The appearance inspection and strength test of the valve

In the whole process of design, manufacturing, installation, working condition, operation and maintenance, every step should not be relaxed. How to determine if there is a problem with the valve before delivery or after complete installation? This needs to pass the appearance inspection and certain performance test to check. Through these test results, the defects can be exposed and adjusted accordingly, and only after all the tests are qualified can they be put into use. So, what details should we pay attention to in appearance inspection? What does the performance test involve?

Why does the valve always fail? In the whole process of design, manufacturing, installation, working condition, operation and maintenance, every step should not be relaxed. How to determine if there is a problem with the valve before delivery or after complete installation? This needs to pass the appearance inspection and certain performance test to check. Through these test results, the defects can be exposed and adjusted accordingly, and only after all the tests are qualified can they be put into use. So, what details should we pay attention to in appearance inspection? What does the performance test involve?

Visual inspection

1. Whether the inner and outer surface of valve body has trachoma, crack and other defects.

2, valve seat and valve body joint is firm, valve core and valve seat is consistent, sealing surface has no defects.

3, stem and spool connection is flexible and reliable, stem bending, thread damage, corrosion.

4, packing, washer aging damage, valve open flexible, etc.

5, there should be a nameplate on the valve body, the valve body and nameplate should include: manufacturer name, valve name, nominal pressure, nominal diameter and other identification.

6. The opening and closing position of the valve during transportation should meet the following requirements:

(a) Gate valve, globe valve, throttle valve, butterfly valve, bottom valve, regulating valve and other valves should be in the fully closed position.

(b) The plug valve and ball valve closing parts should be in the fully open position.

(c) The diaphragm valve should be in the closed position, must not be closed too tight, to prevent damage to the diaphragm valve.

(d) The disc of check valves shall be closed and secured.

7, spring type safety valve should have lead seal, lever type safety valve should have heavy hammer positioning device.

8, check valve disc or spool action should be flexible and accurate, no eccentricity, displacement or skew phenomenon.

9, lining rubber, lining enamel and lining plastic valve inner surface should be smooth, lining and matrix firmly combined, no cracks, bubbling and other defects.

10, flange sealing surface should meet the requirements without radial scratches.

11, the valve shall not be damaged, missing parts, corrosion, nameplate off and other phenomena, and the valve body shall not be dirty.

12, both ends of the valve should be protected by protective cover, handle or handwheel operation should be flexible, no jam phenomenon.

13. The valve quality certificate shall contain the following contents:

(a) Name of manufacturer and date of manufacture.

(b) Product name, model and specification.

(c) Nominal pressure, nominal size, applicable medium and applicable temperature.

(d) Standard, conclusion and date of inspection.

(e) Factory number, signature and seal of inspector and responsible inspector.

Selection of 1 and 2 valve electric actuators

The valve electric actuator is a device used to operate and connect the valve. The device is electrically driven and its movement can be controlled by stroke, torque or axial thrust. Due to the valve electric device should work characteristics and utilization depends on the type of valve, device working specifications and valve position in the pipeline or equipment. Therefore, master the correct choice of valve electric device; It is crucial to consider preventing overload (working torque higher than control torque).

The correct selection of valve electric device should be based on:

1. Operating torque: Operating torque is the main parameter to select valve electric device. The output torque of the electric device should be 1.2 ~ 1.5 times of the large torque of the valve operation.

2. Operation thrust: there are two kinds of host structure of valve electric device, one is not equipped with thrust plate, and the torque is output directly at this time; The other is equipped with a thrust disc, in which the output torque is converted into output thrust through the stem nut of the thrust disc.

3. Output shaft rotation number: the number of output shaft rotation number of the valve electric device is related to the nominal diameter of the valve, valve stem pitch and the number of threads, calculated according to M=H/ZS (in the formula: M is the total rotation number that the electric device should meet; H is the opening height of the valve, mm; S is the pitch of the valve stem drive thread, mm; Z is the number of stem threads.)

4. Stem diameter: for multi-rotation type of open stem valve, if the large stem diameter allowed through the electric device can not pass the valve stem, it can not be assembled into an electric valve. Therefore, the inner diameter of the hollow output shaft of the electric device must be greater than the outer diameter of the stem of the open stem valve. For some rotary valves and multi-rotary valves in the dark rod valve, although do not consider the stem diameter through the problem, but in the selection should also be fully considered stem diameter and keyway size, so that the assembly can work normally.

5. Output speed: the valve opening and closing speed is fast, easy to produce water strike phenomenon. Therefore, according to different conditions of use, choose the appropriate start and close speed.

6. Installation and connection mode: installation mode of electric device includes vertical installation, horizontal installation and ground installation; Connection mode: thrust plate; The valve stem through (stem multi-turn valve); Dark rod multiple rotation; No thrust plate; Valve stem does not pass; Part of the rotary electric device is widely used, is to realize the valve program control, automatic control and remote control indispensable equipment, which is mainly used in the closed circuit valve. However, the special requirements of the valve electric device must be able to limit the torque or axial force. Usually the valve electric device uses a torque limiting coupling.

When the specification of the electric device is determined, its control torque is also determined. When it is running at a predetermined time, the motor is generally not overloaded. However, it can be overloaded if:

1. Low power supply, can not get the required torque, so that the motor stops rotating.

2. The torque limiting mechanism is incorrectly adjusted to be greater than the stopped torque, resulting in continuous generation of excessive torque, so that the motor stops rotating.

3. If the point is used intermittently, the heat generated accumulates and exceeds the allowable temperature appreciation of the motor.

4. For some reason the torque limiting mechanism circuit fails and the torque is too large.

5. High ambient temperature reduces the heat capacity of the motor.

The above are some reasons for overload, for these reasons the phenomenon of motor overheating should be considered in advance, and take measures to prevent overheating.

In the past, the way to protect the motor is to use fuses, overcurrent relays, thermal relays, thermostatic devices, etc., but these methods also have their own advantages and disadvantages. For electric equipment with variable load, there is no reliable protection method. Therefore, a combination of methods must be adopted. However, due to the different load of each electric device, it is difficult to put forward a unified approach. But for the most part, common ground can be found.

The overload protection methods adopted can be summarized into two types:

1. Judge the increase or decrease of motor input current;

2. The motor itself to determine the heat.

The above two ways, regardless of which to consider the motor heat capacity given time margin. It is difficult to make it consistent with the heat capacity characteristics of the motor in a single way. Therefore, we should choose a combination of methods based on reliable action according to the cause of overload to achieve overload protection.

The motor of Rotock electric device, because it is embedded in the windings of the thermostat with the same insulation level of the motor, when the rated temperature is reached, the motor control loop will be cut off. The heat capacity of the thermostat itself is small, and its time-limited characteristics are determined by the heat capacity characteristics of the motor, so this is a reliable method.

The basic protection methods for overload are:

1. For motor continuous operation or point operation of overload protection using thermostat;

2. Thermal relay is used for motor blocking protection;

3. Use fuses or overcurrent relays for short circuit accidents.

阀门的外观检验与强度试验方式方法全解 阀门电动执行器的选择

在设计、制造、安装、工况、操作、维修整个过程中，每一步都不可松懈。阀门在出厂前或者完成完整的安装后，如何确定是否有问题呢?这就需要通过外观检验和一定的性能试验来检查。通过这些试验结果，便可以将缺陷暴露出来，进行相应的调整，只有全部试验都合格以后才能够投入使用。那么，外观检验需要留意哪些细节?性能试验又包括哪些呢?

阀门为何总是故障?在设计、制造、安装、工况、操作、维修整个过程中，每一步都不可松懈。阀门在出厂前或者完成完整的安装后，如何确定是否有问题呢?这就需要通过外观检验和一定的性能试验来检查。通过这些试验结果，便可以将缺陷暴露出来，进行相应的调整，只有全部试验都合格以后才能够投入使用。那么，外观检验需要留意哪些细节?性能试验又包括哪些呢?

外观检验

1、阀体内外表面有无砂眼、裂纹等缺陷。

2、阀座与阀体接合是否牢固，阀芯与阀座是否吻合，密封面有无缺陷。

3、阀杆与阀芯连接是否灵活可靠、阀杆有无弯曲，螺纹有无损坏、腐蚀。

4、填料、垫圈是否老化损坏，阀门开启是否灵活等。

5、阀体上应有铭牌，阀体和铭牌上应包括：制造商名称、阀门名称、公称压力、公称通径等标识。

6、阀门运输时的开闭位置应符合下列要求：

(a)闸阀、截止阀、节流阀、蝶阀、底阀、调节阀等阀门应处于全关闭位置。

(b)旋塞阀、球阀关闭件应处于全开启位置。

(c)隔膜阀应处于关闭位置，切不可关闭过紧，以防止损坏隔膜阀。

(d)止回阀的阀瓣应关闭并予以固定。

7、弹簧式安全阀应具有铅封，杠杆式安全阀应有重锤的定位装置。

8、止回阀的阀瓣或者阀芯动作应灵活准确、无偏心、位移或歪斜现象。

9、衬胶、衬搪瓷及衬塑料的阀门内表面应平整光滑，衬层与基体结合牢固、无裂纹、鼓泡等缺陷。

10、法兰密封面应符合要求不得有径向划痕。

11、阀门不得有损伤、缺件、腐蚀、铭牌脱落等现象，且阀体不得有脏污。

12、阀门两端应有防护盖保护，手柄或者手轮操作应灵活，不得有卡涩现象。

13、阀门质量证明书应包含下列内容：

(a)制造商名称和出厂日期。

(b)产品名称、型号和规格。

(c)公称压力、公称通径、适用介质和适用温度。

(d)依据的标准、检验结论及检验日期。

(e)出厂编号、检验人员及负责检验人签章。

1 2 阀门电动执行器的选择

阀门电动执行器是用于操作阀门并于阀门相连接的装置。该装置由电力来驱动，其运动过程可由行程、转矩或轴向推力的大小来控制。由于阀门电动装置应有的工作特性和利用率取决于阀门的种类、装置的工作规范及阀门在管线或设备上的位置。因此掌握阀门电动装置正确的选择；考虑防止超负荷（工作转矩高于控制转矩）的发生就成为至关重要的一环。

阀门电动装置的正确选择应依据：

1．操作力矩：操作力矩是选择阀门电动装置的主要的参数。电动装置的输出力矩应为阀门操作大力矩的1.2～1.5倍。

2．操作推力：阀门电动装置的主机结构有两种，一种是不配置推力盘的，此时直接输出力矩；另一种是配置有推力盘的，此时输出力矩通过推力盘中的阀杆螺母转换为输出推力。

3．输出轴转动圈数：阀门电动装置输出轴转动圈数的多少与阀门的公称通径、阀杆螺距、螺纹头数有关，按M=H/ZS计算（式中：M为电动装置应满足的总转动圈数；H为阀门的开启高度，mm；S为阀杆传动螺纹的螺距，mm；Z为阀杆螺纹头数。）

4．阀杆直径：对于多回转类的明杆阀门来说，如果电动装置允许通过的大阀杆直径不能通过所配阀门的阀杆，便不能组装成电动阀门。因此，电动装置空心输出轴的内径必须大于明杆阀门的阀杆外径。对于部分回转阀门以及多回转阀门中的暗杆阀门，虽不用考虑阀杆直径的通过问题，但在选配时亦应充分考虑阀杆直径与键槽的尺寸，使组装后能正常工作。

5．输出转速：阀门的启、闭速度快，易产生水击现象。因此，应根据不同的使用条件，选择恰当的启、闭速度。

6．安装、连接方式：电动装置的安装方式有垂直安装、水平安装、落地安装；连接方式为：推力盘；阀杆通过（明杆多回转阀门）；暗杆多回转；无推力盘；阀杆不通过；部分回转电动装置的用途很广，是实现阀门程控、自控和遥控不可缺少的设备，其主要用在闭路阀门上。但不能忽视阀门电动装置的特殊要求必须能够限定转矩或轴向力。通常阀门电动装置采用限制转矩的连轴器。

当电动装置的规格确定之后，其控制转矩也确定了。当其在预先确定的时间内运行时，电机一般不会超负荷。但如出现下列情况便可使其超负荷：

1．电源电压低，得不到所需的转矩，使电机停止转动。

2．错误地调定了转矩限制机构，使其大于停止的转矩，而造成连续产生过大的转矩，使电机停止转动。

3．如点动那样断续使用，产生的热量积蓄起来，超过了电机的容许温升值。

4．因某种原因转矩限制机构电路发生故障，使转矩过大。

5．使用环境温度过高，相对地使电机的热容量下降。

以上是出现超负荷的一些原因，对于这些原因产生的电机过热现象应预先考虑到，并采取措施，防止过热。

过去对电机进行保护的办法是使用熔断器、过流继电器、热继电器、恒温器等，但这些办法也都各有利弊，对于电动装置这种变负荷的设备，可靠的保护办法是没有的。因此必须采取各种方法组合的方式。但由于每台电动装置的负荷情况不同，难以提出一个统一的办法。但概括多数情况，也可以从中找到共同点。

采取的过负荷保护方式，归纳为两种：

1．对电机输入电流的增减进行判断；

2．对电机本身发热进行判断。

上述两种方式，无论那种都要考虑电机热容量给定的时间余量。如果用单一方式使之与电机的热容量特性一致是困难的。所以应选择根据过负荷的原因能可靠的动作的方法组合复合方式，以实现过负荷保护作用。

罗托克电动装置的电机，因其在绕组中埋入了与电机绝缘等级一致的恒温器，当到达额定温度时，电机控制回路便会切断。恒温器本身热容量是较小的，而且其限时特性是由电机的热容量特性决定的，因此这是一个可靠的方法。

过负荷的基本保护方法是：

1．对电机连续运转或点动操作的过负荷保护采用恒温器；

2．对电机堵转的保护采用热继电器；

3．对短路事故采用熔断器或过流继电器。