Weston Common to Holybourne Pipeline

Introduction

Carr Civil Engineering Grouting Ltd were commissioned by Humbly Grove Energy Ltd to decommission a 6” underground Pipeline from Weston Common to Holybourne in Hampshire, which was complete at the end of July 2024. 

HGEL had previously suspended the Pipeline from service and filled with Inhibited Water (biocide/corrosion inhibitor) during the suspension period. The water was displaced, and various cleaning PIG runs were carried out leaving the Pipeline at an acceptable cleanliness level ready for Grouting. 

Scope of Work:

Location and excavation of the 6” Pipeline at the Brockham Hill Lane Excavation site. Cut and remove a section of Pipeline by HGEL supplied third party contractor, Puma Engineering, and terminate each side of the open Pipeline with a new flanged joint to facilitate the Grouting Hose for clean and safe injection operation. The method was to pump the Grout from the Excavation Site down hill to the Holybourne end of the Pipeline, once complete, switch over and pump to the Weston Common end. 

At the Star Energy Holybourne Site, an excavation was also necessary to remove approximately 20 meters of subsurface pipeline that led into the site, as well as the removal of the above ground PIG receiver installation. A blind flange with a vent point was installed at the open end of the pipeline, which was isolated after a continuous flow of grout and remained underground at the pipeline's end on the fence line. 

A Pipeline to Pipework transition spool was removed from the Weston Common end of the Pipeline, and a blind flange with a vent point installed at the open end. 

Steel Pipeline from Weston Common to Holybourne. The material is a grey/white powder in its dry form, changing to blue/purple when mixed with water, before returning to a grey colour after a 28-day curing period. 

Constant Grout testing was carried out by two methods to ensure reliable results, Weight Mud Balance testing (1.126 to 1.130 specific gravity), and Timed Marsh Funnel testing (range between 32 secs to 48 secs depending on temperature at the time). This was achieved by a sample taken from the agitator tank and was then V funnel tested for a timed velocity test, a sample was then taken from vent point, and a V funnel velocity test carried out to ensure the bleed from the grout has been completely removed. This is achieved when both tests from fill point to vent point are comparable. 

The Grout was injected into the high pressure Colloidal mixing pump, and all data downloaded via the on board NANODAC data logger to a USB stick. This contains the flows, pressures and complete volume fill as Appendix 1 

Flow meter/s were monitored to establish flow rates and Pipeline fill status according to the Pipeline volume requirements, viscosity and mud balance was monitored to monitor weight and hence solids content. When the Pipeline calculated volume was achieved, the vent valve was closed, and fill continued an additional 1 cubic meter at no greater than 2 bar. A mix sample (1Ltr) was obtained for test purposes from vent pipework end, with additional samples left for HGEL monitoring purposes.