Taboo 11

The valve is mounted incorrectly. For instance, the globe valve or check valve’s water (or steam) flow direction is the opposite of the sign’s, and the valve stem is mounted downward. The check valve is mounted vertically rather than horizontally. Away from the inspection door, please.

Consequences: The valve malfunctions, the switch is challenging to fix, and the valve stem frequently points downward, leading to water leaks.
Measures: Follow the valve installation instructions to the letter. Leave enough opening height for the stem extensions of gate valves with rising stems. Fully take into account the handle’s turning space while using butterfly valves. The stems of different valves shouldn’t be positioned any lower than horizontal or even downward. In addition to having an inspection door that can accommodate valve opening and closing, concealed valves should also have the valve stem facing the inspection door.

Taboo 12

The installed valves‘ models and specifications do not adhere to the design standards. For instance, the fire pump suction pipe uses a butterfly valve when the pipe diameter is less than or equal to 50mm, and the dry and standpipe of hot water heating uses a stop valve when the nominal pressure of the valve is less than the system test pressure.

Consequences: change how the valve normally opens and closes, as well as how resistance, pressure, and other functions are adjusted. Even worse, it led to the valve becoming broken and needing to be fixed while the system was in use.

Measures: Know the spectrum of applications for different valves, and choose the valve’s specs and model based on the needs of the design. The valve’s nominal pressure must satisfy the system test pressure specifications. According to the building standard, a stop valve should be used when the diameter of the water supply branch pipe is less than or equal to 50mm; when it is higher than 50mm, a gate valve should be used. Butterfly valves should not be used for fire pump suction pipes, and gate valves should be used for hot water heating dry and vertical control valves.

Taboo 13

Before the valve is installed, the required quality inspection is not performed in accordance with the rules.

Consequences: Water (or steam) leakage occurs during system operation because the valve switch is flexible and the closure is not stringent, necessitating rework and repairs and even affecting the regular water (or steam) supply.

Measures: The compressive strength and tightness test should be completed prior to installing the valve. 10% of each batch (same brand, same specification, same model) must be randomly selected for the test, but not less than one. Strength and tightness tests should be performed one at a time on each closed-circuit valve that is put on the main pipe to be cut off. The “Code for Construction Quality Acceptance of Building Water Supply, Drainage and Heating Engineering” (GB 50242-2002) must be followed for the strength and tightness test pressure of the valve.

Taboo 14

The majority of the supplies, machinery, and items used in the construction do not have the product qualification certificates or technical quality appraisal documentation that are required by the state or ministry to fulfill the current criteria.

Consequences: The project’s poor quality, hidden accident hazards, inability to be completed on schedule, and need for rework all contribute to extended construction times and higher labor and material inputs.

Measures: The primary products, materials, and tools used in water supply, drainage, heating, and sanitation projects should have technical quality appraisal documents or product qualification certificates issued by the state or the ministry that meet the current standards; their product names, models, specifications, and national quality standards should be marked. Code name, date of manufacturing, manufacturer’s name and location, inspection certificate, or code name of the ex-factory product.

Taboo 15

Valve Flip

Consequences: Directionality is a feature of many valves, including check valves, throttle valves, pressure reduction valves, and stop valves. The use effect and life of the throttle valve will be impacted if they are set upside down; it may even be deadly.

Measures: There is a direction mark on the valve body for general valves; if there isn’t a direction mark, the valve should be accurately identified based on how it functions. The fluid should flow through the valve port from bottom to top so that the opening is labor-saving (because the medium pressure is upward) and the medium does not press the packing after closing, which is convenient for maintenance. The valve cavity of the stop valve is asymmetrical from left to right. The globe valve cannot be turned around because of this.

Installing the gate valve upside down, with the handwheel down, will cause the medium to stay in the bonnet area for an extended period of time, which is bad for the valve stem’s corrosion and against the rules of some processes. To replace the packing at the same time is very inconvenient. The exposed valve stem will deteriorate from moisture if the rising stem gate valve is installed underground. Make sure the disc is upright when installing the lift check valve so it may be lifted easily. Make sure the pin shaft is horizontal when mounting the swing check valve so that it can be opened freely. On the horizontal pipeline, the pressure-reducing valve ought to be mounted straight; it shouldn’t be inclined in any way.

Taboo 16

Manual valve opening and closing, excessive force

Consequences: varying from valve damage to catastrophic events

Measures: The strength of the sealing surface and the required closing force are taken into consideration while designing the manual valve, as well as its handwheel or handle, for everyday labour. As a result, it cannot be moved with a lengthy wrench or lever. Some people are used to using a wrench, and they should be extremely careful not to use too much power because doing so might easily harm the sealing surface or cause the wrench to break the handwheel and handle. The force applied to open and close the valve should be consistent and without interruption.

Some high-pressure valve parts that impact open and close have taken into account the fact that this impact force cannot be the same as that of standard valves. Before opening, the steam valve needs to be preheated, and the condensed water needs to be drained. To prevent water hammer, it should be opened as gradually as possible. The hand wheel needs to be slightly rotated upside down after the valve is fully opened to tighten the threads and prevent loosening and damage.

For rising stem valves, it’s important to keep in mind where the stem is when fully open and fully closed to prevent hitting the top dead center. Additionally, it is simple to determine if it is typical when fully closed. The valve stem position will shift when it is fully closed if the valve stem breaks off or if there is significant material lodged between the valve core seal. The valve can be slightly opened to allow the medium’s high-speed flow to wash away the pipeline’s heavy buildup of dirt before being gently closed (do not close abruptly or violently to avoid residual impurities pinching the sealing surface). Restart it, do this several times, wash the dirt out, and then use it as usual.

When shutting normally open valves, any debris on the sealing surface should be wiped off using the aforementioned technique before the valve is formally closed. In order to avoid damaging the square of the valve stem, having the valve fail to open and close, and causing production-related accidents, the handwheel and handle should be equipped as soon as possible if they are broken or lost. A flexible wrench cannot be used to replace them. After the valve is closed, some mediums cool, which causes the valve to contract. In order to prevent a slit from appearing on the sealing surface, the operator should close it once more at the right moment. If it emerges during surgery that it is overly taxing, the cause should be investigated.

It is possible to adjust the packing adequately if it is excessively tight. The staff should be alerted to fix the valve stem if it is crooked. If a valve must be opened at this time, the valve cover thread can be loosened by half a circle to one circle to relieve the stress on the valve stem, and then turn the handwheel. For some valves, when the valve is in the closed state, the closing part will expand due to heat, making it difficult to open.

Taboo 17

Improper installation of high temperature environment valves

Consequences: Causing a spill

Measures: Since high-temperature valves above 200°C are fitted at room temperature, they must be retightened in order to maintain “heat tightness” after normal operation when the temperature rises, the bolts expand due to heat, and the gap widens. Operators need to focus on this task because leakage might easily happen without it.

Taboo 18

Lack of drainage in cold weather

Measures: The water that has gathered behind the water valve needs to be removed when it is chilly outside and the water valve has been shut off for a while. Condensed water must be drained when the steam valve has turned off the steam. The valve’s bottom resembles a plug that can be opened to let water out.

Taboo 19

Non-metallic valve, the opening and closing force is too large

Measures: Non-metallic valves come in a variety of strengths, some of which are hard and brittle. When in use, the force used for opening and shutting should not be excessive, especially not aggressive. Pay attention to avoid colliding into things as well.

Taboo 20

New valve packing too tight

Measures: The packing should not be packed too firmly when the new valve is in operation in order to prevent leaks, excessive pressure on the valve stem, accelerated wear, and laborious opening and shutting. Valve construction procedures, valve protection facilities, bypass and instrumentation, and valve packing replacement are all important considerations since the quality of valve installation directly impacts use.