4。6。3Alternate Valve End Connections

Other end connections may be specified by the purchaser。

4。7 Valve Cavity Pressure Relief

The manufacturer shall determine whether fluid can become trapped in the body cavity in the open- and/or closed-valve position。

If fluid trapping is possible, the valve shall be provided with automatic cavity-pressure relief, unless otherwise agreed。

Valve cavity relief pressure when added to the valve pressure rating shall not exceed 133% of the pressure rating of the valve at its maximum specified design temperature。

To achieve a higher cavity relief pressure, the valve shell shall be designed and tested to withstand a higher hydrostatic shell test pressure。

If a relief valve fitted to the cavity is required, purchaser may specify provisions to facilitate in service testing。 External cavity relief valves shall be NPS 1/2 (DN 15) or larger。

Cavity relief testing and functionality may be demonstrated by tests in

H。8。2 for trunnion mounted ball valves and gate valves。 Floating ball valve functionality may be demonstrated by agreement。

4。8Drains

Drain connections shall be drilled and threaded。 The purchaser may specify other types of drain connections, such as welded or flanged。

Caution—Threaded connections can be susceptible to crevice corrosion。

Tapered threads shall be capable of providing a seal and comply with ASME B1。20。1。

If parallel threads are used, the connection shall have a head section for trapping and retaining a sealing member suitable for the specified valve service。 Parallel threads shall comply with ASME B1。20。1 or ISO 228-1。 Sizes shall be in accordance with Table 2。

Table 2—Thread/Pipe Sizes for Drains

Nominal Size of Valve Minimum Pipe Thread/Pipe Size in。 (mm)

NPS DN

1/2 to 1-1/2 15 to 40 1/4(8)

2 to 8 50 to 200 1/2(15)

>8 >200 1(25)

4。9Injection Points

Injection points for sealant, lubrication, or flushing may be provided for seats and/or stem。 When provided, the injection points shall incorporate a check valve and a secondary means of isolation for each injection point。 Sealant fittings shall have a design pressure not less than the greater of the pipeline or piping valve rated pressure and the injection pressure。

NOTE An example is a button head fitting with integral check valve and

sealing cap。

4。10Drain, Vent, and Sealant Lines

Drain, vent, and sealant lines may be provided。 When drain, vent, and sealant lines are provided, the lines shall be composed of rigid pipework。 The lines shall be fastened to the valve and/ or extensions and terminate close to the stem extension top works。

When provided, drain and vent lines shall

—have a design pressure not less than the rated pressure of the valve on which they are installed;

—be capable of withstanding the hydrostatic shell test pressure of the valve;

—be designed in accordance with a recognized design code;

—be suitable for blow-down operation, where applicable。

When provided, sealant lines shall be rated to the same criteria as sealant fittings in 4。10。

The manufacturer shall advise the maximum injection pressure for the system。 The size of the sealant lines shall be by agreement。 Prior to assembly, the internal bores of sealant lines shall be clean and free from rust and any foreign particles。 撑开式闸阀设计英文文献和中文翻译(8):http://www.youerw.com/fanyi/lunwen_97242.html