Challenging subsea environments create significant design problems for subsea gate valves design so selecting the right gate valve for an application takes experience. Many factors must be considered – the process fluid, liquid or gas, corrosive or dirty; the operating temperature; pressure; working environment; duty and shut off performance and finally the field life. Having delivered high integrity subsea gate valve solutions since 1991 we are in the best position to guide our customers through this selection process delivering the right valve choice for their specific applications both technically and commercially.
Why through conduit gate valves, the operational benefits. Gate valves are one of the original valve designs and are ideally suited for severe duty on/off applications. Through conduit slab and expanding gate valves provide superior sealing characteristics to any other type of valve configuration making them the ideal choice for high integrity and zero leakage subsea applications. The superior sealing forces due to the larger sealing area also makes a gate valve more suitable for higher pressures even in combination with high temperatures. In addition the fast closing mechanism makes the gate valve ideal for quick acting safety applications like HIPPS.
When determining which solution to specify, gate valve or ball valve, the end to end dimensions will often factor, especially when weight is also a restriction. Here, clearly due to the inherent design, gate valves may offer a superior solution, as opposed to a height critical choice which may favour a ball valve design. However if height is also an issue , for example in well applications, there are alternative gate valve configurations to consider i.e. a rising stem design – outside screw, which tends to be ‘taller’ or a non-rising stem – inside screw design which tends to be ‘shorter’ and more compact.
Benefits of BEL Valves Gate Valve design. The BEL Valves subsea gate valve design is inherently fail safe due to the assistance delivered by the stem ejection forces, making these the ideal solution for critical on/off applications. With subsea system’s pressures increasing and to meet our customer requirements we offer pressure ratings up to 16,500 psi. Often the high pressure projects are also characterised with higher temperatures, HP/HT, and so we offer valves which deliver superior performance up to 175 deg C. All valve designs have their sealing surfaces hard faced with Tungsten Carbide and can be configured with rising or non-rising stems. The full bore range is from 1/2 to 28 inch and are available in standard and exotic materials including duplex, super duplex and Inconel to meet specific customer applications.
Qualifications are extensive, due to our significant reference of supply and include PR2, hyperbaric, 1200 cycle and sand slurry testing.
Our expanding gate design, sometimes known as split gate or double expanding gate valves deliver positive shut off with a patented two piece gate construction. The mechanical seal provided is independent of pipeline pressure providing up and downstream sealing. The benefit of the expanding gate valve design is the reliable double isolation achieved in a single, compact valve body. This single valve design provides a seal against pressure from both ends of the valve, with a means of venting (bleeding) the cavity between the seating surfaces – often referred to as double isolation and bleed.
Standard and Optional Features.
Materials, specification and approvals. Choosing the materials to be used in gate valves design for subsea applications can be particularly challenging. With the development of deep water well drilling, materials are now having to handle more than just the corrosive challenges of hydrogen sulphide (H2S), carbon dioxide (CO2) and chlorides. Subsea valves now also need to handle chemicals used to minimize paraffin, asphaltene, hydrates and scale formation which have adverse effects on metallic (and non- metallic) materials.
Our primary metal to metal sealing option is tungsten carbide coated to meet these challenging service conditions. Part or fully clad options are available with weld overlay providing full corrosion protection to the internal areas of the valve. Both split and slab gate designs are in accordance with the relevant industry codes and standards including ISO 13628, ISO 14723, API 6DSS, API 17D and API 6AVI.