LETTERS

LATCHED .AUTOMATiC CUT-OFF NOZZLES

In previous correspondence I stated that at the end of the unsuccessful test on the O.P.W. I.AA Automatic Latched No _zzl~, Mr. Symons, representing Link-Hampson the U.K. d1stnbutors of this nozzle, said that he would ask. the maunfacturer's engineers to have a look at the design of the nozzle, with a view to modifying it in some way to make the break-away feature more acceptable to us.

In January, Mr. Symons .wrote to me and asked for a further meeting to demonstrate a red serrated plastic sp_o_u~ sleeve, which he thought would overcome my cntic1sm and also to demonstrate again the anchor spring for spout breakage or disengagement. " In the last paragraph to this letter Mr. Symons says s We d? accept, however, our responsibilities that pout issue~ should be correct from both safety each and general _service standpoints and ask you to see the new alternat~ves we have to offer as a result of the experiences at Haylmg I

s lan~

. From this paragraph I assumed that the. nozzle had. m some way been modified and I wrote askn~g for details of the modification, as I did not think that Just further weakening the link would be totally satisfactory. I never received a reply to this request.

However, a date was fixed for a further test and on the 20~h February, 1968, five Petroleum Inspectors and a Councillor met at the Hornet Service Station, Chichester.

I arrived some time before the others and spoke with Mr. Symons, askin~ him in what way the nozzle to be te s te~ had been modified, and he replied quite categorically that It had n<?t been modified; when I suggested that l w~s then wasting my time he said he was quite sure that tl11s test would be successful as it was being carried out under more ideal Island . . For example, conditions than the petrol pump those was o at f. a . Hayling

mod~rn lo~ design, the hose was new and a different vel11cle with a side fill was to be used. I remarked that I was not sure whether or not I appreciated these 'ideal' conditions, for surely, he would not always under such conditions. expect the nozzles to be used

By this time the other inspectors had arrived and it was suggested that we get on with the test. _Mr. SJ'.mons again worked through the Home Office ~1rcul

item a_ r (v1)items very successfully the drive away test. and finaUy we came to

As J have already stated, the petrol pump including the hose was almost brand new, and the vehicle chosen was a ~ord Anglia _ van with a side fill pipe, which matched in height approximately the height at which the delivery hose leaves the pump.

After the hose had been carefully placed in the fill pipe by Mr. Symons, the van was driven away at a fairly fast rate and, to the pleasure of all, the spout snapped off immediately, the pump did not move nor did the hose stretch, and very little petrol was lost.

I was rather surprised that the whole thing had worked so easily in view of the fact that I had been told that the nozzle had in no way been modified, and maybe it was this that prompted me to examine the break in the spout.

You can imagine my surprise to find that a deep groove had been filed into the spout where it joins the main body of the nozzle to such an extent as to make it quite unsuitable for normal use. The groove had of course been invisible to us during the test as it was naturally hidden by the anchor spring.

During the tests the nozzle was handled only by Mr. Symons and even so the metal remaining to support the spout was so thin that it is a wonder that it remained intact during the other parts of the test.

Under these circumstances l felt that 1 had to inform Mr. Symons that in my opinion the nozzle had not been satisfactorily tested and that I was rather surprised that a nozzle should have been submitted to us for testing in such a weakened condition.

I make no further comment and leave readers to draw their own conclusions.

Ha vant and Waterloo U. D.C.

J. W. H EWISON

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LATCHED AUTOMATIC CUT-OFF NOZZLES

Your January issue contained several references to the Z.V.A. nozzle now manufactured by my company, Permex Ltd. I therefore feel that the following comments on the subject of latched nozzles may be of interest to readers of your excellent journal.

Mr. J. W. Hewison compares the action of a nozzle with a weakened spout with that of our safety swivel in "drive-off" accidents. Our extensive tests have shown that both devices are complementary. The force required to snap a weakened spout varies with the angle of pull. When this is at right angle to the spout this might be 140-160 lbs., but if it is in line with the axis of the spout it could be 500 lbs. If a spout is weakened to snap at a more reasonable axial pull, it would constantly break under normal operating conditions. The safety swivel has made it possible to limit axial pulls to below 200 lbs.-yet the spout will be strong enough to withstand normal wear and tear. The Z.V.A. spout will, however, snap when pulled at angles at which the safety swivel cannot operate.

The point that hoses and foundation bolts should be checked is very valid. The only case known to me, of a pump being pulled over, proved to be due to foundation bolts of this and adjoining pumps not having been grouted in. Yet one of these pumps stood up to an accidental pull resulting in the swivel being pulled apart. We have tested new hoses of the types used on petrol pumps and found that they will resist a pull of 600-800 lbs. without apparent damage, but hoses may be damaged by kinking, particularly near the end fittings, and in that state, may tear at a pull of less than 200 lbs. when this is applied at an angle to the axis of the fitting.

When the Z. V.A. is tested for "impact release" in the "dry" state (i.e. without petrol flowing through it) the latch will release only when the nozzle hits the ground at certain angles. When the test is done "wet" it will release every time, irrespective of angle. This characteristic is peculiar to the Z.V.A. design and has been demonstrated to many authorities, including Glasgow, Leeds, Greater London, Walsall and Worcester. The Z.V.A. also incorporates an additional, internal impact release which trips the mechanism even if the lever is firmly wedged open. This prevents the nozzle from being operated until the lever has been first unlatched.

Mr. F. A. Smith mentions that the safety swivel can be pulled apart for inspection. This should not be necessary as every swivel is tested at the factory, and is rejected if the pull required exceeds 199 lbs. Wear and tear reduce this value, as does repeated pulling apart. ~ convenient way of testing the safety cut-out is to pomt t~e. n<?zzle up ~hile pulling the trigger back. Very little spmt, 1f any, will project, but the spout and body of the nozzle will fill and must be drained.

Mr. R. A. T. Kemp mentions a latch release that would oper~te when the nozzle. is returned to the pump. Devices of ~his type are a pote_ntial menace. The trigger guard on which the nozzle rests 1s one of the two points of maximum we~r(the s~out being the other). Pivots, or linkages at that pomt get distorted and misaligned quickly, and can then prevent easy unlatching. No mechanism now commercially available is free from this defect, and any "do-ityourself" implied by the quoted letter, should be strongly discouraged. As stated by Mr. Smith, the safety cut-out gives very adequate protection, and the chance of spillage due to a nozzle not having been unlatched, is remote. The only case which was reported to us proved, on investigation, to be the spilling of "a cupful" when the nozzle was tilted. Obviously the safety cut-out had worked, as it should and the contents of the nozzle were spilt. The valve could not have been open or much more spillage w~ml? have resulted. The valve cannot operate after tnppmg of the safety cut-out until the lever has first been returned to the "off" position.

The following points arose during contact with other authorities:

One authority wanted a modification which would prevent the use of the lowest of the three speeds. It was felt that this w~uld _?therwise encourage attendants to try and ~JI .up too high, m~tead of topping up manually. The latter is, m fact, less desirable, as the automatic action is slower at low filling speeds, and could even cease at the very slowest rate. Another authority requires a modification to _prevent the use of the highest speed, as this could cause spillage due to blow-back in the case of some "slow fillers". In fact, the automatic shut-off on blow-back is far faster tha~ the m~nual shut-off by the most attentive attendant. Settmg. a higher speed than the fill pipe will take merely results m premature shut-off.

It was also proposed that notices should be displayed o~ the forecourt to warn the motorist to check that he was disconnected before driving off. If such notices would be sufficiently conspicuous they could be of value when latch~d nozzles are first introduced. It has been my experience that stations telling their customers about the n~zzles ,,(as part of thei~, ef!'ort to sell "fill-up without spdla~e ) do not have dnve-off" accidents. On the Contment, where latched nozzles have been in general use for so~e years (~nd w~ere over a quarter of a million Z.V.A s are unknown. now m service) such accidents are practically

. Latched nozzle~ ~re a comparatively new development m the U.K., and it is therefore proper that all authorities co_ncerne~ should carefully consider all problems that might be involved. In these arguments it is, however, easy to overlook that the _conventional, non-automatic nozzle causes J?UCh more ~pillage in day-to-day operation. Even the earlte~ aut~matic nozzles which are used without latch, an~ require higher minimum filling speeds and regular mamtenance, cannot compare in safety and reliability with advanced sealed systems like our z. V.A. I am therefore confide~t that the ".ery widespread introduction of our nozzle m the l:J.K. IS making a positive contribution to the safer handlmg of petroleum which is the aim of your readership. ,,

Director, Perm'ex Ltd.

J. G. HURST

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