WATER JET CONFERENCE - Waterjet Technology Association

TABLE V Casting cleaning impellors
Batch of 100 castings cleaned using
(a) Manual - 75 HP pump @ 9500 psi 10 gym
(b) Machine - 75 HP pump @ 9500 psi 10 gym
Manual costs $ Machine costs $
Capital
equipment
Time taken over
30,000 50,000
100 impellors 100 hours 25 hours
Running costs 500.00
Spares/
125.00
Ancillaries 250.00 62.50
Labour (2 men) 1200.00 (1 man)150.00
Amortisation 300.00 125.00
Total 2250.00 462.50
Cost per unit $22.50 $4.62
From Table V it can be seen that for quite moderate degrees of automation considerable
savings can be made, not only in time and money but in a more attractive and safer working
environment.
The above Tables TV and V can be replicated for many applications but automation is
often not cost effective in certain situations, for example:Where access is limited - eg in situ
condensers in many fossil fueled power station applications or Where fine movements and
manipulation are required - eg small bore passages. Other circumstances may also intervene, for
example heavy and intermittent blockages in tubes can cause damage to fixed motion lances.
4. PRICING - THE CONTRACTOR/CUSTOMER/OPERATOR INTERFACE.
With the economic recession from which we have suffered in the UK over the past
almost ten years we have seen competition grow fiercer, prices become keener and the customer
put more and more pressure on the contractor to produce ever more for less return,
This has in turn been exacerbated by the grossing requirement of the operator for more
pay to survive in a continuing inflationary spiral. Fig V shows hourly charges from a contractor
(Reliance Descaling 1967-82) to a customer, and wages paid by the contractor to operators over
the same period,
From Fig V it will be seen that wages have increased by a factor of X5 whilst charges to
the customer have increased by a factor of X2,3, thus profit margins have been steadily eroded. It
is also interesting to note the considerable decline in the rate of increase of cost to the customer
after the introduction of competition in 1972.
This is now an active policy pursued by many major customers of water jetting
contractors in the UK, That is to say, two contractors are used. In its most unpalatable form one
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