Schoolhill Hydraulic Enginering

September 2017

Subsea Intervention Tooling for Ageing Wells & Small Pool Tiebacks

Schoolhill Hydraulic Engineering has a 30-year history of developing and manufacturing components for subsea engineering projects.  The company is attuned to the cost-savings challenges faced by clients in the North Sea and beyond, and has created a number of innovative engineered solutions in response to these.

Recent examples include:

·         Specialist valves for subsea control modules (SCMs)

·         Tree valve actuator override tools

·         Quick exhaust valves (QEVs)

Specialist Valves For Subsea Control Modules (SCMs)

The problem: Interflow caused by malfunctioning internal shuttle valves that was severely impacting the SCM’s dual redundancy system.

The solution: An external shuttle valve mounted on the top of the SCM that would bypass the malfunctioning internal one and restore the dual redundancy of the original system.

The process: Hydraulic supply is taken from the existing infield header, through the new valve and back into the SCM using the original input locations.

The savings: The stainless steel valves, which can operate at up to 10,000psi, can be diver-installed onto pipeline or manifold mounting, saving time and the costs of recovering the SCM for repairs.

Tree Valve Actuator Override Tools

The problem: Control issues with subsea actuators on tree valves within ageing North Sea trees.

The solution: Fitting an override tool to maintain normal hydraulic functionality of the tree.

The process: Schoolhill’s override tool connects into the original tree hydraulics in place of the problematic actuator. A quick exhaust valve (QEV) is fitted to the override tool to maintain safe shutdown.

The savings: The benefits of the override tool are multiple: it allows the field to keep producing without the need for tree recovery; it also saves on repair and maintenance work and effectively extends the life of an ageing asset.

Quick Exhaust Values (QEVs)


The request: A specialist high-flow QEV (quick exhaust valve) for a HIPPS (high-integrity pressure protection system) within the Caspian Sea.

The solution: An SIL 3-certified QEV that is the first of its kind and a technological step change for the industry.

The process: The design, prototype development, testing and manufacture of the original valve took over four years. More than 40 test procedures were written to ensure various aspects of the valve’s functionality, characterisation and durability.

The outcome: The valve has attracted widespread interest, and indeed orders, from the global subsea industry.