SubscribeBroady Flow Control specialises in delivering solutions to customers with very specific and often challenging problems in fluid flow control. One such example resulted in the development of the ASBRO valve by Broady Flow Control to meet the challenges of reducing customer costs whilst increasing functionality, performance and service life of traditional globe valves used in exacting conditions on ASTUTE Class nuclear submarines.
Existing Screw Down/Screw Lift & Screw Down Non-Return valves for Naval applications, although relatively efficient are extremely expensive to manufacture. Therefore the design team at Broady Flow Control has, by value analysis, examination of similar NATO Ship/Submarine valves and exacting simulated service condition testing developed a New Generation Valve, currently supplied in sizes ranging from NB 6 mm to 200 mm - The ASBRO Valve, see Figure 1.
 Figure 1 - The ASBRO Valve |
This has been achieved without compromising Function, Safety, Quality or Reliability of its predecessor whilst reducing the unit cost by a minimum of 35% compared to existing valve types such as those illustrated in Figure 2 below.
Figure 2 - Traditional Globe Valves
The ASBRO valve delivers significant savings over the traditional design, and in many cases savings in excess of 35% was achieved by;
- Eliminating Fasteners that often require high level of certification
- Significantly reducing the number of cast components
- Reducing the required amount of Radiography & Heat Treatment
- Eliminating expensive weld repair of castings
The Valve Body
Developed using Computational Fluid Dynamics (CFD) to ensure the most efficient fluid path for the smallest body envelope is achieved. This also eliminates severe changes in section thus reducing flow noise, a key factor in submarine valve design (Figure 3), this eliminates/Reduces;
| - Casting Cavities - Shrinkage - Costly Weld Repairs - Heat Treatment - Validation - Flow Noise |  |
The Valve Lid & Seat
Incorporation of a double seal on the seat and lid assembly (Figure 4), the primary seal is a captive 'O' seal whilst the secondary seal is a lapped metal face (also preventing the 'O' ring from being over-compressed). Advantages of this sealing arrangement are:
- Complete Bubble tight shut off is achieved
- Low operating torque
- Low break out torque
Figure 4- Soft Seat
The seat design has been successfully proven on ASC Collins Class submarines and subjected to 200g shock test, after which the seat remained pressure tight, additionally MoD are also incorporating this design of seat into Vanguard Class Feed Pump Relief Valves via Formal Class Modification being undertaken by Broady engineers.
Spindle Sealing
The main spindle sealing is by 'O' ring (Figure 5) and suitable for working pressures up to 103 bar giving the following advantages;
- Improved sealing capability
- Improved life expectancy over conventional packing
- Consistent valve operating torque, a key factor in automating valve operation
Figure 5 - Back up Washer, Figure 6 - Secondary Packing
Secondary Sealing & Backup Washer (Figure 6)
Conventional gland packing is only used if the 'O' ring fails and thus acts as an emergency back up seal. Additionally the gland packing can be completely replaced without the need to remove the valve from service or reduce the pressure in the system by making use of the back up washer. In the unlikely event of the main 'O' seal AND gland packing failing, the new design incorporates a secondary backup washer fitted to the spindle, thus preventing any further leakage when the valve is opened fully.
This feature as been tested at Broady, where ZERO leakage was detected after 1 hour at 90 bar.
Cartridge Design
All of the valve components can be removed from the valve by unscrewing the cover, without removing the valve body from the system (Figure 7). This has the advantage of making changing valve components quick and easy thus reducing operational downtime for emergent defect repair.
Figure 7- Cartridge Assembly
Cover Seal
On larger valves where the screw cartridge assembly is not practical a static 'O' ring has replaced the traditional CNAF joint thus giving longer seal life. The position of the 'O' seal on the inner face of the valve body also stops the potential for ingress of foreign matter to the cartridge screw thread and protects the seal from environmental effects (Figure 8).
Figure 8 - Cover Seal
Materials of Construction
The valve can be manufactured in a range of materials from standard carbon steels to the more exotic materials detailed below;
- Gunmetal to BS1400 LG4 & NES 830 Pt.1 Class III (Def Stan 02-830)
- Al Bronze to BS1400 AB2 & NES 747 Pt.3 (Def Stan 02-747)
- Ni.Al. Bronze to NES 747 Pt.2 & 4 Class I, II & III (Def Stan 02-747)
- Si.Al. Bronze to NES 834 Pt.3 Class I, II & III (Def Stan 02-834)
- Cu.Ni.Cr to NES 824 Pt.1 Class I, II & III (Def Stan 02-824)
- Alloy Steel to ASTM A217 Gr. WC6
- Alloy Steel to ASTM A352 Gr. LC1
- Stainless Steel to ASTM A351 - CF8 (AISI 304) & (CF3M (AISI 316L)
- Monel*
- Inconel 625*
- Hastelloy*
- Duplex & Super Duplex Stainless Steel
- 6Mo
- Titanium
* These Materials are Registered Trade Names
European material number equivalents can be provided upon request, however Broady can supply valves constructed to customers specific duty requirements.
Modus Operandi
ASBRO valves are designed for easy adaptation to automatic/remote operation by either, hydraulic, pneumatic, or electrical power sources making them suitable for the increasing levels of automation required on modern Naval and Paramilitary vessels.
Safety Compliance & Quality Approvals
Using Det Norske Veritas/SSMO trained & qualified Professional Engineers with experience in the development and production of Safety Cases Broady Flow Control can deliver ASBRO valves complete with an accompanying Safety Case in order to comply with the evolving requirements of the Armed Forces both in the UK and overseas.
Alternatively Broady Flow Control can provide SQEP and subject matter experts to support the development of whole system Safety Cases in accordance with JSP 430 Issue 2 for MoD, Shipbuilders/Repairers and external Consultants.
Quality approvals are detailed below;
- ASME Section V111, Division 1: "UV" Stamp
- NB Stamp for the Type 3500 (The National Board of Boiler & Pressure Vessel Inspectors
- LRQA - BS EN ISO 9001: 1994 - Certificate No: 901847
- WRC Approval for the type AB & D Valves - Non Potable Water
- DSQR (Designated Supplier Quality Representative)
Conclusion
The ASBRO valve has been totally designed, developed, tested and manufactured in-house (Figure 9) utilising the depth and breadth of Broady professional engineers from designers and pattern makers to founders and test engineers. This has resulted in the development of a very successful product that has the accolade of replacing BAE designed submarine first level valves fitted on nuclear submarines built in the UK.
Figure 9 - Development of the ASBRO
Since the successful introduction of the ASBRO a number of other shipyards and maritime design consultants have expressed interest in the valve and the soft seating technology incorporated into the seat and lid. These include HDW, Blohm + Voss, BMT, THALES and MoD Equipment IPT's.
In addition to the successes of the ASBRO a new family of valves has emerged from its design, balanced stop valves for use on HP air systems. At the direct request of BAE systems Broady Flow Control designed, tested to 700 bar, manufactured and delivered a range of balance stop valves in six weeks from initial enquiry for use on HMS Albion and Bulwark (Figure 10). And in consultation with German shipbuilders Broady are researching the development of a hybrid version of the ASBRO that will directly integrate with their legacy valves and resolve the difficulties they currently face with manually operating larger valves against deeper diving depth pressures.
Figure 10 - Balanced Stop Valves
For more information on ASBRO and other Broady Flow Control products and services visit our website or contact Broady Flow Control directly and our engineers will be happy to discuss customers' specific requirements and work closely with you to resolve any flow control, technical or supply difficulties currently being encountered.
