The manual gate valve underground series represents a robust yet cost-effective solution for flow isolation and control in critical buried piping infrastructure. Careful consideration of standards compliant design, reliable sealing, and long-term maintenance needs delivers a versatile valve optimized for below grade service.
In this article, we will take a closer look at underground gate valve design with a focus on manual operation models. Understanding the engineering considerations that go into manual underground gate valves can provide valuable insights for specifying, installing and servicing these critical underground infrastructure components.
Compliance with Industry Standards
All underground bs5163 gate valve pn16 must be engineered and manufactured according to relevant industry standards to ensure safety, quality and interchangeability. In the UK, underground gate valves designed for potable water distribution networks up to PN16 pressure rating comply with BS5163:1992. This British Standard specifies technical requirements for the construction, testing and performance of buried sluice valves up to 1200mm in nominal diameter.
Key aspects covered in BS5163 include body and bonnet materials, joint types, operating mechanisms, pressure rating, flow direction indicators and extension stems for underground access. Manufacturers of BS5163 compliant underground gate valves use high strength ductile iron or fabricated steel to construct robust bodies capable of withstanding underground installation and the working pressures of water distribution systems.
Manual Operation Design
When it comes to manual underground gate valves, the operating mechanism is a critical design element that needs to provide reliable actuation from above ground level. Most modern manual underground gate valves utilize a buried valve bonnet with an adjustable valve box and operating stem arrangement.
The valve bonnet houses the gate, seat rings and stem connections below ground. It features a stem guide bushing and rising stem that translates the open/close movement directly from the gate. Extending up from the valve bonnet is the operating stem – a threaded shaft often constructed from bronze, stainless steel or galvanized steel materials.
The operating stem passes up through the center of a concentric valve box installed flush with the final grade. This precast concrete or polymer concrete valve box protects the operating components while providing accessible access. A adjustable extension stem sits atop the valve box and connects to the buried stem with a junction box. T-handled, lever, or nut operated extensions allow manual operation from grade level.
Sealing Design
Reliable sealing is crucial to prevent leakage which could lead to contamination or erosion issues over the lifetime of an underground valve. BS5163 gate valves pn16 utilize resilient wedge sealing which provides drip-tight shutoff with minimal operating torque.
In resilient wedge sealed gate valves, an elastomer wedge mounted on the gate compresses against a dual segmented seat in the valve body. This forms a flexible seal as opposed to metal-to-metal sealing. The resilient wedge maintains sealing integrity in either flow direction and allows for easy replaceability if needed. O-ring stem seals within the valve bonnet further contain pressures and prevent underground contaminants from entering the operating mechanism.
Maintenance Considerations
With underground installation, maintenance access is an important design factor for gate valves. The manual operation arrangement enables valves to be cycled annually and lubricated as needed through the top opening of the adjustable valve box. Valve boxes should be level with final grade and not subject to heavy traffic loads to avoid damage.
Additionally, an air release/vacuum breaker attachment may be included on underground gate valves to release built-up pressure when isolating a section of water main during maintenance activities. This reduces mechanical stresses on the valve and piping system. Gate valves also require occasional external coating touch-ups to protect against corrosion if the factory applied coating becomes damaged over time.