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Service Bulletin No.12

Equipment: Hamworthy Sewage Treatment Plant

Subject: Sewage Discharge Valve Date 1st February 2010
From: Gavin McGirr Pages: 2
Dept. Service Ref: SERV1012

AVT04 Vacuum Toilet Component Upgrade
Sewage Discharge Valve Assembly

Introduction
This Service bulletin covers the modifications to the Hamworthy AVT04 vacuum toilet. The toilet has been upgraded for the use of a larger vacuum hose; this gives improved operation, easier commissioning and increased reliability.

Modification
The 3 main components have been replaced:
• Sewage discharge valve (SDV)
• Vacuum dispensing valve (VDV) (Pilot Valve)
• Vacuum check valve (Mini Check Valve)

All items have larger Vacuum ports to facilitate the new 8mm ID hose; this increases the vacuum transfer speed by more than 4 times compared to the existing system. In addition to this the SDV has been optimised for additional core strength and ease of assembly. The check valve was also completely redesigned to meet our exact requirement against an off the shelf item.

During bench tests and sea trials we saw that the above modifications greatly enhanced the function and overall reliability of the toilets giving the improvements as noted below.

• Much sharper / crisper movement of the SDV operation
• Reduction in the delay of opening / closing of the SDV thus reducing vacuum loss in the system
• Reduction in the risk of partial blockages due to sharper more responsive vacuum action.
• Increased protection of all components (in particular the Flush Control Mechanism FCM) with the new check valve
Spares and upgrades
All new toilets ordered from September 2009 will be fitted with the new parts as our Hamworthy standard.

With regard to replacement parts & spares sales enquiries, we will herewith only offer / supply the