Wuxi Zechuan Environment, a professional manufacturer of RTO incinerators, RTO, RCO, and VCU equipment, on September 27, 2024, excerpted from the VOCs reduction workstation. It is well known that the tank breather valve is a ventilation device installed on the top of the storage tanks for Class A, B, and C liquids in conjunction with the flame arrester. It is an important accessory for protecting the safety of the storage tanks. It consists of two parts: a pressure valve and a vacuum valve. One of its functions is to maintain the airtightness of the oil tank and, to a certain extent, reduce the evaporation loss of the oil. Second, it can automatically regulate and balance the pressure inside and outside the oil tank through ventilation. A good breathing valve is also an important device for reducing VOCs emissions at the source in storage tanks!
I. Inspection of the breathing valve of the storage tank
1 The common faults of breathing valves mainly include: air leakage, jamming, adhesion, blockage, freezing, and the pressure valve and vacuum valve being always open, etc.
(1) Air leakage: It is generally caused by rust, hard objects scratching the contact surface between the valve and the valve disc, deformation of the valve disc or valve seat, and tilting of the valve disc guide rod, etc.
(2) Jamming: This often occurs when the breather valve is installed incorrectly or the oil tank deforms, causing the valve disc guide rod to be skewed and the valve stem to rust. During the up and down movement along the guide rod, the valve seat cannot reach its proper position, resulting in the valve disc getting stuck at a certain part of the guide rod.
(3) Adhesion: It is due to the chemical and physical changes caused by the mixture of oil vapor, moisture and dust and other impurities deposited on the valve disc, valve seat and guide rod. Over time, the valve disc and valve seat or guide rod adhere together.
(4) Clogging: This is mainly due to the long-term lack of maintenance and use of mechanical breathing valves, which causes dust, rust residue and other debris to accumulate inside the breathing valve or inside the breathing tube, as well as bees or birds building nests at the breathing valve opening, etc., leading to clogging of the breathing valve.
(5) Freezing of the breather valve: This is due to temperature changes, where moisture in the air condenses at the valve body, valve disc, valve seat, and guide rod of the breather valve, and then freezes, making it difficult to open the valve.
2 Regularly check the contents
(1) Check whether there are any phenomena such as being constantly open, air leakage, jamming, adhesion, blockage, freezing or rusting;
(2) Check if the sealing gasket is leaking. If any is found, it should be replaced.
(3) Check whether the valve disc can rotate flexibly and whether there is any jamming fault.
(4) Check whether the valve body sealing mesh is frozen or blocked, and whether there is dust or dirt adhering to the mesh.
(5) Check whether the metal parts such as the valve disc, valve seat, guide rod and air guide spring have rusted or accumulated scale. They can be cleaned with kerosene.
(6) When conducting material entry and exit operations in the storage tank, check whether the breathing valve is operating normally.
3 The breather valve should be calibrated once a year on a regular basis. The calibration method shall be carried out in accordance with SY/T 0511.1-2010 "Petroleum Storage Tank Accessories - Part 1: Breather Valves".
Ii. Inspection, maintenance and regulatory requirements for breather valves of storage tanks
1 "Integrity Management of Atmospheric Pressure Storage Tanks" (GB/T37327-2019)
8.6.1 The breather valves used in atmospheric pressure storage tanks shall be inspected at least once a year.
8.6.2 The following materials should be reviewed before inspection:
a) The product model and operating pressure rating of the breathing valve;
b) Manufacturing date, product qualification certificate, installation date, completion acceptance document;
c) Online inspection records during the operation cycle;
d) Previous regular inspection reports.
8.6.3 Before inspection, the inspection items and qualification standards should be clearly defined and approved by the user unit. The user unit should make adequate preparations as required.
8.6.4 The inspection contents of the breathing valve include visual inspection, opening pressure, ventilation volume and leakage volume test, etc.
8.6.5 The appearance of the breathing valve should be free from abnormal rust, leakage and blockage by debris.
8.6.6 The opening pressure, ventilation volume and leakage volume of the breathing valve shall meet the design requirements.
2 Guidelines for the Investigation and Management of Safety Risks and Hidden Dangers in Hazardous Chemicals Enterprises (Emergency [2019] No. 78
(4) The management enterprises of static equipment shall set up safety accessories such as breather valves (hydraulic safety valves), flame arrestors, foam generators, liquid level gauges and vent pipes of storage tanks in accordance with the specifications, and conduct regular inspections or tests, and fill in the inspection and maintenance records.
3 SY 5225-2005 - Technical Regulations for Fire and Explosion Prevention and Safety Production in Oil and Gas Drilling, Development, Storage and Transportation
Article 7.4.1.1 The installation of breather valves, flame arrestors and hydraulic safety valves in oil storage tanks shall be carried out in accordance with SY/T 0511, SY/T 0512 and SY/T 0525.1 respectively. Safety valves should be inspected and calibrated by qualified inspection institutions at least once a year.
Article 7.4.1.2 The base of the breather valve and the hydraulic safety valve shall be equipped with a flame arrester. The breather valve and the hydraulic safety valve shall be inspected at least twice a month in winter and calibrated once a year. The flame arrester should be inspected at least once every quarter. The breathing valve is flexible and easy to use. The oil level of the hydraulic safety valve meets the requirements and the oil quality is qualified. The flame-retardant layer of the flame arrester is in good condition and there is no phenomenon of oil sludge blockage.
