Project Report. Fisheries Development Branch Scotia-Fundy Region Halifax Nova Scotia [ Fisheries Peches and Oceans et Oceans

Transcription

1 [ Fisheries Peches and Oceans et Oceans TC DFO - Lib arj / MPO - Bibliotheque [ Project Report Fisheries Development Branch Scotia-Fundy Region Halifax Nova Scotia

2 THIS IS AN UNEDITED CONSULTANT'S.REpORT INANCED IN FULL OR IN PART BY THE FISHERIES DEIsiLOPM.NT BR ANCH, SCOTIA FUNDY REGION. THE VIEWS EXPREED I I REPORT ARE THOSE. OF THE CONSULTANT Apt) :Nov/ N / E SARILY THOSE OF THE BRANCH. (..1/ THIS REPORT IS NOT TO BE CITED WITHOUT WRITTEN PERMISSION FROM THE BRANCH DIRECTOR. NO.53 CUTTING SCALLOP SHELLS WITH.HIGH SPEED WATER JETS CONSULTANTS REPORT BY M.M.VIJAY AND W.H.BRIERLEY, NATIONAL RESEARCH COUNCIL OTTAWA LTR GD-60 OCTOBER 1980

3 DIVISION OF MECHANICAL ENGINEERING DIVISION DE GENIE MECANIQUE. CANADA PAGES PAGES FIG. DIAG 6 REPORT RAPPORT 6 REPORT RAPPORT LTR-GD-60 DATE O ct DATE FOR POUR REFERENCE REFERENCE SECTION GAS DYNAMICS LAB. ORDER 18003A COMM. LAB FILE DOSSIER W. K. Rodman, Project Engineer Fisheries Development Branch Engineering Services Division, Fisheries and Oceans 1721 Lower Water Street, Halifax, N.S. B3J 2S LTR-GD7-60 CUTTING SCALLOP SHELLS WITH HIGH SPEED WATER JETS ECEPV JUL LIBRANI.43ZDFORD INSTITUTE OF OCEANOGRAPHY SUBMITTED BY PRESENTE PAR R. A. Tyler SECTION HEAD CHEF DE SECTION AUTHOR AUTEUR M. M. Vijay W. H. Brierley APPROVED AP PR OUVE E. H. Dudgeon DIRECTOR MRECTEUR THIS REPORT MAY NOT BE PUBLISHED WHOLLY OR IN PART WITHOUT THE WRITTEN CONSENT OF THE DIVISION OF MECHANICAL ENGINEERING CE RAPPORT NE DOIT PAS 'ETRE REPRODUIT, NI EN ENTIER NI EN PARTIE. SANS UNE AUTORISATION ECRITE DE LA DIVISION DE GENIE MECANIQUE FORM NRC 539 FORMULAIRE NRC 539 COPY No. COPIE NR 2

4 PAGE PAGE 1 REPORT NO. RAPPORT NR. LTR-GD-60 SUMMARY Tests were conducted in the laboratory to investigate the possibility of using high pressure water jets for cutting sea scallop shells (valves). It was not possible, with the available equipment (maximum pressure = psi), to cut through both the top and bottom parts of the shell with a single jet. The feed rate was approximately 3 shells per minute. INTRODUCTION A scallop shell within which the edible portion of the scallop, namely the abductor muscle, exists is shown in Fig. 1. Shucking scallops involves removing this edible portion from its two valves (top and bottom parts of the shell, Fig. 2) and the viscera (internal organs). As this operation is highly labour intensive, the Engineering Services Division of the Fisheries Development Branch, Fisheries and Oceans Canada, has developed and built a prototype "Automated Scallop Shucking Machine" (Ref. 1). The machine employs a pair of circular saws which cut the shells at approximately the locations shown in Fig. 3 and expose the interior of the scallop. The edible portion of the scallop is then removed from the shell and separated from the viscera by means of high pressure (=2000 psi) water jets. The machine is capable of shucking 60 scallops per minute which is approximately three times faster than the rate achieved by a highly skilled manual shucker (Ref. 1). However, the engineers responsible for FORM NRC 540 FORMULAIRE NRC 940 COPY NO. COPIE NR

5 PAGE PAGE 2 REPORT No. RAPPORT NR. LTR-GD-60 the development of the machine were keen to find out if this speed of operation could be increased further by employing high pressure water jets, in place of circular saws, for cutting the shells. Since their existing water jet facility was inadequate for this work, the Gas Dynamics Laboratory was approached for assistance. The objective of the tests conducted in the laboratory was to find, for a given traverse speed, the pressure at which both the top and bottom parts of the shell (Fig. 2) could be cut through simultaneously. According to Fisheries, cutting through both parts at the same time was essential because of the limitations imposed by the shell clamps in the prototype machine. EXPERIMENTS AND RESULTS A total of 14 tests were carried out in the laboratory. A McCartney pump, capable of delivering 0.63 USGPM of water at the rated pressure of 45,000 psi (hydraulic horsepower = hhp = 16.6), was used for the first 11 tests. For the remaining tests, A Union pump, capable of delivering 13 USGPM at 10,000 psi (hhp = 76), was employed. The peculiar shape and curvature of the shell required a special spring loaded clamping device to hold it under the jet (Fig. 4). Fig. 5 shows the shell under the jet. The clamping device was supported on a traverse trolley which was driven by a variable speed electric motor. Sapphire nozzles were used to produce small diameter (<0.010 in.) jets. Larger diameter jets FORM NRC 541) FORMULAIRE NRC 540 COPY No. COPIE NR

6 PAGE PAGE 3 REPORT No. LTR-GD-60 RAPPORT NR. were produced with conical entry stainless steel nozzles. Depending on the size of the shells, a feed rate of 60 scallops per minute required traverse speeds in the range of ft/min. A few preliminary tests were conducted at 20 ft/min using a constant pressure of 45,000 psi. At these conditions, the jets had only the effect of cleaning the shells. Further tests at lower ( 5 ft/min) traverse speeds were also not satisfactory. Subsequent tests were conducted at a constant traverse speed of 1.25 ft/min (corresponds to a feed rate of about 3 scallops per minute), the lowest obtainable in the laboratory. Nominal standoff distance (that is, the distance between the nozzle and the highest point of the shell) was maintained at in. for all the tests. However, because of the curvature of the shell, the actual standoff distance varied, in the direction of traverse, from 0.25 to almost 0.5 in. near the edges of the shell. The ranges of other variables investigated were as follows: Nozzle diameter = in. Nozzle pressure = psi Hydraulic power = hp Photographs of the cut shells are shown in Figs. 6A to 6N. Test numbers are indicated on the shells and the results pertaining to each test are listed in the figure. Top and bottom parts of the shell, as defined in Fig. 2, are clearly marked on FORM NRC 540 FORMULAIRE NRC 540 COPY No. COPIE NR

7 PAGE 4 PAGE REPORT NO. RAPPORT NR. LTR-GD-60 these figures. The symbol 'N' on the photographs indicates that the high pressure jet was unable to cut through the part of the shell so designated. DISCUSSION Figs. 6A to D show the results obtained with the jet impinging vertically on the bottom part of the shell. Using a in. diameter nozzle, the hydraulic power was increased in steps from 5.8 to 10.6 hp. In all these tests, the jets could cut through the bottom part (facing the jet), but were unable to penetrate the other part, especially in the vicinity of the crown. In order to find out if this was due to a difference in strength between the top and bottom parts of the shell, the next two tests (Figs. 6E and F) were conducted with the top part facing the jet. The results were the same as observed before, that is, the part facing the jet was cut through, but not the other. This inability was due to insufficient energy in the jet after penetrating the part of the shell facing it. This was aggravated by the gap (which increased the standoff distance) between the top and bottom parts of the shell due to shell curvature. Since the coherent length of a jet (the length where most of the energy is concentrated) could be increased by increasing its diameter and power, the next three tests (Figs. 6G, H and I) were performed with a larger diameter (0.010 in.) nozzle. FORM NRC 540 FORMULAIRE NRC 540 COPY No. COPIE NR

8 PAGE PAGE 5 REPORT NO. RAPPORT NR. LTR-GD-60 Although the power was increased to 16.6 hp, the jets were unable to cut through both parts simultaneously. Fig. 6(J) shows the result obtained with a slight variation in the method of testing. Here an attempt was made to dislodge the hinge (muscle, Fig. 3) by aiming an angled (at 45 to the horizontal) jet as close to the hinge as possible. Since the result was not encouraging, no further tests were conducted with angled jets. Another method was multi passing of the jet over the same path of traverse. Fig. 6K shows that it was possible, albeit still at a low traverse speed of 1.25 ft/min, to cut through both parts of the shell in two passes under the jet. Results obtained with the Union pump (pressure = 10,000 psi and hydraulic powers up to 69 hp) are depicted in Figs. 6L, M and N. Here the cuts were highly unsatisfactory due to a great deal of spalling and may not be appropriate for processing scallops. CONCLUSION Laboratory tests conducted at pressures in the range of psi (hydraulic power = 6 to 69 hp) and with shell feed rates as low as 3 per minute showed that it was not possible to cut through sea scallop shells, especially on the hinge side. is possible in principle to cut the shells at high feed rates (>60 scallops per minute) by increasing the jet pressure considerably beyond psi, the hydraulic system would be prohibitively expensive in comparison with the pair of circular FORM NRC 540 FORMULAIRE NRC 540 COPY NO. COME NR

9 PAGE PAGE 6 REPORT NO. RAPPORT NRYJT R- GD-6 0 saws. existing at present in the prototype machine. REFERENCES 1. K. Glover, Ed., Fisheries and Oceans News, Vol. 5, No. 5, May 1980, pp FORM NRC 540 FORMULAIRE NRC 540 COPY NO. COPIE NR

10 Fig. 1 General appearance of a scallop shell Fig. 2 Top (highly curved) and bottom (relatively flat) parts of the shell Muscle (hinge) which controls the shell opening or closing Locations of desired cuts Edible portion of the scallop (abductor muscle) Fig. 3 Internal appearance of the shell Fig. 4 A spring loaded clamping device Fig. 5 Scallop shell in position under the high speed jet

11 Fig. 6 Shells cut with high pressure water jets D = nozzle diameter (in.) P = nozzle pressure (psi) Standoff distance = in. for all tests Traverse speed = 1.25 ft/min. for all tests HHP = hydraulic horsepower (hp) INDICATES NOT CUT THROUGH (A) D = P = HHP = 5.8 Bottom part facing the jet (B) D = P = HHP = 7.3 Bottom part facing the jet (C) D = P = HHP = 8.9 Bottom part facing the jet (D) D = P = HHP = 10.6 Bottom part facing the jet

12 Fig. 6(E) D = P = HHP = 8.9 (F) D = P = HHP = 10.6 D = P = HHP = 8.4 Bottom part facing the jet. (H) D = P = HHP = 8.4 (I) D = P = HHP = 16.6

13 Fig. 6 (J) D = P = HHP = 16.6 Jet at 45 o to the horizontal. (K) D = P = HHP = 16.6 Jet vertical. Cut through on two passes. (L) D = P = 10,000 HHP = 27.8 Spalling predominant. (M) D = P = HHP = 69 Irregular cut due to spalling. (N) D = P = HHP = 69 Bottom part facing the jet.