Thanks for pointing me in the right direction chaps. You were both correct on both counts. She was/is indeed a 'trailing suction hopper dredger' built by William Simons & Co, Renfrew.
With many thanks and credit to www.clydesite.co.uk in the dredger section.
There are 2 possibilities and I tend to favour the second:
1. ss Liger built 1924 yard no 667. Last name KERBALA(1958) POR> Basalraq.
1576grt. Status Active 2003!!! Unbelievable if it's true. Photo on site similiar to my image.
2. ss Ongar built 1935 yard no 705. Last name SULAIMANIYAH (1958).
Port of Registry: BasraIraq, Tonnage: 2371 grt, Owner History: Govmt of Iraq
Status: Scrapped - 2000. The photo on site is virtually identical to mine apart from lack of rear mast.
So I suspect that this photo is indeed a W Simons dredger and possible on of the above or a sister vessel. I suppose I ought to ask the Moderators to move this to the correct category.
Just an aside Richard, I was working on a Cardiff bucket dredger in 1958 which had been built in the late 1890s I know that it was still working in 1970, so 70+ years for any sort of dredger is not unusual!