Boiler safety valve

No, the safety valve is primarily a pressure-relief outlet and should not have any resistance

The specifications require a straight pipeline, but this practice is common in reality; the safety valve of our company’s 10-ton boiler was designed with two 90-degree bends due to space constraints. From a pressure relief perspective, the pipe diameter can be increased to reduce resistance. According to Article 5.1.8 of the «Regulations for the Inspection of Boilers in the Power Industry», safety valves must be equipped with exhaust pipes leading outside, and these pipes should be as straight as possible. The exhaust pipe and its accessories (including the silencer if one is installed at the exhaust pipe outlet) must not affect the proper operation of this safety valve. A drain pipe connected to a safe location should be installed at the bottom of the exhaust pipe. Valves are not allowed to be installed on either the exhaust pipe or the drain pipe. From this perspective as well, the use of bends is permitted. This post was last edited by xssn2005 on 2007-12-3 at 11:23.]

It’s possible, but note that the elbows, straight pipes, etc., at the outlet must be at least one nominal size larger.

Thank you all for your insightful comments; I understand now

There are definitely elbows at the outlet, so the selection of the safety valve needs to be considered in advance. For boilers, a full-open type must be used, as their outlet has a nominal diameter that is larger than that of the inlet.

Actually, I think what the original poster meant was not whether there was a bend at the outlet of the safety valve, but rather the fact that a 90-degree angle could not be guaranteed. I’ve encountered a similar situation with the safety valve of a economizer; after discussing it with the design team and the inspection department, we extended the outlet pipeline. To reduce various losses due to resistance, we added an elbow at the outlet after performing some calculations, thereby increasing the pipe diameter and solving the problem.

90-degree elbows are available: handshake

It seems that 90-degree elbows work as well; I’ve seen many that are of this type

It’s absolutely not allowed; the installation specifications for safety valves require them to be connected directly to the atmosphere

The requirements for installing safety valves are as follows: 1. Safety valves should be installed vertically, and they should be placed in the gas phase space above the liquid level of the pressure vessel, or on a pipe connected to the gas phase space of the pressure vessel. 2. The cross-sectional area of the passage in the connecting fitting between the pressure vessel and the safety valve must not be smaller than the inlet cross-sectional area of the safety valve; the piping should be as short and straight as possible. 3. When two or more safety valves are installed on a connection port of a pressure vessel, the area at the inlet of that connection port shall be at least equal to the total cross-sectional area of the inlets of these safety valves. 4. It is generally not advisable to install stop valves between the safety valve and the pressure vessel. To enable online calibration of safety valves, a rupture disc device can be installed between the safety valve and the pressure vessel. For pressure vessels containing media with extremely high, high, or moderate toxicity, flammable media, corrosive or viscous media, or valuable media, in order to facilitate the cleaning and replacement of safety valves, a shut-off valve may be installed between the safety valve (rupture disc device) and the pressure vessel, provided that it is approved by the technical responsible person in charge of pressure vessel safety at the using unit and that reliable preventive measures are put in place. During the normal operation of the pressure vessel, the stop valve must remain fully open (sealed or locked). The design and diameter of the stop valve must not interfere with the safe venting function of the safety valve. 5. The installation location of the safety valve should facilitate inspection and maintenance.

Elbows are allowed, and it is best for the flow to go upward to avoid injury during emptying

It must absolutely not be discharged horizontally, as this can cause injury; an additional elbow fitting that directs the flow upward is necessary

The outlet of the boiler safety valve is required to have low resistance; as long as this condition is met, it is sufficient, and there is no need to follow the specifications strictly

Elbows can be used, but it is necessary to calculate the resistance to ensure that the flow rate is adequate when the safety valve releases pressure in case of overpressure in the boiler. I have seen 220t/h circulating fluidized bed boilers where the superheated steam header is located behind the tail flue, at a certain distance from the ceiling; after calculating the resistance, an elbow was added, and a long section of pipe was also installed leading to outside the top of the boiler room.

Agreeing with the friend upstairs, we used to do it the same way.

Elbows are allowed; boiler specifications require that the safety valve discharge outlet be connected to a safe location

Steam boiler safety valves should generally be equipped with a steam discharge pipe, while hot water boiler safety valves should be fitted with a drain pipe. Valves are not allowed to be installed on either the exhaust pipe or the drain pipe; they must lead directly to a safe location and have sufficient cross-sectional area to ensure smooth drainage. At the bottom of the discharge pipe of the safety valve of a steam boiler, a drain pipe leading to a safe location should be installed, and no valves are allowed to be fitted on this pipe. The safety valve of the economizer should be equipped with a drain pipe leading to a safe location, and no valves shall be installed on this pipe. Based on these principles, 90° elbows can be installed, but it is necessary to ensure sufficient cross-sectional area.