Startseite » Chemie »

Combined safety

Bursting disc arranged directly in front of safety valve
Combined safety

Combined safety
Safety valve and bursting disc combination
Separate sizing and selection of safety valve or bursting disc take place by means of tables in the manufacturer’s catalogues or using special computer software. If both components are combined, several aspects have to be taken into account to ensure safe operation.

Erhard Stork

Safety valves and bursting discs are normally used for pressure protection in containers and pipelines. Both systems are advantageous compared to other pres-sure protection devices, as they are independent of external energy, and they are also allowed to be used without back-up components.
A combination of both systems by aligning the bursting disc in front of the safety valve (Fig.) unites the advantages of both systems: total sealing plus the high media resistance of the bursting disc and the resealing properties of the safety valve. Systems can continue to work even after the safety device has operated. The technical rules in the AD-A1 code of practice (1/95) describe the following requirements for this type of combination:
• insertion of non-fragmenting rupture discs (non-shattering),
• the distance between the bursting disc and the safety valve must be large enough to ensure correct operation of the bursting disc,
• possibility of purging any condensate that emerges between the bursting disc and the safety valve,
• the pressure drop in the inlet lines and between the bursting disc and the safety valve must not exceed 3% of the difference between the permitted operating pressure and the back pressure of the safety valve,
• facility for recognising a damaged bursting disc (pressure gauge, bursting disc sensor, etc.). This simultaneously ventilates the interspace, so that no back pressure which might alter the burst pressure of the bursting disc can develop. Compared to separate sizing of the bursting disc and the safety valve, the following aspects have to be taken into account. Sizing takes place in two steps: First, the safety valve is sized on the basis of the data below. It is a good idea to use Safe, the computer sizing software:
• set pressure,
• back pressure,
• capacity (mass flow/volume flow),
• medium (liquid/gaseous),
• temperature,
• working characteristics (full lift/normal),
• material,
• approvals.
The subsequent choice of bursting disc depends on the following criteria:
• bursting pressure of the bursting disc = set pressure of the safety valve,
• nominal size of the bursting disc = nominal size of the safety valve inlet,
• medium (iquid/gaseous),
• temperature,
• tolerance of 65% for the combination with full lift safety valves or 610% for the combination with standard safety valves,
• pressure rating of holder = inlet pressure rating of the safety valve,
• materials of the bursting disc and holder,
• approvals,
• safeguard device (reference pressure gauge or disc sensor).
The required pressure drop of 3% is guaranteed if the bursting disc is arranged directly in front of the safety valve and the cross-section of the holder fulfils the following condition:
Ageom • a > 1,5 • A0 • aw
where Ageom = geometric area of the bursting disc and holder, a= coefficient of discharge of the bursting disc and holder, A0= narrowest flow area of the safety valve and aw = coefficient of discharge of the safety valve.
ARI Armaturen
Fax: ++49/5207/99 42 97
Further information cpp-204
Unsere Whitepaper-Empfehlung
Newsletter

Jetzt unseren Newsletter abonnieren

cav-Produktreport

Für Sie zusammengestellt

Webinare & Webcasts

Technisches Wissen aus erster Hand

Whitepaper

Hier finden Sie aktuelle Whitepaper

Top-Thema: Instandhaltung 4.0

Lösungen für Chemie, Pharma und Food

Pharma-Lexikon

Online Lexikon für Pharma-Technologie

phpro-Expertenmeinung

Pharma-Experten geben Auskunft

Prozesstechnik-Kalender

Alle Termine auf einen Blick


Industrie.de Infoservice
Vielen Dank für Ihre Bestellung!
Sie erhalten in Kürze eine Bestätigung per E-Mail.
Von Ihnen ausgesucht:
Weitere Informationen gewünscht?
Einfach neue Dokumente auswählen
und zuletzt Adresse eingeben.
Wie funktioniert der Industrie.de Infoservice?
Zur Hilfeseite »
Ihre Adresse:














Die Konradin Verlag Robert Kohlhammer GmbH erhebt, verarbeitet und nutzt die Daten, die der Nutzer bei der Registrierung zum Industrie.de Infoservice freiwillig zur Verfügung stellt, zum Zwecke der Erfüllung dieses Nutzungsverhältnisses. Der Nutzer erhält damit Zugang zu den Dokumenten des Industrie.de Infoservice.
AGB
datenschutz-online@konradin.de