 12 hours.

 

 

 

RATBLOCK™

RATSTOP™ is an adaptation of the DRAINBLOCK BAG™, but with an additional design feature of two articulated steel plate membranes. Once cured, the foam provides a water, odour and gas tight seal within the pipe while the steel membrane prevents the passage of rats and other vermin.

Both RATBLOCK™ and DRAINBLOCK BAG™ are fully approved by the WRc.

 

Filling Voids

The SVI Contract Service is proficient at filling unwanted underground voids safely and permanently. Different methods are available including cementitious grout and polyurethane resin foam.

 

Grout

SVI Contract Team preparing grout using a bespoke mixing rig

Grout offers a low cost solution where there is a need to seal off large diameter utility mains, either inserted or abandoned.

Grout will prevent the possibility of landfill sinking below ground level if the pipe were to break and is ideal when there is a need to uphold heavy and continuous loads above ground; for example busy highways, railways and canals.

SVI ENDSEALS™ are used within the pipe or void to create a dam for the grout to be injected into. Specialised mixing rigs are then used to prepare and syphon the grout through the injection point.

 

Foam

SVI patented foam can provide a low cost method of filling a wide variety of unwanted voids.

In most situations the SVI well proven FOAMBAG™ technique is used to provide plugs at strategic positions to prevent any unwanted flow of foam. Foam is then injected into the void, and once cured, prevents the ingress of potentially dangerous water or gas.

Typical uses of foam include:

  • Abandoned pipework
  • The annulus between an old main or sewer and a new inserted pipe
  • The annulus in sleeved pipework at road, river or railway crossings
  • The annual space following cable insertion in ducts following directional drilling project

 

ENDSEALS™

ENDSEALS™ are used to stop gas tracking back along the annular space of inserted gas mains. This method avoids spending unnecessary time and money excavating.

ENDSEALS™ are also used to avoid reinstatement ‘slump’. By sealing off the annular space, the risk of backfill gradually finding its way into the gap and causing slumping at the surface is removed.

The use of ENDSEALS™ appears in UK gas industry ‘Main Laying Procedures’ and is widely considered to be best practice.

 

FOAMCAPS™

FOAMCAP™ is a lightweight and low cost alternative to metal caps; used by the SVI Contract Services to seal off abandoned dead gas mains. They are simple to fit and may be used on uneven or badly corroded mains.

Once cured a permanent seal against the ingress of gas, water and vermin is provided.