Nov 04, 2011
Stringent legislation drives demand for VCP pressure release valvesBack
© Reuse this
Further, the new pressure equipment regulations (PERs), promulgated under the Occupational Health and Safety Act, of 1993, previously referred to as the vessels-under-pressure regulations, came into effect in October 2009.
Competent persons qualified under the South African Institute of Welding and approved by the South African Qualification and Certification Commit- tee to pressure-test pressure vessels had until April 1 to conform with the new PERs.
“Since the laws on pressure silos have become a matter of safety for personnel and the environment, customers have been resorting to our VCP pressure relief valves,” WAM South Africa GM Emilie Marchand says.Pressure Vessels
She explains that a silo becomes a pressure vessel when it is filled and subjected to overpressure. In such cases, the VCP valve will open and release excess pressure exceeding 1 bar to prevent the silo from exploding or being damaged.
However, when the silo is being discharged, underpressure can also occur. “In this case, the valve will open up and allow pressure from the environment to enter the silo to regulate the pressure,” Marchand adds.
The VCP valve consists of a cylindrical casing with a bottom flange that is connected to a spigot on the silo’s roof. A disc-shaped inner steel lid for nega- tive pressure operation is held in position by a central spring rod, while an outside steel ring for excess pressure is kept in position by three spring rods, gaskets and a weather-protection cover.
Marchand says helical springs keep the valve lids closed when the pressure value remains within the preset limits. The three spring rods on the outside of the valve keep the external ring-shaped lid firmly closed as long as the force generated by the pressure inside the silo does not exceed the spring force.
“Once the pressure exceeds the preset value, the lid is pushed up and the pressure can escape. The smaller lid covers the central circular opening of the external lid from below. It is held in the middle by a single spring rod and is pressed onto the external lid by the normal air pressure inside the silo,” she adds.
In the event of suction pressure, the spring is compressed and enables the lid to drop. The air entering the silo from outside ensures rapid pressure balance and pushes the central lid back up into the closed position.
However, Marchand says, spillage on construction and cement plants is problematic, owing to the lack of a regulating body to monitor the pressure with which tankers offload their product pneumatically into silos.
“Tankers often increase their off- load pressure to help [speed up] the process. “This results in major overpressurisation in the silos, which causes the VCP valves to constantly open and spillage to occur. “This is worrying, as these valves are only supposed to open in the event of an emergency,” she points out.Regulation
It is difficult for plant managers to regu- late the tankers, which are owned and managed by third-party companies.
To deal with this challenge, WAM South Africa has offered its VHS membrane pressure relief valve as a solution.
The VHS is based on the same con- cept as the VCP valve; however, it has an outlet that enables it to be connected to a pipe. “If the valve does open, owing to overpressure, the spillage can be channelled back into the silo. This has various environmental benefits, especially with the spillage of fly ash or cement,” Marchand says.
WAM South Africa’s primary focus has historically been on batching plants; however, she states that the company is turning its attention to other sectors, including the agriculture, food and beverage and glass sectors.
Edited by: Chanel de Bruyn© Reuse this
Creamer Media Senior Deputy Editor Online
To subscribe email email@example.com or click here
To advertise email firstname.lastname@example.org or click here
Other Valves News
Recent Research Reports
Construction 2016: A review of South Africa's construction industry (PDF Report)
Creamer Media’s Construction 2016 Report examines South Africa’s construction industry over the past 12 months. The report provides insight into the business environment; key participants; local demand; geographic diversification; corporate activity; black economic...
Energy Roundup – February 2016 (PDF Report)
The February 2016 roundup covers activities across South Africa for December 2015 and January 2016 and includes details of a Government Gazette notice that confirms Cabinet’s decision to move ahead with the 9 600 MW nuclear procurement programme; State-owned power...
Energy Roundup - December 2015 (PDF Report)
The December 2015 roundup includes details of State-owned utility Eskom’s application to claw back R22.8-billion; South Africa’s ranking as an investment destination for renewable energy; and a nuclear expert’s thoughts on reactor designs for South Africa’s nuclear...
Water 2015: A review of South Africa's water sector (PDF Report)
Creamer Media’s Water 2015 Report considers the aforementioned issues, not only in the South African context but also in the African and global context in terms of supply and demand, water stress and insecurity, and access to water and sanitation, besides others.
Input Sector Review: Pumps 2015 (PDF Report)
Creamer Media’s 2015 Input Sector Review on Pumps provides an overview of South Africa’s pumps industry with particular focus on pump manufacture and supply, aftermarket services, marketing strategies, local and export demand, imports, sector support, investment...
Liquid Fuels 2015: A review of South Africa's liquid fuels sector (PDF Report)
Creamer Media’s Liquid Fuels 2015 Report examines these issues in the context of South Africa’s business environment; oil and gas exploration; fuel pricing; the development of the country’s biofuels industry; the logistics of transporting liquid fuels; and...
This Week's Magazine
Lifting, transporting, installing and ballasting solutions provider Ale has expanded its global fleet of trailers and invested in the latest range of widening trailers that can be mechanically widened from 3 m to the desired width for any project. Ale ordered 48 axle...
The market for the BMW 7 Series in South Africa differs quite significantly from the rest of the world. China, the US and the Middle East almost exclusively buy the long-wheel-base version, using the German manufacturer’s luxury high-end sedan as a chaffeur-driven...
January new-vehicle sales fell by 6.9%, to 48 615 units, compared with the same month last year. Statistics released by the Department of Trade and Industry show that the domestic new passenger-car market declined by 6.1%, to 34 936 units, compared with 12 months ago.
Information technology (IT) equipment and infrastructure multinational Dell is providing open infrastructure systems for clients so that they can use any systems, including innovative new systems, that suit their business needs, says Dell Europe, Middle East and...
South Africa’s State-owned defence industrial group, Denel, has set up another international partnership, based in Hong Kong. This new subsidiary is Denel Asia and it is a joint venture (JV) with South African private sector company VR Laser.
Next ArticleDome valve installation under way at Matla