全包装螺旋式垫圈
Fully-Encased Spiral Wound Gasket
对于低污染排放应用来说，垫圈连接设计是关键性的。为了更好的控制和防止螺旋式垫圈的退绕作用，需要配置完全包装的垫圈腔。
The design of gasketed joints is critical for
low-emission applications. For better control and elimination of unwinding
of spiral wound gaskets, a fully-enclosed gasket cavity is desirable.
更坚固的螺栓保证连接的紧固
Stronger Bolting Ensures Joint Tightness
1972年在我们的实验室，对螺旋式垫圈进行简单应力与缺陷测试进行比较，证实泄漏的控制主要依赖垫圈座应力和当时的ASME法典第III节数据，也就是垫圈座系数m=3和垫圈座应力y=4,500
psi，是不适当的。实验发现y=16,000 psi垫圈座应力对于泄漏连接部是最主要的因素。新版ASME将y值改变为10,000 psi，但是垫圈座系数m保持不变。
Simple stress versus defection tests conducted
in our laboratory in 1972 on spiral wound gaskets confirmed that control
of leakage is highly dependent on gasket seating stress and that the ASME
Section III Code data at the time, namely the seating factor m = 3 and
seating stress y = 4,500 psi, were inadequate. Gasket seating stress of
y = 16,000 psi was found to be essential for a leakproof joint. The ASME
later changed y to 10,000 psi but the seating factor m remains unchanged.
Velan推荐的参数
Velan Recommended Values
垫圈外径
GASKET
OD |
ASME
m |
VELAN
m |
ASME
y |
VELAN
y |
| 2-5.5" |
3 |
7 |
10,000 |
16,000-28,000 |
| 6-11" |
3 |
6 |
10,000 |
16,000-25,000 |
| 12-20" |
3 |
6 |
10,000 |
16,000-20,000 |
更大的螺栓扭矩
Higher Bolting Torques
试验显示在室温环境下，预负载达到70%时，螺栓对于疲劳和蠕变具有更强的抵抗力。SA-193-B7或SA-564-630螺栓扭矩达45,000
psi。
Tests also revealed that bolts are more resistant
to fatigue and creep if pre-loaded to as high as 70% of yield at room
temperature. SA-193-B7 or SA-564-630 bolts are torqued to 45,000 psi.
现代扭矩过程
Modern Torquing Procedure
由于控制垫圈座应力非常重要，施加垫圈负载的方法必须准确。实际的螺栓的初始扭矩比建议的扭矩值高出10至20%。在第二次，每个螺母重新调整并润滑，并且螺栓的扭矩达到最大值（标准值，适用于DN50至DN600的锻造阀门）。
Since it is important to control gasket seating
stress, the method of applying gasket load must be accurate. The first
torquing of bolts is performed at 10-20% higher than recommended values.
In the second round, each nut is removed and lubricated, and the bolts
are retorqued at maximum values (standard for forged valves 2-24",
50-600 mm).
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 密封焊接措施
Seal Welding Provision
对于所有DN65至DN600的螺栓阀帽锻造阀门都可采用密封焊接措施。
Provision for seal welding is available for all
bolted bonnet forged valves sizes 21/2-24"
(65-600 mm).
计算
Calculations
需要计算螺栓负载，以符合更大的工作负载Wm1或垫圈座负载Wm2的需要。在低压应用中，垫圈座负载更大。
The bolt load is calculated to meet the operating
load Wm1 or the gasket seating load Wm2, whichever
is greater. In low pressure applications the seating load is larger.
垫圈负载计算时用到的符号
Notation for calculation of gasket load.
| where |
Wm1 |
= HG + HP + TR |
| Wm2 |
= 3.14 b G y |
| HG |
= 终端水静力 hydrostatic end force = 0.785
G2P |
| HP |
= 最小垫圈压缩 minimum gasket compression |
| |
= 2b x 3.14 G m P |
| TR |
= 阀杆推力 stem thrust |
| b |
= 1/2 垫圈宽度 gasket width |
| m |
= 垫圈座系数 gasket seating factor |
| P |
= 内部压力 inlet pressure |
| y |
= 垫圈座应力 seating stress |
| G |
= 平均垫圈直径 mean gasket diameter |
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